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+The Project Gutenberg EBook of Experiments and Observations on Different
+Kinds of Air, by Joseph Priestley
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Experiments and Observations on Different Kinds of Air
+
+Author: Joseph Priestley
+
+Release Date: August 19, 2009 [EBook #29734]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EXPERIMENTS, OBSERVATIONS ON AIR ***
+
+
+
+
+Produced by Mark C. Orton, Steven Gibbs, Josephine Paolucci
+and the Online Distributed Proofreading Team at
+https://www.pgdp.net.
+
+
+
+
+
+
+
+[Illustration: _To face the Title._]
+
+
+
+
+EXPERIMENTS AND OBSERVATIONS ON DIFFERENT KINDS OF AIR.
+
+[Price 5s. unbound.]
+
+     Quamobrem, si qua est erga Creatorem humilitas, si qua operum
+     ejus reverentia et magnificatio, si qua charitas in homines, si
+     erga necessitates et ærumnas humanas relevandas studium, si
+     quis amor veritatis in naturalibus, et odium tenebrarum, et
+     intellectus purificandi desiderium; orandi sunt homines iterum
+     atque iterum, ut, missis philosophiis istis volaticis et
+     preposteris, quæ theses hypothesibus anterposuerunt, et
+     experientiam captivam duxerunt, atque de operibus dei
+     triumpharunt, summisse, et cum veneratione quadam, ad volumen
+     creaturarum evolvendum accedant; atque in eo moram faciant,
+     meditentur, et ab opinionibus abluti et mundi, caste et integre
+     versentur.----In interpretatione ejus eruenda nulli operæ
+     parcant, sed strenue procedant, persistant, immoriantur.
+
+     LORD BACON IN INSTAURATIONE MAGNA.
+
+
+
+
+
+
+EXPERIMENTS
+
+AND
+
+OBSERVATIONS
+
+ON DIFFERENT KINDS OF
+
+AIR.
+
+
+By JOSEPH PRIESTLEY, LL.D. F.R.S.
+
+The SECOND EDITION Corrected.
+
+     Fert animus Causas tantarum expromere rerum;
+     Immensumque aperitur opus.
+
+                            LUCAN
+
+LONDON:
+
+Printed for J. JOHNSON, No. 72, in St. Paul's Church-Yard.
+
+MDCCLXXV.
+
+
+    TO THE RIGHT HONOURABLE
+    THE EARL OF SHELBURNE,
+    THIS TREATISE IS
+    WITH THE GREATEST GRATITUDE
+    AND RESPECT,
+    INSCRIBED,
+    BY HIS LORDSHIP's
+    MOST OBLIGED,
+    AND OBEDIENT
+    HUMBLE SERVANT,
+    J. PRIESTLEY.
+
+Transcriber's Note: Footnotes have been moved to the end of the chapter.
+The errata listed at the end of the book have been corrected in the
+text. In the text, there are places where the apothecary symbols for
+ounce and dram are used. These are changed to oz. and dr. in the text
+file.
+
+
+
+
+THE PREFACE.
+
+
+One reason for the present publication has been the favourable reception
+of those of my _Observations on different kinds of air_, which were
+published in the Philosophical Transactions for the year 1772, and the
+demand for them by persons who did not chuse, for the sake of those
+papers only, to purchase the whole volume in which they were contained.
+Another motive was the _additions_ to my observations on this subject,
+in consequence of which my papers grew too large for such a publication
+as the _Philosophical Transactions_.
+
+Contrary, therefore, to my intention, expressed Philosophical
+Transactions, vol. 64. p. 90, but with the approbation of the President,
+and of my friends in the society, I have determined to send them no
+more papers for the present on this subject, but to make a separate and
+immediate publication of all that I have done with respect to it.
+
+Besides, considering the attention which, I am informed, is now given to
+this subject by philosophers in all parts of Europe, and the rapid
+progress that has already been made, and may be expected to be made in
+this branch of knowledge, all unnecessary delays in the publication of
+experiments relating to it are peculiarly unjustifiable.
+
+When, for the sake of a little more reputation, men can keep brooding
+over a new fact, in the discovery of which they might, possibly, have
+very little real merit, till they think they can astonish the world with
+a system as complete as it is new, and give mankind a prodigious idea of
+their judgment and penetration; they are justly punished for their
+ingratitude to the fountain of all knowledge, and for their want of a
+genuine love of science and of mankind, in finding their boasted
+discoveries anticipated, and the field of honest fame pre-occupied, by
+men, who, from a natural ardour of mind, engage in philosophical
+pursuits, and with an ingenuous simplicity immediately communicate to
+others whatever occurs to them in their inquiries.
+
+As to myself, I find it absolutely impossible to produce a work on this
+subject that shall be any thing like _complete_. My first publication I
+acknowledged to be very imperfect, and the present, I am as ready to
+acknowledge, is still more so. But, paradoxical as it may seem, this
+will ever be the case in the progress of natural science, so long as the
+works of God are, like himself, infinite and inexhaustible. In
+completing one discovery we never fail to get an imperfect knowledge of
+others, of which we could have no idea before; so that we cannot solve
+one doubt without creating several new ones.
+
+Travelling on this ground resembles Pope's description of travelling
+among the Alps, with this difference, that here there is not only
+_succession_, but an _increase_ of new objects and new difficulties.
+
+     So pleas'd at first the tow'ring Alps we try,
+     Mount o'er the vales, and seem to tread the sky.
+     Th' eternal snows appear already past,
+     And the first clouds and mountains seem the last,
+     But those attain'd, we tremble to survey
+     The growing labours of the lengthen'd way.
+     Th' increasing prospect tires our wand'ring eyes,
+     Hills peep o'er hills, and Alps on Alps arise.
+
+                            ESSAY ON CRITICISM.
+
+Newton, as he had very little knowledge of _air_, so he had few doubts
+concerning it. Had Dr. Hales, after his various and valuable
+investigations, given a list of all his _desiderata_, I am confident
+that he would not have thought of one in ten that had occurred to me at
+the time of my last publication; and my doubts, queries, and hints for
+new experiments are very considerably increased, after a series of
+investigations, which have thrown great light upon many things of which
+I was not able to give any explanation before.
+
+I would observe farther, that a person who means to serve the cause of
+science effectually, must hazard his own reputation so far as to risk
+even _mistakes_ in things of less moment. Among a multiplicity of new
+objects, and new relations, some will necessarily pass without
+sufficient attention; but if a man be not mistaken in the principal
+objects of his pursuits, he has no occasion to distress himself about
+lesser things.
+
+In the progress of his inquiries he will generally be able to rectify
+his own mistakes; or if little and envious souls should take a malignant
+pleasure in detecting them for him, and endeavouring to expose him, he
+is not worthy of the name of a philosopher, if he has not strength of
+mind sufficient to enable him not to be disturbed at it. He who does not
+foolishly affect to be above the failings of humanity, will not be
+mortified when it is proved that he is but a man.
+
+In this work, as well as in all my other philosophical writings, I have
+made it a rule not to conceal the _real views_ with which I have made
+experiments; because though, by following a contrary maxim, I might have
+acquired a character of greater sagacity, I think that two very good
+ends are answered by the method that I have adopted. For it both tends
+to make a narrative of a course of experiments more interesting, and
+likewise encourages other adventurers in experimental philosophy;
+shewing them that, by pursuing even false lights, real and important
+truths may be discovered, and that in seeking one thing we often find
+another.
+
+In some respects, indeed, this method makes the narrative _longer_, but
+it is by making it less tedious; and in other respects I have written
+much more concisely than is usual with those who publish accounts of
+their experiments. In this treatise the reader will often find the
+result of long processes expressed in a few lines, and of many such in a
+single paragraph; each of which, if I had, with the usual parade,
+described it at large (explaining first the _preparation_, then reciting
+the _experiment_ itself, with the _result_ of it, and lastly making
+suitable _reflections_) would have made as many sections or chapters,
+and have swelled my book to a pompous and respectable size. But I have
+the pleasure to think that those philosophers who have but little time
+to spare for _reading_, which is always the case with those who _do_
+much themselves, will thank me for not keeping them too long from their
+own pursuits; and that they will find rather more in the volume, than
+the appearance of it promises.
+
+I do not think it at all degrading to the business of experimental
+philosophy, to compare it, as I often do, to the diversion of _hunting_,
+where it sometimes happens that those who have beat the ground the most,
+and are consequently the best acquainted with it, weary themselves
+without starting any game; when it may fall in the way of a mere
+passenger; so that there is but little room for boasting in the most
+successful termination of the chace.
+
+The best founded praise is that which is due to the man, who, from a
+supreme veneration for the God of nature, takes pleasure in
+contemplating his _works_, and from a love of his fellow-creatures, as
+the offspring of the same all-wise and benevolent parent, with a
+grateful sense and perfect enjoyment of the means of happiness of which
+he is already possessed, seeks, with earnestness, but without murmuring
+or impatience, that greater _command of the powers of nature_, which can
+only be obtained by a more extensive and more accurate _knowledge_ of
+them; and which alone can enable us to avail ourselves of the numerous
+advantages with which we are surrounded, and contribute to make our
+common situation more secure and happy.
+
+Besides, the man who believes that there is a _governor_ as well as a
+_maker_ of the world (and there is certainly equal reason to believe
+both) will acknowledge his providence and favour at least as much in a
+successful pursuit of _knowledge_, as of _wealth_; which is a sentiment
+that entirely cuts off all boasting with respect to ourselves, and all
+envy and jealousy with respect to others; and disposes us mutually to
+rejoice in every new light that we receive, through whose hands soever
+it be conveyed to us.
+
+I shall pass for an enthusiast with some, but I am perfectly easy under
+the imputation, because I am happy in those views which subject me to
+it; but considering the amazing improvements in natural knowledge which
+have been made within the last century, and the many ages, abounding
+with men who had no other object but study, in which, however, nothing
+of this kind was done, there appears to me to be a very particular
+providence in the concurrence of those circumstances which have produced
+so great a change; and I cannot help flattering myself that this will be
+instrumental in bringing about other changes in the state of the world,
+of much more consequence to the improvement and happiness of it.
+
+This rapid progress of knowledge, which, like the progress of a _wave_
+of the sea, of _sound_, or of _light_ from the sun, extends itself not
+this way or that way only, but _in all directions_, will, I doubt not,
+be the means, under God, of extirpating _all_ error and prejudice, and
+of putting an end to all undue and usurped authority in the business of
+_religion_, as well as of _science_; and all the efforts of the
+interested friends of corrupt establishments of all kinds will be
+ineffectual for their support in this enlightened age: though, by
+retarding their downfal, they may make the final ruin of them more
+complete and glorious. It was ill policy in Leo the Xth to patronize
+polite literature. He was cherishing an enemy in disguise. And the
+English hierarchy (if there be any thing unsound in its constitution)
+has equal reason to tremble even at an air-pump, or an electrical
+machine.
+
+There certainly never was any period in which _natural knowledge_ made
+such a progress as it has done of late years, and especially in this
+country; and they who affect to speak with supercilious contempt of the
+publications of the present age in general, or of the Royal Society in
+particular, are only those who are themselves engaged in the most
+trifling of all literary pursuits, who are unacquainted with all real
+science, and are ignorant of the progress and present state of it.[1]
+
+It is true that the rich and the great in this country give less
+attention to these subjects than, I believe, they were ever known to do,
+since the time of Lord Bacon, and much less than men of rank and fortune
+in other countries give to them. But with us this loss is made up by
+men of leisure, spirit, and ingenuity, in the middle ranks of life,
+which is a circumstance that promises better for the continuance of this
+progress in useful knowledge than any noble or royal patronage. With us,
+politics chiefly engage the attention of those who stand foremost in the
+community, which, indeed, arises from the _freedom_ and peculiar
+_excellence_ of our constitution, without which even the spirit of men
+of letters in general, and of philosophers in particular, who never
+directly interfere in matters of government, would languish.
+
+It is rather to be regretted, however, that, in such a number of
+nobility and gentry, so very few should have any taste for scientifical
+pursuits, because, for many valuable purposes of science, _wealth_ gives
+a decisive advantage. If extensive and lasting _fame_ be at all an
+object, literary, and especially scientifical pursuits, are preferable
+to political ones in a variety of respects. The former are as much more
+favourable for the display of the human faculties than the latter, as
+the _system of nature_ is superior to any _political system_ upon earth.
+
+If extensive _usefulness_ be the object, science has the same advantage
+over politics. The greatest success in the latter seldom extends farther
+than one particular country, and one particular age; whereas a
+successful pursuit of science makes a man the benefactor of all mankind,
+and of every age. How trifling is the fame of any statesman that this
+country has ever produced to that of Lord Bacon, of Newton, or of Boyle;
+and how much greater are our obligations to such men as these, than to
+any other in the whole _Biographia Britannica_; and every country, in
+which science has flourished, can furnish instances for similar
+observations.
+
+Here my reader will thank me, and the writer will, I hope, forgive me,
+if I quote a passage from the postscript of a letter which I happen to
+have just received from that excellent, and in my opinion, not too
+enthusiastical philosopher, father Beccaria of Turin.
+
+     _Mi spiace che il mondo politico ch'è pur tanto passeggero,
+     rubbi il grande Franklin al mondo della natura, che non sa ne
+     cambiare, ne mancare._ In English. "I am sorry that the
+     _political world_, which is so very transitory, should take the
+     great Franklin from the _world of nature_, which can never
+     change, or fail."
+
+I own it is with peculiar pleasure that I quote this passage, respecting
+this truly great man, at a time when some of the infatuated politicians
+of this country are vainly thinking to build their wretched and
+destructive projects, on the ruins of his established reputation; a
+reputation as extensive as the spread of science itself, and of which it
+is saying very little indeed, to pronounce that it will last and
+flourish when the names of all his enemies shall be forgotten.
+
+I think it proper, upon this occasion, to inform my friends, and the
+public, that I have, for the present, suspended my design of writing
+_the history and present state of all the branches of experimental
+philosophy_. This has arisen not from any dislike of the undertaking,
+but, in truth, because I see no prospect of being reasonably indemnified
+for so much labour and expence, notwithstanding the specimens I have
+already given of that work (in the _history of electricity_, and of the
+_discoveries relating to vision, light, and colours_) have met with a
+much more favourable reception from the best judges both at home and
+abroad, than I expected. Immortality, if I should have any view to it,
+is not the proper price of such works as these.
+
+I propose, however, having given so much attention to the subject of
+_air_, to write, at my leisure, the history and present state of
+discoveries relating to it; in which case I shall, as a part of it,
+reprint this work, with such improvements as shall have occurred to me
+at that time; and I give this notice of it, that no person who intends
+to purchase it may have reason (being thus apprised of my intention) to
+complain of buying the same thing twice. If any person chuse it, he may
+save his five or six shillings for the present, and wait five or six
+years longer (if I should live so long) for the opportunity of buying
+the same thing, probably much enlarged, and at the same time a complete
+account of all that has been done by others relating to this subject.
+
+Though for the plain, and I hope satisfactory reason above mentioned, I
+shall probably write no other _histories_ of this kind, I shall, as
+opportunity serves, endeavour to provide _materials_ for such histories,
+by continuing my experiments, keeping my eyes open to such new
+appearances as may present themselves, investigating them as far as I
+shall be able, and never failing to communicate to the public, by some
+channel or other, the result of my observations.
+
+In the publication of this work I have thought that it would be
+agreeable to my readers to preserve, in some measure, the order of
+history, and therefore I have not thrown together all that I have
+observed with respect to each kind of air, but have divided the work
+into _two parts_; the former containing what was published before, in
+the Philosophical Transactions, with such observations and corrections
+as subsequent experience has suggested to me; and I have reserved for
+the latter part of the work an account of the experiments which I have
+made since that publication, and after a pretty long interruption in my
+philosophical pursuits, in the course of the last summer. Besides I am
+sensible that in the latter part of this work a different arrangement of
+the subjects will be more convenient, for their mutual illustration.
+
+Some persons object to the term _air_, as applied to _acid_, _alkaline_,
+and even _nitrous air_; but it is certainly very convenient to have a
+common term by which to denote things which have so many common
+properties, and those so very striking; all of them agreeing with the
+air in which we breathe, and with _fixed air_, in _elasticity_, and
+_transparency_, and in being alike affected by heat or cold; so that to
+the eye they appear to have no difference at all. With much more reason,
+as it appears to me, might a person object to the common term _metal_,
+as applied to things so very different from one another as gold,
+quicksilver, and lead.
+
+Besides, _acid_ and _alkaline_ air do not differ from _common air_ (in
+any respect that can countenance an objection to their having a common
+appellation) except in such properties as are common to it with _fixed
+air_, though in a different degree; viz. that of being imbibed by water.
+But, indeed, all kinds of air, common air itself not excepted, are
+capable of being imbibed by water in some degree.
+
+Some may think the terms acid and alkaline _vapour_ more proper than
+acid and alkaline _air_. But the term _vapour_ having always been
+applied to elastic matters capable of being condensed in the temperature
+of the atmosphere, especially the vapour of water, it seems harsh to
+apply it to any elastic substance, which at the same time that it is as
+transparent as the air we breathe, is no more affected by cold than it
+is.
+
+As my former papers were immediately translated into several foreign
+languages, I may presume that this treatise, having a better title to
+it, will be translated also; and, upon this presumption, I cannot help
+expressing a wish, that it may be done by persons who have a competent
+knowledge of _subject_, as well as of the _English language_. The
+mistakes made by some foreigners, have induced me to give this caution.
+
+     _London, Feb._
+     _1774._
+
+
+ADVERTISEMENT.
+
+The _weights_ mentioned in the course of this treatise are _Troy_, and
+what is called _an ounce measure of air_, is the space occupied by an
+ounce weight of water, which is equal to 480 grains, and is, therefore,
+almost two _cubic inches_ of water; for one cubic inch weighs 254
+grains.
+
+FOOTNOTES:
+
+[1] See Sir John Pringle's _Discourse on the different kinds of air_, p.
+29, which, if it became me to do it, I would recommend to the reader, as
+containing a just and elegant account of the several discoveries that
+have been successively made, relating to the subject of this treatise.
+
+
+
+
+THE CONTENTS.
+
+
+THE INTRODUCTION.
+
+Section I. _A general view of PRECEDING DISCOVERIES relating to
+           AIR_                                                    Page 1
+
+Sect. II. _An Account of the APPARATUS with which the following
+           Experiments were made_                                       6
+
+
+PART I.
+
+_Experiments and Observations made in, and before the Year 1772._      23
+
+Sect. I. _Of FIXED AIR_                                                25
+
+Sect. II. _Of AIR in which a CANDLE, or BRIMSTONE, has burned out_     43
+
+Sect. III. _Of INFLAMMABLE AIR_                                        55
+
+Sect. IV. _Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION_   70
+
+Sect. V. _Of AIR in which a mixture of BRIMSTONE and FILINGS of
+         IRON has stood_                                              105
+
+Sect. VI. _Of NITROUS AIR_                                            108
+
+Sect. VII. _Of AIR infected with the FUMES of BURNING CHARCOAL_       129
+
+Sect. VIII. _Of the effect of the CALCINATION of METALS, and of the
+             EFFLUVIA of PAINT made with WHITE-LEAD and OIL, on AIR_  133
+
+Sect. IX. _Of MARINE ACID AIR_                                        143
+
+Sect. X. _Miscellaneous Observations_                                 154
+
+
+PART II.
+
+_Experiments and Observations made in the Year 1773, and the Beginning of
+1774._
+
+Sect. I. _Observations on ALKALINE AIR_                               163
+
+Sect. II. _Of COMMON AIR diminished, and made noxious by various
+          processes_                                                  177
+
+Sect. III. _Of NITROUS AIR_                                           203
+
+Sect. IV. _Of MARINE ACID AIR_                                        229
+
+Sect. V. _Of INFLAMMABLE AIR_                                         242
+
+Sect. VI. _Of FIXED AIR_                                              248
+
+Sect. VII. MISCELLANEOUS EXPERIMENTS                                  252
+
+Sect. VIII. _QUERIES, SPECULATIONS, and HINTS_                        258
+
+
+THE APPENDIX.
+
+Number I. _EXPERIMENTS made by Mr. Hey to prove that there is no
+          OIL of VITRIOL in water impregnated with FIXED AIR_         288
+
+Number II. _A Letter from Mr. HEY to Dr. PRIESTLEY, concerning the
+            effects of fixed Air applied by way of Clyster_           292
+
+Number III. _Observations on the MEDICINAL USES of FIXED AIR. By
+            THOMAS PERCIVAL, M. D. Fellow of the ROYAL SOCIETY,
+            and of the SOCIETY of ANTIQUARIES in LONDON_              300
+
+Number IV. _Extract of a Letter from WILLIAM FALCONER, M. D. of BATH_ 314
+
+Number V. _Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT
+           MASSINGHAM, NORFOLK_                                       317
+
+Num. VI. _A Letter from Dr. FRANKLIN_                                 321
+
+Number VII. _Extract of Letter from Mr. HENRY of MANCHESTER_          323
+
+
+
+
+
+THE INTRODUCTION.
+
+
+
+
+SECTION I.
+
+_A general view of PRECEDING DISCOVERIES relating to air._
+
+
+For the better understanding of the experiments and observations on
+different kinds of air contained in this treatise, it will be useful to
+those who are not acquainted with the history of this branch of natural
+philosophy, to be informed of those facts which had been discovered by
+others, before I turned my thoughts to the subject; which suggested, and
+by the help of which I was enabled to pursue, my inquiries. Let it be
+observed, however, that I do not profess to recite in this place _all_
+that had been discovered concerning air, but only those discoveries the
+knowledge of which is necessary, in order to understand what I have done
+myself; so that any person who is only acquainted with the general
+principles of natural philosophy, may be able to read this treatise,
+and, with proper attention, to understand every part of it.
+
+That the air which constitutes the atmosphere in which we live has
+_weight_, and that it is _elastic_, or consists of a compressible and
+dilatable fluid, were some of the earliest discoveries that were made
+after the dawning of philosophy in this western part of the world.
+
+That elastic fluids, differing essentially from the air of the
+atmosphere, but agreeing with it in the properties of weight,
+elasticity, and transparency, might be generated from solid substances,
+was discovered by Mr. Boyle, though two remarkable kinds of factitious
+air, at least the effects of them, had been known long before to all
+miners. One of these is heavier than common air. It lies at the bottom
+of pits, extinguishes candles, and kills animals that breathe it, on
+which account it had obtained the name of the _choke damp_. The other is
+lighter than common air, taking its place near the roofs of
+subterraneous places, and because it is liable to take fire, and
+explode, like gunpowder, it had been called the _fire damp_. The word
+_damp_ signifies _vapour_ or _exhalation_ in the German and Saxon
+language.
+
+Though the former of these kinds of air had been known to be noxious,
+the latter I believe had not been discovered to be so, having always
+been found in its natural state, so much diluted with common air, as to
+be breathed with safety. Air of the former kind, besides having been
+discovered in various caverns, particularly the _grotta del Cane_ in
+Italy, had also been observed on the surface of fermenting liquors, and
+had been called _gas_ (which is the same with _geist_, or _spirit_) by
+Van Helmont, and other German chymists; but afterwards it obtained the
+name of _fixed air_, especially after it had been discovered by Dr.
+Black of Edinburgh to exist, in a fixed state, in alkaline salts, chalk,
+and other calcareous substances.
+
+This excellent philosopher discovered that it is the presence of the
+fixed air in these substances that renders them _mild_, and that when
+they are deprived of it, by the force of fire, or any other process,
+they are in that state which had been called _caustic_, from their
+corroding or burning animal and vegetable substances.
+
+Fixed air had been discovered by Dr. Macbride of Dublin, after an
+observation of Sir John Pringle's, which led to it, to be in a
+considerable degree antiseptic; and since it is extracted in great
+plenty from fermenting vegetables, he had recommended the use of _wort_
+(that is an infusion of malt in water) as what would probably give
+relief in the sea-scurvy, which is said to be a putrid disease.
+
+Dr. Brownrigg had also discovered that the same species of air is
+contained in great quantities in the water of the Pyrmont spring at Spa
+in Germany, and in other mineral waters, which have what is called an
+_acidulous_ taste, and that their peculiar flavour, briskness, and
+medicinal virtues, are derived from this ingredient.
+
+Dr. Hales, without seeming to imagine that there was any material
+difference between these kinds of air and common air, observed that
+certain substances and operations _generate_ air, and others _absorb_
+it; imagining that the diminution of air was simply a taking away from
+the common mass, without any alteration in the properties of what
+remained. His experiments, however, are so numerous, and various, that
+they are justly esteemed to be the solid foundation of all our knowledge
+of this subject.
+
+Mr. Cavendish had exactly ascertained the specific gravities of fixed
+and inflammable air, shewing the former of them to be 1-1/2 heavier
+than common air, and the latter ten times lighter. He also shewed that
+water would imbibe more than its own bulk of fixed air.
+
+Lastly, Mr. Lane discovered that water thus impregnated with fixed air
+will dissolve a considerable quantity of iron, and thereby become a
+strong chalybeate.
+
+These, I would observe, are by no means all the discoveries concerning
+air that have been made by the gentlemen whose names I have mentioned,
+and still less are they all that have been made by others; but they
+comprise all the previous knowledge of this subject that is necessary to
+the understanding of this treatise; except a few particulars, which will
+be mentioned in the course of the work, and which it is, therefore,
+unnecessary to recite in this place.
+
+
+
+
+SECTION II.
+
+_An account of the APPARATUS with which the following experiments were
+made._
+
+
+Rather than describe at large the manner in which every particular
+experiment that I shall have occasion to recite was made, which would
+both be very tedious, and require an unnecessary multiplicity of
+drawings, I think it more adviseable to give, at one view, an account of
+all my apparatus and instruments, or at least of every thing that can
+require a description, and of all the different operations and processes
+in which I employ them.
+
+It will be seen that my apparatus for experiments on air is, in fact,
+nothing more than the apparatus of Dr. Hales, Dr. Brownrigg, and Mr.
+Cavendish, diversified, and made a little more simple. Yet
+notwithstanding the simplicity of this apparatus, and the ease with
+which all the operations are conducted, I would not have any person, who
+is altogether without experience, to imagine that he shall be able to
+select any of the following experiments, and immediately perform it,
+without difficulty or blundering. It is known to all persons who are
+conversant in experimental philosophy, that there are many little
+attentions and precautions necessary to be observed in the conducting of
+experiments, which cannot well be described in words, but which it is
+needless to describe, since practice will necessarily suggest them;
+though, like all other arts in which the hands and fingers are made use
+of, it is only _much practice_ that can enable a person to go through
+complex experiments, of this or any other kind, with ease and readiness.
+
+For experiments in which air will bear to be confined by water, I first
+used an oblong trough made of earthen ware, as _a_ fig. 1. about eight
+inches deep, at one end of which I put thin flat stones, _b. b._ about
+an inch, or half an inch, under the water, using more or fewer of them
+according to the quantity of water in the trough. But I have since found
+it more convenient to use a larger wooden trough, of the same general
+shape, eleven inches deep, two feet long, and 1-1/2 wide, with a shelf
+about an inch lower than the top, instead of the flat stones
+above-mentioned. This trough being larger than the former, I have no
+occasion to make provision for the water being higher or lower, the bulk
+of a jar or two not making so great a difference as did before.
+
+The several kinds of air I usually keep in _cylindrical jars_, as _c_,
+_c_, fig. 1, about ten inches long, and 2-1/2 wide, being such as I have
+generally used for electrical batteries, but I have likewise vessels of
+very different forms and sizes, adapted to particular experiments.
+
+When I want to remove vessels of air from the large trough, I place them
+in _pots_ or _dishes_, of various sizes, to hold more or less water,
+according to the time that I have occasion to keep the air, as fig. 2.
+These I plunge in water, and slide the jars into them; after which they
+may be taken out together, and be set wherever it shall be most
+convenient. For the purpose of merely removing a jar of air from one
+place to another, where it is not to stand longer than a few days, I
+make use of common _tea-dishes_, which will hold water enough for that
+time, unless the air be in a state of diminution, by means of any
+process that is going on in it.
+
+If I want to try whether an animal will live in any kind of air, I first
+put the air into a small vessel, just large enough to give it room to
+stretch itself; and as I generally make use of _mice_ for this purpose,
+I have found it very convenient to use the hollow part of a tall
+beer-glass, _d_ fig. 1, which contains between two and three ounce
+measures of air. In this vessel a mouse will live twenty minutes, or
+half an hour.
+
+For the purpose of these experiments it is most convenient to catch the
+mice in small wire traps, out of which it is easy to take them, and
+holding them by the back of the neck, to pass them through the water
+into the vessel which contains the air. If I expect that the mouse will
+live a considerable time, I take care to put into the vessel something
+on which it may conveniently sit, out of the reach of the water. If the
+air be good, the mouse will soon be perfectly at its ease, having
+suffered nothing by its passing through the water. If the air be
+supposed to be noxious, it will be proper (if the operator be desirous
+of preserving the mice for farther use) to keep hold of their tails,
+that they may be withdrawn as soon as they begin to shew signs of
+uneasiness; but if the air be thoroughly noxious, and the mouse happens
+to get a full inspiration, it will be impossible to do this before it be
+absolutely irrecoverable.
+
+In order to _keep_ the mice, I put them into receivers open at the top
+and bottom, standing upon plates of tin perforated with many holes, and
+covered with other plates of the same kind, held down by sufficient
+weights, as fig. 3. These receivers stand upon _a frame of wood_, that
+the fresh air may have an opportunity of getting to the bottoms of them,
+and circulating through them. In the inside I put a quantity of paper or
+tow, which must be changed, and the vessel washed and dried, every two
+or three days. This is most conveniently done by having another
+receiver, ready cleaned and prepared, into which the mice may be
+transferred till the other shall be cleaned.
+
+Mice must be kept in a pretty exact temperature, for either much heat or
+much cold kills them presently. The place in which I have generally kept
+them is a shelf over the kitchen fire-place where, as it is usual in
+Yorkshire, the fire never goes out; so that the heat varies very little,
+and I find it to be, at a medium, about 70 degrees of Fahrenheit's
+thermometer. When they had been made to pass through the water, as they
+necessarily must be in order to a change of air, they require, and will
+bear a very considerable degree of heat, to warm and dry them.
+
+I found, to my great surprize, in the course of these experiments, that
+mice will live intirely without water; for though I have kept them for
+three or four months, and have offered them water several times, they
+would never taste it; and yet they continued in perfect health and
+vigour. Two or three of them will live very peaceably together in the
+same vessel; though I had one instance of a mouse tearing another almost
+in pieces, and when there was plenty of provisions for both of them.
+
+In the same manner in which a mouse is put into a vessel of any kind of
+air, a _plant_, or any thing else, may be put into it, viz. by passing
+it through the water; and if the plant be of a kind that will grow in
+water only, there will be no occasion to set it in a pot of earth, which
+will otherwise be necessary.
+
+There may appear, at first sight, some difficulty in opening the mouth
+of a phial, containing any substance, solid or liquid, to which water
+must not be admitted, in a jar of any kind of air, which is an operation
+that I have sometimes had recourse to; but this I easily effect by means
+of _a cork cut tapering_, and a strong, wire thrust through it, as in
+fig. 4, for in this form it will sufficiently fit the mouth of any
+phial, and by holding the phial in one hand, and the wire in the other,
+and plunging both my hands into the trough of water, I can easily convey
+the phial through the water into the jar; which must either be held by
+an assistant, or be fastened by strings, with its mouth projecting over
+the shelf. When the phial is thus conveyed into the jar, the cork may
+easily be removed, and may also be put into it again at pleasure, and
+conveyed the same way out again.
+
+When any thing, as a gallipot, &c. is to be supported at a considerable
+height within a jar, it is convenient to have such _wire stands_ as are
+represented fig. 5. They answer better than any other, because they take
+up but little room, and may be easily bended to any shape or height.
+
+If I have occasion to pour air from a vessel with a wide mouth into
+another with a very narrow one, I am obliged to make use of a funnel,
+fig. 6, but by this means the operation is exceedingly easy; first
+filling the vessel into which the air is to be conveyed with water, and
+holding the mouth of it, together with the funnel, both under water with
+one hand, while the other is employed in pouring the air; which,
+ascending through the funnel up into the vessel, makes the water
+descend, and takes its place. These funnels are best made of glass,
+because the air being visible through them, the quantity of it may be
+more easily estimated by the eye. It will be convenient to have several
+of these funnels of different sizes.
+
+In order to expel air from solid substances by means of heat, I
+sometimes put them into a _gun-barrel_, fig. 7, and filling it up with
+dry sand, that has been well burned, so that no air can come from it, I
+lute to the open end the stem of a tobacco pipe, or a small glass tube.
+Then having put the closed end of the barrel, which contains the
+materials, into the fire, the generated air, issuing through the tube,
+may be received in a vessel of quicksilver, with its mouth immersed in a
+bason of the same, suspended all together in wires, in the manner
+described in the figure: or any other fluid substance may be used
+instead of quicksilver.
+
+But the most accurate method of procuring air from several substances,
+by means of heat, is to put them, if they will bear it, into phials full
+of quicksilver, with the mouths immersed in the same, and then throw the
+focus of a burning mirror upon them. For this purpose the phials should
+be made with their bottoms round, and very thin, that they may not be
+liable to break with a pretty sudden application of heat.
+
+If I want to expel air from any liquid, I nearly fill a phial with it,
+and having a cork perforated, I put through it, and secure with cement,
+a glass tube, bended in the manner represented at _e_ fig. 1. I then put
+the phial into a kettle of water, which I set upon the fire and make to
+boil. The air expelled by the heat, from the liquor contained in the
+phial, issues through the tube, and is received in the bason of
+quicksilver, fig. 7. Instead of this suspended bason, I sometimes
+content myself with tying a flaccid bladder to the end of the tube, in
+both these processes, that it may receive the newly generated air.
+
+In experiments on those kinds of air which are readily imbibed by water,
+I always make use of quicksilver, in the manner represented fig. 8, in
+which _a_ is the bason of quicksilver, _b_ a glass vessel containing
+quicksilver, with its mouth immersed in it, _c_ a phial containing the
+ingredients from which the air is to be produced; and _d_ is a small
+recipient, or glass vessel designed to receive and intercept any liquor
+that may be discharged along with the air, which is to be transmitted
+free from any moisture into the vessel _b_. If there be no apprehension
+of moisture, I make use of the glass tube only, without any recipient,
+in the manner represented _e_ fig. 1. In order to invert the vessel _b_,
+I first fill it with quicksilver, and then carefully cover the mouth of
+it with a piece of soft leather; after which it may be turned upside
+down without any danger of admitting the air, and the leather may be
+withdrawn when it is plunged in the quicksilver.
+
+In order to generate air by the solution of metals, or any process of a
+similar nature, I put the materials into a phial, prepared in the manner
+represented at _e_ fig. 1, and put the end of the glass tube under the
+mouth of any vessel into which I want to convey the air. If heat be
+necessary I can easily apply to it a candle, or a red hot poker while it
+hangs in this position.
+
+When I have occasion to transfer air from a jar standing in the trough
+of water to a vessel standing in quicksilver, or in any other situation
+whatever, I make use of the contrivance represented fig. 9, which
+consists of a bladder, furnished at one end with a small glass tube
+bended, and at the other with a cork, perforated so as just to admit the
+small end of a funnel. When the common air is carefully pressed out of
+this bladder, and the funnel is thrust tightly into the cork, it may be
+filled with any kind of air as easily as a glass jar; and then a string
+being tied above the cork in which the funnel is inserted, and the
+orifice in the other cork closed, by pressing the bladder against it, it
+may be carried to any place, and if the tube be carefully wiped, the air
+may be conveyed quite free from moisture through a body of quicksilver,
+or any thing else. A little practice will make this very useful
+manoeuvre perfectly easy and accurate.
+
+In order to impregnate fluids with any kind of air, as water with fixed
+air, I fill a phial with the fluid larger or less as I have occasion (as
+_a_ fig. 10;) and then inverting it, place it with its mouth downwards,
+in a bowl _b_, containing a quantity of the same fluid; and having
+filled the bladder, fig. 9, with the air, I throw as much of it as I
+think proper into the phial, in the manner described above. To
+accelerate the impregnation, I lay my hand on the top of the phial, and
+shake it as much as I think proper.
+
+If, without having any air previously generated, I would convey it into
+the fluid immediately as it arises from the proper materials, I keep the
+same bladder in connection with a phial _c_ fig. 10, containing the same
+materials (as chalk, salt of tartar, or pearl ashes in diluted oil of
+vitriol, for the generation of fixed air) and taking care, lest, in the
+act of effervescence, any of the materials in the phial _c_ should get
+into the vessel _a_, to place this phial on a stand lower than that on
+which the bason was placed, I press out the newly generated air, and
+make it ascend directly into the fluid. For this purpose, and that I may
+more conveniently shake the phial _c_, which is necessary in some
+processes, especially with chalk and oil of vitriol, I sometimes make
+use of a flexible leathern tube _d_, and sometimes only a glass tube.
+For if the bladder be of a sufficient length, it will give room for the
+agitation of the phial; or if not, it is easy to connect two bladders
+together by means of a perforated cork, to which they may both be
+fastened.
+
+When I want to try whether any kind of air will admit a candle to burn
+in it, I make use of a cylindrical glass vessel, fig. 11. and a bit of
+wax candle _a_ fig. 12, fastened to the end of a wire _b_, and turned
+up, in such a manner as to be let down into the vessel with the flame
+upwards. The vessel should be kept carefully covered till the moment
+that the candle is admitted. In this manner I have frequently
+extinguished a candle more than twenty times successively, in a vessel
+of this kind, though it is impossible to dip the candle into it without
+giving the external air an opportunity of mixing with the air in the
+inside more or less. The candle _c_, at the other end of the wire is
+very convenient for holding under a jar standing in water, in order to
+burn as long as the inclosed air can supply it; for the moment that it
+is extinguished, it may be drawn through the water before any smoke can
+have mixed with the air.
+
+In order to draw air out of a vessel which has its mouth immersed in
+water, and thereby to raise the water to whatever height may be
+necessary, it is very convenient to make use of a glass _syphon_, fig.
+13, putting one of the legs up into the vessel, and drawing the air out
+at the other end by the mouth. If the air be of a noxious quality, it
+may be necessary to have a syringe fastened to the syphon, the manner of
+which needs no explanation. I have not thought it safe to depend upon a
+valve at the top of the vessel, which Dr. Hales sometimes made use of.
+
+If, however, a very small hole be made at the top of a glass vessel, it
+may be filled to any height by holding it under water, while the air is
+issuing out at the hole, which may then be closed with wax or cement.
+
+If the generated air will neither be absorbed by water, nor diminish
+common air, it may be convenient to put part of the materials into a
+cup, supported by a stand, and the other part into a small glass
+vessel, placed on the edge of it, as at _f_, fig. 1. Then having, by
+means of a syphon, drawn the air to at convenient height, the small
+glass vessel may be easily pushed into the cup, by a wire introduced
+through the water; or it may be contrived, in a variety of ways, only to
+discharge the contents of the small vessel into the larger. The distance
+between the boundary of air and water, before and after the operation,
+will shew the quantity of the generated air. The effect of processes
+that _diminish_ air may also be tried by the same apparatus.
+
+When I want to admit a particular kind of air to any thing that will not
+bear wetting, and yet cannot be conveniently put into a phial, and
+especially if it be in the form of a powder, and must be placed upon a
+stand (as in those experiments in which the focus of a burning mirror is
+to be thrown upon it) I first exhaust a receiver, in which it is
+previously placed; and having a glass tube, bended for the purpose, as
+in fig. 14, I screw it to the stem of a transfer of the air pump on
+which the receiver had been exhausted, and introducing it through the
+water into a jar of that kind of air with which I would fill the
+receiver, I only turn the cock, and I gain my purpose. In this method,
+however, unless the pump be very good, and several contrivances, too
+minute to be particularly described, be made use of a good deal of
+common air will get into the receiver.
+
+When I want to measure the goodness of any kind of air, I put two
+measures of it into a jar standing in water; and when I have marked upon
+the glass the exact place of the boundary of air and water, I put to it
+one measure of nitrous air; and after waiting a proper time, note the
+quantity of its diminution. If I be comparing two kinds of air that are
+nearly alike, after mixing them in a large jar, I transfer the mixture
+into a long glass tube, by which I can lengthen my scale to what degree
+I please.
+
+If the quantity of the air, the goodness of which I want to ascertain,
+be exceedingly small, so as to be contained in a part of a glass tube,
+out of which water will not run spontaneously, as _a_ fig. 15; I first
+measure with a pair of compasses the length of the column of air in the
+tube, the remaining part being filled with water, and lay it down upon a
+scale; and then, thrusting a wire of a proper thickness, _b_, into the
+tube, I contrive, by means of a thin plate of iron, bent to a sharp
+angle _c_, to draw it out again, when the whole of this little
+apparatus has been introduced through the water into a jar of nitrous
+air; and the wire being drawn out, the air from the jar must supply its
+place. I then measure the length of this column of nitrous air which I
+have got into the tube, and lay it also down upon the scale, so as to
+know the exact length of both the columns. After this, holding the tube
+under water, with a small wire I force the two separate columns of air
+into contact, and when they have been a sufficient time together, I
+measure the length of the whole, and compare it with the length of both
+the columns taken before. A little experience will teach the operator
+how far to thrust the wire into the tube, in order to admit as much air
+as he wants and no more.
+
+In order to take the electric spark in a quantity of any kind of air,
+which must be very small, to produce a sensible effect upon it, in a
+short time, by means of a common machine, I put a piece of wire into the
+end of a small tube, and fasten it with hot cement, as in fig. 16; and
+having got the air I want into the tube by means of the apparatus fig.
+15, I place it inverted in a bason containing either quicksilver, or any
+other fluid substance by which I chuse to have the air confined. I then,
+by the help of the air pump, drive out as much of the air as I think
+convenient, admitting the quicksilver, &c. to it, as at _a_, and
+putting a brass ball on the end of the wire, I take the sparks or shocks
+upon it, and thereby transmit them through the air to the liquor in the
+tube.
+
+To take the electric sparks in any kind of fluid, as oil, &c. I use the
+same apparatus described above, and having poured into the tube as much
+of the fluid as I conjecture I can make the electric spark pass through,
+I fill the rest with quicksilver; and placing it inverted in a bason of
+quicksilver, I take the sparks as before.
+
+If air be generated very fast by this process, I use a tube that is
+narrow at the top, and grows wider below, as fig. 17, that the
+quicksilver may not recede too soon beyond the striking distance.
+
+Sometimes I have used a different apparatus for this purpose,
+represented fig. 18. Taking a pretty wide glass tube, hermetically
+sealed at the upper-end, and open below, at about an inch, or at what
+distance I think convenient from the top, I get two holes made in it,
+opposite to each other. Through these I put two wires, and fastening
+them with warm cement, I fix them at what distance I please from each
+other. Between these wires I take the sparks, and the bubbles of air
+rise, as they are formed, to the top of the tube.
+
+
+
+
+PART I.
+
+_Experiments and Observations made in, and before the year 1772._
+
+
+In writing upon the subject of _different kinds of air_, I find myself
+at a loss for proper _terms_, by which to distinguish them, those which
+have hitherto obtained being by no means sufficiently characteristic, or
+distinct. The only terms in common use are, _fixed air_, _mephitic_, and
+_inflammable_. The last, indeed, sufficiently characterizes and
+distinguishes that kind of air which takes fire, and explodes on the
+approach of flame; but it might have been termed _fixed_ with as much
+propriety as that to which Dr. Black and others have given that
+denomination, since it is originally part of some solid substance, and
+exists in an unelastic state.
+
+All these newly discovered kinds of air may also be called _factitious_;
+and if, with others, we use the term _fixable_, it is still obvious to
+remark, that it is applicable to them all; since they are all capable of
+being imbibed by some substance or other, and consequently of being
+_fixed_ in them, after they have been in an elastic state.
+
+The term _mephitic_ is equally applicable to what is called _fixed air_,
+to that which is _inflammable_, and to many other kinds; since they are
+equally noxious, when breathed by animals. Rather, however, than either
+introduce new terms, or change the signification of old ones, I shall
+use the term _fixed air_, in the sense in which it is now commonly used,
+and distinguish the other kinds by their properties, or some other
+periphrasis. I shall be under a necessity, however, of giving names to
+those kinds of air, to which no names had been given by others, as
+_nitrous_, _acid_, and _alkaline_.
+
+
+
+
+SECTION I.
+
+_Of FIXED AIR._
+
+
+It was in consequence of living for some time in the neighbourhood of a
+public brewery, that I was induced to make experiments on fixed air, of
+which there is always a large body, ready formed, upon the surface of
+the fermenting liquor, generally about nine inches, or a foot in depth,
+within which any kind of substance may be very conveniently placed; and
+though, in these circumstances, the fixed air must be continually mixing
+with the common air, and is therefore far from being perfectly pure, yet
+there is a constant fresh supply from the fermenting liquor, and it is
+pure enough for many purposes.
+
+A person, who is quite a stranger to the properties of this kind of air,
+would be agreeably amused with extinguishing lighted candles, or chips
+of wood in it, as it lies upon the surface of the fermenting liquor; for
+the smoke readily unites with this kind of air, probably by means of the
+water which it contains; so that very little or none of the smoke will
+escape into the open air, which is incumbent upon it. It is remarkable,
+that the upper surface of this smoke, floating in the fixed air, is
+smooth, and well defined; whereas the lower surface is exceedingly
+ragged, several parts hanging down to a considerable distance within the
+body of the fixed air, and sometimes in the form of balls, connected to
+the upper stratum by slender threads, as if they were suspended. The
+smoke is also apt to form itself into broad flakes, parallel to the
+surface of the liquor, and at different distances from it, exactly like
+clouds. These appearances will sometimes continue above an hour, with
+very little variation. When this fixed air is very strong, the smoke of
+a small quantity of gunpowder fired in it will be wholly retained by it,
+no part escaping into the common air.
+
+Making an agitation in this air, the surface of it, (which still
+continues to be exactly defined) is thrown into the form of waves, which
+it is very amusing to look upon; and if, by this agitation, any of the
+fixed air be thrown over the side of the vessel, the smoke, which is
+mixed with it, will fall to the ground, as if it was so much water, the
+fixed air being heavier than common air.
+
+The red part of burning wood was extinguished in this air, but I could
+not perceive that a red-hot poker was sooner cooled in it.
+
+Fixed air does not instantly mix with common air. Indeed if it did, it
+could not be caught upon the surface of the fermenting liquor. A candle
+put under a large receiver, and immediately plunged very deep below the
+surface of the fixed air, will burn some time. But vessels with the
+smallest orifices, hanging with their mouths downwards in the fixed air,
+will _in time_ have the common air, which they contain, perfectly mixed
+with it. When the fermenting liquor is contained in vessels close
+covered up, the fixed air, on removing the cover, readily affects the
+common air which is contiguous to it; so that, candles held at a
+considerable distance above the surface will instantly go out. I have
+been told by the workmen, that this will sometimes be the case, when the
+candles are held two feet above the mouth of the vessel.
+
+Fixed air unites with the smoke of rosin, sulphur, and other electrical
+substances, as well as with the vapour of water; and yet, by holding the
+wire of a charged phial among these fumes, I could not make any
+electrical atmosphere, which surprized me a good deal, as there was a
+large body of this smoke, and it was so confined, that it could not
+escape me.
+
+I also held some oil of vitriol in a glass vessel within the fixed air,
+and by plunging a piece of red-hot glass into it, raised a copious and
+thick fume. This floated upon the surface of the fixed air like other
+fumes, and continued as long.
+
+Considering the near affinity between water and fixed air, I concluded
+that if a quantity of water was placed near the yeast of the fermenting
+liquor, it could not fail to imbibe that air, and thereby acquire the
+principal properties of Pyrmont, and some other medicinal mineral
+waters. Accordingly, I found, that when the surface of the water was
+considerable, it always acquired the pleasant acidulous taste that
+Pyrmont water has. The readiest way of impregnating water with this
+virtue, in these circumstances, is to take two vessels, and to keep
+pouring the water from one into the other, when they are both of them
+held as near the yeast as possible; for by this means a great quantity
+of surface is exposed to the air, and the surface is also continually
+changing. In this manner, I have sometimes, in the space of two or three
+minutes, made a glass of exceedingly pleasant sparkling water, which
+could hardly be distinguished from very good Pyrmont, or rather Seltzer
+water.
+
+But the _most effectual_ way of impregnating water with fixed air is to
+put the vessels which contain the water into glass jars, filled with
+the purest fixed air made by the solution of chalk in diluted oil of
+vitriol, standing in quicksilver. In this manner I have, in about two
+days, made a quantity of water to imbibe more than an equal bulk of
+fixed air, so that, according to Dr. Brownrigg's experiments, it must
+have been much stronger than the best imported Pyrmont; for though he
+made his experiments at the spring-head, he never found that it
+contained quite so much as half its bulk of this air. If a sufficient
+quantity of quicksilver cannot be procured, _oil_ may be used with
+sufficient advantage, for this purpose, as it imbibes the fixed air very
+slowly. Fixed air may be kept in vessels standing in water for a long
+time, if they be separated by a partition of oil, about half an inch
+thick. Pyrmont water made in these circumstances, is little or nothing
+inferior to that which has stood in quicksilver.
+
+The _readiest_ method of preparing this water for use is to agitate it
+strongly with a large surface exposed to the fixed air. By this means
+more than an equal bulk of air may be communicated to a large quantity
+of water in the space of a few minutes. But since agitation promotes the
+dissipation of fixed air from water, it cannot be made to imbibe so
+great a quantity in this method as in the former, where more time is
+taken.
+
+Easy directions for impregnating water with fixed air I have published
+in a small pamphlet, designed originally for the use of seamen in long
+voyages, on the presumption that it might be of use for preventing or
+curing the sea scurvy, equally with wort, which was recommended by Dr.
+Macbride for this purpose, on no other account than its property of
+generating fixed air, by its fermentation in the stomach.
+
+Water thus impregnated with fixed air readily dissolves iron, as Mr.
+Lane has discovered; so that if a quantity of iron filings be put to it,
+it presently becomes a strong chalybeate, and of the mildest and most
+agreeable kind.
+
+I have recommended the use of _chalk_ and oil of vitriol as the
+cheapest, and, upon the whole, the best materials for this purpose. But
+some persons prefer _pearl ashes_, _pounded marble_, or other calcareous
+or _alkaline substances_; and perhaps with reason. My own experience has
+not been sufficient to enable me to decide in this case.
+
+Whereas some persons had suspected that a quantity of the oil of vitriol
+was rendered volatile by this process, I examined it, by all the
+chemical methods that are in use; but could not find that water thus
+impregnated contained the least perceivable quantity of that acid.
+
+Mr. Hey, indeed, who assisted me in this examination, found that
+distilled water, impregnated with fixed air, did not mix so readily with
+soap as the distilled water itself; but this was also the case when the
+fixed air had passed through a long glass tube filled with alkaline
+salts, which, it may be supposed, would have imbibed any of the oil of
+vitriol that might have been contained in that air[2].
+
+Fixed air itself may be said to be of the nature of an acid, though of a
+weak and peculiar sort.----Mr. Bergman of Upsal, who honoured me with a
+letter upon the subject, calls it the _aërial acid_, and, among other
+experiments to prove it to be an acid, he says that it changes the blue
+juice of tournesole into red. This Mr. Hey found to be true, and he
+moreover discovered that when water tinged blue with the juice of
+tournesole, and then red with fixed air, has been exposed to the open
+air, it recovers its blue colour again.
+
+The heat of boiling water will expel all the fixed air, if a phial
+containing the impregnated water be held in it; but it will often
+require above half an hour to do it completely.
+
+Dr. Percival, who is particularly attentive to every improvement in the
+medical art, and who has thought so well of this impregnation as to
+prescribe it in several cases, informs me that it seems to be much
+stronger, and sparkles more, like the true Pyrmont water, after it has
+been kept some time. This circumstance, however, shews that, in time,
+the fixed air is more easily disengaged from the water; and though, in
+this state, it may affect the taste more sensibly, it cannot be of so
+much use in the stomach and bowels, as when the air is more firmly
+retained by the water.
+
+By the process described in my pamphlet, fixed air may be readily
+incorporated with wine, beer, and almost any other liquor whatever; and
+when beer, wine, or cyder, is become flat or dead (which is the
+consequence of the escape of the fixed air they contained) they may be
+revived by this means; but the delicate and agreeable flavour, or
+acidulous taste, communicated by fixed air, and which is very manifest
+in water, can hardly be perceived in wine, or any liquors which have
+much taste of their own.
+
+I should think that there can be no doubt, but that water thus
+impregnated with fixed air must have all the medicinal virtues of
+genuine Pyrmont or Seltzer water; since these depend upon the fixed air
+they contain. If the genuine Pyrmont water derives any advantage from
+its being a natural chalybeate, this may also be obtained by providing a
+common chalybeate water, and using it in these processes, instead of
+common water.
+
+Having succeeded so well with this artificial Pyrmont water, I imagined
+that it might be possible to give _ice_ the same virtue, especially as
+cold is known to promote the absorption of fixed air by water; but in
+this I found myself quite mistaken. I put several pieces of ice into a
+quantity of fixed air, confined by quicksilver, but no part of the air
+was absorbed in two days and two nights; but upon bringing it into a
+place where the ice melted, the air was absorbed as usual.
+
+I then took a quantity of strong artificial Pyrmont water, and putting
+it into a thin glass phial, I set it in a pot that was filled with snow
+and salt. This mixture instantly freezing the water that was contiguous
+to the sides of the glass, the air was discharged plentifully, so that
+I catched a considerable quantity, in a bladder tied to the mouth of the
+phial.
+
+I also took two quantities of the same Pyrmont water, and placed one of
+them where it might freeze, keeping the other in a cold place, but where
+it would not freeze. This retained its acidulous taste, though the phial
+which contained it was not corked; whereas the other being brought into
+the same place, where the ice melted very slowly, had at the same time
+the taste of common water only. That quantity of water which had been
+frozen by the mixture of snow and salt, was almost as much like snow as
+ice, such a quantity of air-bubbles were contained in it, by which it
+was prodigiously increased in bulk.
+
+The pressure of the atmosphere assists very considerably in keeping
+fixed air confined in water; for in an exhausted receiver, Pyrmont water
+will absolutely boil, by the copious discharge of its air. This is also
+the reason why beer and ale froth so much _in vacuo_. I do not doubt,
+therefore, but that, by the help of a condensing engine, water might be
+much more highly impregnated with the virtues of the Pyrmont spring; and
+it would not be difficult to contrive a method of doing it.
+
+The manner in which I made several experiments to ascertain the
+absorption of fixed air by different fluid substances, was to put the
+liquid into a dish, and holding it within the body of the fixed air at
+the brewery, to set a glass vessel into it, with its mouth inverted.
+This glass being necessarily filled with the fixed air, the liquor would
+rise into it when they were both taken into the common air, if the fixed
+air was absorbed at all.
+
+Making use of _ether_ in this manner, there was a constant bubbling from
+under the glass, occasioned by this fluid easily rising in vapour, so
+that I could not, in this method, determine whether it imbibed the air
+or not. I concluded however, that they did incorporate, from a very
+disagreeable circumstance, which made me desist from making any more
+experiments of the kind. For all the beer, over which this experiment
+was made, contracted a peculiar taste; the fixed air impregnated with
+the ether being, I suppose, again absorbed by the beer. I have also
+observed, that water which remained a long time within this air has
+sometimes acquired a very disagreeable taste. At one time it was like
+tar-water. How this was acquired, I was very desirous of making some
+experiments to ascertain, but I was discouraged by the fear of injuring
+the fermenting liquor. It could not come from the fixed air only.
+
+Insects and animals which breathe very little are stifled in fixed air,
+but are not soon quite killed in it. Butterflies and flies of other
+kinds will generally become torpid, and seemingly dead, after being held
+a few minutes over the fermenting liquor; but they revive again after
+being brought into the fresh air. But there are very great varieties
+with respect to the time in which different kinds of flies will either
+become torpid in the fixed air, or die in it. A large strong frog was
+much swelled, and seemed to be nearly dead, after being held about six
+minutes over the fermenting liquor; but it recovered upon being brought
+into the common air. A snail treated in the same manner died presently.
+
+Fixed air is presently fatal to vegetable life. At least sprigs of mint
+growing in water, and placed over the fermenting liquor, will often
+become quite dead in one day, or even in a less space of time; nor do
+they recover when they are afterwards brought into the common air. I am
+told, however, that some other plants are much more hardy in this
+respect.
+
+A red rose, fresh gathered, lost its redness, and became of a purple
+colour, after being held over the fermenting liquor about twenty-four
+hours; but the tips of each leaf were much more affected than the rest
+of it. Another red rose turned perfectly white in this situation; but
+various other flowers of different colours were very little affected.
+These experiments were not repeated, as I wish they might be done, in
+pure fixed air, extracted from chalk by means of oil of vitriol.
+
+For every purpose, in which it was necessary that the fixed air should
+be as unmixed as possible, I generally made it by pouring oil of vitriol
+upon chalk and water, catching it in a bladder fastened to the neck of
+the phial in which they were contained, taking care to press out all the
+common air, and also the first, and sometimes the second, produce of
+fixed air; and also, by agitation, making it as quickly as I possibly
+could. At other times, I made it pass from the phial in which it was
+generated through a glass tube, without the intervention of any bladder,
+which, as I found by experience, will not long make a sufficient
+separation between several kinds of air and common air.
+
+I had once thought that the readiest method of procuring fixed air, and
+in sufficient purity, would be by the simple process of burning chalk,
+or pounded lime-stone in a gun-barrel, making it pass through the stem
+of a tobacco-pipe, or a glass tube carefully luted to the orifice of it.
+In this manner I found that air is produced in great plenty; but, upon
+examining it, I found, to my very great surprise, that little more than
+one half of it was fixed air, capable of being absorbed by water; and
+that the rest was inflammable, sometimes very weakly, but sometimes
+pretty highly so.
+
+Whence this inflammability proceeds, I am not able to determine, the
+lime or chalk not being supposed to contain any other than fixed air. I
+conjecture, however, that it must proceed from the iron, and the
+separation of it from the calx may be promoted by that small quantity of
+oil of vitriol, which I am informed is contained in chalk, if not in
+lime-stone also.
+
+But it is an objection to this hypothesis, that the inflammable air
+produced in this manner burns blue, and not at all like that which is
+produced from iron, or any other metal, by means of an acid. It also has
+not the smell of that kind of inflammable air which is produced from
+mineral substances. Besides, oil of vitriol without water, will not
+dissolve iron; nor can inflammable air be got from it, unless the acid
+be considerably diluted; and when I mixed brimstone with the chalk,
+neither the quality nor the quantity of the air was changed by it.
+Indeed no air, or permanently elastic vapour, can be got from brimstone,
+or any oil.
+
+Perhaps this inflammable principle may come from some remains of the
+animals, from which it is thought that all calcareous matter proceeds.
+
+In the method in which I generally made the fixed air (and indeed
+always, unless the contrary be particularly mentioned, viz. by diluted
+oil of vitriol and chalk) I found by experiment that it was as pure as
+Mr. Cavendish made it. For after it had patted through a large body of
+water in small bubbles, still 1/50 or 1/60 part only was not absorbed by
+water. In order to try this as expeditiously as possible, I kept pouring
+the air from one glass vessel into another, immersed in a quantity of
+cold water, in which manner I found by experience, that almost any
+quantity may be reduced as far as possible in a very short time. But the
+most expeditious method of making water imbibe any kind of air, is to
+confine it in a jar; and agitate it strongly, in the manner described in
+my pamphlet on the impregnation of water with fixed air, and represented
+fig. 10.
+
+At the same time that I was trying the purity of my fixed air, I had the
+curiosity to endeavour to ascertain whether that part of it which is not
+miscible in water, be equally diffused through the whole mass; and, for
+this purpose, I divided a quantity of about a gallon into three parts,
+the first consisting of that which was uppermost, and the last of that
+which was the lowest, contiguous to the water; but all these parts were
+reduced in about an equal proportion, by passing through the water, so
+that the whole mass had been of an uniform composition. This I have also
+found to be the case with several kinds of air, which will, not properly
+incorporate.
+
+A mouse will live very well, though a candle will not burn in the
+residuum of the purest fixed air that I can make; and I once made a very
+large quantity for the sole purpose of this experiment. This, therefore,
+seems to be one instance of the generation of genuine common air, though
+vitiated in some degree. It is also another proof of the residuum of
+fixed air being, in part at least, common air, that it becomes turbid,
+and is diminished by the mixture of nitrous air, as will be explained
+hereafter.
+
+That fixed air only wants some addition to make it permanent, and
+immiscible with water if not in all respects, common air, I have been
+led to conclude, from several attempts which I once made to mix it with
+air in which a quantity of iron filings and brimstone, made into a paste
+with water, had stood; for, in several mixtures of this kind, I imagined
+that not much more than half of the fixed air could be imbibed by water;
+but, not being able to repeat the experiment, I conclude that I either
+deceived myself in it, or that I overlooked some circumstance on which
+the success of it depended.
+
+These experiments, however, whether they were fallacious or otherwise,
+induced me to try whether any alteration would be made in the
+constitution of fixed air, by this mixture of iron filings and
+brimstone. I therefore put a mixture of this kind into a quantity of as
+pure fixed air as I could make, and confined the whole in quicksilver,
+lest the water should absorb it before the effects of the mixture could
+take place. The consequence was, that the fixed air was diminished, and
+the quicksilver rose in the vessel, till about the fifth part was
+occupied by it; and, as near as I could judge, the process went on, in
+all respects, as if the air in the inside had been common air.
+
+What is most remarkable, in the result of this experiment, is, that the
+fixed air, into which this mixture had been put, and which had been in
+part diminished by it, was in part also rendered insoluble in water by
+this means. I made this experiment four times, with the greatest care,
+and observed, that in two of them about one sixth, and in the other two
+about one fourteenth, of the original quantity, was such as could not be
+absorbed by water, but continued permanently elastic. Lest I should have
+made any mistake with respect to the purity of the fixed air, the last
+time that I made the experiment, I set part of the fixed air, which I
+made use of, in a separate vessel, and found it to be exceedingly pure,
+so as to be almost wholly absorbed by water; whereas the other part, to
+which I had put the mixture, was far from being so.
+
+In one of these cases, in which fixed air was made immiscible with
+water, it appeared to be not very noxious to animals; but in another
+case, a mouse died in it pretty soon. This difference probably arose
+from my having inadvertently agitated the air in water rather more in
+one case than in the other.
+
+As the iron is reduced to a calx by this process, I once concluded, that
+it is phlogiston that fixed air wants, to make it common air; and, for
+any thing I yet know this may be the case, though I am ignorant of the
+method of combining them; and when I calcined a quantity of lead in
+fixed air, in the manner which will be described hereafter, it did not
+seem to have been less soluble in water than it was before.
+
+FOOTNOTES:
+
+[2] An account of Mr. Hey's experiments will be found in the Appendix to
+these papers.
+
+
+
+
+SECTION II.
+
+_Of AIR in which a CANDLE, or BRIMSTONE, has burned out._
+
+
+It is well known that flame cannot subsist long without change of air,
+so that the common air is necessary to it, except in the case of
+substances, into the composition of which nitre enters, for these will
+burn _in vacuo_, in fixed air, and even under water, as is evident in
+some rockets, which are made for this purpose. The quantity of air which
+even a small flame requires to keep it burning is prodigious. It is
+generally said, that an ordinary candle _consumes_, as it is called,
+about a gallon in a minute. Considering this amazing consumption of air,
+by fires of all kinds, volcanos, &c. it becomes a great object of
+philosophical inquiry, to ascertain what change is made in the
+constitution of the air by flame, and to discover what provision there
+is in nature for remedying the injury which the atmosphere receives by
+this means. Some of the following experiments will, perhaps, be thought
+to throw light upon the subject.
+
+The diminution of the quantity of air in which a candle, or brimstone,
+has burned out, is various; But I imagine that, at a medium, it may be
+about one fifteenth, or one sixteenth of the whole; which is one third
+as much as by animal or vegetable substances putrefying in it, by the
+calcination of metals, or by any of the other causes of the complete
+diminution of air, which will be mentioned hereafter.
+
+I have sometimes thought, that flame disposes the common air to deposit
+the fixed air it contains; for if any lime-water be exposed to it, it
+immediately becomes turbid. This is the case, when wax candles, tallow
+candles, chips of wood, spirit of wine, ether, and every other substance
+which I have yet tried, except brimstone, is burned in a close glass
+vessel, standing in lime-water. This precipitation of fixed air (if this
+be the case) may be owing to something emitted from the burning bodies,
+which has a stronger affinity with the other constituent parts of the
+atmosphere[3].
+
+If brimstone be burned in the same circumstances, the lime-water
+continues transparent, but still there may have been the same
+precipitation of the fixed part of the air; but that, uniting with the
+lime and the vitriolic acid, it forms a selenetic salt, which is soluble
+in water. Having evaporated a quantity of water thus impregnated, by
+burning brimstone a great number of times over it, a whitish powder
+remained, which had an acid taste; but repeating the experiment with a
+quicker evaporation, the powder had no acidity, but was very much like
+chalk. The burning of brimstone but once over a quantity of lime-water,
+will affect it in such a manner, that breathing into it will not make it
+turbid, which otherwise it always presently does.
+
+Dr. Hales supposed, that by burning brimstone repeatedly in the same
+quantity of air, the diminution would continue without end. But this I
+have frequently tried, and not found to be the case. Indeed, when the
+ignition has been imperfect in the first instance, a second firing of
+the same substance will increase the effect of the first, &c. but this
+progress soon ceases.
+
+In many cases of the diminution of air, the effect is not immediately
+apparent, even when it stands in water; for sometimes the bulk of air
+will not be much reduced, till it has passed several times through a
+quantity of water, which has thereby a better opportunity of absorbing
+that part of the air, which had not been perfectly detatched from the
+rest. I have sometimes found a very great reduction of a mass of air, in
+consequence of passing but once through cold water. If the air has stood
+in quicksilver, the diminution is generally inconsiderable, till it has
+undergone this operation, there not being any substance exposed to the
+air that could absorb any part of it.
+
+I could not find any considerable alteration in the specific gravity of
+the air, in which candles, or brimstone, had burned out. I am satisfied,
+however, that it is not heavier than common air, which must have been
+manifest, if so great a diminution of the quantity had been owing, as
+Dr. Hales and others supposed, to the elasticity of the whole mass being
+impaired. After making several trials for this purpose, I concluded that
+air, thus diminished in bulk, is rather lighter than common air, which
+favours the supposition of the fixed, or heavier part of the common air,
+having been precipitated.
+
+An animal will live nearly, if not quite as long, in air in which
+candles have burned out, as in common air. This fact surprized me very
+greatly, having imagined that what is called the _consumption_ of air by
+flame, or respiration, to have been of the same nature, and in the same
+degree; but I have since found, that this fact has been observed by many
+persons, and even so early as by Mr. Boyle. I have also observed, that
+air, in which brimstone has burned, is not in the least injurious to
+animals, after the fumes, which at first make it very cloudy, have
+intirely subsided.
+
+I must, in this place, admonish my reader not to confound the simple
+_burning of brimstone_, or of matches (_i. e._ bits of wood dipped in
+it) and the burning of brimstone with a burning mirror, or any _foreign
+heat_. The effect of the former is nothing more than that of any other
+_flame_, or _ignited vapour_, which will not burn, unless the air with
+which it is surrounded be in a very pure state, and which is therefore
+extinguished when the air begins to be much vitiated. Lighted brimstone,
+therefore reduces the air to the same state as lighted wood. But the
+focus of a burning mirror thrown for a sufficient time either upon
+brimstone, or wood, after it has ceased to burn of its own accord, and
+has become _charcoal_, will have a much greater effect: of the same
+kind, diminishing the air to its utmost extent, and making it thoroughly
+noxious. In fact, as will be seen hereafter, more phlogiston is expelled
+from these substances in the latter case than in the former. I never,
+indeed, actually carried this experiment so far with brimstone; but from
+the diminution of air that I did produce by this means, I concluded
+that, by continuing the process some time longer, it would have been
+effected.
+
+Having read, in the Memoirs of the Philosophical Society at Turin, vol.
+I. p. 41. that air in which candles had burned out was perfectly
+restored, so that other candles would burn in it again as well as ever,
+after having been exposed to a considerable degree of _cold_, and
+likewise after having been compressed in bladders, (for the cold had
+been supposed to have produced this effect by nothing but
+_condensation_) I repeated those experiments, and did, indeed, find,
+that when I compressed the air in _bladders_, as the Count de Saluce,
+who made the observation, had done, the experiment succeeded: but having
+had sufficient reason to distrust bladders, I compressed the air in a
+glass vessel standing in water; and then I found, that this process is
+altogether ineffectual for the purpose. I kept the air compressed much
+more, and much longer, than the Count had done, but without producing
+any alteration in it. I also find, that a greater degree of cold than
+that which he applied, and of longer continuance, did by no means
+restore this kind of air: for when I had exposed the phials which
+contained it a whole night, in which the frost was very intense; and
+also when I kept it surrounded with a mixture of snow and salt, I found
+it, in all respects, the same as before.
+
+It is also advanced, in the same Memoir, p. 41. that _heat_ only, as the
+reverse of _cold_, renders air unfit for candles burning in it. But I
+repeated the experiment of the Count for that purpose, without finding
+any such effect from it. I also remember that, many years ago, I filled
+an exhausted receiver with air, which had passed through a glass tube
+made red-hot, and found that a candle would burn in it perfectly well.
+Also, rarefaction by the air-pump does not injure air in the least
+degree.
+
+Though this experiment failed, I have been so happy, as by accident to
+have hit upon a method of restoring air, which has been injured by the
+burning of candles, and to have discovered at least one of the
+restoratives which nature employs for this purpose. It is _vegetation_.
+This restoration of vitiated air, I conjecture, is effected by plants
+imbibing the phlogistic matter with which it is overloaded by the
+burning of inflammable bodies. But whether there be any foundation for
+this conjecture or not, the fact is, I think, indisputable. I shall
+introduce the account of my experiments on this subject, by reciting
+some of the observations which I made on the growing of plants in
+confined air, which led to this discovery.
+
+One might have imagined that, since common air is necessary to
+vegetable, as well as to animal life, both plants and animals had
+affected it in the same manner; and I own I had that expectation, when I
+first put a sprig of mint into a glass jar, standing inverted in a
+vessel of water: but when it had continued growing there for some
+months, I found that the air would neither extinguish a candle, nor was
+it at all inconvenient to a mouse, which I put into it.
+
+The plant was not affected any otherwise than was the necessary
+consequence of its confined situation; for plants growing in several
+other kinds of air, were all affected in the very same manner. Every
+succession of leaves was more diminished in size than the preceding,
+till, at length, they came to be no bigger than the heads of pretty
+small pins. The root decayed, and the stalk also, beginning from the
+root; and yet the plant continued to grow upwards, drawing its
+nourishment through a black and rotten stem. In the third or fourth set
+of leaves, long and white hairy filaments grew from the insertion of
+each leaf and sometimes from the body of the stem, shooting out as far
+as the vessel in which it grew would permit, which, in my experiments,
+was about two inches. In this manner a sprig of mint lived, the old
+plant decaying, and new ones shooting up in its place, but less and less
+continually, all the summer season.
+
+In repeating this experiment, care must be taken to draw away all the
+dead leaves from about the plant, lest they should putrefy, and affect
+the air. I have found that a fresh cabbage leaf, put under a glass
+vessel filled with common air, for the space of one night only, has so
+affected the air, that a candle would not burn in it the next morning,
+and yet the leaf had not acquired any smell of putrefaction.
+
+Finding that candles would burn very well in air in which plants had
+grown a long time, and having had some reason to think, that there was
+something attending vegetation, which restored air that had been injured
+by respiration, I thought it was possible that the same process might
+also restore the air that had been injured by the burning of candles.
+
+Accordingly, on the 17th of August 1771, I put a sprig of mint into a
+quantity of air, in which a wax candle had burned out, and found that,
+on the 27th of the same month, another candle burned perfectly well in
+it. This experiment I repeated, without the least variation in the
+event, not less than eight or ten times in the remainder of the summer.
+
+Several times I divided the quantity of air in which the candle had
+burned out, into two parts, and putting the plant into one of them, left
+the other in the same exposure, contained, also, in a glass vessel
+immersed in water, but without any plant; and never failed to find, that
+a candle would burn in the former, but not in the latter.
+
+I generally found that five or six days were sufficient to restore this
+air, when the plant was in its vigour; whereas I have kept this kind of
+air in glass vessels, immersed in water many months, without being able
+to perceive that the least alteration had been made in it. I have also
+tried a great variety of experiments upon it, as by condensing,
+rarefying, exposing to the light and heat, &c. and throwing into it the
+effluvia of many different substances, but without any effect.
+
+Experiments made in the year 1772, abundantly confirmed my conclusion
+concerning the restoration of air, in which candles had burned out by
+plants growing in it. The first of these experiments was made in the
+month of May; and they were frequently repeated in that and the two
+following months, without a single failure.
+
+For this purpose I used the flames of different substances, though I
+generally used wax or tallow candles. On the 24th of June the experiment
+succeeded perfectly well with air in which spirit of wine had burned
+out, and on the 27th of the same month it succeeded equally well with
+air in which brimstone matches had burned out, an effect of which I had
+despaired the preceding year.
+
+This restoration of air, I found, depended upon the _vegetating state_
+of the plant; for though I kept a great number of the fresh leaves of
+mint in a small quantity of air in which candles had burned out, and
+changed them frequently, for a long space of time, I could perceive no
+melioration in the state of the air.
+
+This remarkable effect does not depend upon any thing peculiar to
+_mint_, which was the plant that I always made use of till July 1772;
+for on the 16th of that month, I found a quantity of this kind of air to
+be perfectly restored by sprigs of _balm_, which had grown in it from
+the 7th of the same month.
+
+That this restoration of air was not owing to any _aromatic effluvia_ of
+these two plants, not only appeared by the _essential oil of mint_
+having no sensible effect of this kind; but from the equally complete
+restoration of this vitiated air by the plant called _groundsel_, which
+is usually ranked among the weeds, and has an offensive smell. This was
+the result of an experiment made the 16th of July, when the plant had
+been growing in the burned air from the 8th of the same month. Besides,
+the plant which I have found to be the most effectual of any that I have
+tried for this purpose is _spinach_, which is of quick growth, but will
+seldom thrive long in water. One jar of burned air was perfectly
+restored by this plant in four days, and another in two days. This last
+was observed on the 22d of July.
+
+In general, this effect may be presumed to have taken place in much less
+time than I have mentioned; because I never chose to make a trial of
+the air, till I was pretty sure, from preceding observations, that the
+event which I had expected must have taken place, if it would succeed at
+all; lest, returning back that part of the air on which I made the
+trial, and which would thereby necessarily receive a small mixture of
+common air, the experiment might not be judged to be quite fair; though
+I myself might be sufficiently satisfied with respect to the allowance
+that was to be made for that small imperfection.
+
+FOOTNOTES:
+
+[3] The supposition, mentioned in this and other passages of the first
+part of this publication, viz. that the diminution of common air, by
+this and other processes is, in part at least, owing to the
+precipitation of the fixed air from it, the reader will find confirmed
+by the experiments and observations in the second part.
+
+
+
+
+SECTION III.
+
+_Of INFLAMMABLE AIR._
+
+
+I have generally made inflammable air in the manner described by Mr.
+Cavendish, in the Philosophical Transactions, from iron, zinc, or tin;
+but chiefly from the two former metals, on account of the process being
+the least troublesome: but when I extracted it from vegetable or animal
+substances, or from coals, I put them into a gun-barrel, to the orifice
+of which I luted a glass tube, or the stem of a tobacco-pipe, and to the
+end of this I tied a flaccid bladder in order to catch the generated
+air; or I received the air in a vessel of quicksilver, in the manner
+represented Fig. 7.
+
+There is not, I believe, any vegetable or animal substance whatever, nor
+any mineral substance, that is inflammable, but what will yield great
+plenty of inflammable air, when they are treated in this manner, and
+urged with a strong heat; but, in order to get the most air, the heat
+must be applied as suddenly, and as vehemently, as possible. For,
+notwithstanding the same care be taken in luting, and in every other
+respect, six or even ten times more air may be got by a sudden heat than
+by a slow one, though the heat that is last applied be as intense as
+that which was applied suddenly. A bit of dry oak, weighing about twelve
+grains, will generally yield about a sheep's bladder full of inflammable
+air with a brisk heat, when it will only give about two or three ounce
+measures, if the same heat be applied to it very gradually. To what this
+difference is owing, I cannot tell. Perhaps the phlogiston being
+extricated more slowly may not be intirely expelled, but form another
+kind of union with its base; so that charcoal made with a heat slowly
+applied shall contain more phlogiston than that which is made with a
+sudden heat. It may be worth while to examine the properties of the
+charcoal with this view.
+
+Inflammable air, when it is made by a quick process, has a very strong
+and offensive smell, from whatever substance it be generated; but this
+smell is of three different kinds, according as the air is extracted
+from mineral, vegetable, or animal substances. The last is exceedingly
+fetid; and it makes no difference, whether it be extracted from a bone,
+or even an old and dry tooth, from soft muscular flesh; or any other
+part of the animal. The burning of any substance occasions the same
+smell: for the gross fume which arises from them, before they flame, is
+the inflammable air they contain, which is expelled by heat, and then
+readily ignited. The smell of inflammable air is the very same, as far
+as I am able to perceive, from whatever substance of the same kingdom it
+be extracted. Thus it makes no difference whether it be got from iron,
+zinc, or tin, from any kind of wood, or, as was observed before, from
+any part of an animal.
+
+If a quantity of inflammable air be contained in a glass vessel standing
+in water, and have been generated very fast, it will smell even through
+the water, and this water will also soon become covered with a thin
+film, assuming all the different colours. If the inflammable air have
+been generated from iron, this matter will appear to be a red okre, or
+the earth of iron, as I have found by collecting a considerable quantity
+of it; and if it have been generated from zinc, it is a whitish
+substance, which I suppose to be the calx of the metal. It likewise
+settles to the bottom of the vessel, and when the water is stirred, it
+has very much the appearance of wool. When water is once impregnated in
+this manner, it will continue to yield this scum for a considerable time
+after the air is removed from it. This I have often observed with
+respect to iron.
+
+Inflammable air, made by a violent effervescence, I have observed to be
+much more inflammable than that which is made by a weak effervescence,
+whether the water or the oil of vitriol prevailed in the mixture. Also
+the offensive smell was much stronger in the former case than in the
+latter. The greater degree of inflammability appeared by the greater
+number of successive explosions, when a candle was presented to the neck
+of a phial filled with it.[4] It is possible, however, that this
+diminution of inflammability may, in some measure, arise from the air
+continuing so much longer in the bladder when it is made very slowly;
+though I think the difference is too great for this cause to have
+produced the whole of it. It may, perhaps, deserve to be tried by a
+different process, without a bladder.
+
+Inflammable air is not thought to be miscible with water, and when kept
+many months, seems, in general, to be as inflammable as ever. Indeed,
+when it is extracted from vegetable or animal substances, a part of it
+will be imbibed by the water in which it stands; but it may be presumed,
+that in this case, there was a mixture of fixed air extracted from the
+substance along with it. I have indisputable evidence, however, that
+inflammable air, standing long in water, has actually lost all its
+inflammability, and even come to extinguish flame much more than that
+air in which candles have burned out. After this change it appears to be
+greatly diminished in quantity, and it still continues to kill animals
+the moment they are put into it.
+
+This very remarkable fact first occurred to my observation on the
+twenty-fifth of May 1771, when I was examining a quantity of inflammable
+air, which had been made from zinc, near three years before. Upon this,
+I immediately set by a common quart-bottle filled with inflammable air
+from iron, and another equal quantity from zinc; and examining them in
+the beginning of December following, that from the iron was reduced near
+one half in quantity, if I be not greatly mistaken; for I found the
+bottle half full of water, and I am pretty clear that it was full of air
+when it was set by. That which had been produced from zinc was not
+altered, and filled the bottle as at first.
+
+Another instance of this kind occurred to my observation on the 19th of
+June 1772, when a quantity of air, half of which had been inflammable
+air from zinc, and half air in which mice had died, and which had been
+put together the 30th of July 1771, appeared not to be in the least
+inflammable, but extinguished flame, as much as any kind of air that I
+had ever tried. I think that, in all, I have had four instances of
+inflammable air losing its inflammability, while it stood in water.
+
+Though air tainted with putrefaction extinguishes flame, I have not
+found that animals or vegetables putrefying in inflammable air render it
+less inflammable. But one quantity of inflammable air, which I had set
+by in May 1771, along with the others above mentioned, had had some
+putrid flesh in it; and this air had lost its inflammability, when it
+was examined at the same time with the other in the December following.
+The bottle in which this air had been kept, smelled exactly like very
+strong Harrogate water. I do not think that any person could have
+distinguished them.
+
+I have made plants grow for several months in inflammable air made from
+zinc, and also from oak; but, though the plants grew pretty well, the
+air still continued inflammable. The former, indeed, was not so highly
+inflammable as when it was fresh made, but the latter was quite as much
+so; and the diminution of inflammability in the former case, I attribute
+to some other cause than the growth of the plant.
+
+No kind of air, on which I have yet made the experiment, will conduct
+electricity; but the colour of an electric spark is remarkably different
+in some different kinds of air, which seems to shew that they are not
+equally good non-conductors. In fixed air, the electric spark is
+exceedingly white; but in inflammable air it is of a purple, or red
+colour. Now, since the most vigorous sparks are always the whitest, and,
+in other cases, when the spark is red, there is reason to think that the
+electric matter passes with difficulty, and with less rapidity: it is
+possible that the inflammable air may contain particles which conduct
+electricity, though very imperfectly; and that the whiteness of the
+spark in the fixed air, may be owing to its meeting with no conducting
+particles at all. When an explosion was made in a quantity of
+inflammable air, it was a little white in the center, but the edges of
+it were still tinged with a beautiful purple. The degree of whiteness in
+this case was probably owing to the electric matter rushing with more
+violence in an explosion than in a common spark.
+
+Inflammable air kills animals as suddenly as fixed air, and, as far as
+can be perceived, in the same manner, throwing them into convulsions,
+and thereby occasioning present death. I had imagined that, by animals
+dying in a quantity of inflammable air, it would in time become less
+noxious; but this did not appear to be the case; for I killed great
+number of mice in a small quantity of this air; which I kept several
+months for this purpose, without its being at all sensibly mended; the
+last, as well as the first mouse, dying the moment it was put into it.
+
+I once imagined that, since fixed and inflammable air are the reverse of
+one another, in several remarkable properties, a mixture of them would
+make common air; and while I made the mixtures in bladders, I imagined
+that I had succeeded in my attempt; but I have since found that thin
+bladders do not sufficiently prevent the air that is contained in them
+from mixing with the external air. Also corks will not sufficiently
+confine different kinds of air, unless the phials in which they are
+confined be set with their mouths downwards, and a little water lie in
+the necks of them, which, indeed, is equivalent to the air standing in
+vessels immersed in water. In this manner, however, I have kept
+different kinds of air for several years.
+
+Whatever methods I took to promote the mixture of fixed and inflammable
+air, they were all ineffectual. I think it my duty, however, to recite
+the issue of an experiment or two of this kind, in which equal mixtures
+of these two kinds of air had stood near three years, as they seem to
+shew that they had in part affected one another, in that long space of
+time. These mixtures I examined April 27, 1771. One of them had stood in
+quicksilver, and the other in a corked phial, with a little water in it.
+On opening the latter in water, the water instantly rushed in, and
+filled almost half of the phial, and very little more was absorbed
+afterwards. In this case the water in the phial had probably absorbed a
+considerable part of the fixed air, so that the inflammable air was
+exceedingly rarefied; and yet the whole quantity that must have been
+rendered non-elastic was ten times more than the bulk of the water, and
+it has not been found that water can contain much more than its own
+bulk of fixed air. But in other cases I have found the diminution of a
+quantity of air, and especially of fixed air, to be much greater than I
+could well account for by any kind of absorption.
+
+The phial which had stood immersed in quicksilver had lost very little
+of its original quantity of air; and being now opened in water, and left
+there, along with another phial, which was just then filled, as this had
+been three years before, viz. with air half inflammable and half fixed,
+I observed that the quantity of both was diminished, by the absorption
+of the water, in the same proportion.
+
+Upon applying a candle to the mouths of the phials which had been kept
+three years, that which had stood in quicksilver went off at one
+explosion, exactly as it would have done if there had been a mixture of
+common air with the inflammable. As a good deal depends upon the
+apertures of the vessels in which the inflammable air is mixed, I mixed
+the two kinds of air in equal proportions in the same phial, and after
+letting the phial stand some days in water, that the fixed air might be
+absorbed, I applied a candle to it, but it made ten or twelve explosions
+(stopping the phial after each of them) before the inflammable matter
+was exhausted.
+
+The air which had been confined in the corked phial exploded in the very
+same manner as an equal and fresh mixture of the two kinds of air in the
+same phial, the experiment being made as soon as the fixed air was
+absorbed, as before; so that in this case, the two kinds of air did not
+seem to have affected one another at all.
+
+Considering inflammable air as air united to, or loaded with phlogiston,
+I exposed to it several substances, which are said to have a near
+affinity with phlogiston, as oil of vitriol, and spirit of nitre (the
+former for above a month), but without making any sensible alteration in
+it.
+
+I observed, however, that inflammable air, mixed with the fumes of
+smoking spirit of nitre, goes off at one explosion, exactly like a
+mixture of half common and half inflammable air. This I tried several
+times, by throwing the inflammable air into a phial full of spirit of
+nitre, with its mouth immersed in a bason containing some of the same
+spirit, and then applying the flame of a candle to the mouth of the
+phial, the moment that it was uncovered, after it had been taken out of
+the bason.
+
+This remarkable effect I hastily concluded to have arisen from the
+inflammable air having been in part deprived of its inflammability, by
+means of the stronger affinity, which the spirit of nitre had with
+phlogiston, and therefore I imagined that by letting them stand longer
+in contact, and especially by agitating them strongly together, I should
+deprive the air of all its inflammability; but neither of these
+operations succeeded, for still the air was only exploded at once, as
+before.
+
+And lastly, when I passed a quantity of inflammable air, which had been
+mixed with the fumes of spirit of nitre, through a body of water, and
+received it in another vessel, it appeared not to have undergone any
+change at all, for it went off in several successive explosions, like
+the purest inflammable air. The effect above-mentioned must, therefore,
+have been owing to the fumes of the spirit of nitre supplying the place
+of common air for the purpose of ignition, which is analogous to other
+experiments with nitre.
+
+Having had the curiosity, on the 25th of July 1772, to expose a great
+variety of different kinds of air to water out of which the air it
+contained had been boiled, without any particular view; the result was,
+in several respects, altogether unexpected, and led to a variety of new
+observations on the properties and affinities of several kinds of air
+with respect to water. Among the rest three fourths of that which was
+inflammable was absorbed by the water in about two days, and the
+remainder was inflammable, but weakly so.
+
+Upon this, I began to agitate a quantity of strong inflammable air in a
+glass jar, standing in a pretty large trough of water, the surface of
+which was exposed to the common air, and I found that when I had
+continued the operation about ten minutes, near one fourth of the
+quantity of air had disappeared; and finding that the remainder made an
+effervescence with nitrous air, I concluded that it must have become fit
+for respiration, whereas this kind of air is, at the first, as noxious
+as any other kind whatever. To ascertain this, I put a mouse into a
+vessel containing 2-1/2 ounce measures of it, and observed that it lived
+in it twenty minutes, which is as long as a mouse will generally live in
+the same quantity of common air. This mouse was even taken out alive,
+and recovered very well. Still also the air in which it had breathed so
+long was inflammable, though very weakly so. I have even found it to be
+so when a mouse has actually died in it. Inflammable air thus diminished
+by agitation in water, makes but one explosion on the approach of a
+candle, exactly like a mixture of inflammable air with common air.
+
+From this experiment I concluded that, by continuing the same process, I
+should deprive inflammable air of all its inflammability, and this I
+found to be the case; for, after a longer agitation, it admitted a
+candle to burn in it, like common air, only more faintly; and indeed by
+the test of nitrous air it did not appear to be near so good as common
+air. Continuing the same process still farther, the air which had been
+most strongly inflammable a little before, came to extinguish a candle,
+exactly like air in which a candle had burned out, nor could they be
+distinguished by the test of nitrous air.
+
+I found, by repeated trials, that it was difficult to catch the time in
+which inflammable air obtained from metals, in coming to extinguish
+flame, was in the state of common air, so that the transition from the
+one to the other must be very short. Indeed I think that in many,
+perhaps in most cases, there may be no proper medium at all, the
+phlogiston passing at once from that mode of union with its base which
+constitutes inflammable air, to that which constitutes an air that
+extinguishes flame, being so much overloaded as to admit of no more. I
+readily, however, found this middle state in a quantity of inflammable
+air extracted from oak, which air I had kept a year, and in which a
+plant had grown, though very poorly, for some part of the time. A
+quantity of this air, after being agitated in water till it was
+diminished about one half, admitted a candle to burn in it exceedingly
+well, and was even hardly to be distinguished from common air by the
+test of nitrous air.
+
+I took some pains to ascertain the quantity of diminution, in fresh made
+and very highly-inflammable air from iron, at which it ceased to be
+inflammable, and, upon the whole, I concluded that it was so when it was
+diminished a little more than one half; for a quantity which was
+diminished exactly one half had something inflammable in it, but in the
+slightest degree imaginable. It is not improbable, however, but there
+may be great differences in the result of this experiment.
+
+Finding that water would imbibe inflammable air, I endeavoured to
+impregnate water with it, by the same process by which I had made water
+imbibe fixed air; but though I found that distilled water would imbibe
+about one fourteenth of its bulk of inflammable air, I could not
+perceive that the taste of it was sensibly altered.
+
+FOOTNOTES:
+
+[4] To try this, after every explosion, which immediately follows the
+presenting of the flame, the mouth of the phial should be closed (I
+generally do it with a finger of the hand in which I hold the phial) for
+otherwise the inflammable air will continue burning, though invisibly in
+the day time, till the whole be consumed.
+
+
+
+
+SECTION IV.
+
+_Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION._
+
+
+That candles will burn only a certain time, in a given quantity of air
+is a fact not better known, than it is that animals can live only a
+certain time in it; but the cause of the death of the animal is not
+better known than that of the extinction of flame in the same
+circumstances; and when once any quantity of air has been rendered
+noxious by animals breathing in it as long as they could, I do not know
+that any methods have been discovered of rendering it fit for breathing
+again. It is evident, however, that there must be some provision in
+nature for this purpose, as well as for that of rendering the air fit
+for sustaining flame; for without it the whole mass of the atmosphere
+would, in time, become unfit for the purpose of animal life; and yet
+there is no reason to think that it is, at present, at all less fit for
+respiration than it has ever been. I flatter myself, however, that I
+have hit upon two of the methods employed by nature for this great
+purpose. How many others there may be, I cannot tell.
+
+When animals die upon being put into air in which other animals have
+died, after breathing in it as long as they could, it is plain that the
+cause of their death is not the want of any _pabulum vitæ,_ which has
+been supposed to be contained in the air, but on account of the air
+being impregnated with something stimulating to their lungs; for they
+almost always die in convulsions, and are sometimes affected so
+suddenly, that they are irrecoverable after a single inspiration, though
+they be withdrawn immediately, and every method has been taken to bring
+them to life again. They are affected in the same manner, when they are
+killed in any other kind of noxious air that I have tried, viz. fixed
+air, inflammable air, air filled with the fumes of brimstone, infected
+with putrid matter, in which a mixture of iron filings and brimstone has
+stood, or in which charcoal has been burned, or metals calcined, or in
+nitrous air, &c.
+
+As it is known that _convulsions_ weaken, and exhaust the vital powers,
+much more than the most vigorous _voluntary_ action of the muscles,
+perhaps these universal convulsions may exhaust the whole of what we may
+call the _vis vitæ_ at once, at least that the lungs may be rendered
+absolutely incapable of action, till the animal be suffocated, or be
+irrecoverable for want of respiration.
+
+If a mouse (which is an animal that I have commonly made use of for the
+purpose of these experiments) can stand the first shock of this
+stimulus, or has been habituated to it by degrees, it will live a
+considerable time in air in which other mice will die instantaneously. I
+have frequently found that when a number of mice have been confined in a
+given quantity of air, less than half the time that they have actually
+lived in it, a fresh mouse being introduced to them has been instantly
+thrown into convulsions, and died. It is evident, therefore, that if the
+experiment of the Black Hole were to be repeated, a man would stand the
+better chance of surviving it, who should enter at the first, than at
+the last hour.
+
+I have also observed, that young mice will always live much longer than
+old ones, or than those which are full grown, when they are confined in
+the same quantity of air. I have sometimes known a young mouse to live
+six hours in the same circumstances in which an old mouse has not lived
+one. On these accounts, experiments with mice, and, for the same reason,
+no doubt, with other animals also, have a considerable degree of
+uncertainty attending them; and therefore, it is necessary to repeat
+them frequently, before the result can be absolutely depended upon. But
+every person of feeling will rejoice with me in the discovery of
+_nitrous air_, to be mentioned hereafter, which supersedes many
+experiments with the respiration of animals, being a much more accurate
+test of the purity of air.
+
+The discovery of the provision in nature for restoring air, which has
+been injured by the respiration of animals, having long appeared to me
+to be one of the most important problems in natural philosophy, I have
+tried a great variety of schemes in order to effect it. In these my
+guide has generally been to consider the influences to which the
+atmosphere is, in fact, exposed; and, as some of my unsuccessful trials
+may be of use to those who are disposed to take pains in the farther
+investigation of this subject, I shall mention the principal of them.
+
+The noxious effluvium with which air is loaded by animal respiration, is
+not absorbed by standing, without agitation; in fresh or salt water. I
+have kept it many months in fresh water, when, instead of being
+meliorated, it has seemed to become even more deadly, so as to require
+more time to restore it, by the methods which will be explained
+hereafter, than air which has been lately made noxious. I have even
+spent several hours in pouring this air from one glass vessel into
+another, in water, sometimes as cold, and sometimes as warm, as my hands
+could bear it, and have sometimes also wiped the vessels many times,
+during the course of the experiment, in order to take off that part of
+the noxious matter, which might adhere to the glass vessels, and which
+evidently gave them an offensive smell; but all these methods were
+generally without any sensible effect. The _motion_, also, which the air
+received in these circumstances, it is very evident, was of no use for
+this purpose. I had not then thought of the simple, but most effectual
+method of agitating air in water, by putting it into a tall jar and
+shaking it with my hand.
+
+This kind of air is not restored by being exposed to the _light_, or by
+any other influence to which it is exposed, when confined in a thin
+phial, in the open air, for some months.
+
+Among other experiments, I tried a great variety of different
+_effluvia_, which are continually exhaling into the air, especially of
+those substances which are known to resist putrefaction; but I could not
+by these means effect any melioration of the noxious quality of this
+kind of air.
+
+Having read, in the memoirs of the Imperial Society, of a plague not
+affecting a particular village, in which there was a large sulphur-work,
+I immediately fumigated a quantity of this kind of air; or (which will
+hereafter appear to be the very same thing) air tainted with
+putrefaction, with the fumes of burning brimstone, but without any
+effect.
+
+I once imagined, that the _nitrous acid_ in the air might be the general
+restorative which I was in quest of; and the conjecture was favoured, by
+finding that candles would burn in air extracted from saltpetre. I
+therefore spent a good deal of time in attempting, by a burning glass,
+and other means, to impregnate this noxious air, with some effluvium of
+saltpetre, and, with the same view, introduced into it the fumes of the
+smoaking spirit of nitre; but both these methods were altogether
+ineffectual.
+
+In order to try the effect of _heat_, I put a quantity of air, in which
+mice had died, into a bladder, tied to the end of the stem of a
+tobacco-pipe, at the other end of which was another bladder, out of
+which the air was carefully pressed. I then put the middle part of the
+stem into a chafing-dish of hot coals, strongly urged with a pair of
+bellows; and, pressing the bladders alternately, I made the air pass
+several times through the heated part of the pipe. I have also made
+this kind of air very hot, standing in water before the fire. But
+neither of these methods were of any use.
+
+_Rarefaction_ and _condensation_ by instruments were also tried, but in
+vain.
+
+Thinking it possible that the _earth_ might imbibe the noxious quality
+of the air, and thence supply the roots of plants with such putrescent
+matter as is known to be nutritive to them, I kept a quantity of air, in
+which mice had died, in a phial, one half of which was filled with fine
+garden-mould; but, though it stood two months in these circumstances, it
+was not the better for it.
+
+I once imagined that, since several kinds of air cannot be long
+separated from common air, by being confined in bladders, in bottles
+well corked; or even closed with ground stopples, the affinity between
+this noxious air and the common air might be so great, that they would
+mix through a body of water interposed between them; the water
+continually receiving from the one, and giving to the other, especially
+as water receives some kind of impregnation from, I believe, every kind
+of air to which it is contiguous; but I have seen no reason to
+conclude, that a mixture of any kind of air with the common air can be
+produced in this manner.
+
+I have kept air in which mice have died, air in which candles have
+burned out, and inflammable air, separated from the common air, by the
+slightest partition of water that I could well make, so that it might
+not evaporate in a day or two, if I should happen not to attend to them;
+but I found no change in them after a month or six weeks. The
+inflammable air was still inflammable, mice died instantly in the air in
+which other mice had died before, and candles would not burn where they
+had burned out before.
+
+Since air tainted with animal or vegetable putrefaction is the same
+thing with air rendered noxious by animal respiration, I shall now
+recite the observations which I have made upon this kind of air, before
+I treat of the method of restoring them.
+
+That these two kinds of air are, in fact, the same thing, I conclude
+from their having several remarkable common properties, and from their
+differing in nothing that I have been able to observe. They equally
+extinguish flame, they are equally noxious to animals, they are
+equally, and in the same way, offensive to the smell, and they are
+restored by the same means.
+
+Since air which has passed through the lungs is the same thing with air
+tainted with animal putrefaction, it is probable that one use of the
+lungs is to carry off a _putrid effluvium_, without which, perhaps, a
+living body might putrefy as soon as a dead one.
+
+When a mouse putrefies in any given quantity of air, the bulk of it is
+generally increased for a few days; but in a few days more it begins to
+shrink up, and in about eight or ten days, if the weather be pretty
+warm, it will be found to be diminished 1/6, or 1/5 of its bulk. If it
+do not appear to be diminished after this time, it only requires to be
+passed through water, and the diminution will not fail to be sensible. I
+have sometimes known almost the whole diminution to take place, upon
+once or twice passing through the water. The same is the case with air,
+in which animals have breathed as long as they could. Also, air in which
+candles have burned out may almost always be farther reduced by this
+means.
+
+All these processes, as I observed before, seem to dispose the compound
+mass of air to part with some constituent part belonging to it (which
+appears to be the _fixed air_ that enters into its constitution) and
+this being miscible with water, must be brought into contact with it, in
+order to mix with it to the most advantage, especially when its union
+with the other constituent principles of the air is but partially
+broken.
+
+I have put mice into vessels which had their mouths immersed in
+quicksilver, and observed that the air was not much contracted after
+they were dead or cold; but upon withdrawing the mice, and admitting
+lime water to the air, it immediately became turbid, and was contracted
+in its dimensions as usual.
+
+I tried the same thing with air tainted with putrefaction, putting a
+dead mouse to a quantity of common air, in a vessel which had its mouth
+immersed in quicksilver, and after a week I took the mouse out, drawing
+it through the quicksilver, and observed that, for some time, there was
+an apparent increase of the air perhaps about 1/20. After this, it stood
+two days in the quicksilver, without any sensible alteration; and then
+admitting water to it, it began to be absorbed, and continued so, till
+the original quantity was diminished about 1/6. If, instead of common
+water, I had made use of lime-water in this experiment, I make no doubt
+but it would have become turbid.
+
+If a quantity of lime-water in a phial be put under a glass vessel
+standing in water, it will not become turbid, and provided the access of
+the common air be prevented, it will continue lime-water, I do not know
+how long; but if a mouse be left to putrefy in the vessel, the water
+will deposit all its lime in a few days. This is owing to the fixed air
+deposited by the common air, and perhaps also from more fixed air
+discharged from the putrefying substances in some part of the process of
+putrefaction.
+
+The air that is discharged from putrefying substances seems, in some
+cases, to be chiefly fixed air, with the addition of some other
+effluvium, which has the power of diminishing common air. The
+resemblance between the true putrid effluvium and fixed air in the
+following experiment, which is as decisive as I can possibly contrive
+it, appeared to be very great; indeed much greater than I had expected.
+I put a dead mouse into a tall glass vessel, and having filled the
+remainder with quicksilver, and set it, inverted, in a pot of
+quicksilver, I let it stand about two months, in which time the putrid
+effluvium issuing from the mouse had filled the whole vessel, and part
+of the dissolved blood, which lodged upon the surface of the
+quicksilver, began to be thrown out. I then filled another glass vessel,
+of the same size and shape, with as pure fixed air as I could make, and
+exposed them both, at the same time, to a quantity of lime-water. In
+both cases the water grew turbid alike, it rose equally fast in both the
+vessels, and likewise equally high; so that about the same quantity
+remained unabsorbed by the water. One of these kinds of air, however,
+was exceedingly sweet and pleasant, and the other insufferably
+offensive; one of them also would have made an addition to any quantity
+of common air, with which it had been mixed, and the other would have
+diminished it. This, at least, would have been the consequence, if the
+mouse itself had putrefied in any quantity of common air.
+
+It seems to depend, in some measure, upon the _time_, and other
+circumstances, in the dissolution of animal or vegetable substances,
+whether they yield the proper putrid effluvium, or fixed, or inflammable
+air; but the experiments which I have made upon this subject, have not
+been numerous enough to enable me to decide with certainty concerning
+those circumstances.
+
+Putrid cabbage, green or boiled, infects the air in the very same manner
+as putrid animal substances. Air thus tainted is equally contracted in
+its dimensions, it equally extinguishes flame, and is equally noxious to
+animals; but they affect the air very differently, if the heat that is
+applied to them be considerable.
+
+If beef or mutton, raw or boiled, be placed so near to the fire, that
+the heat to which it is exposed shall equal, or rather exceed, that of
+the blood, a considerable quantity of air will be generated in a day or
+two, about 1/7th of which I have generally found to be absorbed by
+water, while all the rest was inflammable; but air generated from
+vegetables, in the same circumstances, will be almost all fixed air, and
+no part of it inflammable. This I have repeated again and again, the
+whole process being in quicksilver; so that neither common air nor
+water, had any access to the substance on which the experiment was made;
+and the generation of air, or effluvium of any kind, except what might
+be absorbed by quicksilver, or resorbed by the substance itself, might
+be distinctly noted.
+
+A vegetable substance, after standing a day or two in these
+circumstances, will yield nearly all the air that can be extracted from
+it, in that degree of heat; whereas an animal substance will continue
+to give more air, or effluvium, of some kind or other, with very little
+alteration, for many weeks. It is remarkable, however, that though a
+piece of beef or mutton, plunged in quicksilver, and kept in this degree
+of heat, yield air, the bulk of which is inflammable, and contracts no
+putrid smell (at least, in a day or two) a mouse treated in the same
+manner, yields the proper putrid effluvium, as indeed the smell
+sufficiently indicates.
+
+That the putrid effluvium will mix with water seems to be evident from
+the following experiment. If a mouse be put into a jar full of water,
+standing with its mouth inverted in another vessel of water, a
+considerable quantity of elastic matter (and which may, therefore, be
+called _air_) will soon be generated, unless the weather be so cold as
+to check all putrefaction. After a short time, the water contracts an
+extremely fetid and offensive smell, which seems to indicate that the
+putrid effluvium pervades the water, and affects the neighbouring air;
+and since, after this, there is often no increase of the air, that seems
+to be the very substance which is carried off through the water, as fast
+as it is generated; and the offensive smell is a sufficient proof that
+it is not fixed air. For this has a very agreeable flavour, whether it
+be produced by fermentation, or extracted from chalk by oil of vitriol;
+affecting not only the mouth, but even the nostrils; with a pungency
+which is peculiarly pleasing to a certain degree, as any person may
+easily satisfy himself, who will chuse to make the experiment.
+
+If the water in which the mouse was immersed, and which is saturated
+with the putrid air, be changed, the greater part of the putrid air,
+will, in a day or two, be absorbed, though the mouse continues to yield
+the putrid effluvium as before; for as soon as this fresh water becomes
+saturated with it, it begins to be offensive to the smell, and the
+quantity of the putrid air upon its surface increases as before. I kept
+a mouse producing putrid air in this manner for the space of several
+months.
+
+Six ounce measures of air not readily absorbed by water, appeared to
+have been generated from one mouse, which had been putrefying eleven
+days in confined air, before it was put into a jar which was quite
+filled with water, for the purpose of this observation.
+
+Air thus generated from putrid mice standing in water, without any
+mixture of common air, extinguishes flame, and is noxious to animals,
+but not more so than common air only tainted with putrefaction. It is
+exceedingly difficult and tedious to collect a quantity of this putrid
+air, not miscible in water, so very great a proportion of what is
+collected being absorbed by the water in which it is kept; but what that
+proportion is, I have not endeavoured to ascertain. It is probably the
+same proportion that that part of fixed air, which is not readily
+absorbed by water, bears to the rest; and therefore this air, which I at
+first distinguished by the name of _the putrid effluvium_, is probably
+the same with fixed air, mixed with the phlogistic matter, which, in
+this and other processes, diminishes common air.
+
+Though a quantity of common air be diminished by any substance
+putrefying in it, I have not yet found the same effect to be produced by
+a mixture of putrid air with common air; but, in the manner in which I
+have hitherto made the experiment, I was obliged to let the putrid air
+pass through a body of water, which might instantly absorb the
+phlogistic matter that diminished the common air.
+
+Insects of various kinds live perfectly well in air tainted with animal
+or vegetable putrefaction, when a single inspiration of it would have
+instantly killed any other animal. I have frequently tried the
+experiment with flies and butterflies. The _aphides_ also will thrive as
+well upon plants growing in this kind of air, as in the open air. I
+have even been frequently obliged to take plants out of the putrid air
+in which they were growing, on purpose to brush away the swarms of these
+insects which infected them; and yet so effectually did some of them
+conceal themselves, and so fast did they multiply, in these
+circumstances, that I could seldom keep the plants quite clear of them.
+
+When air has been freshly and strongly tainted with putrefaction, so as
+to smell through the water, sprigs of mint have presently died, upon
+being put into it, their leaves turning black; but if they do not die
+presently, they thrive in a most surprizing manner. In no other
+circumstances have I ever seen vegetation so vigorous as in this kind of
+air, which is immediately fatal to animal life. Though these plants have
+been crouded in jars filled with this air, every leaf has been full of
+life; fresh shoots have branched out in various directions, and have
+grown much faster than other similar plants, growing in the same
+exposure in common air.
+
+This observation led me to conclude, that plants, instead of affecting
+the air in the same manner with animal respiration, reverse the effects
+of breathing, and tend to keep the atmosphere sweet and wholesome, when
+it is become noxious, in consequence of animals either living and
+breathing, or dying and putrefying in it.
+
+In order to ascertain this, I took a quantity of air, made thoroughly
+noxious, by mice breathing and dying in it, and divided it into two
+parts; one of which I put into a phial immersed in water; and to the
+other (which was contained in a glass jar, standing in water) I put a
+sprig of mint. This was about the beginning of August 1771, and after
+eight or nine days, I found that a mouse lived perfectly well in that
+part of the air, in which the sprig of mint had grown, but died the
+moment it was put into the other part of the same original quantity of
+air; and which I had kept in the very same exposure, but without any
+plant growing in it.
+
+This experiment I have several times repeated; sometimes using air in
+which animals had breathed and died, and at other times using air,
+tainted with vegetable or animal putrefaction; and generally with the
+same success.
+
+Once, I let a mouse live and die in a quantity of air which had been
+noxious, but which had been restored by this process, and it lived
+nearly as long as I conjectured it might have done in an equal quantity
+of fresh air; but this is so exceedingly various, that it is not easy to
+form any judgment from it; and in this case the symptom of _difficult
+respiration_ seemed to begin earlier than it would have done in common
+air.
+
+Since the plants that I made use of manifestly grow and thrive in putrid
+air; since putrid matter is well known to afford proper nourishment for
+the roots of plants; and since it is likewise certain that they receive
+nourishment by their leaves as well as by their roots, it seems to be
+exceedingly probable, that the putrid effluvium is in some measure
+extracted from the air, by means of the leaves of plants, and therefore
+that they render the remainder more fit for respiration.
+
+Towards the end of the year some experiments of this kind did not answer
+so well as they had done before, and I had instances of the relapsing of
+this restored air to its former noxious state. I therefore suspended my
+judgment concerning the efficacy of plants to restore this kind of
+noxious air, till I should have an opportunity of repeating my
+experiments, and giving more attention to them. Accordingly I resumed
+the experiments in the summer of the year 1772, when I presently had the
+most indisputable proof of the restoration of putrid air by vegetation;
+and as the fact is of some importance, and the subsequent variation in
+the state of this kind of air is a little remarkable, I think it
+necessary to relate some of the facts pretty circumstantially.
+
+The air, on which I made the first experiments, was rendered exceedingly
+noxious by mice dying in it on the 20th of June. Into a jar nearly
+filled with one part of this air, I put a sprig of mint, while I kept
+another part of it in a phial, in the same exposure; and on the 27th of
+the same month, and not before, I made a trial of them, by introducing a
+mouse into a glass vessel, containing 2-1/2 ounce measures filled with
+each kind of air; and I noted the following facts.
+
+When the vessel was filled with the air in which the mint had grown, a
+very large mouse lived five minutes in it, before it began to shew any
+sign of uneasiness. I then took it out, and found it to be as strong and
+vigorous as when it was first put in; whereas in that air which had been
+kept in the phial only, without a plant growing in it, a younger mouse
+continued not longer than two or three seconds, and was taken out quite
+dead. It never breathed after, and was immediately motionless. After
+half an hour, in which time the larger mouse (which I had kept alive,
+that the experiment might be made on both the kinds of air with the very
+same animal) would have been sufficiently recruited, supposing it to
+have received any injury by the former experiment, was put into the same
+vessel of air; but though it was withdrawn again, after being in it
+hardly one second, it was recovered with difficulty, not being able to
+stir from the place for near a minute. After two days, I put the same
+mouse into an equal quantity of common air, and observed that it
+continued seven minutes without any sign of uneasiness; and being very
+uneasy after three minutes longer, I took it out. Upon the whole, I
+concluded that the restored air wanted about one fourth of being as
+wholesome as common air. The same thing also appeared when I applied the
+test of nitrous air.
+
+In the seven days, in which the mint was growing in this jar of noxious
+air, three old shoots had extended themselves about three inches, and
+several new ones had made their appearance in the same time. Dr.
+Franklin and Sir John Pringle happened to be with me, when the plant had
+been three or four days in this state, and took notice of its vigorous
+vegetation, and remarkably healthy appearance in that confinement.
+
+On the 30th of the same month, a mouse lived fourteen minutes, breathing
+naturally all the time, and without appearing to be much uneasy, till
+the last two minutes, in the vessel containing two ounce measures and a
+half of air which had been rendered noxious, by mice breathing in it
+almost a year before, and which, I had found to be most highly noxious
+on the 19th of this month, a plant having grown in it, but not
+exceedingly well, these eleven days; on which account I had deferred
+making the trial so long. The restored air was affected by a mixture of
+nitrous air, almost as much as common air.
+
+As this putrid air was thus easily restored to a considerable degree of
+fitness for respiration, by plants growing in it, I was in hopes that by
+the same means it might in time be so much more perfectly restored, that
+a candle would burn in it; and for this purpose I kept plants growing in
+the jars which contained this air till the middle of August following,
+but did not take sufficient care to pull out all the old and rotten
+leaves. The plants, however, had grown, and looked so well upon the
+whole, that I had no doubt but that the air must constantly have been in
+a mending state; when I was exceedingly surprized to find, on the 24th
+of that month, that though the air in one of the jars had not grown
+worse, it was no better; and that the air in the other jar was so much
+worse than it had been, that a mouse would have died in it in a few
+seconds. It also made no effervescence with nitrous air, as it had done
+before.
+
+Suspecting that the same plant might be capable of restoring putrid air
+to a certain degree only, or that plants might have a contrary tendency
+in some stages of their growth, I withdrew the old plant, and put a
+fresh one in its place; and found that, after seven days, the air was
+restored to its former wholesome state. This fact I consider as a very
+remarkable one, and well deserving of a farther investigation, as it may
+throw more light upon the principles of vegetation. It is not, however,
+a single fact; for I had several instances of the same kind in the
+preceding year; but it seemed so very extraordinary, that air should
+grow worse by the continuance of the same treatment by which it had
+grown better, that, whenever I observed it, I concluded that I had not
+taken sufficient care to satisfy myself of its previous restoration.
+
+That plants are capable of perfectly restoring air injured by
+respiration, may, I think, be inferred with certainty from the perfect
+restoration, by this means, of air which had passed through my lungs, so
+that a candle would burn in it again, though it had extinguished flame
+before, and apart of the same original quantity of air still continued
+to do so. Of this one instance occurred in the year 1771, a sprig of
+mint having grown in a jar of this kind of air, from the 25th of July to
+the 17th of August following; and another trial I made, with the same
+success, the 7th of July 1772, the plant having grown in it from the
+29th of June preceding. In this case also I found that the effect was
+not owing to any virtue in the leaves of mint; for I kept them
+constantly changed in a quantity of this kind of air, for a considerable
+time, without making any sensible alteration in it.
+
+These proofs of a partial restoration of air by plants in a state of
+vegetation, though in a confined and unnatural situation, cannot but
+render it highly probable, that the injury which is continually done to
+the atmosphere by the respiration of such a number of animals, and the
+putrefaction of such masses of both vegetable and animal matter, is, in
+part at least, repaired by the vegetable creation. And, notwithstanding
+the prodigious mass of air that is corrupted daily by the
+above-mentioned causes; yet, if we consider the immense profusion of
+vegetables upon the face of the earth, growing in places, suited to
+their nature, and consequently at full liberty to exert all their
+powers, both inhaling and exhaling, it can hardly be thought, but that
+it may be a sufficient counterbalance to it, and that the remedy is
+adequate to the evil.
+
+Dr. Franklin, who, as I have already observed, saw some of my plants in
+a very flourishing state, in highly noxious air, was pleased to express
+very great satisfaction with the result of the experiments. In his
+answer to the letter in which I informed him of it, he says,
+
+"That the vegetable creation should restore the air which is spoiled by
+the animal part of it, looks like a rational system, and seems to be of
+a piece with the rest. Thus fire purifies water all the world over. It
+purifies it by distillation, when it raises it in vapours, and lets it
+fall in rain; and farther still by filtration, when, keeping it fluid,
+it suffers that rain to percolate the earth. We knew before that putrid
+animal substances were converted into sweet vegetables, when mixed with
+the earth, and applied as manure; and now, it seems, that the same
+putrid substances, mixed with the air, have a similar effect. The strong
+thriving state of your mint in putrid air seems to shew that the air is
+mended by taking something from it, and not by adding to it." He adds,
+"I hope this will give some check to the rage of destroying trees that
+grow near houses, which has accompanied our late improvements in
+gardening, from an opinion of their being unwholesome. I am certain,
+from long observation, that there is nothing unhealthy in the air of
+woods; for we Americans have every where our country habitations in the
+midst of woods, and no people on earth enjoy better health, or are more
+prolific."
+
+Having rendered inflammable air perfectly innoxious by continued
+_agitation in a trough of water_, deprived of its air, I concluded that
+other kinds of noxious air might be restored by the same means; and I
+presently found that this was the case with putrid air, even of more
+than a year's standing. I shall observe once for all, that this process
+has never failed to restore any kind of noxious air on which I have
+tried it, viz. air injured by respiration or putrefaction, air infected
+with the fumes of burning charcoal, and of calcined metals, air in which
+a mixture of iron filings and brimstone, that in which paint made of
+white lead and oil has stood, or air which has been diminished by a
+mixture of nitrous air. Of the remarkable effect which this process has
+on nitrous air itself, an account will be given in its proper place.
+
+If this process be made in water deprived of air, either by the
+air-pump, by boiling, or by distillation, or if fresh rain-water be
+used, the air will always be diminished by the agitation; and this is
+certainly the fairest method of making the experiment. If the water be
+fresh pump-water, there will always be an increase of the air by
+agitation, the air contained in the water being set loose, and joining
+that which is in the jar. In this case, also, the air has never failed
+to be restored; but then it might be suspected that the melioration was
+produced by the addition of some more wholesome ingredient. As these
+agitations were made in jars with wide mouths, and in a trough which had
+a large surface exposed to the common air, I take it for granted that
+the noxious effluvia, whatever they be, were first imbibed by the water,
+and thereby transmitted to the common atmosphere. In some cases this was
+sufficiently indicated by the disagreeable smell which attended the
+operation.
+
+After I had made these experiments, I was informed that an ingenious
+physician and philosopher had kept a fowl alive twenty-four hours, in a
+quantity of air in which another fowl of the same size had not been able
+to live longer than an hour, by contriving to make the air, which it
+breathed, pass through no very large quantity of acidulated water, the
+surface of which was not exposed to the common air; and that even when
+the water was not acidulated, the fowl lived much longer than it could
+have done, if the air which it breathed had not been drawn through the
+water.
+
+As I should not have concluded that this experiment would have succeeded
+so well, from any observations that I had made upon the subject, I took
+a quantity of air in which mice had died, and agitated it very strongly,
+first in about five times its own quantity of distilled water, in the
+manner in which I had impregnated water with fixed air; but though the
+operation was continued a long time, it made no sensible change in the
+properties of the air. I also repeated the operation with pump-water,
+but with as little effect. In this case, however, though the air was
+agitated in a phial, which had a narrow neck, the surface of the water
+in the bason was considerably large, and exposed to the common
+atmosphere, which must have tended a little to favour the experiment.
+
+In order to judge more precisely of the effect of these different
+methods of agitating air, I transferred the very noxious air, which I
+had hot been able to amend in the least degree by the former method,
+into an open jar, standing in a trough of water; and when I had agitated
+it till it was diminished about one third, I found it to be better than
+air in which candles had burned out, as appeared by the test of the
+nitrous air; and a mouse lived in 2-1/2 ounce measures of it a quarter
+of an hour, and was not sensibly affected the first ten or twelve
+minutes.
+
+In order to determine whether the addition of any _acid_ to the water,
+would make it more capable of restoring putrid air, I agitated a
+quantity of it in a phial containing very strong vinegar; and after that
+in _aqua fortis_, only half diluted with water; but by neither of these
+processes was the air at all mended, though the agitation was repeated,
+at intervals, during a whole day, and it was moreover allowed to stand
+in that situation all night.
+
+Since, however, water in these experiments must have imbibed and
+retained a certain portion of the noxious effluvia, before they could be
+transmitted to the external air, I do not think it improbable but that
+the agitation of the sea and large lakes may be of some use for the
+purification of the atmosphere, and the putrid matter contained in water
+may be imbibed by aquatic plants, or be deposited in some other manner.
+
+Having found, by several experiments above-mentioned that the proper
+putrid effluvium is something quite distinct from fixed air, and
+finding, by the experiments of Dr. Macbride, that fixed air corrects
+putrefaction; it occured to me, that fixed air, and air tainted with
+putrefaction, though equally, noxious when separate, might make a
+wholesome mixture, the one, correcting the other; and I was confirmed in
+this opinion by, I believe, not less than fifty or sixty instances, in
+which air, that had been made in the highest degree noxious, by
+respiration or putrefaction, was so far sweetened, by a mixture of about
+four times as much fixed air, that afterwards mice lived in it
+exceedingly well, and in some cases almost as long as in common air. I
+found it, indeed, to be more difficult to restore _old_ putrid air by
+this means; but I hardly ever failed to do it, when the two kinds of air
+had stood a long time together; by which I mean about a fortnight or
+three weeks.
+
+The reason why I do not absolutely conclude that the restoration of air
+in these cases was the effect of fixed air, is that, when I made a trial
+of the mixture, I sometimes agitated the two kinds of air pretty
+strongly together, in a trough of water, or at least passed it several
+times through water, from one jar to another, that the superfluous fixed
+air might be absorbed, not suspecting at that time that the agitation
+could have any other effect. But having since found that very violent,
+and especially long-continued agitation in water, without any mixture of
+fixed air, never failed to render any kind of noxious air in some
+measure fit for respiration (and in one particular instance the mere
+transferring of the air from one vessel to another through the water,
+though for a much longer time than I ever used for the mixtures of air,
+was of considerable use for the same purpose) I began to entertain some
+doubt of the efficacy of fixed air in this case. In some cases also the
+mixture of fixed air had by no means so much effect on the putrid air
+as, from the generality of my observations, I should have expected.
+
+I was always aware, indeed, that it might be said, that, the residuum of
+fixed air not being very noxious, such an addition must contribute to
+mend the putrid air; but, in order to obviate this objection, I once
+mixed the residuum of as much fixed air as I had found, by a variety of
+trials, to be sufficient to restore a given quantity of putrid air, with
+an equal quantity of that air, without making any sensible melioration
+of it.
+
+Upon the whole, I am inclined to think that this process could hardly
+have succeeded so well as it did with me, and in so great a number of
+trials, unless fixed air have some tendency to correct air tainted with
+respiration or putrefaction; and it is perfectly agreeable to the
+analogy of Dr. Macbride's discoveries, and may naturally be expected
+from them, that it should have such an effect.
+
+By a mixture of fixed air I have made wholesome the residuum of air
+generated by putrefaction only, from mice plunged in water. This, one
+would imagine, _à priori_, to be the most noxious of all kinds of air.
+For if common air only tainted with putrefaction be so deadly, much more
+might one expect that air to be so, which was generated from
+putrefaction only; but it seems to be nothing more than common air (or
+at least that kind of fixed air which is not absorbed by water) tainted
+with putrefaction, and therefore requires no other process to sweeten
+it. In this case, however, we seem to have an instance of the generation
+of genuine common air, though mixed with something that is foreign to
+it. Perhaps the residuum of fixed air may be another instance of the
+same nature, and also the residuum of inflammable air, and of nitrous
+air, especially nitrous air loaded with phlogiston, after long agitation
+in water.
+
+Fixed air is equally diffused through the whole mass of any quantity of
+putrid air with which it is mixed: for dividing the mixture into two
+equal parts, they were reduced in the same proportion by passing through
+water. But this is also the case with some of the kinds of air which
+will not incorporate, as inflammable air, and air in which brimstone has
+burned.
+
+If fixed air tend to correct air which has been injured by animal
+respiration or putrefaction, _lime kilns_, which discharge great
+quantities of fixed air, may be wholesome in the neighbourhood of
+populous cities, the atmosphere of which must abound with putrid
+effluvia. I should think also that physicians might avail themselves of
+the application of fixed air in many putrid disorders, especially as it
+may be so easily administered by way of _clyster_, where it would often
+find its way to much of the putrid matter. Nothing is to be apprehended
+from the distention of the bowels by this kind of air, since it is so
+readily absorbed by any fluid or moist substance.
+
+Since fixed air is not noxious _per se_, but, like fire, only in excess,
+I do not think it at all hazardous to attempt to _breathe_ it. It is
+however easily conveyed into the _stomach_, in natural or artificial
+Pyrmont water, in briskly-fermenting liquors, or a vegetable diet. It
+is even possible, that a considerable quantity of fixed air might be
+imbibed by the absorbing vessels of the skin, if the whole body, except
+the head, should be suspended over a vessel of strongly-fermenting
+liquor; and in some putrid disorders this treatment might be very
+salutary. If the body was exposed quite naked, there would be very
+little danger from the cold in this situation, and the air having freer
+access to the skin might produce a greater effect. Being no physician, I
+run no risk by throwing out these random, and perhaps whimsical
+proposals.[5]
+
+Having communicated my observations on fixed air, and especially my
+scheme of applying it by way of _clyster_ in putrid disorders, to Mr.
+Hey, an ingenious surgeon in Leeds a case presently occurred, in which
+he had an opportunity of giving it a trial; and mentioning it to Dr.
+Hird and Dr. Crowther, two physicians who attended the patient, they
+approved the scheme, and it was put in execution; both by applying the
+fixed air by way of clyster, and at the same time making the patient
+drink plentifully of liquors strongly impregnated with it. The event
+was such, that I requested Mr. Hey to draw up a particular account of
+the case, describing the whole of the treatment, that the public might
+be satisfied that this new application of fixed air is perfectly safe,
+and also, have an opportunity of judging how far it had the effect which
+I expected from it; and as the application is new, and not unpromising,
+I shall subjoin his letter to me on the subject, by way of _Appendix_ to
+these papers.
+
+When I began my inquires into the properties of different kinds of air,
+I engaged my friend Dr. Percival to attend to the _medicinal uses_ of
+them, being sensible that his knowledge of philosophy as well as of
+medicine would give him a singular advantage for this purpose. The
+result of his observations I shall also insert in the Appendix.
+
+FOOTNOTES:
+
+[5] Some time after these papers were first printed, I was pleased to
+find the same proposal in _Dr. Alexander's Experimental Essays_.
+
+
+
+
+SECTION V.
+
+_Of AIR in which a mixture of BRIMSTONE and FILINGS of IRON has stood._
+
+
+Reading in Dr. Hales's account of his experiments, that there was a
+great diminution of the quantity of air in which _a mixture of powdered
+brimstone and filings of iron, made into a paste with water_, had stood,
+I repeated the experiment, and found the diminution greater than I had
+expected. This diminution of air is made as effectually, and as
+expeditiously, in quicksilver as in water; and it may be measured with
+the greatest accuracy, because there is neither any previous expansion
+or increase of the quantity of air, and because it is some time before
+this process begins to have any sensible effect. This diminution of air
+is various; but I have generally found it to be between one fifth and
+one fourth of the whole.
+
+Air thus diminished is not heavier, but rather lighter than common air;
+and though lime-water does not become turbid when it is exposed to this
+air, it is probably owing to the formation of a selenitic salt, as was
+the case with the simple burning of brimstone above-mentioned. That
+something proceeding from the brimstone strongly affects the water which
+is confined in the same place with this mixture, is manifest from the
+very strong smell that it has of the volatile spirit of vitriol.
+
+I conclude that the diminution of air by this, process is of the same
+kind with the diminution of it in the other cases, because when this
+mixture is put into air which has been previously diminished, either by
+the burning of candles, by respiration, or putrefaction, though it never
+fails to diminish it something more, it is, however, no farther than
+this process alone would have done it. If a fresh mixture be introduced
+into a quantity of air which had been reduced by a former mixture, it
+has little or no farther effect.
+
+I once observed, that when a mixture of this kind was taken out of a
+quantity of air in which a candle had before burned out, and in which it
+had stood for several days, it was quite cold and black, as it always
+becomes in a confined place; but it presently grew very hot, smoaked
+copously, and smelled very offensively; and when it was cold, it was
+brown, like the rust of iron.
+
+I once put a mixture of this kind to a quantity of inflammable air, made
+from iron, by which means it was diminished 1/9 or 1/10 in its bulk;
+but, as far as I could judge, it was still as inflammable as ever.
+Another quantity of inflammable air was also reduced in the same
+proportion, by a mouse putrefying in it; but its inflammability was not
+seemingly lessened.
+
+Air diminished by this mixture of iron filings and brimstone, is
+exceedingly noxious to animals, and I have not perceived that it grows
+any better by keeping in water. The smell of it is very pungent and
+offensive.
+
+The quantity of this mixture which I made use of in the preceding
+experiments, was from two to four ounce measures; but I did not
+perceive, but that the diminution of the quantity of air (which was
+generally about twenty ounce measures) was as great with the smallest,
+as with the largest quantity. How small a quantity is necessary to
+diminish a given quantity of air to a _maximum_, I have made no
+experiments to ascertain.
+
+As soon as this mixture of iron filings with, brimstone and water,
+begins to ferment, it also turns black, and begins to swell, and it
+continues to do so, till it occupies twice as much space as it did at
+first. The force with which it expands is great; but how great it is I
+have not endeavoured to determine.
+
+When this mixture is immersed in water, it generates no air, though it
+becomes black, and swells.
+
+
+
+
+SECTION VI.
+
+_Of NITROUS AIR._
+
+
+Ever since I first read Dr. Hales's most excellent _Statical Essays_, I
+was particularly struck with that experiment of his, of which an account
+is given, VOL. I, p. 224. and VOL. II, p. 280. in which common air, and
+air generated from the Walton pyrites, by spirit of nitre, made a turbid
+red mixture, and in which part of the common air was absorbed; but I
+never expected to have the satisfaction of seeing this remarkable
+appearance, supposing it to be peculiar to that particular mineral.
+Happening to mention this subject to the Hon. Mr. Cavendish, when I was
+in London, in the spring of the year 1772, he said that he did not
+imagine but that other kinds of pyrites, or the metals might answer as
+well, and that probably the red appearance of the mixture depended upon
+the spirit of nitre only. This encouraged me to attend to the subject;
+and having no pyrites, I began with the solution of the different metals
+in spirit of nitre, and catching the air which was generated in the
+solution, I presently found what I wanted, and a good deal more.
+
+Beginning with the solution of brass, on the 4th of June 1772, I first
+found this remarkable species of air, only one effect of which, was
+casually observed by Dr. Hales; and he gave so little attention to it,
+and it has been so much unnoticed since his time, that, as far as I
+know, no name has been given to it. I therefore found myself, contrary
+to my first resolution, under an absolute necessity of giving a name to
+this kind of air myself. When I first began to speak and write of it to
+my friends, I happened to distinguish it by the name of _nitrous air_,
+because I had procured it by means of spirit of nitre only; and though I
+cannot say that I altogether like the term, neither myself nor any of my
+friends, to whom I have applied for the purpose, have been able to hit
+upon a better; so that I am obliged, after all, to content myself with
+it.
+
+I have found that this kind of air is readily procured from iron,
+copper, brass, tin, silver, quicksilver, bismuth, and nickel, by the
+nitrous acid only, and from gold and the regulus of antimony by _aqua
+regia_. The circumstances attending the solution of each of these metals
+are various, but hardly worth mentioning, in treating of the properties
+of the _air_ which they yield; which, from what metal soever it is
+extracted, has, as far as I have been able to observe, the very same
+properties.
+
+One of the most conspicuous properties of this kind of air is the great
+diminution of any quantity of common air with which it is mixed,
+attended with a turbid red, or deep orange colour, and a considerable
+heat. The _smell_ of it, also, is very strong, and remarkable, but very
+much resembling that of smoking spirit of nitre.
+
+The diminution of a mixture of this and common air is not an equal
+diminution of both the kinds, which is all that Dr. Hales could observe,
+but of about one fifth of the common air, and as much of the nitrous air
+as is necessary to produce that effect; which, as I have found by many
+trials, is about one half as much as the original quantity of common
+air. For if one measure of nitrous air be put to two measures of common
+air, in a few minutes (by which time the effervescence will be over, and
+the mixture will have recovered its transparency) there will want about
+one ninth of the original two measures; and if both the kinds of air be
+very pure, the diminution will still go on slowly, till in a day or two,
+the whole will be reduced to one fifth less than the original quantity
+of common air. This farther diminution, by long standing, I had not
+observed at the time of the first publication of these papers.
+
+I hardly know any experiment that is more adapted to amaze and surprize
+than this is, which exhibits a quantity of air, which, as it were,
+devours a quantity of another kind of air half as large as itself, and
+yet is so far from gaining any addition to its bulk, that it is
+considerably diminished by it. If, after this full saturation of common
+air with nitrous air, more nitrous air be put to it, it makes an
+addition equal to its own bulk, without producing the least redness, or
+any other visible effect.
+
+If the smallest quantity of common air be put to any larger quantity of
+nitrous air, though the two together will not occupy so much space as
+they did separately, yet the quantity will still be larger than that of
+the nitrous air only. One ounce measure of common air being put to near
+twenty ounce measures of nitrous air, made an addition to it of about
+half an ounce measure. This being a much greater proportion than the
+diminution of common air, in the former experiment, proves that part of
+the diminution in the former case is in the nitrous air. Besides, it
+will presently appear, that nitrous air is subject to a most remarkable
+diminution; and as common air, in a variety of other cases, suffers a
+diminution from one fifth to one fourth, I conclude, that in this case
+also it does not exceed that proportion, and therefore that the
+remainder of the diminution respects the nitrous air.
+
+In order to judge whether the _water_ contributed to the diminution of
+this mixture of nitrous and common air, I made the whole process several
+times in quicksilver, using one third of nitrous, and two thirds of
+common air, as before. In this case the redness continued a very long
+time, and the diminution was not so great as when the mixtures had been
+made in water, there remaining one seventh more than the original
+quantity of common air.
+
+This mixture stood all night upon the quicksilver; and the next morning
+I observed that it was no farther diminished upon the admission of
+water to it, nor by pouring it several times through the water, and
+letting it stand in water two days.
+
+Another mixture, which had stood about six hours on the quicksilver, was
+diminished a little more upon the admission of water, but was never less
+than the original quantity of common air. In another case however, in
+which the mixture had stood but a very short time in quicksilver, the
+farther diminution, which took place upon the admission of water, was
+much more considerable; so that the diminution, upon the whole, was very
+nearly as great as if the process had been intirely in water.
+
+It is evident from these experiments, that the diminution is in part
+owing to the absorption by the water; but that when the mixture is kept
+a long time, in a situation in which there is no water to absorb any
+part of it, it acquires a constitution, by which it is afterwards
+incapable of being absorbed by water, or rather, there is an addition to
+the quantity of air by nitrous air produced by the solution of the
+quicksilver.
+
+It will be seen, in the second part of this work, that, in the
+decomposition of nitrous air by its mixture with common air, there is
+nothing at hand when the process is made in quicksilver, with which the
+acid that entered into its composition can readily unite.
+
+In order to determine whether the fixed part of common air was deposited
+in the diminution of it by nitrous air, I inclosed a vessel full of
+lime-water in the jar in which the process was made, but it occasioned
+no precipitation of the lime; and when the vessel was taken out, after
+it had been in that situation a whole day, the lime was easily
+precipitated by breathing into it as usual.
+
+But though the precipitation of the lime was not sensible in this method
+of making the experiment, it is sufficiently so when the whole process
+is made in lime-water, as will be seen in the second part of this work;
+so that we have here another evidence of the deposition of fixed air
+from common air. I have made no alteration, however, in the preceding
+paragraph, because it may not be unuseful, as a caution to future
+experimenters.
+
+It is exceedingly remarkable that this effervescence and diminution,
+occasioned by the mixture of nitrous air, is peculiar to common air, or
+_air fit for respiration_; and, as far as I can judge, from a great
+number of observations, is at least very nearly, if not exactly, in
+proportion to its fitness for this purpose; so that by this means the
+goodness of air may be distinguished much more accurately than it can be
+done by putting mice, or any other animals, to breathe in it.
+
+This was a most agreeable discovery to me, as I hope it may be an useful
+one to the public; especially as, from this time, I had no occasion for
+so large a stock of mice as I had been used to keep for the purpose of
+these experiments, using them only in those which required to be very
+decisive; and in these cases I have seldom failed to know beforehand in
+what manner they would be affected.
+
+It is also remarkable that, on whatever account air is unfit for
+respiration, this same test is equally applicable. Thus there is not the
+least effervescence between nitrous and fixed air, or inflammable air,
+or any species of diminished air. Also the degree of diminution being
+from nothing at all to more than one third of the whole of any quantity
+of air, we are, by this means, in possession of a prodigiously large
+_scale_, by which we may distinguish very small degrees of difference in
+the goodness of air.
+
+I have not attended much to this circumstance, having used this test
+chiefly for greater differences; but, if I did not deceive myself, I
+have perceived a real difference in the air of my study, after a few
+persons have been with me in it, and the air on the outside of the
+house. Also a phial of air having been sent me, from the neighbourhood
+of York, it appeared not to be so good as the air near Leeds; that is,
+it was not diminished so much by an equal mixture of nitrous air, every
+other circumstance being as nearly the same as I could contrive. It may
+perhaps be possible, but I have not yet attempted it, to distinguish
+some of the different winds, or the air of different times of the year,
+&c. &c. by this test.
+
+By means of this test I was able to determine what I was before in doubt
+about, viz. the _kind_ as well as the _degree_ of injury done to air by
+candles burning in it. I could not tell with certainty, by means of
+mice, whether it was at all injured with respect to respiration; and yet
+if nitrous air may be depended upon for furnishing an accurate test, it
+must be rather more than one third worse than common air, and have been
+diminished by the same general cause of the other diminutions of air.
+For when, after many trials, I put one measure of thoroughly putrid and
+highly noxious air, into the same vessel with two measures of good
+wholesome air, and into another vessel an equal quantity, viz. three
+measures of air in which a candle had burned out; and then put equal
+quantities of nitrous air to each of them, the latter was diminished
+rather more than the former.
+
+It agrees with this observation, that _burned air_ is farther diminished
+both by putrefaction, and a mixture of iron filings and brimstone; and I
+therefore take it for granted by every other cause of the diminution of
+air. It is probable, therefore, that burned air is air so far loaded
+with phlogiston, as to be able to extinguish a candle, which it may do
+long before it is fully saturated.
+
+Inflammable air with a mixture of nitrous air burns with a green flame.
+This makes a very pleasing experiment when it is properly conducted. As,
+for some time, I chiefly made use of _copper_ for the generation of
+nitrous air, I first ascribed this circumstance to that property of this
+metal, by which it burns with a green flame; but I was presently
+satisfied that it must arise from the spirit of nitre, for the effect is
+the very same from which ever of the metals the nitrous air is
+extracted, all of which I tried for this purpose, even silver and gold.
+
+A mixture of oil of vitriol and spirit of nitre in equal proportions
+dissolved iron, and the produce was nitrous air; but a less degree of
+spirit of nitre in the mixture produced air that was inflammable, and
+which burned with a green flame. It also tinged common air a little red,
+and diminished it, though not much.
+
+The diminution of common air by a mixture of nitrous air, is not so
+extraordinary as the diminution which nitrous air itself is subject to
+from a mixture of iron filings and brimstone, made into a paste with
+water. This mixture, as I have already observed, diminishes common air
+between one fifth and one fourth, but has no such effect upon any kind
+of air that has been diminished, and rendered noxious by any other
+process; but when it is put to a quantity of nitrous air, it diminishes
+it so much, that no more than one fourth of the original quantity will
+be left.
+
+The effect of this process is generally perceived in five or six hours,
+about which time the visible effervesence of the mixture begins; and in
+a very short time it advances so rapidly, that in about an hour almost
+the whole effect will have taken place. If it be suffered to stand a day
+or two longer, the air will still be diminished farther, but only a very
+little farther, in proportion to the first diminution. The glass jar,
+in which the air and this mixture have been confined, has generally been
+so much heated in this process, that I have not been able to touch it.
+
+Nitrous air thus diminished has not so strong a smell as nitrous air
+itself, but smells just like common air in which the same mixture has
+stood; and it is not capable of being diminished any farther, by a fresh
+mixture of iron and brimstone.
+
+Common air saturated with nitrous air is also no farther diminished by
+this mixture of iron filings and brimstone, though the mixture ferments
+with great heat, and swells very much in it.
+
+Plants die very soon, both in nitrous air, and also in common air
+saturated with nitrous air, but especially in the former.
+
+Neither nitrous air, nor common air saturated with nitrous air, differ
+in specific gravity from common air. At least, the difference is so
+small, that I could not be sure there was any; sometimes about three
+pints of it seeming to be about half a grain heavier, and at other times
+as much lighter than common air.
+
+Having, among other kinds of air, exposed a quantity of nitrous air to
+water out of which the air had been well boiled, in the experiment to
+which I have more than once referred (as having been the occasion of
+several new and important observations) I found that 19/20 of the whole
+was absorbed. Perceiving, to my great surprize, that so very great a
+proportion of this kind of air was miscible with water, I immediately
+began to agitate a considerable quantity of it, in a jar standing in a
+trough of the same kind of water; and, with about four times as much
+agitation as fixed air requires, it was so far absorbed by the water,
+that only about one fifth remained. This remainder extinguished flame,
+and was noxious to animals.
+
+Afterwards I diminished a pretty large quantity of nitrous air to one
+eighth of its original bulk, and the remainder still retained much of
+its peculiar smell, and diminished common air a little. A mouse also
+died in it, but not so suddenly as it would have done in pure nitrous
+air. In this operation the peculiar smell of nitrous air is very
+manifest, the water being first impregnated with the air, and then
+transmitting it to the common atmosphere.
+
+This experiment gave me the hint of impregnating water with nitrous air,
+in the manner in which I had before done it with fixed air; and I
+presently found that distilled water would imbibe about one tenth of its
+bulk of this kind of air, and that it acquired a remarkably acid and
+astringent taste from it. The smell of water thus impregnated is at
+first peculiarly pungent. I did not chuse to swallow any of it, though,
+for any thing that I know, it may be perfectly innocent, and perhaps, in
+some cases, salutary.
+
+This kind of air is retained very obstinately by water. In an exhausted
+receiver a quantity of water thus saturated emitted a whitish fume, such
+as sometimes issues from bubbles of this air when it is first generated,
+and also some air-bubbles; but though it was suffered to stand a long
+time in this situation, it still retained its peculiar taste; but when
+it had stood all night pretty near the fire, the water was become quite
+vapid, and had deposited a filmy kind of matter, of which I had often
+collected a considerable quantity from the trough in which jars
+containing this air had stood. This I suppose to be a precipitate of the
+metal, by the solution of which the nitrous air was generated. I have
+not given so much attention to it as to know, with certainty, in what
+circumstances this _deposit_ is made, any more than I do the matter
+deposited from inflammable air above-mentioned; for I cannot get it, at
+least in any considerable quantity, when I please; whereas I have often
+found abundance of it, when I did not expect it at all.
+
+The nitrous air with which I made the first impregnation of water was
+extracted from copper; but when I made the impregnation with air from
+quicksilver, the water had the very same taste, though the matter
+deposited from it seemed to be of a different kind; for it was whitish,
+whereas the other had a yellowish tinge. Except the first quantity of
+this impregnated water, I could never deprive any more that I made of
+its peculiar taste. I have even let some of it stand more than a week,
+in phials with their mouths open, and sometimes very near the fire,
+without producing any alteration in it[6].
+
+Whether any of the spirit of nitre contained in the nitrous air be mixed
+with the water in this operation, I have not yet endeavoured to
+determine. This, however, may probably be the case, as the spirit of
+nitre is, in a considerable degree, volatile[7].
+
+It will perhaps be thought, that the most _useful_, if not the most
+remarkable, of all the properties of this extraordinary kind of air, is
+its power of preserving animal substances from putrefaction, and of
+restoring those that are already putrid, which it possesses in a far
+greater degree than fixed air. My first observation of this was
+altogether casual. Having found nitrous air to suffer so great a
+diminution as I have already mentioned by a mixture of iron filings and
+brimstone, I was willing to try whether it would be equally diminished
+by other causes of the diminution of common air, especially by
+putrefaction; and for this purpose I put a dead mouse into a quantity of
+it, and placed it near the fire, where the tendency to putrefaction was
+very great. In this case there was a considerable diminution, viz. from
+5-1/4 to 3-1/4; but not so great as I had expected, the antiseptic power
+of the nitrous air having checked the tendency to putrefaction; for
+when, after a week, I took the mouse out, I perceived, to my very great
+surprize, that it had no offensive smell.
+
+Upon this I took two other mice, one of them just killed, and the other
+soft and putrid, and put them both into the same jar of nitrous air,
+standing in the usual temperature of the weather, in the months of July
+and August of 1772; and after twenty-five days, having observed that
+there was little or no change in the quantity of the air, I took the
+mice out; and, examining them, found them both perfectly sweet, even
+when cut through in several places. That which had been put into the air
+when just dead was quite firm; and the flesh of the other, which had
+been putrid and soft, was still soft, but perfectly sweet.
+
+In order to compare the antiseptic power of this kind of air with that
+of fixed air, I examined a mouse which I had inclosed in a phial full of
+fixed air, as pure as I could make it, and which I had corked very
+close; but upon opening this phial in water about a month after, I
+perceived that a large quantity of putrid effluvium had been generated;
+for it rushed with violence out of the phial; and the smell that came
+from it, the moment the cork was taken out, was insufferably offensive.
+Indeed Dr. Macbride says, that he could only restore very thin pieces
+of putrid flesh by means of fixed air. Perhaps the antiseptic power of
+these kinds of air may be in proportion to their acidity.
+
+If a little pains were taken with this subject, this remarkable
+antiseptic power of nitrous air might possibly be applied to various
+uses, perhaps to the preservation of the more delicate birds, fishes,
+fruits, &c. mixing it in different proportions with common or fixed air.
+Of this property of nitrous air anatomists may perhaps avail themselves,
+as animal substances may by this means be preserved in their natural
+soft state; but how long it will answer for this purpose, experience
+only can shew.
+
+I calcined lead and tin in the manner hereafter described in a quantity
+of nitrous air, but with very little sensible effect; which rather
+surprized me; as, from the result of the experiment with the iron
+filings and brimstone, I had expected a very great diminution of the
+nitrous air by this process; the mixture of iron filings and brimstone,
+and the calcination of metals, having the same effect upon common air,
+both of them diminishing it in nearly the same proportion. But though I
+made the metals _fume_ copiously in nitrous air, there might be no real
+_calcination_, the phlogiston not being separated, and the proper
+calcination prevented by there being no _fixed_ _air_, which is
+necessary to the formation of the calx, to unite with it.
+
+Nitrous air is procured from all the proper metals by spirit of nitre,
+except lead, and from all the semi-metals that I have tried, except
+zinc. For this purpose I have used bismuth and nickel, with spirit of
+nitre only, and regulus of antimony and platina, with _aqua regia_.
+
+I got little or no air from lead by spirit of nitre, and have not yet
+made any experiments to ascertain the nature of this solution. With zinc
+I have taken a little pains.
+
+Four penny-weights and seventeen grains of zinc dissolved in spirit of
+nitre, to which as much water was added, yielded about twelve ounce
+measures of air, which had, in some degree, the properties of nitrous
+air, making a slight effervescence with common air, and diminishing it
+about as much as nitrous air, which had been itself diminished one half
+by washing in water. The smell of them both was also the same; so that I
+concluded it to be the same thing, that part of the nitrous air, which
+is imbibed by water, being retained in this solution.
+
+In order to discover whether this was the case, I made the solution boil
+in a sand-heat. Some air came from it in this state, which seemed to be
+the same thing, with nitrous air diminished about one sixth, or one
+eighth, by washing in water. When the fluid part was evaporated, there
+remained a brown fixed substance, which was observed by Mr. Hellot, who
+describes it, Ac. Par. 1735, M. p. 35. A part of this I threw into a
+small red-hot crucible; and covering it immediately with a receiver,
+standing in water, I observed that very dense red fumes rose from it,
+and filled the receiver. This redness continued about as long as that
+which is occasioned by a mixture of nitrous and common air; the air was
+also considerably diminished within the receiver. This substance,
+therefore, must certainly have contained within it the very same thing,
+or principle, on which the peculiar properties of nitrous air depend.
+
+It is remarkable, however, that though the air within the receiver was
+diminished about one fifth by this process, it was itself as much
+affected with a mixture of nitrous air, as common air is, and a candle
+burned in it very well. This may perhaps be attributed to some effect of
+the spirit of nitre, in the composition of that brown substance.
+
+Nitrous air, I find, will be considerably diminished in its bulk by
+standing a long time in water, about as much as inflammable air is
+diminished in the same circumstances. For this purpose I kept for some
+months a quart-bottle full of each of these kinds of air; but as
+different quantities of inflammable air vary very much in this respect,
+it is not improbable but that nitrous air may vary also.
+
+From one trial that I made, I conclude that nitrous air may be kept in a
+bladder much better than most other kinds of air. The air to which I
+refer was kept about a fortnight in a bladder, through which the
+peculiar smell of the nitrous air was very sensible for several days. In
+a day or two the bladder became red, and was much contracted in its
+dimensions. The air within it had lost very little of its peculiar
+property of diminishing common air.
+
+I did not endeavour to ascertain the exact quantity of nitrous air
+produced from given quantities, of all the metals which yield it; but
+the few observations which I did make for this purpose I shall recite in
+this place:
+
+     dwt. gr.
+
+     6     0      of silver yielded 17-1/2 ounce measures.
+     5    19      of quicksilver     4-1/2
+     1     2-1/2  of copper         14-1/2
+     2     0      of brass          21
+     0    20      of iron           16
+     1     5      of bismuth         6
+     0    12      of nickel          4
+
+FOOTNOTES:
+
+[6] I have since found, that nitrous air has never failed to escape from
+the water, which has been impregnated with it, by long exposure to the
+open air.
+
+[7] This suspicion has been confirmed by the ingenious Mr. Bewley, of
+Great Massingham in Norfolk, who has discovered that the acid taste of
+this water is not the necessary consequence of its impregnation with
+nitrous air, but is the effect of the _acid vapour_, into which part of
+this air is resolved, when it is decomposed by a mixture with common
+air. This, it will be seen, exactly agrees with my own observation on
+the constitution of nitrous air, in the second part of this work. A more
+particular account of Mr. Bewley's observation will be given in the
+_Appendix_.
+
+
+
+
+SECTION VII.
+
+_Of AIR infected with the FUMES of BURNING CHARCOAL._
+
+
+Air infected with the fumes of burning charcoal is well known to be
+noxious; and the Honourable Mr. Cavendish favoured me with an account of
+some experiments of his, in which a quantity of common air was reduced
+from 180 to 162 ounce measures, by passing through a red-hot iron tube
+filled with the dust of charcoal. This diminution he ascribed to such a
+_destruction_ of common air as Dr. Hales imagined to be the consequence
+of burning. Mr. Cavendish also observed, that there had been a
+generation of fixed air in this process, but that it was absorbed by
+sope leys. This experiment I also repeated, with a small variation of
+circumstances, and with nearly the same result.
+
+Afterwards, I endeavoured to ascertain, by what appears to me to be an
+easier and more certain method, in what manner air is affected with the
+fumes of charcoal, viz. by suspending bits of charcoal within glass
+vessels, filled to a certain height with water, and standing inverted
+in another vessel of water, while I threw the focus of a burning mirror,
+or lens, upon them. In this manner I diminished a given quantity of air
+one fifth, which is nearly in the same proportion with other diminutions
+of air.
+
+If, instead of pure water, I used _lime-water_ in this process, it never
+failed to become turbid by the precipitation of the lime, which could
+only be occasioned by fixed air, either discharged from the charcoal, or
+deposited by the common air. At first I concluded that it came from the
+charcoal; but considering that it is not probable that fixed air,
+confined in any substance, can bear so great a degree of heat as is
+necessary to make charcoal, without being wholly expelled; and that in
+other diminutions of common air, by phlogiston only, there appears to be
+a deposition of fixed air, I have now no doubt but that, in this case
+also, it is supplied from the same source.
+
+This opinion is the more probable, from there being the same
+precipitation of lime, in this process, with whatever degree of heat the
+charcoal had been made. If, however, the charcoal had not been made with
+a very considerable degree of heat, there never failed to be a permanent
+addition of inflammable air produced; which agrees with what I observed
+before, that, in converting dry wood into charcoal, the greatest part
+is changed into inflammable air.
+
+I have sometimes found, that charcoal which was made with the most
+intense heat of a smith's fire, which vitrified part of a common
+crucible in which the charcoal was confined, and which had been
+continued above half an hour, did not diminish the air in which the
+focus of a burning mirror was thrown upon it; a quantity of inflammable
+air equal to the diminution of the common air being generated in the
+process: whereas, at other times, I have not perceived that there was
+any generation of inflammable air, but a simple diminution of common
+air, when the charcoal had been made with a much less degree of heat.
+This subject deserves to be farther investigated.
+
+To make the preceding experiment with still more accuracy, I repeated it
+in quicksilver; when I perceived that there was a small increase of the
+quantity of air, probably from a generation of inflammable air. Thus it
+stood without any alteration a whole night, and part of the following
+day; when lime-water, being admitted to it, it presently became turbid,
+and, after some time, the whole quantity of air, which was about four
+ounce measures, was diminished one fifth, as before. In this case, I
+carefully weighed the piece of charcoal, which was exactly two grains,
+and could not find that it was sensibly diminished in weight by the
+operation.
+
+Air thus diminished by the fumes of burning charcoal not only
+extinguishes flame, but is in the highest degree noxious to animals; it
+makes no effervescence with nitrous air, and is incapable of being
+diminished any farther by the fumes of more charcoal, by a mixture of
+iron filings and brimstone, or by any other cause of the diminution of
+air that I am acquainted with.
+
+This observation, which respects all other kinds of diminished air,
+proves that Dr. Hales was mistaken in his notion of the _absorption_ of
+air in those circumstances in which he observed it. For he supposed that
+the remainder was, in all cases, of the same nature with that which had
+been absorbed, and that the operation of the same cause would not have
+failed to produce a farther diminution; whereas all my observations shew
+that air, which has once been fully diminished by any cause whatever, is
+not only incapable of any farther diminution, either from the same or
+from any other cause, but that it has likewise acquired _new
+properties_, most remarkably different from those which it had before,
+and that they are, in a great measure, the same in all the cases. These
+circumstances give reason to suspect, that the cause of diminution is,
+in reality, the same in all the cases. What this cause is, may, perhaps,
+appear in the next course of observations.
+
+
+
+
+SECTION VIII.
+
+_Of the effect of the CALCINATION of METALS, and of the EFFLUVIA of
+PAINT made with WHITE-LEAD and OIL, on AIR._
+
+
+Having been led to suspect, from the experiments which I had made with
+charcoal, that the diminution of air in that case, and perhaps in other
+cases also, was, in some way or other the consequence of its having more
+than its usual quantity of phlogiston, it occurred to me, that the
+calcination of metals, which are generally supposed to consist of
+nothing but a metallic earth united to phlogiston, would tend to
+ascertain the fact, and be a kind of _experimentum crucis_ in the case.
+
+Accordingly, I suspended pieces of lead and tin in given quantities of
+air, in the same manner as I had before treated the charcoal; and
+throwing the focus of a burning mirror or lens upon them, so as to make
+them fume copiously. I presently perceived a diminution of the air. In
+the first trial that I made, I reduced four ounce measures of air to
+three, which is the greatest diminution of common air that I had ever
+observed before, and which I account for, by supposing that, in other
+cases, there was not only a cause of diminution, but causes of addition
+also, either of fixed or inflammable air, or some other permanently
+elastic matter, but that the effect of the calcination of metals being
+simply the escape of phlogiston, the cause of diminution was alone and
+uncontrouled.
+
+The air, which I had thus diminished by calcination of lead, I
+transferred into another clean phial, but found that the calcination of
+more lead in it (or at least the attempt to make a farther calcination)
+had no farther effect upon it. This air also, like that which had been
+infected with the fumes of charcoal, was in the highest degree noxious,
+made no effervescence with nitrous air, was no farther diminished by the
+mixture of iron filings and brimstone, and was not only rendered
+innoxious, but also recovered, in a great measure, the other properties
+of common air, by washing in water.
+
+It might be suspected that the noxious quality of air in which _lead_
+was calcined, might be owing to some fumes peculiar to that metal; but
+I found no sensible difference between the properties of this air, and
+that in which _tin_ was calcined.
+
+The _water_ over which metals are calcined acquires a yellowish tinge,
+and an exceedingly pungent smell and taste, pretty much (as near as I
+can recollect, for I did not compare them together) like that over which
+brimstone has been frequently burned. Also a thin and whitish pellicle
+covered both the surface of the water, and likewise the sides of the
+phial in which the calcination was made; insomuch that, without
+frequently agitating the water, it grew so opaque by this constantly
+accumulating incrustation, that the sun-beams could not be transmitted
+through it in a quantity sufficient to produce the calcination.
+
+I imagined, however, that, even when this air was transferred into a
+clean phial, the metals were not so easily melted or calcined as they
+were in fresh air; for the air being once fully saturated with
+phlogiston, may not so readily admit any more, though it be only to
+transmit it to the water. I also suspected that metals were not easily
+melted or calcined in inflammable, fixed, or nitrous air, or any kind
+of diminished air.[8] None of these kinds of air suffered any change by
+this operation; nor was there any precipitation of lime, when charcoal
+was heated in any of these kinds of air standing in lime-water. This
+furnishes another, and I think a pretty decisive proof, that, in the
+precipitation of lime by charcoal, the fixed air does not come from the
+charcoal, but from the common air. Otherwise it is hard to assign a
+reason, why the same degree of heat (or at least a much greater) should
+not expel the fixed air from this substance, though surrounded by these
+different kinds of air, and why the fixed air might not be transmitted
+through them to the lime-water.
+
+Query. May not water impregnated with phlogiston from calcined metals,
+or by any other method, be of some use in medicine? The effect of this
+impregnation is exceedingly remarkable; but the principle with which it
+is impregnated is volatile, and intirely escapes in a day or two, if the
+surface of the water be exposed to the common atmosphere.
+
+It should seem that phlogiston is retained more obstinately by charcoal
+than it is by lead or tin; for when any given quantity of air is fully
+saturated with phlogiston from charcoal, no heat that I have yet applied
+has been able to produce any more effect upon it; whereas, in the same
+circumstances, lead and tin may still be calcined, at least be made to
+emit a copious fume, in which some part of the phlogiston may be set
+loose. The air indeed, can take no more; but the water receives it, and
+the sides of the phial also receive an addition of incrustation. This is
+a white powdery substance, and well deserves to be examined. I shall
+endeavour to do it at my leisure.
+
+Lime-water never became turbid by the calcination of metals over it, the
+calx immediately seizing the precipitated fixed air, in preference to
+the lime in the water; but the colour, smell, and taste of the water was
+always changed and the surface of it became covered with a yellow
+pellicle, as before.
+
+When this process was made in quicksilver, the air was diminished only
+one fifth; and upon water being admitted to it, no more was absorbed;
+which is an effect similar to that of a mixture of nitrous and common
+air, which was mentioned before.
+
+The preceding experiments on the calcination of metals suggested to me a
+method of explaining the cause of the mischief which is known to arise
+from fresh _paint_, made with white-lead (which I suppose is an
+imperfect calx of lead) and oil.
+
+To verify my hypothesis, I first put a small pot full of this kind of
+paint, and afterwards (which answered much better, by exposing a greater
+surface of the paint) I daubed several pieces of paper with it, and put
+them under a receiver, and observed, that in about twenty-four hours,
+the air was diminished between one fifth and one fourth, for I did not
+measure it very exactly. This air also was, as I expected to find, in
+the highest degree noxious; it did not effervesce with nitrous air, it
+was no farther diminished by a mixture of iron filings and brimstone,
+and was made wholesome by agitation in water deprived of all air.
+
+I think it appears pretty evident, from the preceding experiments on the
+calcination of metals that air is, some way or other, diminished in
+consequence of being highly charged with phlogiston; and that agitation
+in water restores it, by imbibing a great part of the phlogistic
+matter.
+
+That water has a considerable affinity with phlogiston, is evident from
+the strong impregnation which it receives from it. May not plants also
+restore air diminished by putrefaction by absorbing part of the
+phlogiston with which it is loaded? The greater part of a dry plant, as
+well as of a dry animal substance, consists of inflammable air, or
+something that is capable of being converted into inflammable air; and
+it seems to be as probable that this phlogistic matter may have been
+imbibed by the roots and leaves of plants, and afterwards incorporated
+into their substance, as that it is altogether produced by the power of
+vegetation. May not this phlogistic matter be even the most essential
+part of the food and support of both vegetable and animal bodies?
+
+In the experiments with metals, the diminution of air seems to be the
+consequence of nothing but a saturation with phlogiston; and in all the
+other cases of the diminution of air, I do not see but that it may be
+effected by the same means. When a vegetable or animal substance is
+dissolved by putrefaction, the escape of the phlogistic matter (which,
+together with all its other constituent parts, is then let loose from
+it) may be the circumstance that produces the diminution of the air in
+which it putrefies. It is highly improbable that what remains after an
+animal body has been thoroughly dissolved by putrefaction, should yield
+so great a quantity of inflammable air, as the dried animal substance
+would have done. Of this I have not made an actual trial, though I have
+often thought of doing it, and still intend to do it; but I think there
+can be no doubt of the result.
+
+Again, iron, by its fermentation with brimstone and water, is evidently
+reduced to a calx, so that phlogiston must have escaped from it.
+Phlogiston also must evidently be set loose by the ignition of charcoal,
+and is not improbably the matter which flies off from paint, composed of
+white-lead and oil. Lastly, since spirit of nitre is known to have a
+very remarkable affinity with phlogiston, it is far from being
+improbable that nitrous air may also produce the same effect by the same
+means.
+
+To this hypothesis it may be objected, that, if diminished air be air
+saturated with phlogiston, it ought to be inflammable. But this by no
+means follows; since its inflammability may depend upon some particular
+_mode of combination_, or degree of affinity, with which we are not
+acquainted. Besides, inflammable air seems to consist of some other
+principle, or to have some other constituent part, besides phlogiston
+and common air, as is probable from that remarkable deposit, which, as I
+have observed, is made by inflammable air, both from iron and zinc.
+
+It is not improbable, however, but that a greater degree of heat may
+inflame that air which extinguishes a common candle, if it could be
+conveniently applied. Air that is inflammable, I observe, extinguishes
+red-hot wood; and indeed inflammable substances can only be those which,
+in a certain degree of heat, have a less affinity with the phlogiston
+they contain, than the air, or some other contiguous substance, has with
+it; so that the phlogiston only quits one substance, with which it was
+before combined, and enters another, with which it may be combined in a
+very different manner. This substance, however, whether it be air or any
+thing else, being now fully saturated with phlogiston, and not being
+able to take any more, in the same circumstances, must necessarily
+extinguish fire, and put a stop to the ignition of all other bodies,
+that is, to the farther escape of phlogiston from them.
+
+That plants restore noxious air, by imbibing the phlogiston with which
+it is loaded, is very agreeable to the conjectures of Dr. Franklin,
+made many years ago, and expressed in the following extract from the
+last edition of his Letters, p. 346.
+
+"I have been inclined to think that the fluid _fire_, as well as the
+fluid _air_, is attracted by plants in their growth, and becomes
+consolidated with the other materials of which they are formed, and
+makes a great part of their substance; that, when they come to be
+digested, and to suffer in the vessels a kind of fermentation, part of
+the fire, as well as part of the air, recovers its fluid active state
+again, and diffuses itself in the body, digesting and separating it;
+that the fire so re-produced, by digestion and separation, continually
+leaving the body, its place is supplied by fresh quantities, arising
+from the continual separation; that whatever quickens the motion of the
+fluids in an animal, quickens the separation, and re-produces more of
+the fire, as exercise; that all the fire emitted by wood, and other
+combustibles, when burning, existed in them before in a solid state,
+being only discovered when separating; that some fossils, as sulphur,
+sea-coal, &c. contain a great deal of solid fire; and that, in short,
+what escapes and is dissipated in the burning of bodies, besides water
+and earth, is generally the air and fire, that before made parts of the
+solid."
+
+FOOTNOTES:
+
+[8] I conclude from the experiments of M. Lavoisier, which were made
+with a much better burning lens than I had an opportunity of making use
+of, that there was no _real calcination_ of the metals, though they were
+made to _fume_ in inflammable or nitrous air; because he was not able to
+produce more than a slight degree of calcination in any given quantity
+of common air.
+
+
+
+
+SECTION IX.
+
+_Of MARINE ACID AIR._
+
+
+Being very much struck with the result of an experiment of the Hon. Mr.
+Cavendish, related Phil. Trans. Vol. LVI. p. 157, by which, though, he
+says, he was not able to get any inflammable air from copper, by means
+of spirit of salt, he got a much more remarkable kind of air, viz. one
+that lost its elasticity by coming into contact with water, I was
+exceedingly desirous of making myself acquainted with it. On this
+account, I began with making the experiment in quicksilver, which I
+never failed to do in any case in which I suspected that air might
+either be absorbed by water, or be in any other manner affected by it;
+and by this means I presently got a much more distinct idea of the
+nature and effects of this curious solution.
+
+Having put some copper filings into a small phial, with a quantity of
+spirit of salt; and making the air (which was generated in great plenty,
+on the application of heat) ascend into a tall glass vessel full of
+quicksilver, and standing in quicksilver, the whole produce continued a
+considerable time without any change of dimensions. I then introduced a
+small quantity of water to it; when about three fourths of it (the whole
+being about four ounce measures) presently, but gradually, disappeared,
+the quicksilver rising in the vessel. I then introduced a considerable
+quantity of water; but there was no farther diminution of the air, and
+the remainder I found to be inflammable.
+
+Having frequently continued this process a long time after the admission
+of the water, I was much amused with observing the large bubbles of the
+newly generated air, which came through the quicksilver, the sudden
+diminution of them when they came to the water, and the very small
+bubbles which went through the water. They made, however, a continual,
+though slow, increase of inflammable air.
+
+Fixed air, being admitted to the whole produce of this air from copper,
+had no sensible effect upon it. Upon the admission of water, a great
+part of the mixture presently disappeared; another part, which I suppose
+to have been the fixed air, was absorbed slowly; and in this particular
+case the very small permanent residuum did not take fire; but it is
+very possible that it might have done so, if the quantity had been
+greater.
+
+The solution of _lead_ in the marine acid is attended with the very same
+phænomena as the solution of copper in the same acid; about three
+fourths of the generated air disappearing on the admission of water; and
+the remainder being inflammable.
+
+The solutions of iron, tin, and zinc, in the marine acid, were all
+attended with the same phænomena as the solutions of copper and lead,
+but in a less degree; for in iron one eighth, in tin one sixth, and in
+zinc one tenth of the generated air disappeared on the admission of
+water. The remainder of the air from iron, in this case, burned with a
+green, or very light blue flame.
+
+I had always thought it something extraordinary that a species of air
+should _lose its elasticity_ by the mere _contact_ of any thing, and
+from the first suspected that it must have been _imbibed_ by the water
+that was admitted to it; but so very great a quantity of this air
+disappeared upon the admission of a very small quantity of water, that
+at first I could not help concluding that appearances favoured the
+former hypothesis. I found, however, that when I admitted a much
+smaller quantity of water, confined in a narrow glass tube, a part only
+of the air disappeared, and that very slowly, and that more of it
+vanished upon the admission of more water. This observation put it
+beyond a doubt, that this air was properly _imbibed_ by the water,
+which, being once fully saturated with it, was not capable of receiving
+any more.
+
+The water thus impregnated tasted very acid, even when it was much
+diluted with other water, through which the tube containing it was
+drawn. It even dissolved iron very fast, and generated inflammable air.
+This last observation, together with another which immediately follows,
+led me to the discovery of the true nature of this remarkable kind of
+air.
+
+Happening, at one time, to use a good deal of copper and a small
+quantity of spirit of salt, in the generation of this kind of air, I was
+surprized to find that air was produced long after, I could not but
+think that the acid must have been saturated with the metal; and I also
+found that the proportion of inflammable air to that which was absorbed
+by the water continually diminished, till, instead of being one fourth
+of the whole, as I had first observed, it was not so much as one
+twentieth. Upon this, I concluded that this subtle air did not arise
+from the copper, but from the spirit of salt; and presently making the
+experiment with the acid only, without any copper, or metal of any kind,
+this air was immediately produced in as great plenty as before; so that
+this remarkable kind of air is, in fact, nothing more than the vapour,
+or fumes of spirit of salt, which appear to be of such a nature, that
+they are not liable to be condensed by cold, like the vapour of water,
+and other fluids, and therefore may be very properly called an _acid
+air_, or more restrictively, the _marine acid air_.
+
+This elastic acid vapour, or acid air, extinguishes flame, and is much
+heavier than common air; but how much heavier, will not be easy to
+ascertain. A cylindrical glass vessel, about three fourths of an inch in
+diameter, and four inches deep, being filled with it, and turned upside
+down, a lighted candle may be let down into it more than twenty times
+before it will burn at the bottom. It is pleasing to observe the colour
+of the flame in this experiment; for both before the candle goes out,
+and also when it is first lighted again, it burns with a beautiful
+green, or rather light-blue flame, such as is seen when common salt is
+thrown into the fire.
+
+When this air is all expelled from any quantity of spirit of salt, which
+is easily perceived by the subsequent vapour being condensed by cold,
+the remainder is a very weak acid, barely capable of dissolving iron.
+
+Being now in the possession of a new subject of experiments, viz. an
+elastic acid vapour, in the form of a permanent air, easily procured,
+and effectually confined by glass and quicksilver, with which it did not
+seem to have any affinity; I immediately began to introduce a variety of
+substances to it; in order to ascertain its peculiar properties and
+affinities, and also the properties of those other bodies with respect
+to it.
+
+Beginning with _water_, which, from preceding observations, I knew would
+imbibe it, and become impregnated with it; I found that 2-1/2 grains of
+rain-water absorbed three ounce measures of this air, after which it was
+increased one third in its bulk, and weighed twice as much as before; so
+that this concentrated vapour seems to be twice as heavy as rain-water:
+Water impregnated with it makes the strongest spirit of salt that I have
+seen, dissolving iron with the most rapidity. Consequently, two thirds
+of the best spirit of salt is nothing more than mere phlegm or water.
+
+Iron filings, being admitted to this air, were dissolved by it pretty
+fast, half of the air disappearing, and the other half becoming
+inflammable air, not absorbed by water. Putting chalk to it, fixed air
+was produced.
+
+I had not introduced many substances to this air, before I discovered
+that it had an affinity with _phlogiston_, so that it would deprive
+other substances of it, and form with it such an union as constitutes
+inflammable air; which seems to shew, that inflammable air universally
+consists of the union of some acid vapour with phlogiston.
+
+Inflammable air was produced, when to this acid air I put spirit of
+wine, oil of olives, oil of turpentine, charcoal, phosphorus, bees-wax,
+and even sulphur. This last observation, I own, surprized me; for, the
+marine acid being reckoned the weakest of the three mineral acids, I did
+not think that it had been capable of dislodging the oil of vitriol from
+this substance; but I found that it had the very same effect both upon
+alum and nitre; the vitriolic acid in the former case, and the nitrous
+in the latter, giving place to the stronger vapour of spirit of salt.
+
+The rust of iron, and the precipitate of nitrous air made from copper,
+also imbibed this air very fast, and the little that remained of it was
+inflammable air; which proves, that these calces contain phlogiston. It
+seems also to be pretty evident, from this experiment, that the
+precipitate above mentioned is a real calx of the metal, by the solution
+of which the nitrous air is generated.
+
+As some remarkable circumstances attend the absorption of this acid air,
+by the substances above-mentioned, I shall briefly mention them.
+
+Spirit of wine absorbs this air as readily as water itself, and is
+increased in bulk by that means. Also, when it is saturated, it
+dissolves iron with as much rapidity, and still continues inflammable.
+
+Oil of olives absorbs this air very slowly, and at the same time, it
+turns almost black, and becomes glutinous. It is also less miscible with
+water, and acquires a very disagreeable smell. By continuing upon the
+surface of the water, it became white, and its offensive smell went off
+in a few days.
+
+Oil of turpentine absorbed this air very fast, turning brown, and almost
+black. No inflammable air was formed, till I raised more of the acid
+air than the oil was able to absorb, and let it stand a considerable
+time; and still the air was but weakly inflammable. The same was the
+case with the oil of olives, in the last mentioned experiment; and it
+seems to be probable, that, the longer this acid air had continued in
+contact with the oil, the more phlogiston it would have extracted from
+it. It is not wholly improbable, but that, in the intermediate state,
+before it becomes inflammable air, it may be nearly of the nature of
+common air.
+
+Bees-wax absorbed this air very slowly. About the bigness of a hazel-nut
+of the wax being put to three ounce measures of the acid air, the air
+was diminished one half in two days, and, upon the admission of water,
+half of the remainder also disappeared. This air was strongly
+inflammable.
+
+Charcoal absorbed this air very fast. About one fourth of it was
+rendered immiscible in water, and was but weakly inflammable.
+
+A small bit of _phosphorus_, perhaps about half a grain, smoked, and
+gave light in the acid air, just as it would have done in common air
+confined. It was not sensibly wasted after continuing about twelve
+hours in that state, and the bulk of the air was very little diminished.
+Water being admitted to it absorbed it as before, except about one fifth
+of the whole. It was but weakly inflammable.
+
+Putting several pieces of _sulphur_ to this air, it was absorbed but
+slowly. In about twenty-four hours about one fifth of the quantity had
+disappeared; and water being admitted to the remainder, very little more
+was absorbed. The remainder was inflammable, and burned with a blue
+flame.
+
+Notwithstanding the affinity which this acid air appears to have with
+phlogiston, it is not capable of depriving all bodies of it. I found
+that dry wood, crusts of bread, and raw flesh, very readily imbibed this
+air, but did not part with any of their phlogiston to it. All these
+substances turned very brown, after they had been some time exposed to
+this air, and tasted very strongly of the acid when they were taken out;
+but the flesh, when washed in water, became very white, and the fibres
+easily separated from one another, even more than they would have done
+if it had been boiled or roasted[9].
+
+When I put a piece of _saltpetre_ to this air it was presently
+surrounded with a white fume, which soon filled the whole vessel,
+exactly like the fume which bursts from the bubbles of nitrous air, when
+it is generated by a vigorous fermentation, and such as is seen when
+nitrous air is mixed with this acid air. In about a minute, the whole
+quantity of air was absorbed, except a very little, which might be the
+common air that had lodged upon the surface of the spirit of salt within
+the phial.
+
+A piece of _alum_ exposed to this air turned yellow, absorbed it as fast
+as the saltpetre had done, and was reduced by it to the form of a
+powder. Common salt, as might be expected, had no effect whatever on
+this marine acid air.
+
+I had also imagined, that if air diminished by the processes
+above-mentioned was affected in this manner, in consequence of its being
+saturated with phlogiston, a mixture of this acid air might imbibe that
+phlogiston, and render it wholesome again; but I put about one fourth of
+this air to a quantity of air in which metals had been calcined, without
+making any sensible alteration in it. I do not, however, infer from
+this, that air is not diminished by means of phlogiston, since the
+common air, like some other substances, may hold the phlogiston too
+fast, to be deprived of it by this acid air.
+
+I shall conclude my account of these experiments with observing, that
+the electric spark is visible in acid air, exactly as it is in common
+air; and though I kept making this spark a considerable time in a
+quantity of it, I did not perceive that any sensible alteration was made
+in it. A little inflammable air was produced, but not more than might
+have come from the two iron nails which I made use of in taking the
+sparks.
+
+FOOTNOTES:
+
+[9] It will be seen, in the second part of this work, that, in some of
+these processes, I had afterwards more success.
+
+
+
+
+SECTION X.
+
+MISCELLANEOUS OBSERVATIONS.
+
+
+1. As many of the preceding observations relate to the _vinous_ and
+_putrefactive_ fermentations, I had the curiosity to endeavour to
+ascertain in what manner the air would be affected by the _acetous_
+fermentation. For this purpose I inclosed a phial full of small beer in
+a jar standing in water; and observed that, during the first two or
+three days, there was an increase of the air in the jar, but from that
+time it gradually decreased, till at length there appeared to be a
+diminution of about one tenth of the whole quantity.
+
+During this time the whole surface of it was gradually covered with a
+scum, beautifully corrugated. After this there was an increase of the
+air till there was more than the original quantity; but this must have
+been fixed air, not incorporated with the rest of the mass; for,
+withdrawing the beer, which I found to be sour, after it had stood 18 or
+20 days under the jar, and passing the air several times through cold
+water, the original quantity was diminished about one ninth. In the
+remainder a candle would not burn, and a mouse would have died
+presently.
+
+The smell of this air was exceedingly pungent, but different from that
+of the putrid effluvium. A mouse lived perfectly well in this air, thus
+affected with the acetous fermentation; after it had stood several days
+mixed with four times the quantity of fixed air.
+
+2. All the kinds of factitious air on which I have yet made the
+experiment are highly noxious, except that which is extracted from
+saltpetre, or alum; but in this even a candle burned just as in common
+air[10]. In one quantity which I got from saltpetre a candle not only
+burned, but the flame was increased, and something was heard like a
+hissing, similar to the decrepitation of nitre in an open fire. This
+experiment was made when the air was fresh made, and while it probably
+contained some particles of nitre, which would have been deposited
+afterwards. The air was extracted from these substances by heating them
+in a gun-barrel, which was much corroded and soon spoiled by the
+experiment. What effect this circumstance may have had upon the air I
+have not considered.
+
+November 6, 1772, I had the curiosity to examine the state of a quantity
+of this air which had been extracted from saltpetre above a year, and
+which at first was perfectly wholesome; when, to my very great surprize,
+I found that it was become, in the highest degree, noxious. It made no
+effervescence with nitrous air, and a mouse died the moment it was put
+into it. I had not, however, washed it in rain-water quite ten minutes
+(and perhaps less time would have been sufficient) when I found, upon
+trial, that it was restored to its former perfectly wholesome state. It
+effervesced with nitrous air as much as the best common air ever does;
+and even a candle burned in it very well, which I had never before
+observed of any kind of noxious air meliorated by agitation in water.
+This series of facts, relating to air extracted from nitre, appear to me
+to be very extraordinary and important, and, in able hands, may lead to
+considerable discoveries.
+
+3. There are many substances which impregnate common air in a very
+remarkable manner, but without making it noxious to animals. Among other
+things I tried volatile alkaline salts, and camphor; the latter of which
+I melted with a burning-glass, in air inclosed in a phial. The mouse,
+which was put into this air, sneezed and coughed very much, especially
+after it was taken out; but it presently recovered, and did not appear
+to have been sensibly injured.
+
+4. Having made several experiments with a mixture of iron filings and
+brimstone, kneaded to a paste with water, I had the curiosity to try
+what would be the effect of substituting _brass dust_ in the place of
+the iron filings. The result was, that when this mixture had stood about
+three weeks, in a given quantity of air, it had turned black, but was
+not increased in bulk. The air also was neither sensibly increased nor
+decreased, but the nature of it was changed; for it extinguished flame,
+it would have killed a mouse presently, and was not restored by fixed
+air, which had been mixed with it several days.
+
+5. I have frequently mentioned my having, at one time, exposed equal
+quantities of different kinds of air in jars standing in boiled water.
+_Common air_ in this experiment was diminished four sevenths, and the
+remainder extinguished flame. This experiment demonstrates that water
+does not absorb air equally, but that it decomposes it, taking one part,
+and leaving the rest. To be quite sure of this fact, I agitated a
+quantity of common air in boiled water, and when I had reduced it from
+eleven ounce measures to seven, I found that it extinguished a candle,
+but a mouse lived in it very well. At another time a candle barely went
+out when the air was diminished one third, and at other times I have
+found this effect lake place at other very different degrees of
+diminution.
+
+This difference I attribute to the differences in the state of the water
+with respect to the air contained in it; for sometimes it had stood
+longer than at other times before I made use of it. I also used
+distilled-water, rain-water, and water out of which the air had been
+pumped, promiscuously with rain water. I even doubt, not but that, in a
+certain state of the water, there might be no sensible difference in
+the bulk of the agitated air, and yet at the end of the process it would
+extinguish a candle, air being supplied from the water in the place of
+that part of the common air which had been absorbed.
+
+It is certainly a little extraordinary that the very same process should
+so far mend putrid air, as to reduce it to the standard of air in which
+candles have burned out; and yet that it should so far injure common and
+wholesome air as to reduce it to about the same standard: but so the
+fact certainly is. If air extinguish flame in consequence of its being
+previously saturated with phlogiston, it must, in this case, have been
+transferred from the water to the air, and it is by no means
+inconsistent with this hypothesis to suppose, that, if the air be over
+saturated with phlogiston, the water will imbibe it, till it be reduced
+to the same proportion that agitation in water would have communicated
+to it.
+
+To a quantity of common air, thus diminished by agitation in water, till
+it extinguished a candle, I put a plant, but it did not so far restore
+it as that a candle would burn in it again; which to me appeared not a
+little extraordinary, as it did not seem to be in a worse state than air
+in which candles had burned out, and which had never failed to be
+restored by the same means.
+
+I had no better success with a quantity of permanent air which I had
+collected from my pump-water. Indeed these experiments were begun before
+I was acquainted with that property of nitrous air, which makes it so
+accurate a measure of the goodness of other kinds of air; and it might
+perhaps be rather too late in the year when I made the experiments.
+Having neglected these two jars of air, the plants died and putrefied in
+both of them; and then I found the air in them both to be highly
+noxious, and to make no effervescence with nitrous air.
+
+I found that a pint of my pump-water contained about one fourth of an
+ounce measure of air, one half of which was afterwards absorbed by
+standing in fresh pump-water. A candle would not burn in this air, but a
+mouse lived in it very well. Upon the whole, it seemed to be in about
+the same state as air in which a candle had burned out.
+
+6. I once imagined that, by mere _stagnation_, air might become unfit
+for respiration, or at least the burning of candles; but if this be the
+case, and the change be produced gradually, it must require a long time
+for the purpose. For on the 22d of September 1772, I examined a quantity
+of common air, which had been kept in a phial, without agitation, from
+May 1771, and found it to be in no respect worse than fresh air, even by
+the test of the nitrous air.
+
+7. The crystallization of nitre makes no sensible alteration in the air
+in which the process is made. For this purpose I dissolved as much nitre
+as a quantity of hot water would contain, and let it cool under a
+receiver, standing in water.
+
+8. November 6, 1772, a quantity of inflammable air, which, by long
+keeping, had come to extinguish flame, I observed to smell very much
+like common air in which a mixture of iron filings and brimstone had
+stood. It was not, however, quite so strong, but it was equally noxious.
+
+9. Bismuth and nickel are dissolved in the marine acid with the
+application of a considerable degree of heat; but little or no air is
+got from either of them; but, what I thought a little remarkable, both
+of them smelled very much like Harrowgate water, or liver of sulphur.
+This smell I have met with several times in the course of my
+experiments, and in processes very different from one another.
+
+FOOTNOTES:
+
+[10] Experiments, of which an account will be given in the second part
+of this work, make it probable, that though a candle burned even _more
+than well_ in this air, an animal would not have lived in it. At the
+time of this first publication, however, I had no idea of this being
+possible in nature.
+
+
+
+
+PART II.
+
+_Experiments and Observations made in the Year 1773, and the Beginning
+of 1774._
+
+
+
+
+SECTION I.
+
+_Observations on ALKALINE AIR._
+
+
+After I had made the discovery of the _marine acid air_, which the
+vapour of spirit of salt may properly enough be called, and had made
+those experiments upon it, of which I have given an account in the
+former part of this work, and others which I propose to recite in this
+part; it occurred to me, that, by a process similar to that by which
+this _acid_ air is expelled from the spirit of salt, an _alkaline_ air
+might be expelled from substances containing volatile alkali.
+
+Accordingly I procured some volatile spirit of sal ammoniac, and having
+put it into a thin phial, and heated it with the flame of a candle, I
+presently found that a great quantity of vapour was discharged from it;
+and being received in a vessel of quicksilver, standing in a bason of
+quicksilver, it continued in the form of a transparent and permanent
+air, not at all condensed by cold; so that I had the same opportunity of
+making experiments upon it, as I had before on the acid air, being in
+the same favourable circumstances.
+
+With the same ease I also procured this air from _spirit of hartshorn_,
+and _sal volatile_ either in a fluid or solid form, i. e. from those
+volatile alkaline salts which are produced by the distillation of sal
+ammoniac with fixed alkalis. But in this case I soon found that the
+alkaline air I procured was not pure; for the fixed air, which entered
+into the composition of my materials, was expelled along with it. Also,
+uniting again with the alkaline air, in the glass tube through which
+they were conveyed, they stopped it up, and were often the means of
+bursting my vessels.
+
+While these experiments were new to me, I imagined that I was able to
+procure this air with peculiar advantage and in the greatest abundance,
+either from the salts in a dry state, when they were just covered with
+water, or in a perfectly fluid state; for, upon applying a candle to the
+phials in which they were contained, there was a most astonishing
+production of air; but having examined it, I found it to be chiefly
+fixed air, especially after the first or second produce from the same
+materials; and removing my apparatus to a trough of water and using the
+water instead of quicksilver, I found that it was not presently absorbed
+by it.
+
+This, however, appears to be an easy and elegant method of procuring
+fixed air, from a small quantity of materials, though there must be a
+mixture of alkaline air along with it; as it is by means of its
+combination with this principle only, that it is possible, that so much
+fixed air should be retained in any liquid. Water, at least, we know,
+cannot be made to contain much more than its own bulk of fixed air.
+
+After this disappointment, I confined myself to the use of that volatile
+spirit of sal ammoniac which is procured by a distillation with slaked
+lime, which contains no fixed air; and which seems, in a general state,
+to contain about as much alkaline air, as an equal quantity of spirit of
+salt contains of the acid air.
+
+Wanting, however, to procure this air in greater quantities, and this
+method being rather expensive, it occurred to me, that alkaline air
+might, probably, be procured, with the most ease and convenience, from
+the original materials, mixed in the same proportions that chemists had
+found by experience to answer the best for the production of the
+volatile spirit of sal ammoniac. Accordingly I mixed one fourth of
+pounded sal ammoniac, with three fourths of slaked lime; and filling a
+phial with the mixture, I presently found it completely answered my
+purpose. The heat of a candle expelled from this mixture a prodigious
+quantity of alkaline air; and the same materials (as much as filled an
+ounce phial) would serve me a considerable time, without changing;
+especially when, instead of a glass phial, I made use of a small iron
+tube, which I find much more convenient for the purpose.
+
+As water soon begins to rise in this process, it is necessary, if the
+air is intended to be conveyed perfectly _dry_ into the vessel of
+quicksilver, to have a small vessel in which this water (which is the
+common volatile spirit of sal ammoniac) may be received. This small
+vessel must be interposed between the vessel which contains the
+materials for the generation of the air, and that in which it is to be
+received, as _d_ fig. 8.
+
+This _alkaline_ air being perfectly analogous to the _acid_ air, I was
+naturally led to investigate the properties of it in the same manner,
+and nearly in the same order. From this analogy I concluded, as I
+presently found to be the fact, that this alkaline air would be readily
+imbibed by water, and, by its union with it, would form a volatile
+spirit of sal ammoniac. And as the water, when admitted to the air in
+this manner, confined by quicksilver, has an opportunity of fully
+saturating itself with the alkaline vapour, it is made prodigiously
+stronger than any volatile spirit of sal ammoniac that I have ever seen;
+and I believe stronger than it can be made in the common way.
+
+In order to ascertain what addition, with respect to quantity and
+weight, water would acquire by being saturated with alkaline air, I put
+1-1/4 grains of rain-water into a small glass tube, closed at one end
+with cement, and open at the other, the column of water measuring 7/10
+of an inch; and having introduced it through the quicksilver into a
+vessel containing alkaline air, observed that it absorbed 7/8 of an
+ounce measure of the _air_, and had then gained about half a grain in
+weight, and was increased to 8-1/2 tenths of an inch in length. I did
+not make a second experiment of this kind, and therefore will not answer
+for the exactness of these proportions in future trials. What I did
+sufficiently answered my purpose, in a general view of the subject.
+
+When I had, at one time, saturated a quantity of distilled water with
+alkaline air, so that a good deal of the air remained unabsorbed on the
+surface of the water, I observed that, as I continued to throw up more
+air, a considerable proportion of it was imbibed, but not the whole; and
+when I had let the apparatus stand a day, much more of the air that lay
+on the surface was imbibed. And after the water would imbibe no more of
+the _old_ air, it imbibed _new_. This shews that water requires a
+considerable time to saturate itself with this kind of air, and that
+part of it more readily unites with water than the rest.
+
+The same is also, probably, the case with all the kinds of air with
+which water can be impregnated. Mr. Cavendish made this observation with
+respect to fixed air, and I repeated the whole process above-mentioned
+with acid air, and had precisely the same result. The alkaline water
+which I procured in this experiment was, beyond comparison, stronger to
+the smell, than any spirit of sal ammoniac that I had seen.
+
+This experiment led me to attempt the making of spirit of sal ammoniac
+in a larger quantity, by impregnating distilled water with this alkaline
+air. For this purpose I filled a piece of a gun-barrel with the
+materials above-mentioned, and luted to the open end of it a small glass
+tube, one end of which was bent, and put within the mouth of a glass
+vessel, containing a quantity of distilled water upon quicksilver,
+standing in a bason of quicksilver, as in fig. 7. In these circumstances
+the heat of the fire, applied gradually, expelled the alkaline air,
+which, passing through the tube, and the quicksilver, came at last to
+the water, which, in time, became fully saturated with it.
+
+By this means I got a very strong alkaline liquor, from which I could
+again expel the alkaline air which I had put into it, whenever it
+happened to be more convenient to me to get it in that manner. This
+process may easily be performed in a still larger way; and by this means
+a liquor of the same nature with the volatile spirit of sal ammoniac,
+might be made much stronger, and much cheaper, than it is now made.
+
+Having satisfied myself with respect to the relation that alkaline air
+bears to water, I was impatient to find what would be the consequence
+of mixing this new air with the other kinds with which I was acquainted
+before, and especially with _acid_ air; having a notion that these two
+airs, being of opposite natures, might compose a _neutral air_, and
+perhaps the very same thing with common air. But the moment that these
+two kinds of air came into contact, a beautiful white cloud was formed,
+and presently filled the whole vessel in which they were contained. At
+the same time the quantity of air began to diminish, and, at length,
+when the cloud was subsided, there appeared to be formed a solid _while
+salt_, which was found to be the common _sal ammoniac_, or the marine
+acid united to the volatile alkali.
+
+The first quantity that I produced immediately deliquesced, upon being
+exposed to the common air; but if it was exposed in a very dry and warm
+place, it almost all evaporated, in a white cloud. I have, however,
+since, from the same materials, produced the salt above-mentioned in a
+state not subject to deliquesce or evaporate. This difference, I find,
+is owing to the proportion of the two kinds of air in the compound. It
+is only volatile when there is more than a due proportion of either of
+the constituent parts. In these cases the smell of the salts is
+extremely pungent, but very different from one another; being manifestly
+acid, or alkaline, according to the prevalence of each of these airs
+respectively.
+
+_Nitrous air_ admitted to alkaline air likewise occasioned a whitish
+cloud, and part of the air was absorbed; but it presently grew clear
+again; leaving only a little dimness on the sides of the vessel. This,
+however, might be a kind of salt, formed by the union of the two kinds
+of air. There was no other salt formed that I could perceive. Water
+being admitted to this mixture of nitrous and alkaline air presently
+absorbed the latter, and left the former possessed of its peculiar
+properties.
+
+_Fixed air_ admitted to alkaline air formed oblong and slender crystals,
+which crossed one another, and covered the sides of the vessel in the
+form of net-work. These crystals must be the same thing with the
+volatile alkalis which chemists get in a solid form, by the distillation
+of sal ammoniac with fixed alkaline salts.
+
+_Inflammable air_ admitted to alkaline air exhibited no particular
+appearance. Water, as in the former experiment, absorbed the alkaline
+air, and left the inflammable air as it was before. It was remarkable,
+however, that the water which was admitted to them became whitish, and
+that this white cloud settled, in the form of a white powder, to the
+bottom of the vessel.
+
+Alkaline air mixed with _common air_, and standing together several
+days, first in quicksilver, and then in water (which absorbed the
+alkaline air) it did not appear that there was any change produced in
+the common air: at least it was as much diminished by nitrous air as
+before. The same was the case with a mixture of acid air and common air.
+
+Having mixed air that had been diminished by the fermentation of a
+mixture of iron filings and brimstone with alkaline air, the water
+absorbed the latter, but left the former, with respect to the test of
+nitrous air (and therefore, as I conclude, with respect to all its
+properties) the same that it was before.
+
+_Spirit of wine_ imbibes alkaline air as readily as water, and seems to
+be as inflammable afterwards as before.
+
+Alkaline air contracts no union with _olive oil_. They were in contact
+almost two days, without any diminution of the air. Oil of turpentine,
+and essential oil of mint, absorbed a very small quantity of alkaline
+air, but were not sensibly changed by it.
+
+_Ether_, however, imbibed alkaline air pretty freely; but it was
+afterwards as inflammable as before, and the colour was not changed. It
+also evaporated as before, but I did not attend to this last
+circumstance very accurately.
+
+_Sulphur_, _nitre_, _common salt_, and _flints_, were put to alkaline
+air without imbibing any part of it; but _charcoal_, _spunge_, bits of
+_linen cloth_, and other substances of that nature, seemed to condense
+this air upon their surfaces; for it began to diminish immediately upon
+their being put to it; and when they were taken out the alkaline smell
+they had contracted was so pungent as to be almost intolerable,
+especially that of the spunge. Perhaps it might be of use to recover
+persons from swooning. A bit of spunge, about as big as a hazel nut,
+presently imbibed an ounce measure of alkaline air.
+
+A piece of the inspissated juice of _turnsole_ was made very dry and
+warm, and yet it imbibed a great quantity of the air; by which it
+contracted a most pungent smell, but the colour of it was not changed.
+
+_Alum_ undergoes a very remarkable change by the action of alkaline air.
+The outward shape and size remain the same, but the internal structure
+is quite changed, becoming opaque, beautifully white, and, to
+appearance, in all respects, like alum which had been roasted; and so as
+not to be at all affected by a degree of heat that would have reduced it
+to that state by roasting. This effect is produced slowly; and if a
+piece of alum be taken out of alkaline air before the operation is over,
+the inside will be transparent, and the outside, to an equal thickness,
+will be a white crust.
+
+I imagine that the alkaline vapour seizes upon the water that enters
+into the constitution of crude alum, and which would have been expelled
+by heat. Roasted alum also imbibes alkaline air, and, like the raw alum
+that has been exposed to it, acquires a taste that is peculiarly
+disagreeable.
+
+_Phosphorus_ gave no light in alkaline air, and made no lasting change
+in its dimensions. It varied, indeed, a little, being sometimes
+increased and sometimes diminished, but after a day and a night, it was
+in the same state as at the first. Water absorbed this air just as if
+nothing had been put to it.
+
+Having put some _spirit of salt_ to alkaline air, the air was presently
+absorbed, and a little of the white salt above-mentioned was formed. A
+little remained unabsorbed, and transparent, but upon the admission of
+common air to it, it instantly became white.
+
+_Oil of vitriol_, also formed a white salt with alkaline air, and this
+did not rise in white fumes.
+
+Acid air, as I have observed in my former papers, extinguishes a candle.
+Alkaline air, on the contrary, I was surprized to find, is slightly
+inflammable; which, however, seems to confirm the opinion of chemists,
+that the volatile alkali contains phlogiston.
+
+I dipped a lighted candle into a tall cylindrical vessel, filled with
+alkaline air, when it went out three or four times successively; but at
+each time the flame was considerably enlarged, by the addition of
+another flame, of a pale yellow colour; and at the last time this light
+flame descended from the top of the vessel to the bottom. At another
+time, upon presenting a lighted candle to the mouth of the same vessel,
+filled with the same kind of air, the yellowish flame ascended two
+inches higher than the flame of the candle. The electric spark taken in
+alkaline air is red, as it is in common inflammable air.
+
+Though alkaline air be inflammable, it appeared, by the following
+experiment, to be heavier than the common inflammable air, as well as to
+contract no union with it. Into a vessel containing a quantity of
+inflammable air, I put half as much alkaline air, and then about the
+same quantity of acid air. These immediately formed a white cloud, but
+it did not rise within the space that was occupied by the inflammable
+air; so that this latter had kept its place above the alkaline air, and
+had not mixed with it.
+
+That alkaline air is lighter than acid air is evident from the
+appearances that attend the mixture, which are indeed very beautiful.
+When acid air is introduced into a vessel containing alkaline air, the
+white cloud which they form appears at the bottom only, and ascends
+gradually. But when the alkaline air is put to the acid, the whole
+becomes immediately cloudy, quite to the top of the vessel.
+
+In the last place, I shall observe that alkaline air, as well as acid,
+dissolves _ice_ as fast as a hot fire can do it. This was tried when
+both the kinds of air, and every instrument made use of in the
+experiment, had been exposed to a pretty intense frost several hours. In
+both cases, also, the water into which the ice was melted dissolved more
+ice, to a considerable quantity.
+
+
+
+
+SECTION II.
+
+_Of COMMON AIR diminished and made noxious by various processes._
+
+
+It will have been observed that, in the first publication of my papers,
+I confined myself chiefly to the narration of the new _facts_ which I
+had discovered, barely mentioning any _hypotheses_ that occurred to me,
+and never seeming to lay much stress upon them. The reason why I was so
+much upon my guard in this respect was, left, in consequence of
+attaching myself to any hypothesis too soon, the success of my future
+inquiries might be obstructed. But subsequent experiments having thrown
+great light upon the preceding ones and having confirmed the few
+conjectures I then advanced, I may now venture to speak of my hypotheses
+with a little less diffidence. Still, however, I shall be ready to
+relinquish any notions I may now entertain, if new facts should
+hereafter appear not to favour them.
+
+In a great variety of cases I have observed that there is a remarkable
+_diminution_ of common, or respirable air, in proportion to which it is
+always rendered unfit for respiration, indisposed to effervesce with
+nitrous air, and incapable of farther diminution from any other cause.
+The circumstances which produce this effect I had then observed to be
+the burning of candles, the respiration of animals, the putrefaction of
+vegetables or animal substances, the effervescence of iron filings and
+brimstone, the calcination of metals, the fumes of charcoal, the
+effluvia of paint made of white-lead and oil, and a mixture of nitrous
+air.
+
+All these processes, I observed, agree in this one circumstance, and I
+believe in no other, that the principle which the chemists call
+_phlogiston_ is set loose; and therefore I concluded that the diminution
+of the air was, in some way or other, the consequence of the air
+becoming overcharged with phlogiston,[11] and that water, and growing
+vegetables, tend to restore this air to a state fit for respiration, by
+imbibing the superfluous phlogiston. Several experiments which I have
+since made tend to confirm this supposition.
+
+Common air, I find, is diminished, and rendered noxious, by _liver of
+sulphur_, which the chemists say exhales phlogiston, and nothing else.
+The diminution in this case was one fifth of the whole, and afterwards,
+as in other similar cases, it made no effervescence with nitrous air.
+
+I found also, after Dr. Hales, that air is diminished by _Homberg's
+pyrophorus_.
+
+The same effect is produced by firing _gunpowder_ in air. This I tried
+by firing the gunpowder in a receiver half exhausted, by which the air
+was rather more injured than it would have been by candles burning in
+it.
+
+Air is diminished by a cement made with one half common coarse
+turpentine and half bees-wax. This was the result of a very casual
+observation. Having, in an air-pump of Mr. Smeaton's construction,
+closed that end of the syphon-gage, which is exposed to the outward air,
+with this cement (which I knew would make it perfectly air-light)
+instead of sealing it hermetically; I observed that, in a course of
+time, the quicksilver in that leg kept continually rising, so that the
+measures I marked upon it were of no use to me; and when I opened that
+end of the tube, and closed it again, the same consequence always took
+place. At length, suspecting that this effect must have arisen from the
+bit of _cement_ diminishing the air to which it was exposed, I covered
+all the inside of a glass tube with it, and one end of it being quite
+closed with the cement, I set it perpendicular, with its open end
+immersed in a bason of quicksilver; and was presently satisfied that my
+conjecture was well founded: for, in a few days, the quicksilver rose so
+much within the tube, that the air in the inside appeared to be
+diminished about one sixth.
+
+To change this air I filled the tube with quicksilver, and pouring it
+out again, I replaced the tube in its former situation; when the air was
+diminished again, but not so fast as before. The same lining of cement
+diminished the air a third time. How long it will retain this power I
+cannot tell. This cement had been made several months before I made
+this experiment with it. I must observe, however, that another quantity
+of this kind of cement, made with a finer and more liquid turpentine,
+had not the power of diminishing air, except in a very small proportion.
+Also the common red cement has this property in the same small degree.
+Common air, however, which had been confined in a glass vessel lined
+with this cement about a month, was so far injured that a candle would
+not burn in it. In a longer time it would, I doubt not, have become
+thoroughly noxious.
+
+Iron that has been suffered to rust in nitrous air diminishes common air
+very fast, as I shall have occasion to mention when I give a
+continuation of my experiments on nitrous air.
+
+Lastly, the same effect, I find, is produced by the _electric spark_,
+though I had no expectation of this event when I made the experiment.
+
+This experiment, however, and those which I have made in pursuance of
+it, has fully confirmed another of my conjectures, which relates to the
+_manner_ in which air is diminished by being overcharged with
+phlogiston, viz. the phlogiston having a nearer affinity with some of
+the constituent parts of the air than the fixed air which enters into
+the composition of it, in consequence of which the fixed air is
+precipitated.
+
+This I first imagined from perceiving that lime-water became turbid by
+burning candles over it, p. 44. This was also the case with lime-water
+confined in air in which an animal substance was putrefying, or in which
+an animal died, p. 79. and that in which charcoal was burned, p. 81.
+But, in all these cases, there was a possibility of the fixed air being
+discharged from the candle, the putrefying substance, the lungs of the
+animal, or the charcoal. That there is a precipitation of lime when
+nitrous air is mixed with common air, I had not then observed, but I
+have since found it to be the case.
+
+That there was no precipitation of lime when brimstone was burned, I
+observed, p. 45. might be owing to the fixed air and the lime uniting
+with the vitriolic acid, and making a salt, which was soluble in water;
+which salt I, indeed, discovered by the evaporation of the water.
+
+I also observed, p. 46, 105. that diminished air being rather lighter
+than common air is a circumstance in favour of the fixed, or the
+heavier part of the common air, having been precipitated.
+
+It was upon this idea, together with others similar to it, that I took
+so much pains to mix fixed air with air diminished by respiration or
+putrefaction, in order to make it fit for respiration again; and I
+thought that I had, in general, succeeded to a considerable degree, p.
+99, &c. I will add, also, what I did not mention before, that I once
+endeavoured, but without effect, to preserve mice alive in the same
+unchanged air, by supplying them with fixed air, when the air in which
+they were confined began to be injured by their respiration. Without
+effect, also, I confined for some months, a quantity of quick lime in a
+given quantity of common air, thinking it might extract the fixed air
+from it.
+
+The experiments which I made with electricity were solely intended to
+ascertain what has often been attempted, but, as far as I know, had
+never been fully accomplished, viz. to change the blue colour of
+liquors, tinged with vegetable juices, red.
+
+For this purpose I made use of a glass tube, about one tenth of an inch
+diameter in the inside, as in fig. 16. In one end of this I cemented a
+piece of wire _b_, on which I put a brass ball. The lower part from _a_
+was filled with water tinged blue, or rather purple, with the juice of
+turnsole, or archil. This is easily done by an air-pump, the tube being
+set in a vessel of the tinged water.
+
+Things being thus prepared, I perceived that, after I had taken the
+electric spark, between the wire _b_, and the liquor at _a_, about a
+minute, the upper part of it began to look red, and in about two minutes
+it was very manifestly so; and the red part, which was about a quarter
+of an inch in length, did not readily mix with the rest of the liquor. I
+observed also, that if the tube lay inclined while I took the sparks,
+the redness extended twice as far on the lower side as on the upper.
+
+The most important, though the least expected observation, however, was
+that, in proportion as the liquor became red, it advanced nearer to the
+wire, so that the space of air in which the sparks were taken was
+diminished; and at length I found that the diminution was about one
+fifth of the whole space; after which more electrifying produced no
+sensible effect.
+
+To determine whether the cause of the change of colour was in the _air_,
+or in the _electric matter_, I expanded the air which had been
+diminished in the tube by means of an air-pump, till it expelled all the
+liquor, and admitted fresh blue liquor into its place; but after that,
+electricity produced no sensible effect, either on the air, or on the
+liquor; so that it was evident that the electric matter had decomposed
+the air, and had made it deposite something that was of an acid nature.
+
+In order to determine whether the _wire_ had contributed any thing to
+this effect, I used wires of different metals, iron, copper, brass, and
+silver; but the result was the very same with them all.
+
+It was also the same when, by means of a bent glass tube, I made the
+electric spark without any wire at all, in the following manner. Each
+leg of the tube, fig. 19. stood in a bason of quicksilver; which, by
+means of an air-pump, was made to ascend as high as _a, a_, in each leg,
+while the space between _a_ and _b_ in each contained the blue liquor,
+and the space between _b_ and _b_ contained common air. Things being
+thus disposed, I made the electric spark perform the circuit from one
+leg to the other, passing from the liquor in one leg of the tube to the
+liquor in the other leg, through the space of air. The effect was, that
+the liquor, in both the legs, became red, and the space of air between
+them was contracted, as before.
+
+Air thus diminished by electricity makes no effervescence with, and is
+no farther diminished by a mixture of nitrous air; so that it must have
+been in the highest degree noxious, exactly like air diminished by any
+other process.
+
+In order to determine what the _acid_ was, which was deposited by the
+air, and which changed the colour of the blue liquor, I exposed a small
+quantity of the liquor so changed to the common air, and found that it
+recovered its blue colour, exactly as water, tinged with the same blue,
+and impregnated with fixed air, will do. But the following experiment
+was still more decisive to this purpose. Taking the electric spark upon
+_lime-water_, instead of the blue liquor, the lime was precipitated as
+the air diminished.
+
+From these experiments it pretty clearly follows, that the electric
+matter either is, or contains phlogiston; since it does the very same
+thing that phlogiston does. It is also probable, from these experiments,
+that the sulphureous smell, which is occasioned by electricity, being
+very different from that of fixed air, the phlogiston in the electric
+matter itself may contribute to it.
+
+It was now evident that common air diminished by any one of the
+processes above-mentioned being the same thing, as I have observed, with
+air diminished by any other of them (since it is not liable to be
+farther diminished by any other) the loss which it sustains, in all the
+cases, is, in part, that of the _fixed air_ which entered into its
+constitution. The fixed air thus precipitated from common air by means
+of phlogiston unites with lime, if any lime water be ready to receive
+it, unless there be some other substance at hand, with which it has a
+greater affinity, as the _calces of metals_.
+
+If the whole of the diminution of common air was produced by the
+deposition of fixed air, it would be easy to ascertain the quantity of
+fixed air that is contained in any given quantity of common air. But it
+is evident that the whole of the diminution of common air by phlogiston
+is not owing to the precipitation of fixed air, because a mixture of
+nitrous air will make a great diminution in all kinds of air that are
+fit for respiration, even though they never were common air, and though
+nothing was used in the process for generating them that can be supposed
+to yield fixed air.
+
+Indeed, it appears, from some of the experiments, that the diminution of
+some of these kinds of air by nitrous air is so great, and approaches so
+nearly to the quantity of the diminution of common air by the same
+process, as to shew that, unless they be very differently affected by
+phlogiston, very little is to be allowed to the loss of fixed air in the
+diminution of common air by nitrous air.
+
+The kinds of air on which this experiment was made were inflammable air,
+nitrous air diminished by iron filings and brimstone, and nitrous air
+itself; all of which are produced by the solution of metals in acids;
+and also on common air diminished and made noxious, and therefore
+deprived of its fixed air by phlogistic processes; and they were
+restored to a great degree of purity by agitation in water, out of which
+its own air had been carefully boiled.
+
+To five parts of inflammable air, which had been agitated in water till
+it was diminished about one half (at which time part of it fired with a
+weak explosion) I put one part of nitrous air, which diminished it one
+eighth of the whole. This was done in lime-water, without any
+precipitation of lime. To compare this with common air, I mixed the same
+quantity, viz. five parts of this, and one part of nitrous air: when
+considerable crust of lime was formed upon the surface of the lime
+water, though the diminution was very little more than in the former
+process. It is possible, however, that the common air might have taken
+more nitrous air before it was fully saturated, so as to begin to
+receive an addition to its bulk.
+
+I agitated in water a quantity of nitrous air phlogisticated with iron
+filings and brimstone, and found it to be so far restored, that three
+fourths of an ounce measure of nitrous air being put to two ounce
+measures of it, made no addition to it.
+
+But the most remarkable of these experiments is that which I made with
+_nitrous air_ itself which I had no idea of the possibility of reducing
+to a state fit for respiration by any process whatever, at the time of
+my former publication on this subject. This air, however, itself,
+without any previous phlogistication, is purified by agitation in water
+till it is diminished by fresh nitrous air, and to a very considerable
+degree.
+
+In a pretty long time I agitated nitrous air in water, supplying it from
+time to time with more, as the former quantity diminished, till only one
+eighteenth of the whole quantity remained; in which state it was so
+wholesome, that a mouse lived in two ounce measures of it more than ten
+minutes, without shewing any sign of uneasiness; so that I concluded it
+must have been about as good as air in which candles had burned out.
+After agitating it again in water, I put one part of fresh nitrous air
+to five parts of this air, and it was diminished one ninth part. I then
+agitated it a third time, and putting more nitrous air to it, it was
+diminished again in the same proportion, and so a fourth time; so that,
+by continually repeating the process, it would, I doubt not, have been
+all absorbed. These processes were made in lime-water, without forming
+any incrustation on the surface of it.
+
+Lastly, I took a quantity of common air, which had been diminished and
+made noxious by phlogistic processes; and when it had been agitated in
+water, I found that it was diminished by nitrous air, though not so much
+as it would have been at the first. After cleansing it a second time, it
+was diminished again by the same means; and, after that, a third time;
+and thus there can be no doubt but that, in time, the whole quantity
+would have disappeared. For I have never found that agitation in water,
+deprived of its own air, made any addition to a quantity of noxious air;
+though, _a priori_, it might have been imagined that, as a saturation
+with phlogiston diminishes air, the extraction of phlogiston would
+increase the bulk of it. On the contrary, agitation in water always
+diminished noxious air a little; indeed, if water be deprived of all its
+own air, it is impossible to agitate any kind of air in it without some
+loss. Also, when noxious air has been restored by plants, I never
+perceived that it gained any addition to its bulk by that means. There
+was no incrustation of the lime-water in the above-mentioned experiment.
+
+It is not a little remarkable, that those kinds of air which never had
+been common air, as inflammable air, phlogisticated nitrous air, and
+nitrous air itself, when rendered wholesome by agitation in water,
+should be more diminished by fresh nitrous air, than common air which
+had been made noxious, and restored by the same process; and yet, from
+the few trials that I have made, I could not help concluding that this
+is the case.
+
+In this course of experiments I was very near deceiving myself, in
+consequence of transferring the nitrous air which I made use of in a
+bladder, in the manner described, p. 15. fig. 9. so as to conclude that
+there was a precipitation of lime in all the above-mentioned cases, and
+that even nitrous air itself produced that effect. But after repeated
+trials, I found that there was no precipitation of lime, except, in the
+first diminution of common air, when the nitrous air was transferred in
+a glass vessel.
+
+That the calces of metals contain air, of some kind or other, and that
+this air contributes to the additional weight of the calces, above that
+of the metals from which they are made, had been observed by Dr. Hales;
+and Mr. Hartley had informed me, that when red-lead is boiled in linseed
+oil, there is a prodigious discharge of air before they incorporate. I
+had likewise found, that no weight is either gained or lost by the
+calcination of tin in a close glass vessel; but I purposely deferred
+making any more experiments on the subject, till we should have some
+weather in which I could make use of a large burning lens, which I had
+provided for that and other purposes; but, in the mean time, I was led
+to the discovery in a different manner.
+
+Having, by the last-recited experiments, been led to consider the
+electric matter as phlogiston, or something containing phlogiston, I was
+endeavouring to revivify the calx of lead with it; when I was surprized
+to perceive a considerable generation of air. It occurred to me, that
+possibly this effect might arise from the _heat_ communicated to the
+red-lead by the electric sparks, and therefore I immediately filled a
+small phial with the red-lead, and heating it with a candle, I presently
+expelled from it a quantity of air about four or five times the bulk of
+the lead, the air being received in a vessel of quicksilver. How much
+more air it would have yielded, I did not try.
+
+Along with the air, a small quantity of _water_ was likewise thrown out;
+and it immediately occurred to me, that this water and air together must
+certainly be the cause of the addition of weight in the calx. It still
+remained to examine what kind of air this was; but admitting water to
+it, I found that it was imbibed by it, exactly like _fixed air_, which I
+therefore immediately concluded it must be[12].
+
+After this, I found that Mr. Lavoisier had completely discovered the
+same thing, though his apparatus being more complex, and less accurate
+than mine, he concluded that more of the air discharged from the calces
+of metals was immiscible with water than I found it to be. It appeared
+to me that I had never obtained fixed air more pure.
+
+It being now pretty clearly determined, that common air is made to
+deposit the fixed air which entered into the constitution of it, by
+means of phlogiston, in all the cases of diminished air, it will follow,
+that in the precipitation of lime, by breathing into lime-water the
+fixed air, which incorporates with lime, comes not from the lungs, but
+from the common air, decomposed by the phlogiston exhaled from them, and
+discharged, after having been taken in with the aliment, and having
+performed its function in the animal system.
+
+Thus my conjecture is more confirmed, that the cause of the death of
+animals in confined air is not owing to the want of any _pabulum vitæ_,
+which the air had been supposed to contain, but to the want of a
+discharge of the phlogistic matter, with which the system was loaded;
+the air, when once saturated with it, being no sufficient _menstruum_ to
+take it up.
+
+The instantaneous death of animals put into air so vitiated, I still
+think is owing to some _stimulus_, which, by causing immediate,
+universal and violent convulsions, exhausts the whole of the _vis vitæ_
+at once; because, as I have observed, the manner of their death is the
+very same in all the different kinds of noxious air.
+
+To this section on the subject of diminished, and noxious air, or as it
+might have been called _phlogisticated air_, I shall subjoin a letter
+which I addressed to Sir John Pringle, on the noxious quality of the
+effluvia of putrid marshes, and which was read at a meeting of the Royal
+Society, December 16, 1773.
+
+This letter which is printed in the Philosophical Transactions, Vol. 74,
+p. 90. is immediately followed by another paper, to which I would refer
+my reader. It was written by Dr. Price, who has so greatly distinguished
+himself, and done such eminent service to his country, and to mankind,
+by his calculations relating to the probabilities of human life, and was
+suggested by his hearing this letter read at the Royal Society. It
+contains a confirmation of my observations on the noxious effects of
+stagnant waters by deductions from Mr. Muret's account of the Bills of
+Mortality for a parish situated among marshes, in the district of Vaud,
+belonging to the Canton of Bern in Switzerland.
+
+     To Sir JOHN PRINGLE, Baronet.
+
+     DEAR SIR,
+
+Having pursued my experiments on different kinds of air considerably
+farther, in several respects, than I had done when I presented the last
+account of them to the Royal Society; and being encouraged by the
+favourable notice which the Society has been pleased to take of them, I
+shall continue my communications on this subject; but, without waiting
+for the result of a variety of processes, which I have now going on, or
+of other experiments, which I propose to make, I shall, from time to
+time, communicate such detached articles, as I shall have given the most
+attention to, and with respect to which, I shall have been the most
+successful in my inquiries.
+
+Since the publication of my papers, I have read two treatises, written
+by Dr. Alexander, of Edinburgh, and am exceedingly pleased with the
+spirit of philosophical inquiry, which they discover. They appear to me
+to contain many new, curious, and valuable observations; but one of the
+_conclusions_, which he draws from his experiments, I am satisfied, from
+my own observations, is ill founded, and from the nature of it, must be
+dangerous. I mean his maintaining, that there is nothing to be
+apprehended from the neighbourhood of putrid marshes.
+
+I was particularly surprised, to meet with such an opinion as this, in a
+book inscribed to yourself, who have so clearly explained the great
+mischief of such a situation, in your excellent treatise _on the
+diseases of the army_. On this account, I have thought it not improper,
+to address to you the following observations and experiments, which I
+think clearly demonstrate the fallacy of Dr. Alexander's reasoning,
+indisputably establish your doctrine, and indeed justify the
+apprehensions of all mankind in this case.
+
+I think it probable enough, that putrid matter, as Dr. Alexander has
+endeavoured to prove, will preserve other substances from putrefaction;
+because, being already saturated with the putrid effluvium, it cannot
+readily take any more; but Dr. Alexander was not aware, that air thus
+loaded with putrid effluvium is exceedingly noxious when taken into the
+lungs. I have lately, however, had an opportunity of fully ascertaining
+how very noxious such air is.
+
+Happening to use at Calne, a much larger trough of water, for the
+purpose of my experiments, than I had done at Leeds, and not having
+fresh water so near at hand as I had there, I neglected to change it,
+till it turned black, and became offensive, but by no means to such a
+degree, as to deter me from making use of it. In this state of the
+water, I observed bubbles of air to rise from it, and especially in one
+place, to which some shelves, that I had in it, directed them; and
+having set an inverted glass vessel to catch them, in a few days I
+collected, a considerable quantity of this air, which issued
+spontaneously from the putrid water; and putting nitrous air to it, I
+found that no change of colour or diminution ensued, so that it must
+have been, in the highest degree, noxious. I repeated the same
+experiment several times afterwards, and always with the same result.
+
+After this, I had the curiosity to try how wholesome air would be
+affected by this water; when, to my real surprise, I found, that after
+only one minute's agitation in it, a candle would not burn in it; and,
+after three or four minutes, it was in the same state with the air,
+which had issued spontaneously from the same water.
+
+I also found, that common air, confined in a glass vessel, in _contact_
+only with this water, and without any agitation, would not admit a
+candle to burn in it after two days.
+
+These facts certainly demonstrate, that air which either arises from
+stagnant and putrid water, or which has been for some time in contact
+with it, must be very unfit for respiration; and yet Dr. Alexander's
+opinion is rendered so plausible by his experiments, that it is very
+possible that many persons may be rendered secure, and thoughtless of
+danger, in a situation in which they must necessarily breathe it. On
+this account, I have thought it right to make this communication as
+early as I conveniently could; and as Dr. Alexander appears to be an
+ingenuous and benevolent man, I doubt not but he will thank me for it.
+
+That air issuing from water, or rather from the soft earth, or mud, at
+the bottom of pits containing water, is not always unwholesome, I have
+also had an opportunity of ascertaining. Taking a walk, about two years
+ago, in the neighbourhood of Wakefield, in Yorkshire, I observed bubbles
+of air to arise, in remarkably great plenty, from a small pool of water,
+which, upon inquiry, I was informed had been the place, where some
+persons had been boring the ground, in order to find coal. These
+bubbles of air having excited my curiosity, I presently returned, with a
+bason, and other vessels proper for my purpose, and having stirred the
+mud with a long stick, I soon got about a pint of this air; and,
+examining it, found it to be good, common air; at least a candle burned
+in it very well. I had not then discovered the method of ascertaining
+the goodness of common air, by a mixture of nitrous air. Previous to the
+trial, I had suspected that this air would have been found to be
+inflammable.
+
+I shall conclude this letter with observing, that I have found a
+remarkable difference in different kinds of water, with respect to their
+effect on common air agitated in them, and which I am not yet able to
+account for. If I agitate common air in the water of a deep well, near
+my house in Calne, which is hard, but clear and sweet, a candle will not
+burn in it after three minutes. The same is the case with the
+rain-water, which I get from the roof of my house. But in distilled
+water, or the water of a spring-well near the house, I must agitate the
+air about twenty minutes, before it will be so much injured. It may be
+worth while, to make farther experiments with respect to this property
+of water.
+
+In consequence of using the rain-water, and the well-water above
+mentioned, I was very near concluding, contrary to what I have asserted
+in this treatise, that common air suffers a decomposition by great
+rarefaction. For when I had collected a considerable quantity of air,
+which had been rarefied about four hundred times, by an excellent pump
+made for me by Mr. Smeaton, I always found, that if I filled my
+receivers with the water above mentioned, though I did it so gradually
+as to occasion as little agitation as possible, a candle would not burn
+in the air that remained in them. But when I used distilled water, or
+fresh spring-water, I undeceived myself.
+
+I think myself honoured by the attention, which, from the first, you
+have given to my experiments, and am, with the greatest respect,
+
+     Dear Sir,
+
+       Your most obliged
+
+         Humble Servant,
+
+     London, 7 Dec. 1773.
+
+           J. PRIESTLEY.
+
+
+POSTSCRIPT.
+
+I cannot help expressing my surprize, that so clear and intelligible an
+account, of Mr. SMEATON'S air-pump, should have been before the public
+so long, as ever since the publication of the forty-seventh volume of
+the Philosophical Transactions, printed in 1752, and yet that none of
+our philosophical instrument-makers should use the construction. The
+superiority of this pump, to any that are made upon the common plan, is,
+indeed, prodigious. Few of them will rarefy more than 100 times, and, in
+a general way, not more than 60 or 70 times; whereas this instrument
+must be in a poor state indeed, if it does not rarefy 200 or 300 times;
+and when it is in good order, it will go as far as 1000 times, and
+sometimes even much farther than that; besides, this instrument is
+worked with much more ease, than a common air-pump, and either exhausts
+or condenses at pleasure. In short, to a person engaged in philosophical
+pursuits, this instrument is an invaluable acquisition. I shall have
+occasion to recite some experiments, which I could not have made, and
+which, indeed, I should hardly have dared to attempt, if I had not been
+possessed of such an air-pump as this. It is much to be wished, that
+some person of spirit in the trade would attempt the construction of an
+instrument, which would do great credit to himself, as well as be of
+eminent service to philosophy.
+
+FOOTNOTES:
+
+[11] On this account, if it was thought convenient to introduce a new
+term (or rather make a new application of a term already in use among
+chemists) it might not be amiss to call air that has been diminished,
+and made noxious by any of the processes above mentioned, or others
+similar to them, by the common appellation of _phlogisticated air_; and,
+if it was necessary, the particular process by which it was
+phlogisticated might be added; as common air phlogisticated by charcoal,
+air phlogisticated by the calcination of metals, nitrous air
+phlogisticated with the liver of sulphur, &c.
+
+[12] Here it becomes me to ask pardon of that excellent philosopher
+Father Beccaria of Turin, for conjecturing that the phlogiston, with
+which he revivified metals, did not come from the electric matter
+itself, but from what was discharged from other pieces of metal with
+which he made the experiment. See History of Electricity, p. 277, &c.
+This _revivification of metals_ by electricity completes the proof of
+the electric matter being, or containing phlogiston.
+
+
+
+
+SECTION III.
+
+_Of NITROUS AIR._
+
+
+Since the publication of my former papers I have given more attention to
+the subject of nitrous air than to any other species of air; and having
+been pretty fortunate in my inquiries, I shall be able to lay before my
+reader a more satisfactory account of the curious phenomena occasioned
+by it, and also of its nature and constitution, than I could do before,
+though much still remains to be investigated concerning it, and many new
+objects of inquiry are started.
+
+With a view to discover where the power of nitrous air to diminish
+common air lay, I evaporated to dryness a quantity of the solution of
+copper in diluted spirit of nitre; and having procured from it a
+quantity of a _green precipitate_, I threw the focus of a burning-glass
+upon it, when it was put into a vessel of quicksilver, standing inverted
+in a bason of quicksilver. In this manner I procured air from it, which
+appeared to be, in all respects, nitrous air; so that part of the same
+principle which had escaped during the solution, in the form of _air_,
+had likewise been retained in it, and had not left it in the evaporation
+of the water.
+
+With great difficulty I also procured a small quantity of the same kind
+of air from a solution of _iron_ in spirit of nitre, by the same
+process.
+
+Having, for a different purpose, fired some paper, which had been dipped
+in a solution of copper in diluted spirit of nitre, in nitrous air, I
+found there was a considerable addition to the quantity of it; upon
+which I fired some of the same kind of paper in quicksilver and
+presently observed that air was produced from it in great plenty. This
+air, at the first, seemed to have some singular properties, but
+afterwards I found that it was nothing more than a mixture of nitrous
+air, from the precipitate of the solution, and of inflammable air, from
+the paper; but that the former was predominant.
+
+In the mixture of this kind of air with common air, in a trough of water
+which had been putrid, but which at that time seemed to have recovered
+its former sweetness (for it was not in the least degree offensive to
+the smell) a phenomenon sometimes occurred, which for a long time
+exceedingly delighted and puzzled me; but which was afterwards the means
+of letting me see much farther into the constitution of nitrous air than
+I had been able to see before.
+
+When the diminution of the air was nearly completed, the vessel in which
+the mixture was made began to be filled with the most beautiful _white
+fumes_, exactly resembling the precipitation of some white substance in
+a transparent menstruum, or the falling of very fine snow; except that
+it was much thicker below than above, as indeed is the case in all
+chemical precipitations. This appearance continued two or three minutes.
+
+At other times I went over the same process, as nearly as possible in
+the same manner, but without getting this remarkable appearance, and was
+several times greatly disappointed and chagrined, when I baulked the
+expectations of my friends, to whom I had described, and meant to have
+shewn it. This made me give all the attention I possibly could to this
+experiment, endeavouring to recollect every circumstance, which, though
+unsuspected at the time, might have contributed to produce this new
+appearance; and I took a great deal of pains to procure a quantity of
+this air from the paper above mentioned for the purpose, which, with a
+small burning lens, and an uncertain sun, is not a little troublesome.
+But all that I observed for some time was, that I stood the best chance
+of succeeding when I _warmed_ the vessel in which the mixture was made,
+and _agitated_ the air during the effervescence.
+
+Finding, at length, that, with the same preparation and attentions, I
+got the same appearance from a mixture of nitrous and common air in the
+same trough of water, I concluded that it could not depend upon any
+thing peculiar to the precipitate of the _copper_ contained in the
+_paper_ from which the air was procured, as I had at first imagined, but
+upon what was common to it, and pure nitrous air.
+
+Afterwards, having, (with a view to observe whether any crystals would
+be formed by the union of volatile alkali, and nitrous air, similar to
+those formed by it and fixed air, as described by Mr. Smeth in his
+_Dissertation on fixed Air_) opened the mouth of a phial which was half
+filled with a volatile alkaline liquor, in a jar of nitrous air (in the
+manner described p. 11. fig. 4.) I had an appearance which perfectly
+explained the preceding. All that part of the phial which was above the
+liquor, and which contained common air, was filled with beautiful
+_white clouds_, as if some fine white powder had been instantly thrown
+into it, and some of these clouds rose within the jar of nitrous air.
+This appearance continued about a minute, and then intirely disappeared,
+the air becoming transparent.
+
+Withdrawing the phial, and exposing it to the common air, it there also
+became turbid, and soon after the transparency returned. Introducing it
+again into the nitrous air, the clouds appeared as before. In this
+manner the white fumes, and transparency, succeeded each other
+alternately, as often as I chose to repeat the experiment, and would no
+doubt have continued till the air in the jar had been thoroughly diluted
+with common air. These appearances were the same with any substance that
+contained _volatile alkali_, fluid or solid.
+
+When, instead of the small phial, I used a large and tall glass jar,
+this appearance was truly fine and striking, especially when the water
+in the trough was very transparent. For I had only to put the smallest
+drop of a volatile alkaline liquor, or the smallest bit of the solid
+salt, into the jar, and the moment that the mouth of it was opened in a
+jar of nitrous air, the white clouds above mentioned began to be formed
+at the mouth, and presently descended to the bottom, so as to fill the
+whole, were it ever so large, as with fine snow.
+
+In considering this experiment, I soon perceived that this curious
+appearance must have been occasioned by the mixture of the nitrous and
+common air, and therefore that the white clouds must be _nitrous
+ammoniac_, formed by the acid of the nitrous air, set loose in the
+decomposition of it by common air, while the phlogiston, which must be
+another constituent part of nitrous air, entering the common air, is the
+cause of the diminution it suffers in this process; as it is the cause
+of a similar diminution, in a variety of other processes.
+
+I would observe, that it is not peculiar to nitrous air to be a test of
+the fitness of air for respiration. Any other process by which air is
+diminished and made noxious answers the same purpose. Liver of sulphur
+for instance, the calcination of metals, or a mixture of iron filings
+and brimstone will do just the same thing; but the application of them
+is not so easy, or elegant, and the effect is not so soon perceived. In
+fact, it is _phlogiston_ that is the test. If the air be so loaded with
+this principle that it can take no more, which is seen by its not being
+diminished in any of the processes above mentioned, it is noxious; and
+it is wholesome in proportion to the quantity of phlogiston that it is
+able to take.
+
+This, I have no doubt, is the true theory of the diminution of common
+air by nitrous air, the redness of the appearance being nothing more
+than the usual colour of the fumes, of spirit of nitre, which is now
+disengaged from the superabundant phlogiston with which it was combined
+in the nitrous air, and ready to form another union with any thing that
+is at hand, and capable of it.
+
+With the volatile alkali it forms nitrous ammoniac, water imbibes it
+like any other acid, even quicksilver is corroded by it; but this action
+being slow, the redness in this mixture of nitrous and common air
+continues much longer when the process is made in quicksilver, than when
+it is made in water, and the diminution, as I have also observed; is by
+no means so great.
+
+I was confirmed in this opinion when I put a bit of volatile alkaline
+salt into the jar of quicksilver in which I made the mixture of nitrous
+and common air. In these circumstances, the vessel being previously
+filled with the alkaline fumes, the acid immediately joined them, formed
+the white clouds above mentioned, and the diminution proceeded almost
+as far as when the process was made in water. That it did not proceed
+quite so far, I attribute chiefly to the small quantity of calx formed
+by the slight solution of mercury with the acid fumes not being able to
+absorb all the fixed air that is precipitated from the common air by the
+phlogiston.
+
+In part, also, it may be owing to the small quantify of surface in the
+quicksilver in the vessels that I made use of; in consequence of which
+the acid fumes could act upon it only in a slow succession, so that part
+of them, as well as of the fixed air, had an opportunity of forming
+another union with the diminished air.
+
+This, as I have observed before, was so much the case when the process
+was made in quicksilver, without any volatile alkali, that when water
+was admitted to it, after some time, it was not capable of dissolving
+that union, tho' it would not have taken place if the process had been
+in water from the first.
+
+In diversifying this experiment, I found that it appeared to very great
+advantage when I suspended a piece of volatile salt in the common air,
+previous to the admission of nitrous air to it, inclosing it in a bit
+of gauze, muslin, or a small net of wire. For, presently after the
+redness of the mixture begins to go off, the white cloud, like snow,
+begins to descend from the salt, as if a white powder was shaken out of
+the bag that contains it. This white cloud presently fills the whole
+vessel, and the appearance will last about five minutes.
+
+If the salt be not put to the mixture of these two kinds of air till it
+has perfectly recovered its transparency, the effervescence being
+completely over, no white cloud will be formed; and, what is rather more
+remarkable, there is nothing of this appearance when the salt is put
+into the nitrous air itself. The reason of this must be, that the acid
+of the nitrous air has a nearer affinity with its phlogiston than with
+the volatile alkali; though the phlogiston having a nearer affinity with
+something in the common air, the acid being thereby set loose, will
+unite with the alkaline vapour, if it be at hand to unite with it.
+
+There is also very little, if any white cloud formed upon holding a
+piece of the volatile salt within the mouth of a phial containing
+smoking spirit of nitre. Also when I threw the focus of a burning mirror
+upon some sal ammoniac in nitrous air, and filled the whole vessel with
+white fumes which arose from it, they were soon dispersed, and the air
+was neither diminished nor altered.
+
+I was now fully convinced, that the white cloud which I casually
+observed, in the first of these experiments, was occasioned by the
+volatile alkali emitted from the water, which was in a slight degree
+putrid; and that the warming, and agitation of the vessels, had promoted
+the emission of the putrid, or alkaline effluvium.
+
+I could not perceive that the diminution of common air by the mixture of
+nitrous air was sensibly increased by the presence of the volatile
+alkali. It is possible, however, that, by assisting the water to take up
+the acid, something less of it may be incorporated with the remaining
+diminished air than would otherwise have been; but I did not give much
+attention to this circumstance.
+
+When the phial in which I put the alkaline salts contained any kind of
+noxious air, the opening of it in nitrous air was not followed by any
+thing of the appearance above mentioned. This was the case with
+inflammable air. But when, after agitating the inflammable air in water,
+I had brought it to a state in which it was diminished a little by the
+mixture of nitrous air, the cloudy appearance was in the same
+proportion; so that this appearance seems to be equally a test of the
+fitness of air for respiration, with the redness which attends the
+mixture of it with nitrous air only.
+
+Having generally fastened the small bag which contained the volatile
+salt to a piece of brass wire in the preceding experiment, I commonly
+found the end of it corroded, and covered with a blue substance. Also
+the salt itself, and sometimes the bag was died blue. But finding that
+this was not the case when I used an iron wire in the same
+circumstances, but that it became _red_, I was satisfied that both the
+metals had been dissolved by the volatile alkali. At first I had a
+suspicion that the blue might have come from the copper, out of which
+the nitrous air had been made. But when the nitrous air was made from
+iron, the appearances were, in all respects, the same.
+
+I have observed, in the preceding section, that if nitrous air be mixed
+with common air in _lime-water_, the surface of the water, where it is
+contiguous to that mixture, will be covered with an incrustation of
+lime, shewing that some fixed air had been deposited in the process. It
+is remarkable, however, as I there also just mentioned, that this is
+the case when nitrous air alone is put to a vessel of lime-water, after
+it has been kept in a _bladder_, or only transferred from one vessel to
+another by a bladder, in the manner described, p. 15. fig. 9.
+
+As I had used the same bladder for transferring various kinds of air,
+and among the rest _fixed air_, I first imagined that this effect might
+have been occasioned by a mixture of this fixed air with the nitrous
+air, and therefore took a fresh bladder; but still the effect was the
+same. To satisfy myself farther, that the bladder had produced this
+effect, I put one into a jar of nitrous air, and after it had continued
+there a day and a night, I found that the nitrous air in this jar,
+though it was transferred in a glass vessel, made lime-water turbid.
+
+Whether there was any thing in the preparation of these bladders that
+occasioned their producing this effect, I cannot tell. They were such as
+I procure from the apothecaries. The thing seems to deserve farther
+examination, as there seems, in this case, to be the peculiar effect of
+fixed air from other causes, or else a production of fixed air from
+materials that have not been supposed to yield it, at least not in
+circumstances similar to these.
+
+As fixed air united to water dissolves iron, I had the curiosity to try
+whether fixed air alone would do it; and as nitrous air is of an _acid_
+nature, as well as fixed air, I, at the same time, exposed a large
+surface of iron to both the kinds; first filling two eight ounce phials
+with nails, and then with quicksilver, and after that displacing the
+quicksilver in one of the phials by fixed air, and in the other by
+nitrous air; then inverting them, and leaving them with their mouths
+immersed in basons of quicksilver.
+
+In these circumstances the two phials stood about two months, when no
+sensible change at all was produced in the fixed air, or in the iron
+which had been exposed to it, but a most remarkable, and most unexpected
+change was made in the nitrous air; and in pursuing the experiment, it
+was transformed into a species of air, with properties which, at the
+time of my first publication on this subject, I should not have
+hesitated to pronounce impossible, viz. air in which a candle burns
+quite naturally and freely, and which is yet in the highest degree
+noxious to animals, insomuch that they die the moment they are put into
+it; whereas, in general, animals live with little sensible inconvenience
+in air in which candles have burned out. Such, however, is nitrous air,
+after it has been long exposed to a large surface of iron.
+
+It is not less extraordinary, that a still longer continuance of nitrous
+air in these circumstances (but _how long_ depends upon too many, and
+too minute circumstances to be ascertained with exactness) makes it not
+only to admit a candle to burn in it, but enables it to burn with an
+_enlarged flame_, by another flame (extending every where to an equal
+distance from that of the candle, and often plainly distinguishable from
+it) adhering to it. Sometimes I have perceived the flame of the candle,
+in these circumstances, to be twice as large as it is naturally, and
+sometimes not less than five or six times larger; and yet without any
+thing like an _explosion_, as in the firing of the weakest inflammable
+air.
+
+Nor is the farther progress in the transmutation of nitrous air, in
+these circumstances, less remarkable. For when it has been brought to
+the state last mentioned, the agitation of it in fresh water almost
+instantly takes off that peculiar kind of inflammability, so that it
+extinguishes a candle, retaining its noxious quality. It also retains
+its power of diminishing common air in a very great degree.
+
+But this noxious quality, like the noxious quality of all other kinds of
+air that will bear agitation in water, is taken out of it by this
+operation, continued about five minutes; in which process it suffers a
+farther and very considerable diminution. It is then itself diminished
+by fresh nitrous air, and animals live in it very well, about as well as
+in air in which candles have burned out.
+
+Lastly, One quantity of nitrous air, which had been exposed to iron in
+quicksilver, from December 18 to January 20, and which happened to stand
+in water till January 31 (the iron still continuing in the phial) was
+fired with an explosion, exactly like a weak inflammable air. At the
+same time another quantity of nitrous air, which had likewise been
+exposed to iron, standing in quicksilver, till about the same time, and
+had then stood in water only, without iron, only admitted a candle to
+burn in it with an enlarged flame, as in the cases above mentioned. But
+whether the difference I have mentioned in the circumstances of these
+experiments contributed to this difference in the result, I cannot tell.
+
+Nitrous air treated in the manner above mentioned is diminished about
+one fourth by standing in quicksilver; and water admitted to it will
+absorb about half the remainder; but if water only, and no quicksilver,
+be used from the beginning, the nitrous air will be diminished much
+faster and farther; so that not more than one fourth, one sixth, or one
+tenth of the original quantity will remain. But I do not know that there
+is any difference in the constitution of the air which remains in these
+two cases.
+
+The water which has imbibed this nitrous air exposed to iron is
+remarkably green, also the phial containing it becomes deeply, and, I
+believe, indelibly tinged with green; and if the water be put into
+another vessel, it presently deposits a considerable quantity of matter,
+which when dry appears to be the earth or ochre of iron; from which it
+is evident, that the acid of the nitrous air dissolves the iron; while
+the phlogiston, being set loose, diminishes nitrous air, as in the
+process of the iron filings and brimstone.
+
+Upon this hint, instead of using _iron_, I introduced a pot of _liver of
+sulphur_ into a jar of nitrous air, and presently found, that what I had
+before done by means of iron in six weeks, or two months, I could do by
+liver of sulphur (in consequence, no doubt, of its giving its phlogiston
+more freely) in less than twenty-four hours, especially when the process
+was kept warm.
+
+It is remarkable, however, that if the process with liver of sulphur be
+suffered to proceed, the nitrous air will be diminished much farther.
+At one time not more than one twentieth of the original quantity
+remained, and how much farther it right have been diminished, I cannot
+tell. In this great diminution, it does not admit a candle to burn in it
+at all; and I generally found this to be the case whenever the
+diminution had proceeded beyond three fourths of the original
+quantity[13].
+
+It is something remarkable, that though the diminution of nitrous air by
+iron filings and brimstone very much resembles the diminution of it by
+iron only, or by liver of sulphur, yet the iron filings and brimstone
+never bring it to such a state as that a candle will burn in it; and
+also that, after this process, it is never capable of diminishing common
+air. But when it is considered that these properties are destroyed by
+agitation in water, this difference in the result of processes, in other
+respects similar, will appear less extraordinary; and they agree in
+this, that long agitation in water makes both these kinds of nitrous air
+equally fit for respiration, being equally diminished by fresh nitrous
+air. It is possible that there would have been a more exact agreement
+in the result of these processes, if they had been made in equal degrees
+of _heat_; but the process with iron was made in the usual temperature
+of the atmosphere, and that with liver of sulphur generally near a fire.
+
+It may clearly, I think, be inferred from these experiments, that all
+the difference between fresh nitrous air, that state of it in which it
+is partially inflammable, or wholly so, that in which it again
+extinguishes candles, and that in which it finally becomes fit for
+respiration, depends upon some difference in the _mode of the
+combination_ of its acid with phlogiston, or on the _proportion_ between
+these two ingredients in its composition; and it is not improbable but
+that, by a little more attention to these experiments, the whole mystery
+of this proportion and combination may be explained.
+
+I must not omit to observe that there was something peculiar in the
+result of the first experiment which I made with nitrous air exposed to
+iron; which was that, without any agitation in water, it was diminished
+by fresh nitrous air, and that a candle burned in it quite naturally. To
+what this difference was owing I cannot tell. This air, indeed, had been
+exposed to the iron a week or two longer than in any of the other
+cases, but I do not imagine that this circumstance could have produced
+that difference.
+
+When the process is in water with iron, the time in which the diminution
+is accomplished is exceedingly various; being sometimes completed in a
+few days, whereas at other times it has required a week or a fortnight.
+Some kinds of iron also produced this effect much sooner than others,
+but on what circumstances this difference depends I do not know. What
+are the varieties in the result of this experiment when it is made in
+quicksilver I cannot tell, because, on account of its requiring more
+time, I have not repeated it so often; but I once found that nitrous air
+was not sensibly changed by having been exposed to iron in quicksilver
+nine days; whereas in water a very considerable alteration was always
+made in much less than half that time.
+
+It may just deserve to be mentioned, that nitrous air extremely rarified
+in an air-pump dissolves iron, and is diminished by it as much as when
+it is in its native state of condensation.
+
+It is something remarkable, though I never attended to it particularly
+before I made these last experiments, and it may tend to throw some
+light upon them, that when a candle is extinguished, as it never fails
+to be, in nitrous air, the flame seems to be a little enlarged at its
+edges, by another bluish flame added to it, just before its extinction.
+
+It is proper to observe in this place, that the electric spark taken in
+nitrous air diminishes it to one fourth of its original quantity, which
+is about the quantity of its diminution by iron filings and brimstone,
+and also by liver of sulphur without heat. The air is also brought by
+electricity to the same state as it is by iron filings and brimstone,
+not diminishing common air. If the electric spark be taken in it when it
+is confined by water tinged with archil, it is presently changed from
+blue to red, and that to a very great degree.
+
+When the iron nails or wires, which I have used to diminish nitrous air,
+had done their office, I laid them aside, not suspecting that they could
+be of any other philosophical use; but after having lain exposed to the
+open air almost a fortnight; having, for some other purpose, put some of
+them into a vessel containing common air, standing inverted, and
+immersed in water, I was surprized to observe that the air in which they
+were confined was diminished. The diminution proceeded so fast, that
+the process was completed in about twenty-four hours; for in that time
+the air was diminished about one fifth, so that it made no effervescence
+with nitrous air, and was, therefore, no doubt, highly noxious, like air
+diminished by any other process.
+
+This experiment I have repeated a great number of times, with the same
+phials, filled with nails or wires that have been suffered to rust in
+nitrous air, but their power of diminishing common air grows less and
+less continually. How long it will be before it is quite exhausted I
+cannot tell. This diminution of air I conclude must arise from the
+phlogiston, either of the nitrous air or the iron, being some way
+entangled in the rust, in which the wires were encrusted, and afterwards
+getting loose from it.
+
+To the experiments upon iron filings and brimstone in nitrous air, I
+must add, that when a pot full of this mixture had absorbed as much as
+it could of a jar of nitrous air (which is about three fourths of the
+whole) I put fresh nitrous air to it, and it continued to absorb, till
+three or four jars full of it disappeared; but the absorption was
+exceedingly slow at the last. Also when I drew this pot through the
+water, and admitted fresh nitrous air to it, it absorbed another jar
+full, and then ceased. But when I scraped off the outer surface of this
+mixture, which had been so long exposed to the nitrous air, the
+remainder absorbed more of the air.
+
+When I took the top of the mixture which I had scraped off and threw
+upon it the focus of a burning-glass, the air in which it was confined
+was diminished, and became quite noxious; yet when I endeavoured to get
+air from this matter in a jar full of quicksilver, I was able to procure
+little or nothing.
+
+It is not a little remarkable that nitrous air diminished by iron
+filings and brimstone, which is about one fourth, cannot, by agitation
+in water, be diminished much farther; whereas pure nitrous air may, by
+the same process, be diminished to one twentieth of its whole bulk, and
+perhaps much more. This is similar to the effect of the same mixture,
+and of phlogiston in other cases, on fixed air; for it so far changes
+its constitution, that it is afterwards incapable of mixing with water.
+It is similar also to the effect of phlogiston in acid air, which of
+itself is almost instantly absorbed by water; but by this addition it is
+first converted into inflammable air, which does not readily mix with
+water, and which, by long agitation in water, becomes of another
+constitution, still less miscible with water.
+
+I shall close this section with a few other observations of a
+miscellaneous nature.
+
+Nitrous air is as much diminished both by iron filings, and also by
+liver of sulphur, when confined in quicksilver, as when it is exposed to
+water.
+
+Distilled water tinged blue with the juice of turnsole becomes red on
+being impregnated with nitrous air; but by being exposed a week or a
+fortnight to the common atmosphere, in open and shallow vessels, it
+recovers its blue colour; though, in that time, the greater part of the
+water will be evaporated. This shews that in time nitrous air escapes
+from the water with which it is combined, just as fixed air does, though
+by no means so readily[14].
+
+Having dissolved silver, copper, and iron in equal quantities of spirit
+of nitre diluted with water, the quantities of nitrous air produced from
+them were in the following proportion; from iron 8, from copper 6-1/4,
+from silver 6. In about the same proportion also it was necessary to
+mix water with the spirit of nitre in each case, in order to make it
+dissolve these metals with equal rapidity, silver requiring the least
+water, and iron the most.
+
+Phosphorus gave no light in nitrous air, and did not take away from its
+power of diminishing common air; only when the redness of the mixture
+went off, the vessel in which it was made was filled with white fumes,
+as if there had been some volatile alkali in it. The phosphorus itself
+was unchanged.
+
+There is something remarkable in the effect of nitrous air on _insects_
+that are put into it. I observed before that this kind of air is as
+noxious as any whatever, a mouse dying the moment it is put into it; but
+frogs and snails (and therefore, probably, other animals whose
+respiration is not frequent) will bear being exposed to it a
+considerable time, though they die at length. A frog put into nitrous
+air struggled much for two or three minutes, and moved now and then for
+a quarter of an hour, after which it was taken out, but did not recover.
+_Wasps_ always died the moment they were put into the nitrous air. I
+could never observe that they made the least motion in it, nor could
+they be recovered to life afterwards. This was also the case in general
+with _spiders_, _flies_, and _butterflies_. Sometimes, however, spiders
+would recover after being exposed about a minute to this kind of air.
+
+Considering how fatal nitrous air is to insects, and likewise its great
+antiseptic power, I conceived that considerable use might be made of it
+in medicine, especially in the form of _clysters_, in which fixed air
+had been applied with some success; and in order to try whether the
+bowels of an animal would bear the injection of it, I contrived, with
+the help of Mr. Hey, to convey a quantity of it up the anus of a dog.
+But he gave manifest signs of uneasiness, as long as he retained it,
+which was a considerable time, though in a few hours afterwards he was
+as lively as ever, and seemed to have suffered nothing from the
+operation.
+
+Perhaps if nitrous air was diluted either with common air, or fixed air,
+the bowels might bear it better, and still it might be destructive to
+_worms_ of all kinds, and be of use to check or correct putrefaction in
+the intestinal canal, or other parts of the system. I repeat it once
+more that, being no physician, I run no risk by such proposals as these;
+and I cannot help flattering myself that, in time, very great medicinal
+use will be made of the application of these different kinds of air to
+the animal system. Let ingenious physicians attend to this subject, and
+endeavour to lay hold of the new _handle_ which is now presented them,
+before it be seized by rash empiricks; who, by an indiscriminate and
+injudicious application, often ruin the credit of things and processes
+which might otherwise make an useful addition to the _materia_ and _ars
+medica_.
+
+In the first publication of my papers, having experienced the remarkable
+antiseptic power of nitrous air, I proposed an attempt to preserve
+anatomical preparations, &c. by means of it; but Mr. Hey, who made the
+trial, found that, after some months, various animal substances were
+shriveled, and did not preserve their natural forms in this kind of
+air.
+
+FOOTNOTES:
+
+[13] The result of several of these experiments I had the pleasure of
+trying in the presence of the celebrated Mr. De Luc of Geneva, when he
+was upon a visit to Lord Shelburne in Wiltshire.
+
+[14] I have not repeated this experiment with that variation of
+circumstances which an attention to Mr. Bewley's observation will
+suggest.
+
+
+
+
+SECTION IV.
+
+_Of MARINE ACID AIR._
+
+
+In my former experiments on this species of air I procured it from
+spirit of salt, but I have since hit upon a much less expensive method
+of getting it, by having recourse to the process by which the spirit of
+salt is itself originally made. For this purpose I fill a small phial
+with common salt, pour upon it a small quantity of concentrated oil of
+vitriol, and receive the fumes emitted by it in a vessel previously
+filled with quicksilver, and standing in a bason of quicksilver, in
+which it appears in the form of a perfectly _transparent air_, being
+precisely the same thing with that which I had before expelled from the
+spirit of salt.
+
+This method of procuring acid air is the more convenient, as a phial,
+once prepared in this manner, will suffice, for common experiments, many
+weeks; especially if a little more oil of vitriol be occasionally put to
+it. It only requires a little more heat at the last than at the first.
+Indeed, at the first, the heat of a person's hand will often be
+sufficient to make it throw out the vapour. In warm weather it will
+even keep smoking many days without the application of any other heat.
+
+On this account, it should be placed where there are no instruments, or
+any thing of metal, that can be corroded by this acid vapour. It is from
+dear-bought experience that I give this advice. It may easily be
+perceived when this phial is throwing out this acid vapour, as it always
+appears, in the open air, in the form of a light cloud; owing, I
+suppose, to the acid attracting to itself, and uniting with, the
+moisture that is in the common atmosphere.
+
+By this process I even made a stronger spirit of salt than can be
+procured in any other way. For having a little water in the vessel which
+contains the quicksilver, it imbibes the acid vapour, and at length
+becomes truly saturated with it. Having, in this manner, impregnated
+pure water with acid air, I could afterwards expel the same air from it,
+as from common spirit of salt.
+
+I observed before that this acid vapour, or air, has a strong affinity
+with _phlogiston_, so that it decomposes many substances which contain
+it, and with them forms a permanently inflammable air, no more liable to
+be imbibed by water than inflammable air procured by any other process,
+being in fact the very same thing; and that, in some cases, it even
+dislodges spirit of nitre and oil of vitriol, which in general appear to
+be stronger acids than itself. I have since observed that, by giving it
+more time, it will extract phlogiston from substances from which I at
+first concluded that it was not able to do it, as from dry wood, crusts
+of bread not burnt, dry flesh, and what is more extraordinary from
+flints. As there was something peculiar to itself in the process or
+result of each of these experiments, it may not be improper to mention
+them distinctly.
+
+Pieces of dry _cork wood_ being put to the acid air, a small quantity
+remained not imbibed by water, and was inflammable.
+
+Very dry pieces of _oak_, being exposed to this air a day and a night,
+after imbibing a considerable quantity of it, produced air which was
+inflammable indeed, but in the slightest degree imaginable. It seemed to
+be very nearly in the state of common air.
+
+A piece of _ivory_ imbibed the acid vapour very slowly. In a day and a
+night, however, about half an ounce measure of permanent air was
+produced, and it was pretty strongly inflammable. The ivory was not
+discoloured, but was rendered superficially soft, and clammy, tasting
+very acid.
+
+Pieces of _beef_, roasted, and made quite dry, but not burnt, absorbed
+the acid vapour slowly; and when it had continued in this situation all
+night, from five ounce measures of the air, half a measure was
+permanent, and pretty strongly inflammable. This experiment succeeded a
+second time exactly in the same manner; but when I used pieces of white
+dry _chicken-flesh_ though I allowed the same time, and in other
+respects the process seemed to go on in the same manner, I could not
+perceive that any part of the remaining air was inflammable.
+
+Some pieces of a whitish kind of _flint_, being put into a quantity of
+acid air, imbibed but a very little of it in a day and a night; but of
+2-1/2 ounce measures of it, about half a measure remained unabsorbed by
+water, and this was strongly inflammable, taking fire just like an equal
+mixture of inflammable and common air. At another time, however, I could
+not procure any inflammable air by this means, but to what circumstance
+these different results were owing I cannot tell.
+
+That inflammable air is produced from _charcoal_ in acid air I observed
+before. I have since found that it may likewise be procured from _pit
+coal_, without being charred.
+
+Inflammable air I had also observed to arise from the exposure of spirit
+of wine, and various _oily_ substances, to the vapour of spirit of salt.
+I have since made others of a similar nature, and as peculiar
+circumstances attended some of these experiments, I shall recite them
+more at large.
+
+_Essential oil of mint_ absorbed this air pretty fast, and presently
+became of a deep brown colour. When it was taken out of this air it was
+of the consistence of treacle, and sunk in water, smelling differently
+from what it did before; but still the smell of the mint was
+predominant. Very little or none of the air was fixed, so as to become
+inflammable; but more time would probably have produced this effect.
+
+_Oil of turpentine_ was also much thickened, and became of a deep brown
+colour, by being saturated with acid air.
+
+_Ether_ absorbed acid air very fast, and became first of a turbid white,
+and then of a yellow and brown colour. In one night a considerable
+quantity of permanent air was produced, and it was strongly inflammable.
+
+Having, at one time, fully saturated a quantity of ether with acid air,
+I admitted bubbles of common air to it, through the quicksilver, by
+which it was confined, and observed that white fumes were made in it, at
+the entrance of every bubble, for a considerable time.
+
+At another time, having fully saturated a small quantity of ether with
+acid air, and having left the phial in which it was contained nearly
+full of the air, and inverted, it was by some accident overturned; when,
+instantly, the whole room was filled with a visible fume, like a white
+cloud, which had very much the smell of ether, but peculiarly offensive.
+Opening the door and window of the room, this light cloud filled a long
+passage, and another room. In the mean time the ether was seemingly all
+vanished, but some time after the surface of the quicksilver in which
+the experiment had been made was covered with a liquor that tasted very
+acid; arising, probably, from the moisture in the atmosphere attracted
+by the acid vapour with which the ether had been impregnated.
+
+This visible cloud I attribute to the union of the moisture in the
+atmosphere with the compound of the acid air and ether. I have since
+saturated other quantities of ether with acid air, and found it to be
+exceedingly volatile, and inflammable. Its exhalation was also visible,
+but not in so great a degree as in the case above mentioned.
+
+_Camphor_ was presently reduced into a fluid state by imbibing acid air,
+but there seemed to be something of a whitish sediment in it. After
+continuing two days in this situation I admitted water to it;
+immediately upon which the camphor resumed its former solid state, and,
+to appearance, was the very same substance that it had been before; but
+the taste of it was acid, and a very small part of the air was
+permanent, and slightly inflammable.
+
+The acid air seemed to make no impression upon a piece of Derbyshire
+_spar_, of a very dark colour, and which, therefore, seemed to contain a
+good deal of phlogiston.
+
+As the acid air has so near an affinity with phlogiston, I expected that
+the fumes of _liver of sulphur_, which chemists agree to be phlogistic,
+would have united with it, so as to form inflammable air; but I was
+disappointed in that expectation. This substance imbibed half of the
+acid air to which it was introduced: one fourth of the remainder, after
+standing one day in quicksilver, was imbibed by water, and what was left
+extinguished a candle. This experiment, however, seems to prove that
+acid air and phlogiston may form a permanent kind of air that is not
+inflammable. Perhaps it may be air in such a state as common air loaded
+with phlogiston, and from which the fixed air has been precipitated. Or
+rather, it may be the same thing with inflammable air, that has lost its
+inflammability by long standing in water. It well deserves a farther
+examination.
+
+The following experiments are those in which the _stronger acids_ were
+made use of, and therefore they may assist us farther to ascertain their
+affinities with certain substances, with respect to this marine acid in
+the form of air.
+
+I put a quantity of strong concentrated _oil of vitriol_ to acid air,
+but it was not at all affected by it in a day and a night. In order to
+try whether it would not have more power in a more condensed state, I
+compressed it with an additional atmosphere; but upon taking off this
+pressure, the air expanded again, and appeared to be not at all
+diminished. I also put a quantity of strong _spirit of nitre_ to it
+without any sensible effect. We may conclude, therefore, that the
+marine acid, in this form of air, is not able to dislodge the other
+acids from their union with water.
+
+_Blue vitriol_, which is formed by the union of the vitriolic acid with
+copper, turned to a dark green the moment that it was put to the acid
+air, which it absorbed, though slowly. Two pieces, as big as small nuts,
+absorbed three ounce measures of the air in about half an hour. The
+green colour was very superficial; for it was easily wiped or washed
+off.
+
+_Green copperas_ turned to a deeper green upon being put into acid air,
+which it absorbed slowly. _White copperas_ absorbed this air very fast,
+and was dissolved in it.
+
+_Sal ammoniac_, being the union of spirit of salt with volatile alkali,
+was no more affected with the acid air than, as I have observed before,
+common salt was.
+
+I also introduced to the acid air various other substances, without any
+particular expectation; and it may be worth while to give an account of
+the results, that the reader may draw from them such conclusions as he
+shall think reasonable.
+
+_Borax_ absorbed acid air about as fast as blue vitriol, but without any
+thing else that was observable.
+
+Fine white _sugar_ absorbed this air slowly, was thoroughly penetrated
+with it, became of a deep brown colour, and acquired a smell that was
+peculiarly pungent.
+
+A piece of _quick lime_ being put to about twelve or fourteen ounce
+measures of acid air, and continuing in that situation about two days,
+there remained one ounce measure of air that was not absorbed by water,
+and it was very strongly inflammable, as much so as a mixture of half
+inflammable and half common air. Very particular care was taken that no
+common air mixed with the acid air in this process. At another time,
+from about half the quantity of acid air above mentioned, with much less
+quick-lime, and in the space of one day, I got half an ounce measure of
+air that was inflammable in a slight degree only. This experiment proves
+that some part of the phlogiston which escapes from the fuel, in contact
+with which the lime is burned, adheres to it. But I am very far from
+thinking that the causticity of quick-lime is at all owing to this
+circumstance.
+
+I have made a few more experiments on the mixture of acid air with
+_other kinds of air_, and think that it may be worth while to mention
+them, though nothing of consequence, at least nothing but negative
+conclusions, can be drawn from them.
+
+A quantity of common air saturated with nitrous air was put to a
+quantity of acid air, and they continued together all night, without any
+sensible effect. The quantity of both remained the same, and water being
+admitted to them, it absorbed all the acid air, and left the other just
+as before.
+
+A mixture of two thirds of air diminished by iron filings and brimstone,
+and one third acid air, were mixed together, and left to stand four
+weeks in quicksilver. But when the mixture was examined, water presently
+imbibed all the acid air, and the diminished air was found to be just
+the same that it was before. I had imagined that the acid air might have
+united with the phlogiston with which the diminished air was
+overcharged, so as to render it wholsome; and I had read an account of
+the stench arising from putrid bodies being corrected by acid fumes.
+
+The remaining experiments, in which the acid air was principally
+concerned, are of a miscellaneous nature.
+
+I put a piece of dry _ice_ to a quantity of acid air (as was observed in
+the section concerning _alkaline_ air) taking it with a forceps, which,
+as well as the air itself, and the quicksilver by which it had been
+confined; had been exposed to the open air for an hour, in a pretty
+strong frost. The moment it touched the air it was dissolved as fast as
+it would have been by being thrown into a hot fire, and the air was
+presently imbibed. Putting fresh pieces of ice to that which was
+dissolved before, they were also dissolved immediately, and the water
+thus procured did not freeze again, though it was exposed a whole night,
+in a very intense frost.
+
+Flies and spiders die in acid air, but not so quickly as in nitrous air.
+This surprized me very much; as I had imagined that nothing could be
+more speedily fatal to all animal life than this pure acid vapour.
+
+As inflammable air, I have observed, fires at one explosion in the
+vapour of smoking spirit of nitre, just like an equal mixture of
+inflammable and common air, I thought it was possible that the fume
+which naturally rises from common spirit of salt might have the same
+effect, but it had not. For this purpose I treated the spirit of salt,
+as I had before done the smoking spirit of nitre; first filling a phial
+with it, then inverting it in a vessel containing a quantity of the same
+acid; and having thrown the inflammable air into it, and thereby driven
+out all the acid, turning it with its mouth upwards, and immediately
+applying a candle to it.
+
+Acid air not being so manageable as most of the other kinds of air, I
+had recourse to the following peculiar method, in order to ascertain its
+_specific gravity_. Having filled an eight ounce phial with this air,
+and corked it up, I weighed it very accurately; and then, taking out the
+cork, I blew very strongly into it with a pair of bellows, that the
+common air might take place of the acid; and after this I weighed it
+again, together with the cork, but I could not perceive the least
+difference in the weight. I conclude, however, from this experiment,
+that the acid air is heavier than the common air, because the mouth of
+the phial and the inside of it were evidently moistened by the water
+which the acid vapour had attracted from the air, which moisture must
+have added to the weight of the phial.
+
+
+
+
+SECTION V.
+
+_Of INFLAMMABLE AIR._
+
+
+It will have appeared from my former experiments, that inflammable air
+consists chiefly, if not wholly, of the union of an acid vapour with
+phlogiston; that as much of the phlogiston as contributes to make air
+inflammable is imbibed by the water in which it is agitated; that in
+this process it soon becomes fit for respiration, and by the continuance
+of it comes at length to extinguish flame. These observations, and
+others which I have made upon this kind of air, have been confirmed by
+my later experiments, especially those in which I have connected
+_electrical experiments_ with those on air.
+
+The electric spark taken in any kind of _oil_ produces inflammable air,
+as I was led to observe in the following manner. Having found, as will
+be mentioned hereafter, that ether doubles the quantity of any kind of
+air to which it is admitted; and being at that time engaged in a course
+of experiments to ascertain the effect of the electric matter on all the
+different kinds of air, I had the curiosity to try what it would do with
+_common air_, thus increased by means of ether. The very first spark, I
+observed, increased the quantity of this air very considerably, so that
+I had very soon six or eight times as much as I began with; and whereas
+water imbibes all the ether that is put to any kind of air, and leaves
+it without any visible change, with respect to quantity or quality, this
+air, on the contrary, was not imbibed by water. It was also very little
+diminished by the mixture of nitrous air. From whence it was evident,
+that it had received an addition of some other kind of air, of which it
+now principally consisted.
+
+In order to determine whether this effect was produced by the _wire_, or
+the _cement_ by which the air was confined (as I thought it possible
+that phlogiston might be discharged from them) I made the experiment in
+a glass syphon, fig. 19, and by that means I contrived to make the
+electric spark pass from quicksilver through the air on which I made the
+experiment, and the effect was the same as before. At one time there
+happened to be a bubble of common air, without any ether, in one part of
+the syphon, and another bubble with ether in another part of it; and it
+was very amusing to observe how the same electric sparks diminished the
+former of these bubbles, and increased the latter.
+
+It being evident that the _ether_ occasioned the difference that was
+observable in these two cases, I next proceeded to take the electric
+spark in a quantity of ether only, without any air whatever; and
+observed that every spark produced a small bubble; and though, while the
+sparks were taken in the ether itself, the generation of air was slow,
+yet when so much air was collected, that the sparks were obliged to pass
+through it, in order, to come to the ether and the quicksilver on which
+it rested, the increase was exceedingly rapid; so that, making the
+experiment in small tubes, as fig. 16, the quicksilver soon receded
+beyond the striking distance. This air, by passing through water, was
+diminished to about one third, and was inflammable.
+
+One quantity of air produced in this manner from ether I suffered to
+stand two days in water, and after that I transferred it several times
+through the water, from one vessel to another, and still found that it
+was very strongly inflammable; so that I have no doubt of its being
+genuine inflammable air, like that which is produced from metals by
+acids, or by any other chemical process.
+
+Air produced from ether, mixed both with common and nitrous air, was
+likewise inflammable; but in the case of the nitrous air, the original
+quantity bore a very small proportion to the quantity generated.
+
+Concluding that the inflammable matter in this air came from the ether,
+as being of the class of _oils_, I tried other kinds of oil, as _oil of
+olives_, _oil of turpentine_, and _essential oil of mint_, taking the
+electric spark in them, without any air to begin with, and found that
+inflammable air was produced in this manner from them all. The
+generation of air from oil of turpentine was the quickest, and from the
+oil of olives the slowest in these three cases.
+
+By the same process I got inflammable air from _spirit of wine_, and
+about as copiously as from the essential oil of mint. This air continued
+in water a whole night, and when it was transferred into another vessel
+was strongly inflammable.
+
+In all these cases the inflammable matter might be supposed to arise
+from the inflammable substances on which the experiments were made. But
+finding that, by the same process I could get inflammable air from the
+_volatile spirit of sal ammoniac_, I conclude that the phlogiston was in
+part supplied by the electric matter itself. For though, as I have
+observed before, the alkaline air which is expelled from the spirit of
+sal ammoniac be inflammable, it is so in a very slight degree, and can
+only be perceived to be so when there is a considerable quantity of it.
+
+Endeavouring to procure air from a caustic alkaline liquor, accurately
+made for me by Mr. Lane, and also from spirit of salt, I found that the
+electric spark could not be made visible in either of them; so that they
+must be much more perfect conductors of electricity than water, or other
+fluid substances. This experiment well deserves to be prosecuted.
+
+I observed before that inflammable air, by standing long in water, and
+especially by agitation in water, loses its inflammability; and that in
+the latter case, after passing through a state in which it makes some
+approach to common air (just admitting a candle to burn in it) it comes
+to extinguish a candle. I have since made another observation of this
+kind, which well deserves to be recited. It relates to the inflammable
+air generated from oak the 27th of July 1771, of which I have made
+mention before.
+
+This air I have observed to have been but weakly inflammable some months
+after it was generated, and to have been converted into pretty good or
+wholesome air by no great degree of agitation in water; but on the 27th
+of March 1773, I found the remainder of it to be exceedingly good air. A
+candle burned in it perfectly well, and it was diminished by nitrous air
+almost as much as common air.
+
+I shall conclude this section with a few miscellaneous observations of
+no great importance.
+
+Inflammable air is not changed by being made to pass many times through
+a red-hot iron tube. It is also no more diminished or changed by the
+fumes of liver of sulphur, or by the electric spark, than I have before
+observed it to have been by a mixture of iron filings and brimstone.
+When the electric spark was taken in it, it was confined by a quantity
+of water tinged blue with the juice of archil, but the colour remained
+unchanged.
+
+I put two _wasps_ into inflammable air, and let them remain there a
+considerable time, one of them near an hour. They presently ceased to
+move, and seemed to be quite dead for about half an hour after they were
+taken into the open air; but then they came to life again, and presently
+after seemed to be as well as ever they had been.
+
+
+
+
+SECTION VI.
+
+_Of FIXED AIR._
+
+
+The additions I have made to my observations on _fixed air_ are neither
+numerous nor considerable.
+
+The most important of them is a confirmation of my conjecture, that
+fixed air is capable of forming an union with phlogiston, and thereby
+becoming a kind of air that is not miscible with water. I had produced
+this effect before by means of iron filings and brimstone, fermenting in
+this kind of air; but I have since had a much more decisive and elegant
+proof of it by _electricity_. For after taking a small electric
+explosion, for about an hour, in the space of an inch of fixed air,
+confined in a glass tube one tenth of an inch in diameter, fig. 16, I
+found that when water was admitted to it, only one fourth of the air was
+imbibed. Probably the whole of it would have been rendered immiscible in
+water, if the electrical operation had been continued a sufficient time.
+This air continued several days in water, and was even agitated in water
+without any farther diminution. It was not, however, common air, for it
+was not diminished by nitrous air.
+
+By means of iron filings and brimstone I have, since my former
+experiments, procured a considerable quantity of this kind of air in a
+method something different from that which I used before. For having
+placed a pot of this mixture under a receiver, and exhausted it with a
+pump of Mr. Smeaton's construction, I filled it with fixed air, and then
+left it plunged under water; so that no common air could have access to
+it. In this manner, and in about a week, there was, as near as I can
+recollect, one sixth, or at least one eighth of the whole converted into
+a permanent air, not imbibed by water.
+
+From this experiment I expected that the same effect would have been
+produced on fixed air by the fumes of _liver of sulphur_; but I was
+disappointed in that expectation, which surprised me not a little;
+though this corresponds in some measure, to the effect of phlogiston
+exhaled from this substance on acid air. Perhaps more time may be
+requisite for this purpose, for this process was not continued more than
+a day and a night.
+
+Iron filings and brimstone, I have observed, ferment with great heat in
+nitrous air, and I have since observed that this process is attended
+with greater heat in fixed air than in common air.
+
+Though fixed air incorporated with water dissolves iron, fixed air
+without water has no such power, as I observed before. I imagined that,
+if it could have dissolved iron, the phlogiston would have united with
+the air, and have made it immiscible with water, as in the former
+instances; but after being confined in a phial full of nails from the
+15th of December to the 4th of October following, neither the iron nor
+the air appeared to have been affected by their mutual contact.
+
+Having exposed equal quantities of common and fixed air, in equal and
+similar cylindrical glass vessels, to equal degrees of heat, by placing
+them before a fire, and frequently changing their situations, I observed
+that they were expanded exactly alike, and when removed from the fire
+they both recovered their former dimensions.
+
+Having had some small suspicion that liver of sulphur, besides emitting
+phlogiston, might also yield some fixed air (which is known to be
+contained in the salt of tartar from which it is made) I mixed the two
+ingredients, viz. salt of tartar and brimstone, and putting them into a
+thin phial, and applying the flame of a candle to it, so as to form the
+liver of sulphur, I received the air that came from it in this process
+in a vessel of quicksilver. In this manner I procured a very
+considerable quantity of fixed air, so that I judged it was all
+discharged from the tartar. But though it is possible that a small
+quantity of it may remain in liver of sulphur, when it is made in the
+most perfect manner, it is not probable that it can be expelled without
+heat.
+
+
+
+
+SECTION VII.
+
+MISCELLANEOUS EXPERIMENTS.
+
+
+1. It is something extraordinary that, though ether, as I found, cannot
+be made to assume the form of air (the vapour arising from it by heat,
+being soon condensed by cold, even in quicksilver) yet that a very small
+quantity of ether put to any kind of air, except the acid, and alkaline,
+which it imbibes, almost instantly doubles the apparent quantity of it;
+but upon passing this air through water, it is presently reduced to its
+original quantity again, with little or no change of quality.
+
+I put about the quantity of half a nut-shell full of ether, inclosed in
+a glass tube, through a body of quicksilver, into an ounce measure of
+common air, confined by quicksilver; upon which it presently began to
+expand, till it occupied the space of two ounce measures. It then
+gradually contracted about one sixth of an ounce measure. Putting more
+ether to it, it again expanded to two ounce measures; but no more
+addition of ether would make it expand any farther. Withdrawing the
+quicksilver, and admitting water to this air, without any agitation, it
+began to be absorbed; but only about half an ounce measure had
+disappeared after it had stood an hour in the water. But by once passing
+it through water the air was reduced to its original dimensions. Being
+tried by a mixture of nitrous air, it appeared not to be so good as
+fresh air, though the injury it had received was not considerable.
+
+All the phenomena of dilatation and contraction were nearly the same,
+when, instead of common air, I used nitrous air, fixed air, inflammable
+air, or any species of phlogisticated common air. The quantity of each
+of these kinds of air was nearly doubled while they were kept in
+quicksilver, but fixed air was not so much increased as the rest, and
+phlogisticated air less; but after passing through the water, they
+appeared not to have been sensibly changed by the process.
+
+2. Spirit of wine yields no air by means of heat, the vapours being soon
+condensed by cold, like the vapour of water; yet when, in endeavouring
+to procure air from it, I made it boil, and catched the air which had
+rested on the surface of the spirit, and which had been expelled by the
+heat together with the vapour, in a vessel of quicksilver, and
+afterwards admitted acid air to it, the vessel was filled with white
+fumes, as if there had been a mixture of alkaline air along with it. To
+what this appearance was owing I cannot tell, and indeed I did not
+examine into it.
+
+3. Having been informed by Dr. Small and Mr. Bolton of Birmingham, that
+paper dipped in a solution of copper in spirit of nitre would take fire
+with a moderate heat (a fact which I afterwards found mentioned in the
+Philosophical Transactions) it occurred to me that this would be very
+convenient for experiments relating to _ignition_ in different kinds of
+air; and indeed I found that it was easily fired, either by a burning
+lens, or the approach of red-hot iron on the outside of the phial in
+which it was contained, and that any part of it being once fired, the
+whole was presently reduced to ashes; provided it was previously made
+thoroughly dry, which, however, it is not very easy to do.
+
+With this preparation, I found that this paper burned freely in all
+kinds of air, but not in _vacuo_, which is also the case with gunpowder;
+and, as I have in effect observed before, all the kinds of air in which
+this paper was burned received an addition to their bulk, which
+consisted partly of nitrous air, from the nitrous precipitate, and
+partly of inflammable air, from the paper. As some of the circumstances
+attending the ignition of this paper in some of the kinds of air were a
+little remarkable, I shall just recite them.
+
+Firing this paper in _inflammable_ air, which it did without any
+ignition of the inflammable air itself, the quantity increased
+regularly, till the phial in which the process was made was nearly full;
+but then it began to decrease, till one third of the whole quantity
+disappeared.
+
+A piece of this paper being put to three ounce measures of _acid_ air, a
+great part of it presently turned yellow, and the air was reduced to one
+third of the original quantity, at the same time becoming reddish,
+exactly like common air in a phial containing smoking spirit of nitre.
+After this, by the approach of hot iron, I set fire to the paper;
+immediately upon which there was a production of air which more than
+filled the phial. This air appeared, upon examination, to be very little
+different from pure nitrous air. I repeated this experiment with the
+same event.
+
+Paper dipped in a solution of mercury, zinc, or iron, in nitrous acid,
+has, in a small degree, the same property with paper dipped in a
+solution of copper in the same acid.
+
+4. Gunpowder is also fired in all kinds of air, and, in the quantity in
+which I tried it, did not make any sensible change in them, except that
+the common air in which it was fired would not afterwards admit a candle
+to burn in it. In order to try this experiment I half exhausted a
+receiver, and then with a burning-glass fired the gunpowder which had
+been previously put into it. By this means I could fire a greater
+quantity of gunpowder in a small quantity of air, and avoid the hazard
+of blowing up, and breaking my receiver.
+
+I own that I was rather afraid of firing gunpowder in inflammable air,
+but there was no reason for my fear; for it exploded quite freely in
+this air, leaving it, in all respects, just as it was before.
+
+In order to make this experiment, and indeed almost all the experiments
+of firing gunpowder in different kinds of air, I placed the powder upon
+a convenient stand within my receiver, and having carefully exhausted it
+by a pump of Mr. Smeaton's construction, I filled the receiver with any
+kind of air by the apparatus described, p. 19, fig. 14, taking the
+greatest care that the tubes, &c. which conveyed the air should contain
+little or no common air. In the experiment with inflammable air a
+considerable mixture of common air would have been exceedingly
+hazardous: for, by that assistance, the inflammable air might have
+exploded in such a manner, as to have been dangerous to the operator.
+Indeed, I believe I should not have ventured to have made the experiment
+at all with any other pump besides Mr. Smeaton's.
+
+Sometimes, I filled a glass vessel with quicksilver, and introduced the
+air to it, when it was inverted in a bason of quicksilver. By this means
+I intirely avoided any mixture of common air; but then it was not easy
+to convey the gunpowder into it, in the exact quantity that was
+requisite for my purpose. This, however, was the only method by which I
+could contrive to fire gunpowder in acid or alkaline air, in which it
+exploded just as it did in nitrous or fixed air.
+
+I burned a considerable quantity of gunpowder in an exhausted receiver
+(for it is well known that it will not explode in it) but the air I got
+from it was very inconsiderable, and in these circumstances was
+necessarily mixed with common air. A candle would not burn in it.
+
+
+
+
+SECTION VIII.
+
+_QUERIES, SPECULATIONS, and HINTS._
+
+
+I begin to be apprehensive lest, after being considered as a _dry
+experimenter_, I should pass, with many of my readers, into the opposite
+character of a _visionary theorist_. A good deal of theory has been
+interspersed in the course of this work, but, not content with this, I
+am now entering upon a long section, which contains nothing else.
+
+The conjectures that I have ventured to advance in the body of the work
+will, I hope, be found to be pretty well supported by facts; but the
+present section will, I acknowledge, contain many _random thoughts_. I
+have, however, thrown them together by themselves, that readers of less
+imagination, and who care not to advance beyond the regions of plain
+fact, may, if they please, proceed no farther, that their delicacy be
+not offended.
+
+In extenuation of my offence, let it, however, be considered, that
+_theory_ and _experiment_ necessarily go hand in hand, every process
+being intended to ascertain some particular _hypothesis_, which, in
+fact, is only a conjecture concerning the circumstances or the cause of
+some natural operation; consequently that the boldest and most original
+experimenters are those, who, giving free scope to their imaginations,
+admit the combination of the most distant ideas; and that though many of
+these associations of ideas, will be wild and chimerical, yet that
+others will have the chance of giving rise to the greatest and most
+capital discoveries; such as very cautious, timid, sober, and
+slow-thinking people would never have come at.
+
+Sir Isaac Newton himself, notwithstanding the great advantage which he
+derived from a habit of _patient thinking_, indulged bold and excentric
+thoughts, of which his Queries at the end of his book of Optics are a
+sufficient evidence. And a quick conception of distant analogies, which
+is the great key to unlock the secret of nature, is by no means
+incompatible with the spirit of _perseverance_, in investigations
+calculated to ascertain and pursue those analogies.
+
+
+§ 1. _Speculations concerning the CONSTITUENT PRINCIPLES of the
+different kinds of AIR, and the CONSTITUTION and ORIGIN of the
+ATMOSPHERE, &c._
+
+All the kinds of air that appear to me to be essentially distinct from
+each other are _fixed air_, _acid_ and _alkaline_; for these, and
+another principle, called _phlogiston_, which I have not been able to
+exhibit in the form of _air_, and which has never yet been exhibited by
+itself in _any form_, seem to constitute all the kinds of air that I am
+acquainted with.
+
+Acid air and phlogiston constitute an air which either extinguishes
+flame, or is itself inflammable, according, probably, to the quantity of
+phlogiston combined in it, or the mode of combination. When it
+extinguishes flame, it is probably so much charged with the phlogistic
+matter, as to take no more from a burning candle, which must, therefore,
+necessarily go out in it. When it is inflammable, it is probably so much
+charged with phlogiston, that the heat communicated by a burning candle
+makes it immediately separate itself from the other principle with which
+it was united, in which separation _heat_ is produced, as in other cases
+of ignition; the action and reaction, which necessarily attends the
+separation of the constituent principles, exciting probably a vibratory
+motion in them.
+
+Since inflammable, air, by agitation in water, first comes to lose its
+inflammability, so as to be fit for respiration, and even to admit a
+candle to burn in it, and then comes to extinguish a candle; it seems
+probable that water imbibes a great part of this extraordinary charge of
+phlogiston. And that water _can_ be impregnated with phlogiston, is
+evident from many of my experiments, especially those in which metals
+were calcined over it.
+
+Water having this affinity with phlogiston, it is probable that it
+always contains a considerable portion of it; which phlogiston having a
+stronger affinity with the acid air, which is perhaps the basis of
+common air, may by long agitation be communicated to it, so as to leave
+it over saturated, in consequence of which it will extinguish a candle.
+
+It is possible, however, that inflammable air and air which extinguishes
+a candle may differ from one another in the _mode_ of the combination of
+these two constituent principles, as well as in the proportional
+quantity of each; and by agitation in water, or long standing, that mode
+of combination may change. This we know to be the case with other
+substances, as with _milk_, from which, by standing only, _cream_ is
+separated; which by agitation becomes _butter_. Also many substances,
+being at rest, putrefy, and thereby become quite different from what
+they were before. If this be the case with inflammable air, the water
+may imbibe either of the constituent parts, whenever any proportion of
+it is spontaneously separated from the rest; and should this ever be
+that phlogiston, with which air is but slightly overcharged, as by the
+burning of a candle, it will be recovered to a state in which a candle
+may burn in it again.
+
+It will be observed, however, that it was only in one instance that I
+found that strong inflammable air, in its transition to a state in which
+it extinguishes a candle, would admit a candle to burn in it, and that
+was very faintly; that then the air was far from being pure, as appeared
+by the test of nitrous air; and that it was only from a particular
+quantity of inflammable air which I got from oak, and which had stood a
+long time in water, that I ever got air which was as pure as common air.
+Indeed, it is much more easy to account for the passing of inflammable
+air into a state in which it extinguishes candles, without any
+intermediate state, in which it will admit a candle to burn in it, than
+otherwise. This subject requires and deserves farther investigation. It
+will also be well worth while to examine what difference the agitation
+of air in natural or artificial _sea-water_ will occasion.
+
+Since acid air and phlogiston make inflammable air, and since
+inflammable air is convertible into air fit for respiration, it seems
+not to be improbable, that these two ingredients are the only essential
+principles of common air. For this change is produced by agitation in
+water only, without the addition of any fixed air, though this kind of
+air, like various other things of a foreign nature, may be combined with
+it.
+
+Considering also what prodigious quantities of inflammable air are
+produced by the burning of small pieces of wood or pit-coal, it may not
+be improbable but that the _volcanos_, with which there are evident
+traces of almost the whole surface of the earth having been overspread,
+may have been the origin of our atmosphere, as well as (according to the
+opinion of some) of all the solid land.
+
+The superfluous phlogiston of the air, in the state in which it issues
+from volcanos, may have been imbibed by the waters of the sea, which it
+is probable originally covered the surface of the earth, though part of
+it might have united with the acid vapour exhaled from the sea, and by
+this union have made a considerable and valuable addition to the common
+mass of air; and the remainder of this over-charge of phlogiston may
+have been imbibed by plants as soon as the earth was furnished with
+them.
+
+That an acid vapour is really exhaled from the sea, by the heat of the
+sun, seems to be evident from the remarkably different states of the
+atmosphere, in this respect, in hot and cold climates. In Hudson's bay,
+and also in Russia, it is said, that metals hardly ever rust, whereas
+they are remarkably liable to rust in Barbadoes, and other islands
+between the tropics. See Ellis's Voyage, p. 288. This is also the case
+in places abounding with salt-springs, as Nantwich in Cheshire.
+
+That mild air should consist of parts of so very different a nature as
+an acid vapour and phlogiston, one of which is so exceedingly corrosive,
+will not appear surprising to a chemist, who considers the very strong
+affinity which these two principles are known to have with each other,
+and the exceedingly different properties which substances composed by
+them possess. This is exemplified in common _sulphur_, which is as mild
+as air, and may be taken into the stomach with the utmost safety, though
+nothing can be more destructive than one of its constituent parts,
+separately taken, viz. oil of vitriol. Common air, therefore,
+notwithstanding its mildness, may be composed of similar principles, and
+be a real _sulphur_.
+
+That the fixed air which makes part of the atmosphere is not presently
+imbibed by the waters of the sea, on which it rests, may be owing to the
+union which this kind of air also appears to be capable of forming with
+phlogiston. For fixed air is evidently of the nature of an acid; and it
+appears, in fact, to be capable of being combined with phlogiston, and
+thereby of constituting a species of air not liable to be imbibed by
+water. Phlogiston, however, having a stronger affinity with acid air,
+which I suppose to be the basis of common air, it is not surprising
+that, uniting with this, in preference to the fixed air, the latter
+should be precipitated, whenever a quantity of common air is made
+noxious by an over-charge of phlogiston.
+
+The fixed air with which our atmosphere abounds may also be supplied by
+volcanos, from the vast masses of calcareous matter lodged in the earth,
+together with inflammable air. Also a part of it may be supplied from
+the fermentation of vegetables upon the surface of it. At present, as
+fast as it is precipitated and imbibed by one process, it may be set
+loose by others.
+
+Whether there be, upon, the whole, an increase or a decrease of the
+general mass of the atmosphere is not easy to conjecture, but I should
+imagine that it rather increases. It is true that many processes
+contribute to a great visible diminution of common air, and that when by
+other processes it is restored to its former wholesomeness, it is not
+increased in its dimensions; but volcanos and fires still supply vast
+quantities of air, though in a state not yet fit for respiration; and it
+will have been seen in my experiments, that vegetable and animal
+substances, dissolved by putrefaction, not only emit phlogiston, but
+likewise yield a considerable quantity of permanent elastic air,
+overloaded indeed with phlogiston, as might be expected, but capable of
+being purified by those processes in nature by which other noxious air
+is purified.
+
+That particles are continually detaching themselves from the surfaces of
+all solid bodies, even the metallic ones, and that these particles
+constitute the most permanent part of the atmosphere, as Sir Isaac
+Newton supposed, does not appear to me to be at all probable.
+
+My readers will have observed, that not only is common air liable to be
+diminished by a mixture of nitrous air, but likewise air originally
+produced from inflammable air, and even from nitrous air itself, which
+never contained any fixed air. From this it may be inferred, that the
+whole of the diminution of common air by phlogiston is not owing to the
+precipitation of fixed air, but from a real contraction of its
+dimensions, in consequence of its union with phlogiston. Perhaps an
+accurate attention to the specific gravity of air procured from these
+different materials, and in these different states, may determine this
+matter, and assist us in investigating the nature of phlogiston.
+
+In what _manner_ air is diminished by phlogiston, independent of the
+precipitation of any of its constituent parts, is not easy to conceive;
+unless air thus diminished be heavier than air not diminished, which I
+did not find to be the case. It deserves, however, to be tried with more
+attention. That phlogiston should communicate absolute _levity_ to the
+bodies with which it is combined, is a supposition that I am not willing
+to have recourse to, though it would afford an easy solution of this
+difficulty.
+
+I have likewise observed, that a mouse will live almost as long in
+inflammable air, when it has been agitated in water, and even before it
+has been deprived of all its inflammability, as in common air; and yet
+that in this state it is not, perhaps, so much diminished by nitrous air
+as common air is. In this case, therefore, the diminution seems to have
+been occasioned by a contraction of dimensions, and not by a loss of any
+constituent part; so that the air is really better, that is, more fit
+for respiration, than, by the test of nitrous air, it would seem to be.
+
+If this be the case (for it is not easy to judge with accuracy by
+experiments with small animals) nitrous air will be an accurate test of
+the goodness of _common air_ only, that is, air containing a
+considerable proportion of fixed air. But this is the most valuable
+purpose for which a test of the goodness of air can be wanted. It will
+still, indeed, serve for a measure of the goodness of air that does not
+contain fixed air; but, a smaller degree of diminution in this case,
+must be admitted to be equivalent to a greater diminution in the other.
+
+As I could never, by means of growing vegetables, bring air which had
+been thoroughly noxious to so pure a state as that a candle would burn
+in it, it may be suspected that something else besides _vegetation_ is
+necessary to produce this effect. But it should be considered, that no
+part of the common atmosphere can ever be in this highly noxious state,
+or indeed in a state in which a candle will not burn in it; but that
+even air reduced to this state, either by candles actually burning out
+in it, or by breathing it, has never failed to be perfectly restored by
+vegetation, at least so far that candles would burn in it again, and, to
+all appearance, as well, and as long as ever; so that the growing
+vegetables, with which the surface of the earth is overspread, may, for
+any thing that appears to the contrary, be a cause of the purification
+of the atmosphere sufficiently adequate to the effect.
+
+It may likewise be suspected, that since _agitation in water_ injures
+pure common air, the agitation of the sea may do more harm than good in
+this respect. But it requires a much more violent and longer continued
+agitation of air in water than is ever occasioned by the waves of the
+sea to do the least sensible injury to it. Indeed a light agitation of
+air in _putrid water_ injures it very materially; but if the water be
+sweet, this effect is not produced, except by a long and tedious
+operation, whereas it requires but a very short time, in comparison, to
+restore a quantity of any of the most noxious kinds of air to a very
+great degree of wholesomeness by the same process.
+
+Dr. Hales found that he could breathe the same air much longer when, in
+the course of his respiration, it was made to pass through several folds
+of cloth dipped in vinegar, in a solution of sea-salt, or in salt of
+tartar, especially the last. Statical Essays, vol. 1. p. 266. The
+experiment is valuable, and well deserves to be repeated with a greater
+variety of circumstances. I imagine that the effect was produced by
+those substances, or by the _water_ which they attracted from the air,
+imbibing the phlogistic matter discharged from the lungs. Perhaps the
+phlogiston may unite with the watery part of the atmosphere, in
+preference to any other part of it, and may by that means be more easily
+transferred to such salts as imbibe moisture.
+
+Sir Isaac Newton defines _flame_ to be _fumus candens_, considering all
+_smoke_ as being of the same nature, and capable of ignition. But the
+smoke of common fuel consists of two very different things. That which
+rises first is mere _water_, loaded with some of the grosser parts of
+the fuel, and is hardly more capable of becoming red hot than water
+itself; but the other kind of smoke, which alone is capable of ignition,
+is properly _inflammable air_, which is also loaded with other
+heterogeneous matter, so as to appear like a very dense smoke. A lighted
+candle soon shews them to be essentially different from each other. For
+one of them instantly takes fire, whereas the other extinguishes a
+candle.
+
+It is remarkable that gunpowder will take fire, and explode in all kinds
+of air, without distinction, and that other substances which contain
+_nitre_ will burn freely in those circumstances. Now since nothing can
+burn, unless there be something at hand to receive the phlogiston, which
+is set loose in the act of ignition, I do not see how this fact can be
+accounted for, but by supposing that the acid of nitre, being peculiarly
+formed to unite with phlogiston, immediately receives it. And if the
+sulphur, which is thereby formed, be instantly decomposed again, as the
+chemists in general say, thence comes the explosion of gunpowder, which,
+however, requires the reaction of some incumbent atmosphere, and without
+which the materials will only _melt_, and be _dispersed_ without
+explosion.
+
+Nitrous air seems to consist of the nitrous acid vapour united to
+phlogiston, together, perhaps, with some small portion of the metallic
+calx; just as inflammable air consists of the vitriolic or marine acid,
+and the same phlogistic principle. It should seem, however, that
+phlogiston has a stronger affinity with the marine acid, if that be the
+basis of common air; for nitrous air being admitted to common air, it is
+immediately decomposed; probably by the phlogiston joining with the acid
+principle of the common air, while the fixed air which it contained is
+precipitated, and the acid of the nitrous air is absorbed by the water
+in which the mixture is made, or unites with any volatile alkali that
+happens to be at hand.
+
+This, indeed, is hardly agreeable to the hypothesis of most chemists,
+who suppose that the nitrous acid is stronger than the marine, so as to
+be capable of dislodging it from any base with which it may be combined;
+but it agrees with my own experiments on marine acid air, which shew
+that, in many cases, this _weaker acid_, as it is called, is capable of
+separating both the vitriolic and the nitrous acids from the phlogiston
+with which they are combined.
+
+On the other hand, the solution of metals in the different acids seems
+to shew, that the nitrous acid forms a closer union with phlogiston than
+the other two; because the air which is formed by the nitrous acid is
+not inflammable, like that which is produced by the oil of vitriol, or
+the spirit of salt. Also, the same weight of iron does not yield half
+the quantity of nitrous air that it does of inflammable.
+
+The great diminution of nitrous air by phlogiston is not easily
+accounted for, unless we suppose that its superabundant acid, uniting
+more intimately with the phlogiston, constitutes a species of _sulphur_
+that is not easily perceived or catched; though, in the process with
+iron, and also in that with liver of sulphur, part of the redundant
+phlogiston forms such an union with the acid as gives it a kind of
+inflammability.
+
+It appears to me to be very probable, that the spirit of nitre might be
+exhibited in the form of _air_, if it were possible to find any fluid by
+which it could be confined; but it unites with quicksilver as well as
+with water, so that when, by boiling the spirit of nitre, the fumes are
+driven through the glass tube, fig. 8, they instantly seize upon the
+quicksilver through which they are to be conveyed, and uniting with it,
+form a substance that stops up the tube: a circumstance which has more
+than once exposed me to very disagreeable accidents, in consequence of
+the bursting of the phials.
+
+I do not know any inquiry more promising than the investigation of the
+properties of _nitre_, the _nitrous acid_, and _nitrous air_. Some of
+the most wonderful phenomena in nature are connected with them, and the
+subject seems to be fully within our reach.
+
+
+§ 2. _Speculations arising from the consideration of the similarity of
+the ELECTRIC MATTER and PHLOGISTON._
+
+There is nothing in the history of philosophy more striking than the
+rapid progress of _electricity_. Nothing ever appeared more trifling
+than the first effects which were observed of this agent in nature, as
+the attraction and repulsion of straws, and other light substances. It
+excited more attention by the flashes of _light_ which it exhibited. We
+were more seriously alarmed at the electrical _shock_, and the effects
+of the electrical _battery_; and we were astonished to the highest
+degree by the discovery of the similarity of electricity with
+_lightning_, and the _aurora borealis_, with the connexion it seems to
+have with _water-spouts_, _hurricanes_, and _earthquakes_, and also with
+the part that is probably assigned to it in the system of _vegetation_,
+and other the most important processes in nature.
+
+Yet, notwithstanding all this, we have been, within a few years, more
+puzzled than ever with the electricity of the _torpedo_, and of the
+_anguille temblante_ of Surinam, especially since that most curious
+discovery of Mr. Walsh's, that the former of these wonderful fishes has
+the power of giving a proper electrical shock; the electrical matter
+which proceeds from it performing a real circuit from one part of the
+animal to the other; while both the fish which performs this experiment
+and all its apparatus are plunged in water, which is known to be a
+conducting substance.
+
+Perhaps, however, by considering this fact in connexion with a few
+others, and especially with what I have lately observed concerning the
+identity of electricity and phlogiston, a little light may be thrown
+upon this subject, in consequence of which we may be led to consider
+electricity in a still more important light. Many of my readers, I am
+aware, will smile at what I am going to advance; but the apprehension of
+this shall not interrupt my speculations, how chimerical soever they may
+be thought to be.
+
+The facts, the consideration of which I would combine with that of the
+electricity of the torpedo, are the following.
+
+First, The remarkable electricity of the feathers of a paroquet,
+observed by Mr. Hartmann, an account of which may be seen in Mr.
+Rozier's Journal for Sept. 1771. p. 69. This bird never drinks, but
+often washes itself; but the person who attended it having neglected to
+supply it with water for this purpose, its feathers appeared to be
+endued with a proper electrical virtue, repelling one another, and
+retaining their electricity a long time after they were plucked from the
+body of the bird, just as they would have done if they had received
+electricity from an excited glass tube.
+
+Secondly, The electric matter directed through the body of any muscle
+forces it to contract. This is known to all persons who attend to what
+is called the electrical shock; which certainly occasions a proper
+_convulsion_, but has been more fully illustrated by Father Beccaria.
+See my _History of Electricity_, p. 402.
+
+Lastly, Let it be considered that the proper nourishment of an animal
+body, from which the source and materials of all muscular motion must be
+derived, is probably some modification of phlogiston. Nothing will
+nourish that does not contain phlogiston, and probably in such a state
+as to be easily separated from it by the animal functions.
+
+That the source of muscular motion is phlogiston is still more probable,
+from the consideration of the well known effects of vinous and
+spirituous liquors, which consist very much of phlogiston, and which
+instantly brace and strengthen the whole nervous and muscular system;
+the phlogiston in this case being, perhaps, more easily extricated, and
+by a less tedious animal process, than in the usual method of extracting
+it from mild aliments. Since, however, the mildest aliments do the same
+thing more slowly and permanently, that spirituous liquors do suddenly
+and transiently, it seems probable that their operation is ultimately
+the same.
+
+This conjecture is likewise favoured by my observation, that respiration
+and putrefaction affect common air in the same manner, and in the same
+manner in which all other processes diminish air and make it noxious,
+and which agree in nothing but the emission of phlogiston. If this be
+the case, it should seem that the phlogiston which we take in with our
+aliment, after having discharged its proper function in the animal
+system (by which it probably undergoes some unknown alteration) is
+discharged as _effete_ by the lungs into the great common _menstruum_,
+the atmosphere.
+
+My conjecture suggested (whether supported or not) by these facts, is,
+that animals have a power of converting phlogiston, from the state in
+which they receive it in their nutriment, into that state in which it is
+called the electrical fluid; that the brain, besides its other proper
+uses, is the great laboratory and repository for this purpose; that by
+means of the nerves this great principle, thus exalted, is directed into
+the muscles, and forces them to act, in the same manner as they are
+forced into action when the electric fluid is thrown into them _ab
+extra_.
+
+I farther suppose, that the generality of animals have no power of
+throwing this generated electricity any farther than the limits of their
+own system; but that the _torpedo_, and animals of a similar
+construction, have likewise the power, by means of an additional
+apparatus, of throwing it farther, so as to affect other animals, and
+other substances at a distance from them.
+
+In this case, it should seem that the electric matter discharged from
+the animal system (by which it is probably more exhausted and fatigued
+than by ordinary muscular motion) would never return to it, at least so
+as to be capable of being made use of a second time, and yet if the
+structure of these animals be such as that the electric matter shall
+dart from one part of them only, while another part is left suddenly
+deprived of it, it may make a circuit, as in the Leyden phial.
+
+As to the _manner_ in which the electric matter makes a muscle contract,
+I do not pretend to have any conjecture worth mentioning. I only imagine
+that whatever can make the muscular fibres recede from one another
+farther than the parts of which they consist, must have this effect.
+
+Possibly, the _light_ which is said to proceed from some animals, as
+from cats and wild beasts, when they are in pursuit of their prey in the
+night, may not only arise, as it has hitherto been supposed to do, from
+the friction of their hairs or bristles, &c. but that violent muscular
+exertion may contribute to it. This may assist them occasionally to
+catch their prey; as glow-worms, and other insects, are provided with a
+constant light for that purpose, to the supply of which light their
+nutriment may also contribute.
+
+I would not even say that the light which is said to have proceeded from
+some human bodies, of a particular temperament, and especially on some
+extraordinary occasions, may not have been of the electrical kind, that
+is, produced independently of friction, or with less friction than
+would have produced it in other persons; as in those cases related by
+Bartholin in his treatice _De luce animalium_. See particularly what he
+says concerning Theodore king of the Goths, p. 54, concerning Gonzaga
+duke of Mantua, p. 57, and Gothofred Antonius, p. 123: But I would not
+have my readers suppose that I lay much stress upon stories no better
+authenticated than these.
+
+The electric matter in passing through non-conducting substances always
+emits _light_. This light I have been sometimes inclined to suspect
+might have been supplied from the substance through which it passes. But
+I find that after the electric spark has diminished a quantity of air as
+much as it possibly can, so that it has no more visible effect upon it,
+the electric light in that air is not at all lessened. It is probable,
+therefore, that electric light comes from the electric matter itself;
+and this being a modification of phlogiston, it is probable that _all
+light_ is a modification of phlogiston also. Indeed, since no other
+substances besides such as contain phlogiston are capable of ignition,
+and consequently of becoming luminous, it was on this account pretty
+evident, prior to these deductions from electrical phenomena, that light
+and phlogiston are the same thing, in different forms or states.
+
+It appears to me that _heat_ has no more proper connexion with
+phlogiston than it has with water, or any other constituent part of
+bodies; but that it is a state into which the parts of bodies are thrown
+by their action and reaction with respect to one another; and probably
+(as the English philosophers in general have supposed) the heated state
+of bodies may consist of a subtle vibratory motion of their parts. Since
+the particles which constitute light are thrown from luminous bodies
+with such amazing velocity, it is evident that, whatever be the cause of
+such a projection, the reaction consequent upon it must be considerable.
+This may be sufficient not only to keep up, but also to increase the
+vibration of the parts of those bodies in which the phlogiston is not
+very firmly combined; and the difference between the substances which
+are called _inflammable_ and others which also contain phlogiston may be
+this, that in the former the heat, or the vibration occasioned by the
+emission of their own phlogiston, may be sufficient to occasion the
+emission of more, till the whole be exhausted; that is, till the body be
+reduced to ashes. Whereas in bodies which are not inflammable, the heat
+occasioned by the emission of their own phlogiston may not be sufficient
+for this purpose, but an additional heat _ab extra_ may be necessary.
+
+Some philosophers dislike the term _phlogiston_; but, for my part, I can
+see no objection to giving that, or any other name, to a _real
+something_, the presence or absence of which makes so remarkable
+difference in bodies, as that of _metallic calces_ and _metals_, _oil of
+vitriol_ and _brimstone_, &c. and which may be transferred from one
+substance to another, according to certain known laws, that is, in
+certain definite circumstances. It is certainly hard to conceive how any
+thing that answers this description can be only a mere _quality_, or
+mode of bodies, and not _substance_ itself, though incapable of being
+exhibited alone. At least, there can be no harm in giving this name to
+any _thing_, or any _circumstance_ that is capable of producing these
+effects. If it should hereafter appear not to be a substance, we may
+change our phraseology, if we think proper.
+
+On the other hand I dislike the use of the term _fire_, as a constituent
+principle of natural bodies, because, in consequence of the use that has
+generally been made of that term, it includes another thing or
+circumstance, viz. _heat_, and thereby becomes ambiguous, and is in
+danger of misleading us. When I use the term phlogiston, as a principle
+in the constitution of bodies, I cannot mislead myself or others,
+because I use one and the same term to denote only one and the same
+_unknown cause_ of certain well-known effects. But if I say that _fire_
+is a principle in the constitution of bodies, I must, at least,
+embarrass myself with the distinction of fire _in a state of action_,
+and fire _inactive_, or quiescent. Besides I think the term phlogiston
+preferable to that of fire, because it is not in common use, but
+confined to philosophy; so that the use of it may be more accurately
+ascertained.
+
+Besides, if phlogiston and the electric matter be the same thing, though
+it cannot be exhibited alone, in a _quiescent state_, it may be
+exhibited alone under one of its modifications, when it is in _motion_.
+And if light be also phlogiston, or some modification or subdivision of
+phlogiston, the same thing is capable of being exhibited alone in this
+other form also.
+
+In my paper on the _conducting power of charcoal_, (See Philosophical
+Transactions, vol. 60. p. 221) I observed that there is a remarkable
+resemblance between metals and charcoal; as in both these substances
+there is an intimate union of phlogiston with an earthy base; and I said
+that, had there been any phlogiston in _water_, I should have concluded,
+that there had been no conducting power in nature, but in consequence of
+an union of this principle with some base; for while metals have
+phlogiston they conduct electricity, but when they are deprived of it
+they conduct no longer. Now the affinity which I have observed between
+phlogiston and water leads me to conclude that water, in its natural
+state, does contain some portion of phlogiston; and according to the
+hypothesis just now mentioned they must be intimately united, because
+water is not inflammable.
+
+I think, therefore, that after this state of hesitation and suspence, I
+may venture to lay it down as a characteristic distinction between
+conducting and non-conducting substances, that the former contain
+phlogiston intimately united with some base, and that the latter, if
+they contain phlogiston at all, retain it more loosely. In what manner
+this circumstance facilitates the passing of the electric matter through
+one substance, and obstructs its passage through another, I do not
+pretend to say. But it is no inconsiderable thing to have advanced but
+_one step_ nearer to an explanation of so very capital a distinction of
+natural bodies, as that into conductors and non-conductors of
+electricity.
+
+I beg leave to mention in this place, as favourable to this hypothesis,
+a most curious discovery made very lately by Mr. Walsh, who being
+assisted by Mr. De Luc to make a more perfect vacuum in the double or
+arched barometer, by boiling the quicksilver in the tube, found that the
+electric spark or shock would no more pass through it, than through a
+stick of solid glass. He has also noted several circumstances that
+affect this vacuum in a very extraordinary manner. But supposing that
+vacuum to be perfect, I do not see how we can avoid inferring from the
+fact, that some _substance_ is necessary to conduct electricity; and
+that it is not capable, by its own expansive power, of extending itself
+into spaces void of all matter, as has generally been supposed, on the
+idea of there being nothing to obstruct its passage.
+
+Indeed if this was the case, I do not see how the electric matter could
+be retained within the body of the earth, or any of the planets, or
+solid orbs of any kind. In nature we see it make the most splendid
+appearance in the upper and thinner regions of the atmosphere, just as
+it does in a glass tube nearly exhausted; but if it could expand itself
+beyond that degree of rarity, it would necessarily be diffused into the
+surrounding vacuum, and continue and be condensed there, at least in a
+greater proportion than in or near any solid body, as Newton supposed
+concerning his _ether_.
+
+If that mode of vibration which constitutes heat be the means of
+converting phlogiston from that state in which it makes a part of solid
+bodies, and eminently contributes to the firmness of their texture into
+that state in which it diminishes common air; may not that peculiar kind
+of vibration by which Dr. Hartley supposes the brain to be affected, and
+by which he endeavours to explain all the phenomena of sensation, ideas,
+and muscular motion, be the means by which the phlogiston, which is
+conveyed into the system by nutriment, is converted into that form or
+modification of it of which the electric fluid consists.
+
+These two states of phlogiston may be conceived to resemble, in some
+measure, the two states of fixed air, viz. elastic, or non-elastic; a
+solid, or a fluid.
+
+
+
+
+THE APPENDIX.
+
+
+In this Appendix I shall present the reader with the communications of
+several of my friends on the subject of the preceding work. Among them I
+should with pleasure have inserted some curious experiments, made by Dr.
+Hulme of Halifax, on the air extracted from Buxton water, and on the
+impregnation of several fluids, with different kinds of air; but that he
+informs me he proposes to make a separate publication on the subject.
+
+
+NUMBER I.
+
+     _EXPERIMENTS made by Mr. Hey to prove that there is no OIL of
+     VITRIOL in water impregnated with FIXED AIR._
+
+It having been suggested, that air arising from a fermenting mixture of
+chalk and oil of vitriol might carry up with it a small portion of the
+vitriolic acid, rendered volatile by the act of fermentation; I made the
+following experiments, in order to discover whether the acidulous taste,
+which water impregnated with such air affords, was owing to the presence
+of any acid, or only to the fixed air it had absorbed.
+
+EXPERIMENT I.
+
+I mixed a tea-spoonful of syrup of violets with an ounce of distilled
+water, saturated with fixed air procured from chalk by means of the
+vitriolic acid; but neither upon the first mixture, nor after standing
+24 hours, was the colour of the syrup at all changed, except by its
+simple dilution.
+
+EXPERIMENT II.
+
+A portion of the same distilled water, unimpregnated with fixed air, was
+mixed with the syrup in the same proportion: not the least difference in
+colour could be perceived betwixt this and the above-mentioned mixture.
+
+EXPERIMENT III.
+
+One drop of oil of vitriol being mixed with a pint of the same distilled
+water, an ounce of this water was mixed with a tea-spoonful of the
+syrup. This mixture was very distinguishable in colour from the two
+former, having a purplish cast, which the others wanted.
+
+EXPERIMENT IV.
+
+The distilled water impregnated with so small a quantity of vitriolic
+acid, having a more agreeable taste than when alone, and yet manifesting
+the presence of an acid by means of the syrup of violets; I subjected it
+to some other tests of acidity. It formed curds when agitated with soap,
+lathered with difficulty, and very imperfectly; but not the least
+ebullition could be discovered upon dropping in spirit of sal ammoniac,
+or solution of salt of tartar, though I had taken care to render the
+latter free from causticity by impregnating it with fixed air.
+
+EXPERIMENT V.
+
+The distilled water saturated with fixed air neither effervesced, nor
+shewed any clouds, when mixed with the fixed or volatile alkali.
+
+EXPERIMENT VI.
+
+No curd was formed by pouring this water upon an equal quantity of milk,
+and boiling them together.
+
+EXPERIMENT VII.
+
+When agitated with soap, this water produced curds, and lathered with
+some difficulty; but not so much as the distilled water mixed with
+vitriolic acid in the very small proportion above-mentioned. The same
+distilled water without any impregnation of fixed air lathered with soap
+without the least previous curdling. River-water, and a pleasant
+pump-water not remarkably hard, were compared with these. The former
+produced curds before it lathered, but not quite in so great a quantity
+as the distilled water impregnated with fixed air: the latter caused a
+stronger curd than any of the others above-mentioned.
+
+EXPERIMENT VIII.
+
+Apprehending that the fixed air in the distilled water occasioned the
+coagulation, or separation of the oily part of the soap, only by
+destroying the causticity of the _lixivium_, and thereby rendering the
+union less perfect betwixt that and the tallow, and not by the presence
+of any acid; I impregnated a fresh quantity of the same distilled water
+with fixed air, which had passed through half a yard of a wide
+barometer-tube filled with salt of tartar; but this water caused the
+same curdling with soap as the former had done, and appeared in every
+respect to be exactly the same.
+
+EXPERIMENT IX.
+
+Distilled water saturated with fixed air formed a white cloud and
+precipitation, upon being mixed with a solution of _saccharum saturni_.
+I found likewise, that fixed air, after passing through the tube filled
+with alkaline salt, upon being let into a phial containing a solution of
+the metalic salt in distilled water, caused a perfect separation of the
+lead, in the form of a white powder; for the water, after this
+precipitation, shewed no cloudiness upon a fresh mixture of the
+substances which had before rendered it opaque.
+
+
+NUMBER II.
+
+     _A Letter from Mr. HEY to Dr. PRIESTLEY, concerning the Effects
+     of fixed Air applied by way of Clyster._
+
+                                      Leeds, Feb. 15th, 1772.
+
+     Reverend Sir,
+
+Having lately experienced the good effects of fixed air in a putrid
+fever, applied in a manner, I believe not heretofore made use of, I
+thought it proper to inform you of the agreeable event, as the method of
+applying this powerful corrector of putrefaction took its rise
+principally from your observations and experiments on factitious air;
+and now, at your request, I send the particulars of the case I mentioned
+to you, as far as concerns the administration of this remedy.
+
+January 8, 1772, Mr. Lightbowne, a young gentleman who lives with me,
+was seized with a fever, which, after continuing about ten days, began
+to be attended with those symptoms that indicate a putrescent state of
+the fluids.
+
+18th, His tongue was black in the morning when I first visited him, but
+the blackness went off in the day-time upon drinking: He had begun to
+doze much the preceding day, and now he took little notice of those that
+were about him: His belly was loose, and had been so for some days: his
+pulse beat 110 strokes in a minute, and was rather low: he was ordered
+to take twenty-five grains of Peruvian bark with five of tormentil-root
+in powder every four hours, and to use red wine and water cold as his
+common drink.
+
+19th, I was called to visit him early in the morning, on account of a
+bleeding at the nose which had come on: he lost about eight ounces of
+blood, which was of a loose texture: the hæmorrhage was suppressed,
+though not without some difficulty, by means of tents made of soft lint,
+dipped in cold water strongly impregnated with tincture of iron, which
+were introduced within the nostrils quite through to their posterior
+apertures; a method which has never yet failed me in like cases. His
+tongue was now covered with a thick black pellicle, which was not
+diminished by drinking: his teeth were furred with the same kind of
+sordid matter, and even the roof of his mouth and sauces were not free
+from it: his looseness and stupor continued, and he was almost
+incessantly muttering to himself: he took this day a scruple of the
+Peruvian bark with ten grains of tormentil every two or three hours: a
+starch clyster, containing a drachm of the compound powder of bole,
+without opium, was given morning and evening: a window was set open in
+his room, though it was a severe frost, and the floor was frequently
+sprinkled with vinegar.
+
+20th, He continued nearly in the same state: when roused from his
+dozing, he generally gave a sensible answer to the questions asked him;
+but he immediately relapsed, and repeated his muttering. His skin was
+dry, and harsh, but without _petechiæ_. He sometimes voided his urine
+and _fæces_ into the bed, but generally had sense enough to ask for the
+bed-pan: as he now nauseated the bark in substance, it was exchanged
+for Huxham's tincture, of which he took a table spoonful every two hours
+in a cup full of cold water: he drank sometimes a little of the tincture
+of roses, but his common liquors were red wine and water, or rice-water
+and brandy acidulated with elixir of vitriol: before drinking, he was
+commonly requested to rinse his mouth with water to which a little honey
+and vinegar had been added. His looseness rather increased, and the
+stools were watery, black, and foetid: It was judged necessary to
+moderate this discharge, which seemed to sink him, by mixing a drachm of
+the _theriaca Andromachi_ with each clyster.
+
+21st. The same putrid symptoms remained, and a _subsultus tendinum_ came
+on: his stools were more foetid; and so hot, that the nurse assured me
+she could not apply her hand to the bed-pan, immediately after they were
+discharged, without feeling pain on this account: The medicine and
+clysters were repeated.
+
+Reflecting upon the disagreeable necessity we seemed to lie under of
+confining this putrid matter in the intestines, lest the evacuation
+should destroy the _vis vitæ_ before there was time to correct its bad
+quality, and overcome its bad effects, by the means we were using; I
+considered, that, if this putrid ferment could be more immediately
+corrected, a stop would probably be put to the flux, which seemed to
+arise from, or at least to be encreased by it; and the _fomes_ of the
+disease would likewise be in a great measure removed. I thought nothing
+was so likely to effect this, as the introduction of fixed air into the
+alimentary canal, which, from the experiments of Dr. Macbride, and
+those you have made since his publication, appears to be the most
+powerful corrector of putrefaction hitherto known. I recollected what
+you had recommended to me as deserving to be tried in putrid diseases, I
+mean, the injection of this kind of air by way of clyster, and judged
+that in the present case such a method was clearly indicated.
+
+The next morning I mentioned my reflections to Dr. Hird and Dr.
+Crowther, who kindly attended this young gentleman at my request, and
+proposed the following method of treatment, which, with their
+approbation, was immediately entered upon. We first gave him five grains
+of ipecacuanha, to evacuate in the most easy manner part of the putrid
+_colluvies_: he was then allowed to drink freely of brisk orange-wine,
+which contained a good deal of fixed air, yet had not lost its
+sweetness. The tincture of bark was continued as before; and the water
+which he drank along with it, was impregnated with fixed air from the
+atmosphere of a large vat of fermenting wort, in the manner I had
+learned from you. Instead of the astringent clyster, air alone was
+injected, collected from a fermenting mixture of chalk and oil of
+vitriol: he drank a bottle of orange-wine in the course of this day, but
+refused any other liquor except water and his medicine: two bladders
+full of air were thrown up in the afternoon.
+
+23d. His stools were less frequent; their heat likewise and peculiar
+_foetor_ were considerably diminished; his muttering was much abated,
+and the _subsultus tendinum_ had left him. Finding that part of the air
+was rejected when given with a bladder in the usual way, I contrived a
+method of injecting it which was not so liable to this inconvenience. I
+took the flexible tube of that instrument which is used for throwing up
+the fume of tobacco, and tied a small bladder to the end of it that is
+connected with the box made for receiving the tobacco, which I had
+previously taken off from the tube: I then put some bits of chalk into a
+six ounce phial until it was half filled; upon these I poured such a
+quantity of oil of vitriol as I thought capable of saturating the chalk,
+and immediately tied the bladder, which I had fixed to the tube, round
+the neck of the phial: the clyster-pipe, which was fastened to the other
+end of the tube, was introduced into the _anus_ before the oil of
+vitriol was poured upon the chalk. By this method the air passed
+gradually into the intestines as it was generated; the rejection of it
+was in a great measure prevented; and the inconvenience of keeping the
+patient uncovered during the operation was avoided.
+
+24th, He was so much better, that there seemed to be no necessity for
+repeating the clysters: the other means were continued. The window of
+his room was now kept shut.
+
+25th, All the symptoms of putrescency had left him; his tongue and teeth
+were clean; there remained no unnatural blackness or _foetor_ in his
+stool, which had now regained their proper consistence; his dozing and
+muttering were gone off; and the disagreeable odour of his breath and
+perspiration was no longer perceived. He took nourishment to-day, with
+pleasure; and, in the afternoon, sat up an hour in his chair.
+
+His fever, however, did not immediately leave him; but this we
+attributed to his having caught cold from being incautiously uncovered,
+when the window was open, and the weather extremely severe; for a cough,
+which had troubled him in some degree from the beginning, increased, and
+he became likewise very hoarse for several days, his pulse, at the same
+time, growing quicker: but these complaints also went off, and he
+recovered, without any return of the bad symptoms above-mentioned.
+
+     I am, Reverend Sir,
+
+       Your obliged humble Servant,
+
+         WM. HEY.
+
+
+POSTSCRIPT
+
+                                      October 29, 1772.
+
+Fevers of the putrid kind have been so rare in this town, and in its
+neighbourhood, since the commencement of the present year, that I have
+not had an opportunity of trying again the effects of fixed air, given
+by way of clyster, in any case exactly similar to Mr. Lightbowne's. I
+have twice given water saturated with fixed air in a fever of the
+putrescent kind, and it agreed very well with the patients. To one of
+them the aërial clysters were administred, on account of a looseness,
+which attended the fever, though the stools were not black, nor
+remarkably hot or foetid.
+
+These clysters did not remove the looseness, though there was often a
+greater interval than usual betwixt the evacuations, after the injection
+of them. The patient never complained of any uneasy distention of the
+belly from the air thrown up, which, indeed, is not to be wondered at,
+considering how readily this kind of air is absorbed by aqueous and
+other fluids, for which sufficient time was given, by the gradual manner
+of injecting it. Both those patients recovered though the use of fixed
+air did not produce a crisis before the period at which such fevers
+usually terminate. They had neither of them the opportunity of drinking
+such wine as Mr. Lightbowne took, after the use of fixed air was entered
+upon; and this, probably, was some disadvantage to them.
+
+I find the methods of procuring fixed air, and impregnating water with
+it, which you have published, are preferable to those I made use of in
+Mr. Lightbowne's case.
+
+The flexible tube used for conveying the fume of tobacco into the
+intestines, I find to be a very convenient instrument in this case, by
+the method before-mentioned (only adding water to the chalk, before the
+oil of vitriol is instilled, as you direct) the injection of air may be
+continued at pleasure, without any other inconvenience to the patient,
+than what may arise from his continuing in one position during the
+operation, which scarcely deserves to be mentioned, or from the
+continuance of the clyster-pipe within the anus, which is but trifling,
+if it be not shaken much, or pushed against the rectum.
+
+When I said in my letter, that fixed air appeared to be the greatest
+corrector of putrefaction hitherto known, your philosophical researches
+had not then made you acquainted with that most remarkably antiseptic
+property of nitrous air. Since you favoured me with a view of some
+astonishing proofs of this, I have conceived hopes, that this kind of
+air may likewise be applied medicinally to great advantage.
+
+     W. H.
+
+
+NUMBER III.
+
+     _Observations on the MEDICINAL USES of FIXED AIR. By THOMAS
+     PERCIVAL, M. D. Fellow of the ROYAL SOCIETY, and of the SOCIETY
+     of ANTIQUARIES in LONDON._
+
+These Observations on the MEDICINAL USES OF FIXED AIR have been before
+published in the Second Volume of my Essays; but are here reprinted with
+considerable additions. They form a part of an experimental inquiry into
+this interesting and curious branch of Physics; in which the friendship
+of Dr. Priestley first engaged me, in concert with himself.
+
+                                      Manchester, March 16, 1774.
+
+In a course of Experiments, which is yet unfinished, I have had frequent
+opportunities of observing that FIXED AIR may in no inconsiderable
+quantity be breathed without danger or uneasiness. And it is a
+confirmation of this conclusion, that at Bath, where the waters
+copiously exhale this mineral spirit,[15] the bathers inspire it with
+impunity. At Buxton also, where the Bath is in a close vault, the
+effects of such _effluvia_, if noxious, must certainly be perceived.
+
+Encouraged by these considerations, and still more by the testimony of a
+very judicious Physician at Stafford, in favour of this powerful
+antiseptic remedy, I have administered fixed air in a considerable
+number of cases of the PHTHISIS PULMONALIS, by directing my patients to
+inspire the steams of an effervescing mixture of chalk and vinegar; or
+what I have lately preferred, of vinegar and potash. The hectic fever
+has in several instances been considerably abated, and the matter
+expectorated has become less offensive, and better digested. I have not
+yet been so fortunate in any one case, as to effect a cure; although the
+use of mephitic air has been accompanied with proper internal medicines.
+But Dr. Withering, the gentleman referred to above, informs me, that he
+has been more successful. One Phthisical patient under his care has by a
+similar course intirely recovered; another was rendered much better; and
+a third, whose case was truly deplorable, seemed to be kept alive by it
+more than two months. It may be proper to observe that fixed air can
+only be employed with any prospect of success, in the latter stages of
+the _phthisis pulmonalis_, when a purulent expectoration takes place.
+After the rupture and discharge of a VOMICA also, such a remedy promises
+to be a powerful palliative. Antiseptic fumigations and vapours have
+been long employed, and much extolled in cases of this kind. I made the
+following experiment, to determine whether their efficacy, in any
+degree, depends on the separation of fixed air from their substance.
+
+One end of a bent tube was fixed in a phial full of lime-water; the
+other end in a bottle of the tincture of myrrh. The junctures were
+carefully luted, and the phial containing the tincture of myrrh was
+placed in water, heated almost to the boiling point, by the lamp of a
+tea-kettle. A number of air-bubbles were separated, but probably not of
+the mephitic kind, for no precipitation ensued in the lime water. This
+experiment was repeated with the _tinct. tolutanæ, ph. ed._ and with
+_sp, vinos. camp._ and the result was entirely the same. The medicinal
+action therefore of the vapours raised from such tinctures, cannot be
+ascribed to the extrication of fixed air; of which it is probable bodies
+are deprived by _chemical solution_ as well as by _mixture_.
+
+If mephitic air be thus capable of correcting purulent matter in the
+lungs, we may reasonably infer it will be equally useful when applied
+externally to foul ULCERS. And experience confirms the conclusion. Even
+the sanies of a CANCER, when the carrot poultice failed, has been
+sweetened by it, the pain mitigated, and a better digestion produced.
+The cases I refer to are now in the Manchester infirmary, under the
+direction of my friend Mr. White, whose skill as a surgeon, and
+abilities as a writer are well known to the public.
+
+Two months have elapsed since these observations were written,[16] and
+the same remedy, during that period, has been assiduously applied, but
+without any further success. The progress of the cancers seems to be
+checked by the fixed air; but it is to be feared that a cure will not be
+effected. A palliative remedy, however, in a disease so desperate and
+loathsome, may be considered as a very valuable acquisition. Perhaps
+NITROUS AIR might be still more efficacious. This species of factitious
+air is obtained from all the metals except zinc, by means of the nitrous
+acid; and Dr. Priestley informs me, that as a sweetener and antiseptic
+it far surpasses fixed air. He put two mice into a quantity of it, one
+just killed, the other offensively putrid. After twenty-five days they
+were both perfectly sweet.
+
+In the ULCEROUS SORE THROAT much advantage has been experienced from the
+vapours of effervescing mixtures drawn into the _fauces_[17]. But this
+remedy should not supersede the use of other antiseptic
+applications.[18]
+
+A physician[19] who had a very painful APTHOUS ULCER at the point of his
+tongue, found great relief, when other remedies failed, from the
+application of fixed air to the part affected. He held his tongue over
+an effervescing mixture of potash and vinegar; and as the pain was
+always mitigated, and generally removed by this vaporisation, he
+repeated it, whenever the anguish arising from the ulcer was more than
+usually severe. He tried a combination of potash and oil of vitriol well
+diluted with water; but this proved stimulant and increased his pain;
+probably owing to some particles of the acid thrown upon the tongue, by
+the violence of the effervescence. For a paper stained with the purple
+juice of radishes, when held at an equal distance over two vessels, the
+one containing potash and vinegar, the other the same alkali and
+_Spiritus vitrioli tenuis_, was unchanged by the former, but was spotted
+with red, in various parts, by the latter.
+
+In MALIGNANT FEVERS wines abounding with fixed air may be administered,
+to check the septic ferment, and sweeten the putrid _colluvies_ in the
+_primæ viæ_. If the laxative quality of such liquors be thought an
+objection to the use of them, wines of a greater age may be given,
+impregnated with mephitic air, by a simple but ingenious contrivance of
+my friend Dr. Priestley.[20]
+
+The patient's common drink might also be medicated in the same way. A
+putrid DIARRH[OE]A frequently occurs in the latter stage of such
+disorder, and it is a most alarming and dangerous symptom. If the
+discharge be stopped by astringents, a putrid _fomes_ is retained in the
+body, which aggravates the delirium and increases the fever. On the
+contrary, if it be suffered to take its course, the strength of the
+patient must soon be exhausted, and death unavoidably ensue. The
+injection of mephitic air into the intestines, under these
+circumstances, bids fair to be highly serviceable. And a case of this
+deplorable kind, has lately been communicated to me, in which the vapour
+of chalk and oil of vitriol conveyed into the body by the machine
+employed for tobacco clysters, quickly restrained the _diarrhoea_,
+corrected the heat and foetor of the stools, and in two days removed
+every symptom of danger[21]. Two similar instances of the salutary
+effects of mephitic air, thus administered, have occurred also in my own
+practice, the history of which I shall briefly lay before the reader.
+May we not presume that the same remedy would be equally useful in the
+DYSENTERY? The experiment is at least worthy of trial.
+
+Mr. W----, aged forty-four years, corpulent, inactive, with a short
+neck, and addicted to habits of intemperance, was attacked on the 7th of
+July 1772, with symptoms which seemed to threaten an apoplexy. On the
+8th, a bilious looseness succeeded, with a profuse hoemorrhage from
+the nose. On the 9th, I was called to his assistance. His countenance
+was bloated, his eyes heavy, his skin hot, and his pulse hard, full, and
+oppressed. The diarrhoea continued; his stools were bilious and very
+offensive; and he complained of griping pains in his bowels. He had
+lost, before I saw him, by the direction of Mr. Hall, a surgeon of
+eminence in Manchester, eight ounces of blood from the arm, which was of
+a lax texture; and he had taken a saline mixture every sixth hour. The
+following draught was prescribed, and a dose of rhubarb directed to be
+administered at night.
+
+      Rx. _Aq. Cinnam. ten._        oz. j.
+     _Succ. Limon. recent._         oz. ß.
+     _Salis Nitri gr. xij. Syr. è Succo Limon. dr. j. M. f. Haust._
+     _4tis horis sumendus._
+
+July 11. The _Diarrhoea_ was more moderate; his griping pains were
+abated; and he had less stupor and dejection in his countenance. Pulse
+90, not so hard or oppressed. As his stools continued to be foetid,
+the dose of rhubarb was repeated; and instead of simple cinnamon-water,
+his draughts were prepared with an infusion of columbo root.
+
+12. The _Diarrhoea_ continued; his stools were involuntary; and he
+discharged in this way a quantity of black, grumous, and foetid blood.
+Pulse hard and quick; skin hot; tongue covered with a dark fur; abdomen
+swelled; great stupor. Ten grains of columbo root, and fifteen of the
+_Gummi rubrum astringens_ were added to each draught. Fixed air, under
+the form of clysters, was injected every second or third hour; and
+directions were given to supply the patient plentifully with water,
+artificially impregnated with mephitic air. A blister was also laid
+between his shoulders.
+
+13. The Diarrhoea continued, with frequent discharges of blood; but
+the stools had now lost their foetor. Pulse 120; great flatulence in
+the bowels, and fulness in the belly. The clysters of fixed air always
+diminished the tension of the _Abdomen_, abated flatulence, and made the
+patient more easy and composed for some time after their injection. They
+were directed to be continued, together with the medicated water. The
+nitre was omitted, and a scruple of the _Confect. Damocratis_ was given
+every fourth hour, in an infusion of columbo root.
+
+14. The Diarrhoea was how checked, His other symptoms continued as
+before. Blisters were applied to the arms; and a drachm and a half of
+the _Tinctura Serpentariæ_ was added to each draught.
+
+15. His pulse was feeble, quicker and more irregular. He dosed much;
+talked incoherently; and laboured under a slight degree of _Dyspnæa_.
+His urine, which had hitherto assumed no remarkable appearance, now
+became pale. Though he discharged wind very freely, his belly was much
+swelled, except for a short time after the injection of the
+air-clysters. The following draughts were then prescribed.
+
+     Rx _Camphoræ mucilag. G. Arab, solutæ gr. viij. Infus. Rad.
+     Columbo oz. jfs Tinct. Serpent. dr. ij Confect. Card.
+     scruple j Syr. è Cort. Aurant dr. i m. f. Haust. 4tis horis
+     sumendus._
+
+Directions were given to foment his feet frequently with vinegar and
+warm water.
+
+16. He has had no stools since the 14th. His _Abdomen_ is tense. No
+change in the other symptoms. The _Tinct. Serpent._ was omitted in his
+draughts, and an equal quantity of _Tinct. Rhæi Sp._ substituted in its
+place.
+
+In the evening he had a motion to stool, of which he was for the first
+time so sensible, as to give notice to his attendants. But the
+discharge, which was considerable and slightly offensive, consisted
+almost entirely of blood, both in a coagulated and in a liquid state.
+His medicines were therefore varied as follows:
+
+     Rx. _Decoct. Cort. Peruv. oz. iss Tinct. Cort. ejusd. dr. ij. Confect.
+     Card. scruple j Gum. Rubr. Astring. gr.
+     xv. Pulv. Alnmin. gr. vij. m. f. Haustus 4tis horis
+     sumendus._
+
+Red Port wine was now given more freely in his medicated water; and his
+nourishment consisted of sago and salep.
+
+In this state, with very little variation, he continued for several
+days; at one time ostive, and at another discharging small quantities of
+fæces, mixed with grumous blood. The air-clysters were continued, and
+the astringents omitted.
+
+20. His urine was now of an amber colour, and deposited a slight
+sediment. His pulse was more regular, and although still very quick,
+abated in number ten strokes in a minute. His head was less confused,
+and his sleep seemed to be refreshing. No blood appeared in his stools,
+which were frequent, but small in quantity; and his _Abdomen_ was less
+tense than usual. He was extremely deaf; but gave rational answers to
+the few questions which were proposed to him; and said he felt no pain.
+
+21. He passed a very restless night; his delirium recurred; his pulse
+beat 125 strokes in a minute; his urine was of a deep amber colour when
+first voided; but when cold assumed the appearance of cow's whey. The
+_Abdomen_ was not very tense, nor had he any further discharge of blood.
+
+Directions were given to shave his head, and to wash it with a mixture
+of vinegar and brandy; the quantity of wine in his drink was diminished;
+and the frequent use of the pediluvium was enjoined. The air-clysters
+were discontinued, as his stools were not offensive, and his _Abdomen_
+less distended.
+
+22. His pulse was now small, irregular, and beat 130 strokes in a
+minute. The _Dyspnoea_ was greatly increased; his skin was hot, and
+bedewed with a clammy moisture; and every symptom seemed to indicate the
+approach of death. In this state he continued till evening, when he
+recruited a little. The next day he had several slight convulsions. His
+urine which was voided plentifully, still put on the appearance of whey
+when cold. Cordial and antispasmodic draughts, composed of camphor,
+tincture of castor, and _Sp. vol. aromat._ were now directed; and wine
+was liberally administered.
+
+24. He rose from his bed, and by the assistance of his attendants walked
+across the chamber. Soon after he was seized with a violent convulsion,
+in which he expired.
+
+To adduce a case which terminated fatally as a proof of the efficacy of
+any medicine, recommended to the attention of the public, may perhaps
+appear singular; but cannot be deemed absurd, when that remedy answered
+the purposes for which it was intended. For in the instance before us;
+fixed air was employed, not with an expectation that it would cure the
+fever, but to obviate the symptoms of putrefaction, and to allay the
+uneasy irritation in the bowels. The disease was too malignant, the
+nervous system too violently affected, and the strength of the patient
+too much exhausted by the discharges of blood which he suffered, to
+afford hopes of recovery from the use of the most powerful antiseptics.
+
+But in the succeeding case the event proved more fortunate.
+
+Elizabeth Grundy, aged seventeen, was attacked on the 10th of December
+1772, with the usual symptoms of a continued fever. The common method of
+cure was pursued; but the disease increased, and soon assumed a putrid
+type.
+
+On the 23d I found her in a constant delirium, with a _subsultus
+tendinum_. Her skin was hot and dry, her tongue black, her thirst
+immoderate, and her stools frequent, extremely offensive, and for the
+most part involuntary. Her pulse beat 130 strokes in a minute; she dosed
+much; and was very deaf. I directed wine to be administered freely; a
+blister to be applied to her back; the _pediluvium_ to be used several
+times in the day; and mephitic air to be injected under the form of a
+clyster every two hours. The next day her stools were less frequent, had
+lost their foetor, and were no longer discharged involuntarily; her
+pulse was reduced to 110 strokes in the minute; and her delirium was
+much abated. Directions were given to repeat the clysters, and to supply
+the patient liberally with wine. These means were assiduously pursued
+several days; and the young woman was so recruited by the 28th, that the
+injections were discontinued. She was now quite rational, and not averse
+to medicine. A decoction of Peruvian bark was therefore prescribed, by
+the use of which she speedily recovered her health.
+
+I might add a third history of a putrid disease, in which the mephitic
+air is now under trial, and which affords the strongest proof both of
+the _antiseptic_, and of the _tonic_ powers of this remedy; but as the
+issue of the case remains yet undetermined (though it is highly
+probable, alas! that it will be fatal) I shall relate only a few
+particulars of it. Master D. a boy of about twelve years of age, endowed
+with an uncommon capacity, and with the most amiable dispositions, has
+laboured many months under a hectic fever, the consequence of several
+tumours in different parts of his body. Two of these tumours were laid
+open by Mr. White, and a large quantity of purulent matter was
+discharged from them. The wounds were very properly treated by this
+skilful surgeon, and every suitable remedy, which my best judgment could
+suggest, was assiduously administered. But the matter became sanious, of
+a brown colour, and highly putrid. A _Diarrhoea_ succeeded; the
+patient's stools were intolerably offensive, and voided without his
+knowledge. A black fur collected about his teeth; his tongue was covered
+with _Aphthæ_; and his breath was so foetid, as scarcely to be
+endured. His strength was almost exhausted; a _subsultus tendinum_ came
+on; and the final period of his sufferings seemed to be rapidly
+approaching. As a last, but almost hopeless, effort, I advised the
+injection of clysters of mephitic air. These soon corrected the foetor
+of the patient's stools; restrained his _Diarrhoea_; and seemed to
+recruit his strength and spirits. Within the space of twenty-four hours
+his wounds assumed a more favourable appearance; the matter discharged
+from them became of a better colour and consistence; and was no longer
+so offensive to the smell. The use of this remedy has been continued
+several days, but is now laid aside. A large tumour is suddenly formed
+under the right ear; swallowing is rendered difficult and painful; and
+the patient refuses all food and medicine. Nourishing clysters are
+directed; but it is to be feared that these will renew the looseness,
+and that this amiable youth will quickly sink under his disorder[22].
+
+The use of _wort_ from its saccharine quality, and disposition to
+ferment, has lately been proposed as a remedy for the SEA SCURVY. Water
+or other liquors, already abounding with fixed air in a separate state,
+should seem to be better adapted to this purpose; as they will more
+quickly correct the putrid disposition of the fluids, and at the same
+time, by their gentle stimulus[23] increase the powers of digestion, and
+give new strength to the whole system.
+
+Dr. Priestley, who suggested both the idea and the means of executing
+it, has under the sanction of the College of Physicians, proposed the
+scheme to the Lords of the Admiralty, who have ordered trial to be made
+of it, on board some of his Majesty's ships of war. Might it not however
+give additional efficacy to this remedy, if instead of simple water, the
+infusion of malt were to be employed?
+
+I am persuaded such a medicinal drink might be prescribed also with
+great advantage in SCROPHULOUS COMPLAINTS, when not attended with a
+hectic fever; and in other disorders in which a general acrimony
+prevails, and the crasis of the blood is destroyed. Under such
+circumstances, I have seen _vibices_ which spread over the body,
+disappear in a few days from the use of wort.
+
+A gentleman who is subject to a scorbutic eruption in his face, for
+which he has used a variety of remedies with no very beneficial effect,
+has lately applied the fumes of chalk and oil of vitriol to the parts
+affected. The operation occasions great itching and pricking in the
+skin, and some degree of drowsiness, but evidently abates the serous
+discharge, and diminishes the eruption. This patient has several
+symptoms which indicate a genuine scorbutic DIATHESIS; and it is
+probable that fixed air, taken internally, would be an useful medicine
+in this case.
+
+The saline draughts of Riverius are supposed to owe their antiemetic
+effects to the air, which is separated from the salt of wormwood during
+the act of effervescence. And the tonic powers of many mineral waters
+seem to depend on this principle. I was lately desired to visit a lady
+who had most severe convulsive REACHINGS. Various remedies had been
+administered without effect, before I saw her. She earnestly desired a
+draught of malt liquor, and was indulged with half a pint of Burton beer
+in brisk effervescence. The vomitings ceased immediately, and returned
+no more. Fermenting liquors, it is well known, abound with fixed air. To
+this, and to the cordial quality of the beer, the favourable effect
+which it produced, may justly be ascribed. But I shall exceed my design
+by enlarging further on this subject. What has been advanced it is
+hoped, will suffice to excite the attention of physicians to a remedy
+which is capable of being applied to so many important medicinal
+purposes.
+
+
+NUMBER IV.
+
+_Extract of a Letter from WILLIAM FALCONER, M.D. of BATH._
+
+                                      Jan 6, 1774,
+
+     Reverend Sir,
+
+I once observed the same taste you mention (Philosophical Transactions,
+p. 156. of this Volume, p. 35.) viz. like tar water, in some water that
+I impregnated with fixed air about three years ago. I did not then know
+to what to attribute it, but your experiment seems to clear it up. I
+happened to have spent all my acid for raising effervescence, and to
+supply its place I used a bottle of dulcified spirit of nitre, which I
+knew was greatly under-saturated with spirit of wine; from which, as
+analogous to your observation, I imagine the effect proceeded.
+
+As[24] to the coagulation of the blood of animals by fixed Air, I fear
+it will scarce stand the test of experiment, as I this day gave it, I
+think, a fair trial, in the following manner.
+
+A young healthy man, at 20 years old, received a contusion by a fall,
+was instantly carried to a neighbouring surgeon, and, at my request,
+bled in the following manner.
+
+I inserted a glass funnel into the neck of a large clear phial about oz.
+x. contents, and bled him into it to about oz. viii. By these means the
+blood was exposed to the air as little a time as possible, as it flowed
+into the bottle as it came from the orifice.
+
+As soon as the quantity proposed was drawn, the bottle was carefully
+corked, and brought to me. It was then quite fluid, nor was there the
+least separation of its parts.
+
+On the surface of this I conveyed several streams of fixed air (having
+first placed the bottle with the blood in a bowl of water, heated as
+nearly to the human heat as possible) from the mixture of the vitriolic
+acid and lixiv. tartar, which I use preferably to other alkalines, as
+being (as Dr. Cullen observes) in the mildest state, and therefore most
+likely to generate most air.
+
+I shook the phial often, and threw many streams of air on the blood, as
+I have often practised with success for impregnating water; but could
+not perceive the smallest signs of coagulation, although it stood in an
+atmosphere of fixed air 20 minutes or more. I then uncorked the bottles,
+and poured off about oz. ii to which I added about 6 or 7 gtts of spirit
+of vitriol, which coagulated it immediately. I set the remainder in a
+cold place and it coagulated, as near as I could judge, in the same time
+that blood would have done newly drawn from the vein.
+
+P. 82. Perhaps the circumilance of putrid vegetables yielding all fixed
+and no inflammable air may be the causes of their proving so antiseptic,
+even when putrid, as appears by Mr. Alexander's Experiments.
+
+P. 86. Perhaps the putrid air continually exhaled may be one cause of
+the luxuriancy of plants growing on dunghills or in very rich soils.
+
+P. 146. Your observation that inflammable air consists of the union of
+some acid vapour with phlogiston, puts me in mind of an old observation
+of Dr. Cullen, that the oil separated from soap by an acid was much more
+inflammable than before, resembling essential oil, and soluble in V. sp.
+
+I have tried fixed air as an antiseptic taken in by respiration, but
+with no great success. In one case it seemed to be of service, in two it
+seemed indifferent, and in one was injurious, by exciting a cough.
+
+
+NUMBER V.
+
+_Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT MASSINGHAM,
+NORFOLK._
+
+                                      March 23, 1774.
+
+     Dear Sir,
+
+When I first received your paper, I happened to have a process going on
+for the preparation of _nitrous ether_, without distillation.[25] I had
+heretofore always taken for granted that the elastic fluid generated in
+that preparation was _fixed_ air: but on examination I found this
+combination of the nitrous acid with inflammable spirits, produced an
+elastic fluid that had the same general properties with the air that you
+unwillingly, though very properly, in my opinion, term _nitrous_; as I
+believe it is not to be procured without employing the _nitrous_ acid,
+either in a simple state, or compounded, as in _aqua regia_. I shall
+suggest, however, by and by some doubts with respect to it's title to
+the appellation of _air_.
+
+Water impregnated with your nitrous air _certainly_, as you suspected
+from it's taste, contains the nitrous acid. On saturating a quantity of
+this water with a fixed alcali, and then evaporating, &c. I have
+procured two chrystals of nitre. But the principal observations that
+have occurred to me on the subject of nitrous air are the following. My
+experiments have been few and made by snatches, under every disadvantage
+as to apparatus, &c. and with frequent interruptions; and yet I think
+they are to be depended upon.
+
+My first remark is, that nitrous air does not give water a sensibly acid
+impregnation, unless it comes into contact, or is mixed with a portion
+of common or atmospherical air: and my second, that nitrous air
+principally consists of the nitrous acid itself, reduced to the state of
+a _permanent_ vapour not condensable by cold, like other vapours, but
+which requires the presence and admixture of common air to restore it to
+its primitive state of a liquid. I am beholden for this idea, you will
+perceive, to your own very curious discovery of the true nature of Mr.
+Cavendish's _marine_ vapour.
+
+When I first repeated your experiment of impregnating water with nitrous
+air, the water, I must own tasted acid; as it did in one, or perhaps two
+trials afterwards; but, to my great astonishment, in all the following
+experiments, though some part of the factitious air, or vapour, was
+visibly absorbed by the water, I could not perceive the latter to have
+acquired any sensible acidity. I at length found, however, that I could
+render this same water _very_ acid, by means only of the nitrous air
+already included in the phial with it. Taking the inverted phial out of
+the water, I remove my finger from the mouth of it, to admit a little
+of the common air, and instantly replace my finger. The redness,
+effervescence, and diminution take place. Again taking off my finger,
+and instantly replacing it, more common, air rushes in, and the same
+phenomena recur. The process sometimes requires to be seven or eight
+times repeated, before the whole of the nitrous _vapour_ (as I shall
+venture to call it) is condensed into nitrous _acid_, by the successive
+entrance of fresh parcels of common air after each effervescence; and
+the water becomes evidently more and more acid after every such fresh
+admission of the external air, which at length ceases to enter, when the
+whole of the vapour has been condensed. No agitation of the water is
+requisite, except a gentle motion, just sufficient to rince the sides of
+the phial, in order to wash off the condensed vapour.
+
+The acidity which you (and I likewise, at first) observed in the water
+agitated with nitrous air _alone_, I account for thus. On bringing the
+phial to the mouth, the common air meeting with the nitrous vapour in
+the neck of the phial, condenses it, and impregnates the water with the
+acid, in the very act of receiving it upon the tongue. On stopping the
+mouth of the phial with my tongue for a short time and afterwards
+withdrawing it a very little, to suffer the common air to rush past it
+into the phial, the sensation of acidity has been sometimes intolerable:
+but taking a large gulph of the water at the same time, it has been
+found very slightly acid.--The following is one of the methods by which
+I have given water a very strong acid impregnation, by means of a
+mixture of nitrous and common air.
+
+Into a small phial, containing only common air, I force a quantity of
+nitrous air at random, out of a bladder, and instantly clap my finger on
+the mouth of the bottle. I then immerse the neck of it into water, a
+small quantity of which I suffer to enter, which squirts into it with
+violence; and immediately replacing my finger, remove the phial. The
+water contained in it is already _very_ acid, and it becomes more and
+more so (if a sufficient quantity of nitrous air was at first thrown in)
+on alternately stopping the mouth of the phial, and opening it, as often
+as fresh air will enter.
+
+Since I wrote the above, I have frequently converted a small portion of
+water in an ounce phial into a weak _Aqua fortis_, by repeated mixtures
+of common and nitrous air; throwing in alternately the one or the other,
+according to the circumstances; that is, as long as there was a
+superabundance of nitrous air, suffering the common air to enter and
+condense it; and, when that was effected, forcing in more nitrous air
+from the bladder, to the common air which now predominated in the
+phial--and so alternately. I have wanted leisure, and conveniences, to
+carry on this process to its _maximum_, or to execute it in a different
+and better manner; but from what I have done, I think we may conclude
+that nitrous air consists principally of the nitrous acid,
+phlogisticated, or otherwise so modified, by a previous commenstruation
+with metals, inflammable spirits, &c. as to be reduced into a durably
+elastic vapour: and that, in order to deprive it of its elasticity, and
+restore it to its former state, an addition of common air is requisite,
+and, as I suspect, of water likewise, or some other fluid: as in the
+course of my few trials, I have not yet been able to condense it in a
+perfectly dry bottle.
+
+
+NUMBER VI.
+
+_A Letter from_ Dr. FRANKLIN.
+
+                              Craven Street, April 10, 1774.
+
+     Dear Sir,
+
+In compliance with your request, I have endeavoured to recollect the
+circumstances of the American experiments I formerly mentioned to you,
+of raising a flame on the surface of some waters there.
+
+When I passed through New Jersey in 1764, I heard it several times
+mentioned, that by applying a lighted candle near the surface of some of
+their rivers, a sudden flame Would catch and spread on the water,
+continuing to burn for near half a minute. But the accounts I received
+were so imperfect that I could form no guess at the cause of such an
+effect, and rather doubted the truth of it. I had no opportunity of
+seeing the experiment; but calling to see a friend who happened to be
+just returned home from making it himself, I learned from him the manner
+of it; which was to choose a shallow place, where the bottom could be
+reached by a walking-stick, and was muddy; the mud was first to be
+stirred with the stick, and when a number of small bubbles began to
+arise from it, the candle was applied. The flame was so sudden and so
+strong, that it catched his ruffle and spoiled it, as I saw. New-Jersey
+having many pine-trees in different parts of it, I then imagined that
+something like a volatile oil of turpentine might be mixed with the
+waters from a pine-swamp, but this supposition did not quite satisfy me.
+I mentioned the fact to some philosophical friends on my return to
+England, but it was not much attended to. I suppose I was thought a
+little too credulous.
+
+In 1765, the Reverend Dr. Chandler received a letter from Dr. Finley,
+President of the College in that province, relating the same experiment.
+It was read at the Royal Society, Nov. 21, of that year, but not printed
+in the Transactions; perhaps because it was thought too strange to be
+true, and some ridicule might be apprehended if any member should
+attempt to repeat it in order to ascertain or refute it. The following
+is a copy of that account.
+
+"A worthy gentleman, who lives at a few miles distance, informed me that
+in a certain small cove of a mill-pond, near his house, he was surprized
+to see the surface of the water blaze like inflamed spirits. I soon
+after went to the place, and made the experiment with the same success.
+The bottom of the creek was muddy, and when stirred up, so as to cause a
+considerable curl on the surface, and a lighted candle held within two
+or three inches of it, the whole surface was in a blaze, as instantly as
+the vapour of warm inflammable spirits, and continued, when strongly
+agitated, for the space of several seconds. It was at first imagined to
+be peculiar to that place; but upon trial it was soon found, that such a
+bottom in other places exhibited the same phenomenon. The discovery was
+accidentally made by one belonging to the mill."
+
+I have tried the experiment twice here in England, but without success.
+The first was in a slow running water with a muddy bottom. The second in
+a stagnant water at the bottom of a deep ditch. Being some time employed
+in stirring this water, I ascribed an intermitting fever, which seized
+me a few days after, to my breathing too much of that foul air which I
+stirred up from the bottom, and which I could not avoid while I stooped
+in endeavouring to kindle it.--The discoveries you have lately made of
+the manner in which inflammable air is in some cases produced, may throw
+light on this experiment, and explain its succeeding in some cases, and
+not in others. With the highest esteem and respect,
+
+     I am, Dear Sir,
+
+       Your most obedient humble servant,
+
+         B. FRANKLIN.
+
+
+NUMBER VII.
+
+_Extract of a Letter from_ Mr. HENRY _of_ Manchester.
+
+It is with great pleasure I hear of your intended publication _on air_,
+and I beg leave to communicate to you an experiment or two which I
+lately made.
+
+Dr. Percival had tried, without effect, to dissolve lead in water
+impregnated with fixed air. I however thought it probable, that the
+experiment might succeed with nitrous air. Into a quantity of water
+impregnated with it, I put several pieces of sheet-lead, and suffered
+them, after agitation, to continue immersed about two hours. A few drops
+of vol. tincture of sulphur changed the water to a deep orange colour,
+but not so deep as when the same tincture was added to a glass of the
+same water, into which one drop of a solution of sugar of lead had been
+instilled. The precipitates of both in the morning, were exactly of the
+same kind; and the water in which the lead had been infused all night,
+being again tried by the same test, gave signs of a still stronger
+saturnine impregnation--Whether the nitrous air acts as an acid on the
+lead, or in the same manner that fixed air dissolves iron, I do not
+pretend to determine. Syrup of violets added to the nitrous water became
+of a pale red, but on standing about an hour, grew of a turbid brown
+cast.
+
+Though the nitrous acid is not often found, except produced by art, yet
+as there is a probability that nitre may be formed in the earth in large
+towns, and indeed fossile nitre has been actually found in such
+situations, it should be an additional caution against the use of leaden
+pumps.
+
+I tried to dissolve mercury by the same means, but without success.
+
+     I am, with the most sincere esteem,
+
+       Dear Sir,
+
+         Your obliged and obedient servant,
+
+           THO. HENRY.
+
+
+_FINIS._
+
+FOOTNOTES:
+
+[15] See Dr. Falconer's very useful and ingenious treatise on the Bath
+water, 2d edit. p. 313.
+
+[16] May, 1772.
+
+[17] Vid. Mr. White's useful treatise on the management of pregnant and
+lying-in women, p. 279.
+
+[18] See the author's observations on the efficacy of external
+applications in the ulcerous sore throats, Essays medical and
+experimental, Vol. I. 2d edit. p. 377.
+
+[19] The author of these observations.
+
+[20] Directions for impregnating water with fixed air, in order to
+communicate to it the peculiar spirit and virtues of Pyrmont water, and
+other mineral waters of a similar nature.
+
+[21] Referring to the case communicated by Mr. Hey.
+
+[22] He languished about a week, and then died.
+
+[23] The vegetables which are most efficacious in the cure of the
+scurvy, possess some degree of a stimulating power.
+
+[24] This refers, to an experiment mentioned in the first publication of
+these papers in the Philosophical Transactions, but omitted in this
+volume.
+
+[25] The first account of this curious process was, I believe, given in
+the Mem. de l'Ac. de Sc. de Paris for 1742. Though seemingly less
+volatile than the vitriolic ether, it boils with a much smaller degree
+of heat. One day last summer, it boiled in the coolest room of my house;
+as it gave me notice by the explosion attending its driving out the
+cork. To save the bottle, and to prevent the total loss of the liquor by
+evaporation, I found myself obliged instantly to carry it down to my
+cellar.
+
+
+
+
+ERRATA.
+
+
+     P. 15. l. 13.  _for_  it to  _read_  to it
+
+     p. 24. l. 20.    ----       has      ----      had
+
+     p. 60. l. 22.    ----     inflammable ----     in inflammable
+
+     p. 84. l. 5.     ----     experiments ----     experiment
+
+     p. 145. l. 16.   ----     with        ----     of
+
+     p. 153. l. 1.    ----     that is     ----     this air
+
+     p. 199. l. 17.   ----     ingenious   ----     ingenuous
+
+     p. 211. l. 23.   ----     of          ----     , if
+
+     p. 243. l. 27.   ----     diminishing ----     diminished
+
+     p. 272. l. 21.   ----     seem        ----     seems
+
+     p. 301. l. 31.   ----     ----        ----     one end
+
+     p. 303. l. 5.    ----     ----        ----     the nitrous
+
+     p. 304. l. 21.   ----     deslrium    ----     delirium
+
+     p. 306. l. 2.    ----     recet.      ----     recent.
+
+     p. 308. l. 7.    ----     per         ----     Peruv.
+
+     p. 313. l. 27.   ----     usual       ----     useful
+
+     p. 300. to 314.  passim   ----        Diarrhæa ---- Diarrhoea
+
+     p. 316. l. 11.   ----     remains     ----     remainder
+
+     p. 524. l. 15.   ----     it          ----     iron.
+
+
+
+
+A CATALOGUE of BOOKS written by
+
+JOSEPH PRIESTLEY, LL.D. F.R.S.,
+
+_And printed for_
+
+J. JOHNSON, BOOKSELLER, at No. 72,
+
+St. Paul's Church-Yard, London.
+
+
+1. The HISTORY and PRESENT STATE of ELECTRICITY, with original
+Experiments, illustrated with Copper Plates. 4th Edit, corrected and
+enlarged, 4to. 1l. 1s.
+
+2. A FAMILIAR INTRODUCTION to the STUDY of ELECTRICITY, 2d Edit. 8vo.
+2s. 6d.
+
+3. The HISTORY and PRESENT STATE of DISCOVERIES relating to VISION,
+LIGHT, and COLOURS, 2 vols. 4to. illustrated with a great Number of
+Copper Plates, 1l. 11s. 6d. in Boards.
+
+4. A FAMILIAR INTRODUCTION to the THEORY and PRACTICE of PERSPECTIVE,
+with Copper Plates, 5s. in Boards.
+
+5. DIRECTIONS for impregnating Water with FIXED AIR, in order to
+communicate to it the peculiar Spirit and Virtues of PYRMONT WATER, and
+other Mineral Waters of a similar Nature, 1s.
+
+6. Experiments and Observations on different Kinds of Air, with Copper
+Plates, 2d Edit. 5s. in Boards.
+
+7. A NEW CHART of HISTORY, containing a View of the principal
+Revolutions of Empire that have taken Place in the World; with a Book
+describing it, containing an Epitome of Universal History, 10s. 6d.
+
+8. A CHART of BIOGRAPHY, with a Book, containing an Explanation of it,
+and a Catalogue of all the Names inserted in it, 4th Edit, very much
+improved, 10s. 6d.
+
+9. An Essay on a Course of liberal Education for Civil and Active Life;
+with Plans of Lectures on, 1. The Study of History and general Policy.
+2. The History of England. 3. The Constitution and Laws of England. To
+which are added Remarks on Dr. Browne's proposed Code of Education.
+
+10. The RUDIMENTS of ENGLISH GRAMMAR, adapted to the Use of Schools, 1s.
+6d.
+
+11. The above GRAMMAR, with Notes and Observations, for the Use of those
+who have made some Proficiency in the Language, 4th Ed. 3s.
+
+12. An ESSAY on the FIRST PRINCIPLES of GOVERNMENT, and on the Nature of
+POLITICAL, CIVIL, and RELIGIOUS LIBERTY, 2d Edit, much enlarged, 5s.
+
+13. INSTITUTES of NATURAL and REVEALED RELIGION, Vol. I. containing the
+Elements of Natural Religion; to which is prefixed, An Essay on the best
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+Societies, 2s. 6d. sewed.--Vol. II. containing the Evidences of the
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+Doctrines of Revelation, 2s. 6d. sewed.--Preparing for the Press (March
+1775) the fourth and last Part of this Work, containing a View of the
+Corruptions of Christianity.
+
+14. An Examination of Dr. Reid's Enquiry into the Human Mind, on the
+Principles of Common Sense, Dr. Beattie's Essay on the Nature and
+Immutability of Truth, and Dr. Oswald's Appeal to Common Sense in behalf
+of Religion. To which is added the Correspondence of Dr. Beattie and Dr.
+Oswald with the Author, 2d Edit. 5s. unbound.
+
+15. A FREE ADDRESS to PROTESTANT DISSENTERS, on the Subject of the
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+
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+
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+
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+Letter to the Rev. Mr. VENN, in Answer to his Examination of the Address
+to Protestant Dissenters, 1s. 6d.
+
+19. A CATECHISM for CHILDREN and YOUNG PERSONS, 2d Edit. 3d.
+
+20. A SCRIPTURE CATECHISM, consisting of a Series of Questions, with
+References to the Scriptures instead of Answers, 3d.
+
+21. A Serious ADDRESS to MASTERS of FAMILIES, with Forms of Family
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+
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+at Mill Hill Chapel, in Leeds, May 16, 1773, on Occasion of his
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+
+25. A FREE ADDRESS to PROTESTANT DISSENTERS, as such. By a Dissenter. A
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+those who buy this Pamphlet to give away.
+
+26. Letters to the Author of _Remarks on several late Publications
+relative to the Dissenters, in a Letter to Dr. Priestley_, 1s.
+
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+
+28. A FAMILIAR ILLUSTRATION of certain Passages of Scripture relating to
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+
+29. The TRIUMPH of TRUTH; being an Account of the Trial of Mr. E.
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+
+30. CONSIDERATIONS for the USE of YOUNG MEN, and the Parents of YOUNG
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+
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+End of the Project Gutenberg EBook of Experiments and Observations on
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+    <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" />
+    <title>
+      The Project Gutenberg eBook of Experiments And Observations On Different Kinds Of Air, by Joseph Priestley.
+    </title>
+    <style type="text/css">
+
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+<pre>
+
+The Project Gutenberg EBook of Experiments and Observations on Different
+Kinds of Air, by Joseph Priestley
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Experiments and Observations on Different Kinds of Air
+
+Author: Joseph Priestley
+
+Release Date: August 19, 2009 [EBook #29734]
+
+Language: English
+
+Character set encoding: ISO-8859-1
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EXPERIMENTS, OBSERVATIONS ON AIR ***
+
+
+
+
+Produced by Mark C. Orton, Steven Gibbs, Josephine Paolucci
+and the Online Distributed Proofreading Team at
+https://www.pgdp.net.
+
+
+
+
+
+
+</pre>
+
+
+
+<div class="figcenter" style="width: 700px;">
+<img src="images/illus-001.jpg" width="700" height="562" alt="To face the Title." title="" />
+<span class="caption">To face the Title.</span>
+</div>
+
+
+<h1>EXPERIMENTS AND OBSERVATIONS ON DIFFERENT KINDS OF AIR.</h1>
+
+<h4>[Price 5s. unbound.]</h4>
+
+<div class="blockquot"><p>Quamobrem, si qua est erga Creatorem humilitas, si qua operum
+ejus reverentia et magnificatio, si qua charitas in homines, si
+erga necessitates et &aelig;rumnas humanas relevandas studium, si
+quis amor veritatis in naturalibus, et odium tenebrarum, et
+intellectus purificandi desiderium; orandi sunt homines iterum
+atque iterum, ut, missis philosophiis istis volaticis et
+preposteris, qu&aelig; theses hypothesibus anterposuerunt, et
+experientiam captivam duxerunt, atque de operibus dei
+triumpharunt, summisse, et cum veneratione quadam, ad volumen
+creaturarum evolvendum accedant; atque in eo moram faciant,
+meditentur, et ab opinionibus abluti et mundi, caste et integre
+versentur.&mdash;&mdash;In interpretatione ejus eruenda nulli oper&aelig;
+parcant, sed strenue procedant, persistant, immoriantur.</p>
+
+<p class="right">
+<span class="smcap">Lord Bacon in Instauratione Magna.</span><br />
+</p>
+
+</div>
+
+
+
+<hr style="width: 65%;" />
+<h2>EXPERIMENTS</h2>
+
+<h4>AND</h4>
+
+<h2>OBSERVATIONS</h2>
+
+<h3>ON DIFFERENT KINDS OF</h3>
+
+<h1>AIR.</h1>
+
+
+<h2>By JOSEPH PRIESTLEY, LL.D. F.R.S.</h2>
+
+<h4>The SECOND EDITION Corrected.</h4>
+
+<p>
+<span style="margin-left: 2.5em;">Fert animus Causas tantarum expromere rerum;</span><br />
+<span style="margin-left: 2.5em;">Immensumque aperitur opus.</span><br />
+<br />
+<span style="margin-left: 14em;"><span class="smcap">Lucan</span></span><br />
+</p>
+
+<p class="center">LONDON:<br /><br />
+
+Printed for <span class="smcap">J. Johnson</span>, No. 72, in St. Paul's Church-Yard.<br /><br />
+
+MDCCLXXV.</p>
+
+
+<p class="center">
+TO THE RIGHT HONOURABLE<br />
+THE EARL OF SHELBURNE,<br />
+THIS TREATISE IS<br />
+WITH THE GREATEST GRATITUDE<br />
+AND RESPECT,<br />
+INSCRIBED,<br />
+BY HIS LORDSHIP's<br />
+MOST OBLIGED,<br />
+AND OBEDIENT<br />
+HUMBLE SERVANT,<br />
+J. PRIESTLEY.<br />
+</p>
+
+<p class="notes">Transcriber's Note: Footnotes have been moved to the end of the chapter.
+The errata listed at the end of the book have been corrected in the
+text.</p>
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_v" id="Page_v">[Pg v]</a></span></p>
+<h2>THE PREFACE.</h2>
+
+
+<p>One reason for the present publication has been the favourable reception
+of those of my <i>Observations on different kinds of air</i>, which were
+published in the Philosophical Transactions for the year 1772, and the
+demand for them by persons who did not chuse, for the sake of those
+papers only, to purchase the whole volume in which they were contained.
+Another motive was the <i>additions</i> to my observations on this subject,
+in consequence of which my papers grew too large for such a publication
+as the <i>Philosophical Transactions</i>.</p>
+
+<p>Contrary, therefore, to my intention, expressed Philosophical
+Transactions, vol. 64. p. 90, but with the approbation of the President,
+and of my friends in the society,<span class='pagenum'><a name="Page_vi" id="Page_vi">[Pg vi]</a></span> I have determined to send them no
+more papers for the present on this subject, but to make a separate and
+immediate publication of all that I have done with respect to it.</p>
+
+<p>Besides, considering the attention which, I am informed, is now given to
+this subject by philosophers in all parts of Europe, and the rapid
+progress that has already been made, and may be expected to be made in
+this branch of knowledge, all unnecessary delays in the publication of
+experiments relating to it are peculiarly unjustifiable.</p>
+
+<p>When, for the sake of a little more reputation, men can keep brooding
+over a new fact, in the discovery of which they might, possibly, have
+very little real merit, till they think they can astonish the world with
+a system as complete as it is new, and give mankind a prodigious idea of
+their judgment and penetration; they are justly punished for their
+ingratitude to the fountain of all knowledge, and for their want of a
+genuine love of science and of<span class='pagenum'><a name="Page_vii" id="Page_vii">[Pg vii]</a></span> mankind, in finding their boasted
+discoveries anticipated, and the field of honest fame pre-occupied, by
+men, who, from a natural ardour of mind, engage in philosophical
+pursuits, and with an ingenuous simplicity immediately communicate to
+others whatever occurs to them in their inquiries.</p>
+
+<p>As to myself, I find it absolutely impossible to produce a work on this
+subject that shall be any thing like <i>complete</i>. My first publication I
+acknowledged to be very imperfect, and the present, I am as ready to
+acknowledge, is still more so. But, paradoxical as it may seem, this
+will ever be the case in the progress of natural science, so long as the
+works of God are, like himself, infinite and inexhaustible. In
+completing one discovery we never fail to get an imperfect knowledge of
+others, of which we could have no idea before; so that we cannot solve
+one doubt without creating several new ones.</p>
+
+<p>Travelling on this ground resembles Pope's description of travelling
+among<span class='pagenum'><a name="Page_viii" id="Page_viii">[Pg viii]</a></span> the Alps, with this difference, that here there is not only
+<i>succession</i>, but an <i>increase</i> of new objects and new difficulties.</p>
+
+<p>
+<span style="margin-left: 2.5em;">So pleas'd at first the tow'ring Alps we try,</span><br />
+<span style="margin-left: 2.5em;">Mount o'er the vales, and seem to tread the sky.</span><br />
+<span style="margin-left: 2.5em;">Th' eternal snows appear already past,</span><br />
+<span style="margin-left: 2.5em;">And the first clouds and mountains seem the last,</span><br />
+<span style="margin-left: 2.5em;">But those attain'd, we tremble to survey</span><br />
+<span style="margin-left: 2.5em;">The growing labours of the lengthen'd way.</span><br />
+<span style="margin-left: 2.5em;">Th' increasing prospect tires our wand'ring eyes,</span><br />
+<span style="margin-left: 2.5em;">Hills peep o'er hills, and Alps on Alps arise.</span><br />
+<br />
+<span style="margin-left: 14em;"><span class="smcap">Essay on Criticism.</span></span><br />
+</p>
+
+<p>Newton, as he had very little knowledge of <i>air</i>, so he had few doubts
+concerning it. Had Dr. Hales, after his various and valuable
+investigations, given a list of all his <i>desiderata</i>, I am confident
+that he would not have thought of one in ten that had occurred to me at
+the time of my last publication; and my doubts, queries, and hints for
+new experiments are very considerably increased, after a series of
+investigations, which have thrown great light upon many things of which
+I was not able to give any explanation before.<span class='pagenum'><a name="Page_ix" id="Page_ix">[Pg ix]</a></span></p>
+
+<p>I would observe farther, that a person who means to serve the cause of
+science effectually, must hazard his own reputation so far as to risk
+even <i>mistakes</i> in things of less moment. Among a multiplicity of new
+objects, and new relations, some will necessarily pass without
+sufficient attention; but if a man be not mistaken in the principal
+objects of his pursuits, he has no occasion to distress himself about
+lesser things.</p>
+
+<p>In the progress of his inquiries he will generally be able to rectify
+his own mistakes; or if little and envious souls should take a malignant
+pleasure in detecting them for him, and endeavouring to expose him, he
+is not worthy of the name of a philosopher, if he has not strength of
+mind sufficient to enable him not to be disturbed at it. He who does not
+foolishly affect to be above the failings of humanity, will not be
+mortified when it is proved that he is but a man.</p>
+
+<p>In this work, as well as in all my other philosophical writings, I have
+made it a<span class='pagenum'><a name="Page_x" id="Page_x">[Pg x]</a></span> rule not to conceal the <i>real views</i> with which I have made
+experiments; because though, by following a contrary maxim, I might have
+acquired a character of greater sagacity, I think that two very good
+ends are answered by the method that I have adopted. For it both tends
+to make a narrative of a course of experiments more interesting, and
+likewise encourages other adventurers in experimental philosophy;
+shewing them that, by pursuing even false lights, real and important
+truths may be discovered, and that in seeking one thing we often find
+another.</p>
+
+<p>In some respects, indeed, this method makes the narrative <i>longer</i>, but
+it is by making it less tedious; and in other respects I have written
+much more concisely than is usual with those who publish accounts of
+their experiments. In this treatise the reader will often find the
+result of long processes expressed in a few lines, and of many such in a
+single paragraph; each of which, if I had, with the usual parade,
+described it at large (explaining first the <i>preparation</i>, then reciting
+the <i>experiment</i><span class='pagenum'><a name="Page_xi" id="Page_xi">[Pg xi]</a></span> itself, with the <i>result</i> of it, and lastly making
+suitable <i>reflections</i>) would have made as many sections or chapters,
+and have swelled my book to a pompous and respectable size. But I have
+the pleasure to think that those philosophers who have but little time
+to spare for <i>reading</i>, which is always the case with those who <i>do</i>
+much themselves, will thank me for not keeping them too long from their
+own pursuits; and that they will find rather more in the volume, than
+the appearance of it promises.</p>
+
+<p>I do not think it at all degrading to the business of experimental
+philosophy, to compare it, as I often do, to the diversion of <i>hunting</i>,
+where it sometimes happens that those who have beat the ground the most,
+and are consequently the best acquainted with it, weary themselves
+without starting any game; when it may fall in the way of a mere
+passenger; so that there is but little room for boasting in the most
+successful termination of the chace.<span class='pagenum'><a name="Page_xii" id="Page_xii">[Pg xii]</a></span></p>
+
+<p>The best founded praise is that which is due to the man, who, from a
+supreme veneration for the God of nature, takes pleasure in
+contemplating his <i>works</i>, and from a love of his fellow-creatures, as
+the offspring of the same all-wise and benevolent parent, with a
+grateful sense and perfect enjoyment of the means of happiness of which
+he is already possessed, seeks, with earnestness, but without murmuring
+or impatience, that greater <i>command of the powers of nature</i>, which can
+only be obtained by a more extensive and more accurate <i>knowledge</i> of
+them; and which alone can enable us to avail ourselves of the numerous
+advantages with which we are surrounded, and contribute to make our
+common situation more secure and happy.</p>
+
+<p>Besides, the man who believes that there is a <i>governor</i> as well as a
+<i>maker</i> of the world (and there is certainly equal reason to believe
+both) will acknowledge his providence and favour at least as much<span class='pagenum'><a name="Page_xiii" id="Page_xiii">[Pg xiii]</a></span> in a
+successful pursuit of <i>knowledge</i>, as of <i>wealth</i>; which is a sentiment
+that entirely cuts off all boasting with respect to ourselves, and all
+envy and jealousy with respect to others; and disposes us mutually to
+rejoice in every new light that we receive, through whose hands soever
+it be conveyed to us.</p>
+
+<p>I shall pass for an enthusiast with some, but I am perfectly easy under
+the imputation, because I am happy in those views which subject me to
+it; but considering the amazing improvements in natural knowledge which
+have been made within the last century, and the many ages, abounding
+with men who had no other object but study, in which, however, nothing
+of this kind was done, there appears to me to be a very particular
+providence in the concurrence of those circumstances which have produced
+so great a change; and I cannot help flattering myself that this will be
+instrumental in bringing about other changes in the state<span class='pagenum'><a name="Page_xiv" id="Page_xiv">[Pg xiv]</a></span> of the world,
+of much more consequence to the improvement and happiness of it.</p>
+
+<p>This rapid progress of knowledge, which, like the progress of a <i>wave</i>
+of the sea, of <i>sound</i>, or of <i>light</i> from the sun, extends itself not
+this way or that way only, but <i>in all directions</i>, will, I doubt not,
+be the means, under God, of extirpating <i>all</i> error and prejudice, and
+of putting an end to all undue and usurped authority in the business of
+<i>religion</i>, as well as of <i>science</i>; and all the efforts of the
+interested friends of corrupt establishments of all kinds will be
+ineffectual for their support in this enlightened age: though, by
+retarding their downfal, they may make the final ruin of them more
+complete and glorious. It was ill policy in Leo the Xth to patronize
+polite literature. He was cherishing an enemy in disguise. And the
+English hierarchy (if there be any thing unsound in its constitution)
+has equal reason to tremble even at an air-pump, or an electrical
+machine.<span class='pagenum'><a name="Page_xv" id="Page_xv">[Pg xv]</a></span></p>
+
+<p>There certainly never was any period in which <i>natural knowledge</i> made
+such a progress as it has done of late years, and especially in this
+country; and they who affect to speak with supercilious contempt of the
+publications of the present age in general, or of the Royal Society in
+particular, are only those who are themselves engaged in the most
+trifling of all literary pursuits, who are unacquainted with all real
+science, and are ignorant of the progress and present state of it.<a name="FNanchor_1_1" id="FNanchor_1_1"></a><a href="#Footnote_1_1" class="fnanchor">[1]</a></p>
+
+<p>It is true that the rich and the great in this country give less
+attention to these subjects than, I believe, they were ever known to do,
+since the time of Lord Bacon, and much less than men of rank and fortune
+in other countries give to them. But with us this loss is<span class='pagenum'><a name="Page_xvi" id="Page_xvi">[Pg xvi]</a></span> made up by
+men of leisure, spirit, and ingenuity, in the middle ranks of life,
+which is a circumstance that promises better for the continuance of this
+progress in useful knowledge than any noble or royal patronage. With us,
+politics chiefly engage the attention of those who stand foremost in the
+community, which, indeed, arises from the <i>freedom</i> and peculiar
+<i>excellence</i> of our constitution, without which even the spirit of men
+of letters in general, and of philosophers in particular, who never
+directly interfere in matters of government, would languish.</p>
+
+<p>It is rather to be regretted, however, that, in such a number of
+nobility and gentry, so very few should have any taste for scientifical
+pursuits, because, for many valuable purposes of science, <i>wealth</i> gives
+a decisive advantage. If extensive and lasting <i>fame</i> be at all an
+object, literary, and especially scientifical pursuits, are preferable
+to political ones in a variety of respects. The former are as much more
+favourable for the display of the<span class='pagenum'><a name="Page_xvii" id="Page_xvii">[Pg xvii]</a></span> human faculties than the latter, as
+the <i>system of nature</i> is superior to any <i>political system</i> upon earth.</p>
+
+<p>If extensive <i>usefulness</i> be the object, science has the same advantage
+over politics. The greatest success in the latter seldom extends farther
+than one particular country, and one particular age; whereas a
+successful pursuit of science makes a man the benefactor of all mankind,
+and of every age. How trifling is the fame of any statesman that this
+country has ever produced to that of Lord Bacon, of Newton, or of Boyle;
+and how much greater are our obligations to such men as these, than to
+any other in the whole <i>Biographia Britannica</i>; and every country, in
+which science has flourished, can furnish instances for similar
+observations.</p>
+
+<p>Here my reader will thank me, and the writer will, I hope, forgive me,
+if I quote a passage from the postscript of a letter which I happen to
+have just received from that excellent, and in my<span class='pagenum'><a name="Page_xviii" id="Page_xviii">[Pg xviii]</a></span> opinion, not too
+enthusiastical philosopher, father Beccaria of Turin.</p>
+
+<div class="blockquot"><p><i>Mi spiace che il mondo politico ch'&egrave; pur tanto passeggero,
+rubbi il grande Franklin al mondo della natura, che non sa ne
+cambiare, ne mancare.</i> In English. "I am sorry that the
+<i>political world</i>, which is so very transitory, should take the
+great Franklin from the <i>world of nature</i>, which can never
+change, or fail."</p></div>
+
+<p>I own it is with peculiar pleasure that I quote this passage, respecting
+this truly great man, at a time when some of the infatuated politicians
+of this country are vainly thinking to build their wretched and
+destructive projects, on the ruins of his established reputation; a
+reputation as extensive as the spread of science itself, and of which it
+is saying very little indeed, to pronounce that it will last and
+flourish when the names of all his enemies shall be forgotten.<span class='pagenum'><a name="Page_xix" id="Page_xix">[Pg xix]</a></span></p>
+
+<p>I think it proper, upon this occasion, to inform my friends, and the
+public, that I have, for the present, suspended my design of writing
+<i>the history and present state of all the branches of experimental
+philosophy</i>. This has arisen not from any dislike of the undertaking,
+but, in truth, because I see no prospect of being reasonably indemnified
+for so much labour and expence, notwithstanding the specimens I have
+already given of that work (in the <i>history of electricity</i>, and of the
+<i>discoveries relating to vision, light, and colours</i>) have met with a
+much more favourable reception from the best judges both at home and
+abroad, than I expected. Immortality, if I should have any view to it,
+is not the proper price of such works as these.</p>
+
+<p>I propose, however, having given so much attention to the subject of
+<i>air</i>, to write, at my leisure, the history and<span class='pagenum'><a name="Page_xx" id="Page_xx">[Pg xx]</a></span> present state of
+discoveries relating to it; in which case I shall, as a part of it,
+reprint this work, with such improvements as shall have occurred to me
+at that time; and I give this notice of it, that no person who intends
+to purchase it may have reason (being thus apprised of my intention) to
+complain of buying the same thing twice. If any person chuse it, he may
+save his five or six shillings for the present, and wait five or six
+years longer (if I should live so long) for the opportunity of buying
+the same thing, probably much enlarged, and at the same time a complete
+account of all that has been done by others relating to this subject.</p>
+
+<p>Though for the plain, and I hope satisfactory reason above mentioned, I
+shall probably write no other <i>histories</i> of this kind, I shall, as
+opportunity serves, endeavour to provide <i>materials</i> for such histories,
+by continuing my experiments, keeping my eyes open to such new
+appearances as may present themselves, investigating them as far as I
+shall be able, and<span class='pagenum'><a name="Page_xxi" id="Page_xxi">[Pg xxi]</a></span> never failing to communicate to the public, by some
+channel or other, the result of my observations.</p>
+
+<p>In the publication of this work I have thought that it would be
+agreeable to my readers to preserve, in some measure, the order of
+history, and therefore I have not thrown together all that I have
+observed with respect to each kind of air, but have divided the work
+into <i>two parts</i>; the former containing what was published before, in
+the Philosophical Transactions, with such observations and corrections
+as subsequent experience has suggested to me; and I have reserved for
+the latter part of the work an account of the experiments which I have
+made since that publication, and after a pretty long interruption in my
+philosophical pursuits, in the course of the last summer. Besides I am
+sensible that in the latter part of this work a different arrangement of
+the subjects will be more convenient, for their mutual illustration.<span class='pagenum'><a name="Page_xxii" id="Page_xxii">[Pg xxii]</a></span></p>
+
+<p>Some persons object to the term <i>air</i>, as applied to <i>acid</i>, <i>alkaline</i>,
+and even <i>nitrous air</i>; but it is certainly very convenient to have a
+common term by which to denote things which have so many common
+properties, and those so very striking; all of them agreeing with the
+air in which we breathe, and with <i>fixed air</i>, in <i>elasticity</i>, and
+<i>transparency</i>, and in being alike affected by heat or cold; so that to
+the eye they appear to have no difference at all. With much more reason,
+as it appears to me, might a person object to the common term <i>metal</i>,
+as applied to things so very different from one another as gold,
+quicksilver, and lead.</p>
+
+<p>Besides, <i>acid</i> and <i>alkaline</i> air do not differ from <i>common air</i> (in
+any respect that can countenance an objection to their having a common
+appellation) except in such properties as are common to it with <i>fixed
+air</i>, though in a different degree; viz. that of being imbibed by water.
+But, indeed, all kinds of air, common air itself not excepted, are
+capable of being imbibed by water in some degree.<span class='pagenum'><a name="Page_xxiii" id="Page_xxiii">[Pg xxiii]</a></span></p>
+
+<p>Some may think the terms acid and alkaline <i>vapour</i> more proper than
+acid and alkaline <i>air</i>. But the term <i>vapour</i> having always been
+applied to elastic matters capable of being condensed in the temperature
+of the atmosphere, especially the vapour of water, it seems harsh to
+apply it to any elastic substance, which at the same time that it is as
+transparent as the air we breathe, is no more affected by cold than it
+is.</p>
+
+<p>As my former papers were immediately translated into several foreign
+languages, I may presume that this treatise, having a better title to
+it, will be translated also; and, upon this presumption, I cannot help
+expressing a wish, that it may be done by persons who have a competent
+knowledge of <i>subject</i>, as well as of the <i>English language</i>. The
+mistakes made by some foreigners, have induced me to give this caution.</p>
+
+<p>
+<span style="margin-left: 2.5em;"><i>London, Feb.</i></span><br />
+<span style="margin-left: 5em;"><i>1774.</i></span><br />
+</p>
+
+<hr style="width: 45%;" /><p><span class='pagenum'><a name="Page_xxiv" id="Page_xxiv">[Pg xxiv]</a></span></p>
+
+<h3>ADVERTISEMENT.</h3>
+
+<p>The <i>weights</i> mentioned in the course of this treatise are <i>Troy</i>, and
+what is called <i>an ounce measure of air</i>, is the space occupied by an
+ounce weight of water, which is equal to 480 grains, and is, therefore,
+almost two <i>cubic inches</i> of water; for one cubic inch weighs 254
+grains.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_1_1" id="Footnote_1_1"></a><a href="#FNanchor_1_1"><span class="label">[1]</span></a> See Sir John Pringle's <i>Discourse on the different kinds of
+air</i>, p. 29, which, if it became me to do it, I would recommend to the
+reader, as containing a just and elegant account of the several
+discoveries that have been successively made, relating to the subject of
+this treatise.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>THE CONTENTS.</h2>
+
+
+<p>
+<span class="smcap">The</span> INTRODUCTION.<br />
+<br />
+Section I. <i>A general view of <span class="smcap">preceding
+Discoveries</span> relating to <span class="smcap">Air</span></i>                  <span class="tocnum">Page <a href='#Page_1'>1</a></span> <br />
+<br />
+Sect. II. <i>An Account of the <span class="smcap">Apparatus</span>
+with which the following Experiments were made</i>                  <span class="tocnum"><a href='#Page_6'>6</a></span> <br />
+<br />
+<br />
+PART I.<br />
+<br />
+<i>Experiments and Observations made in, and before the Year 1772.</i>      <span class="tocnum"><a href='#Page_23'>23</a></span> <br />
+<br />
+Sect. I. <i>Of <span class="smcap">Fixed Air</span></i>                              <span class="tocnum"><a href='#Page_25'>25</a></span> <br />
+<br />
+Sect. II. <i>Of <span class="smcap">Air</span> in which a <span class="smcap">Candle</span>, or
+<span class="smcap">Brimstone</span>, has burned out</i>                             <span class="tocnum"><a href='#Page_43'>43</a></span> <br />
+<br />
+Sect. III. <i>Of <span class="smcap">inflammable Air</span></i>                      <span class="tocnum"><a href='#Page_55'>55</a></span> <br />
+<br />
+Sect. IV. <i>Of <span class="smcap">Air</span> infected with <span class="smcap">Animal
+Respiration</span>, or <span class="smcap">Putrefaction</span></i>                     <span class="tocnum"><a href='#Page_70'>70</a></span> <br />
+<br />
+Sect. V. <i>Of <span class="smcap">Air</span> in which a mixture of <span class="smcap">Brimstone</span>
+and <span class="smcap">Filings</span> of <span class="smcap">Iron</span> has stood</i>               <span class="tocnum"><a href='#Page_105'>105</a></span> <br />
+<br />
+Sect. VI. <i>Of <span class="smcap">Nitrous Air</span></i>                          <span class="tocnum"><a href='#Page_108'>108</a></span> <br />
+<br />
+Sect. VII. <i>Of <span class="smcap">Air</span> infected with the <span class="smcap">fumes</span>
+of <span class="smcap">burning Charcoal</span></i>                                      <span class="tocnum"><a href='#Page_129'>129</a></span> <br />
+<br />
+Sect. VIII. <i>Of the effect of the <span class="smcap">calcination</span>
+of <span class="smcap">Metals</span>, and of the <span class="smcap">effluvia</span> of
+<span class="smcap">Paint</span> made with <span class="smcap">White-Lead</span> and <span class="smcap">Oil</span>,
+on <span class="smcap">Air</span></i>                                            <span class="tocnum"><a href='#Page_133'>133</a></span> <br />
+<br />
+Sect. IX. <i>Of <span class="smcap">Marine Acid Air</span></i>                      <span class="tocnum"><a href='#Page_143'>143</a></span> <br />
+<br />
+Sect. X. <i>Miscellaneous Observations</i>                        <span class="tocnum"><a href='#Page_154'>154</a></span> <br />
+<br />
+<br />
+PART II.<br />
+<br />
+<i>Experiments and Observations made in the Year 1773, and the Beginning of
+1774.</i><br />
+<br />
+Sect. I. <i>Observations on <span class="smcap">Alkaline Air</span></i>             <span class="tocnum"><a href='#Page_163'>163</a></span> <br />
+<br />
+Sect. II. <i>Of <span class="smcap">common Air</span> diminished, and
+made noxious by various processes</i>                             <span class="tocnum"><a href='#Page_177'>177</a></span> <br />
+<br />
+Sect. III. <i>Of <span class="smcap">Nitrous Air</span></i>                         <span class="tocnum"><a href='#Page_203'>203</a></span> <br />
+<br />
+Sect. IV. <i>Of <span class="smcap">Marine Acid Air</span></i>                      <span class="tocnum"><a href='#Page_229'>229</a></span> <br />
+<br />
+Sect. V. <i>Of <span class="smcap">Inflammable Air</span></i>                       <span class="tocnum"><a href='#Page_242'>242</a></span> <br />
+<br />
+Sect. VI. <i>Of <span class="smcap">Fixed Air</span></i>                            <span class="tocnum"><a href='#Page_248'>248</a></span> <br />
+<br />
+Sect. VII. <span class="smcap">Miscellaneous Experiments</span>                     <span class="tocnum"><a href='#Page_252'>252</a></span> <br />
+<br />
+Sect. VIII. <i><span class="smcap">Queries, Speculations</span>, and
+<span class="smcap">Hints</span></i>                                                <span class="tocnum"><a href='#Page_258'>258</a></span> <br />
+<br />
+<br />
+<span class="smcap">The</span> APPENDIX.<br />
+<br />
+Number I. <i><span class="smcap">Experiments</span> made by Mr. Hey to
+prove that there is no <span class="smcap">Oil</span> of <span class="smcap">Vitriol</span> in water impregnated
+with <span class="smcap">Fixed Air</span></i>                                       <span class="tocnum"><a href='#Page_288'>288</a></span> <br />
+<br />
+Number II. <i>A Letter from Mr. <span class="smcap">Hey</span> to Dr.
+<span class="smcap">Priestley</span>, concerning the effects of fixed Air applied
+by way of Clyster</i>                                             <span class="tocnum"><a href='#Page_292'>292</a></span> <br />
+<br />
+Number III. <i>Observations on the <span class="smcap">Medicinal
+Uses</span> of <span class="smcap">Fixed Air</span>. By <span class="smcap">Thomas Percival</span>,
+M. D. Fellow of the <span class="smcap">Royal Society</span>, and of
+the <span class="smcap">Society</span> of <span class="smcap">Antiquaries</span> in <span class="smcap">London</span></i>      <span class="tocnum"><a href='#Page_300'>300</a></span> <br />
+<br />
+Number IV. <i>Extract of a Letter from <span class="smcap">William
+Falconer</span>, M. D. of <span class="smcap">Bath</span></i>                      <span class="tocnum"><a href='#Page_314'>314</a></span> <br />
+<br />
+Number V. <i>Extract of a Letter from Mr. <span class="smcap">William
+Bewley</span>, of <span class="smcap">Great Massingham,
+Norfolk</span></i>                                                      <span class="tocnum"><a href='#Page_317'>317</a></span> <br />
+<br />
+Num. VI. <i>A Letter from Dr. <span class="smcap">Franklin</span></i>               <span class="tocnum"><a href='#Page_321'>321</a></span> <br />
+<br />
+Number VII. <i>Extract of Letter from Mr.
+<span class="smcap">Henry</span> of <span class="smcap">Manchester</span></i>                      <span class="tocnum"><a href='#Page_323'>323</a></span> <br />
+</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span></p>
+<h2>THE INTRODUCTION.</h2>
+
+
+
+<hr style="width: 65%;" />
+<h2>SECTION I.</h2>
+
+<h3><i>A general view of <span class="smcap">preceding discoveries</span> relating to air.</i></h3>
+
+
+<p>For the better understanding of the experiments and observations on
+different kinds of air contained in this treatise, it will be useful to
+those who are not acquainted with the history of this branch of natural
+philosophy, to be informed of those facts which had been discovered by
+others, before I turned my thoughts to the subject; which suggested, and
+by the help of which I was enabled to pursue, my inquiries. Let it be
+observed, however, that I do not profess to recite in this place <i>all</i>
+that had been discovered concerning air, but only those discoveries the
+knowledge of which is necessary, in order to understand what I have done
+myself; so that any person who is only acquainted with the general
+principles of natural philosophy, may be able to<span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span> read this treatise,
+and, with proper attention, to understand every part of it.</p>
+
+<p>That the air which constitutes the atmosphere in which we live has
+<i>weight</i>, and that it is <i>elastic</i>, or consists of a compressible and
+dilatable fluid, were some of the earliest discoveries that were made
+after the dawning of philosophy in this western part of the world.</p>
+
+<p>That elastic fluids, differing essentially from the air of the
+atmosphere, but agreeing with it in the properties of weight,
+elasticity, and transparency, might be generated from solid substances,
+was discovered by Mr. Boyle, though two remarkable kinds of factitious
+air, at least the effects of them, had been known long before to all
+miners. One of these is heavier than common air. It lies at the bottom
+of pits, extinguishes candles, and kills animals that breathe it, on
+which account it had obtained the name of the <i>choke damp</i>. The other is
+lighter than common air, taking its place near the roofs of
+subterraneous places, and because it is liable to take fire, and
+explode, like gunpowder, it had been called the <i>fire damp</i>. The word
+<i>damp</i> signifies <i>vapour</i> or <i>exhalation</i> in the German and Saxon
+language.<span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span></p>
+
+<p>Though the former of these kinds of air had been known to be noxious,
+the latter I believe had not been discovered to be so, having always
+been found in its natural state, so much diluted with common air, as to
+be breathed with safety. Air of the former kind, besides having been
+discovered in various caverns, particularly the <i>grotta del Cane</i> in
+Italy, had also been observed on the surface of fermenting liquors, and
+had been called <i>gas</i> (which is the same with <i>geist</i>, or <i>spirit</i>) by
+Van Helmont, and other German chymists; but afterwards it obtained the
+name of <i>fixed air</i>, especially after it had been discovered by Dr.
+Black of Edinburgh to exist, in a fixed state, in alkaline salts, chalk,
+and other calcareous substances.</p>
+
+<p>This excellent philosopher discovered that it is the presence of the
+fixed air in these substances that renders them <i>mild</i>, and that when
+they are deprived of it, by the force of fire, or any other process,
+they are in that state which had been called <i>caustic</i>, from their
+corroding or burning animal and vegetable substances.</p>
+
+<p>Fixed air had been discovered by Dr. Macbride of Dublin, after an
+observation of Sir John Pringle's, which led to it, to be in a
+considerable degree antiseptic; and since it is<span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span> extracted in great
+plenty from fermenting vegetables, he had recommended the use of <i>wort</i>
+(that is an infusion of malt in water) as what would probably give
+relief in the sea-scurvy, which is said to be a putrid disease.</p>
+
+<p>Dr. Brownrigg had also discovered that the same species of air is
+contained in great quantities in the water of the Pyrmont spring at Spa
+in Germany, and in other mineral waters, which have what is called an
+<i>acidulous</i> taste, and that their peculiar flavour, briskness, and
+medicinal virtues, are derived from this ingredient.</p>
+
+<p>Dr. Hales, without seeming to imagine that there was any material
+difference between these kinds of air and common air, observed that
+certain substances and operations <i>generate</i> air, and others <i>absorb</i>
+it; imagining that the diminution of air was simply a taking away from
+the common mass, without any alteration in the properties of what
+remained. His experiments, however, are so numerous, and various, that
+they are justly esteemed to be the solid foundation of all our knowledge
+of this subject.</p>
+
+<p>Mr. Cavendish had exactly ascertained the specific gravities of fixed
+and inflammable air, shewing the former of them to be 1-1/2 heavier<span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span>
+than common air, and the latter ten times lighter. He also shewed that
+water would imbibe more than its own bulk of fixed air.</p>
+
+<p>Lastly, Mr. Lane discovered that water thus impregnated with fixed air
+will dissolve a considerable quantity of iron, and thereby become a
+strong chalybeate.</p>
+
+<p>These, I would observe, are by no means all the discoveries concerning
+air that have been made by the gentlemen whose names I have mentioned,
+and still less are they all that have been made by others; but they
+comprise all the previous knowledge of this subject that is necessary to
+the understanding of this treatise; except a few particulars, which will
+be mentioned in the course of the work, and which it is, therefore,
+unnecessary to recite in this place.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span></p>
+<h2>SECTION II.</h2>
+
+<h3><i>An account of the <span class="smcap">apparatus</span> with which the following experiments were
+made.</i></h3>
+
+
+<p>Rather than describe at large the manner in which every particular
+experiment that I shall have occasion to recite was made, which would
+both be very tedious, and require an unnecessary multiplicity of
+drawings, I think it more adviseable to give, at one view, an account of
+all my apparatus and instruments, or at least of every thing that can
+require a description, and of all the different operations and processes
+in which I employ them.</p>
+
+<p>It will be seen that my apparatus for experiments on air is, in fact,
+nothing more than the apparatus of Dr. Hales, Dr. Brownrigg, and Mr.
+Cavendish, diversified, and made a little more simple. Yet
+notwithstanding the simplicity of this apparatus, and the ease with
+which all the operations are conducted, I would not have any person, who
+is altogether without experience, to imagine that he shall be able to
+select any of the following experiments, and immediately perform it,
+without difficulty or<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span> blundering. It is known to all persons who are
+conversant in experimental philosophy, that there are many little
+attentions and precautions necessary to be observed in the conducting of
+experiments, which cannot well be described in words, but which it is
+needless to describe, since practice will necessarily suggest them;
+though, like all other arts in which the hands and fingers are made use
+of, it is only <i>much practice</i> that can enable a person to go through
+complex experiments, of this or any other kind, with ease and readiness.</p>
+
+<p>For experiments in which air will bear to be confined by water, I first
+used an oblong trough made of earthen ware, as <i>a</i> fig. 1. about eight
+inches deep, at one end of which I put thin flat stones, <i>b. b.</i> about
+an inch, or half an inch, under the water, using more or fewer of them
+according to the quantity of water in the trough. But I have since found
+it more convenient to use a larger wooden trough, of the same general
+shape, eleven inches deep, two feet long, and 1-1/2 wide, with a shelf
+about an inch lower than the top, instead of the flat stones
+above-mentioned. This trough being larger than the former, I have no
+occasion to make provision for the water being higher or lower, the bulk
+of a jar or two not making so great a difference as did before.<span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span></p>
+
+<p>The several kinds of air I usually keep in <i>cylindrical jars</i>, as <i>c</i>,
+<i>c</i>, fig. 1, about ten inches long, and 2-1/2 wide, being such as I have
+generally used for electrical batteries, but I have likewise vessels of
+very different forms and sizes, adapted to particular experiments.</p>
+
+<p>When I want to remove vessels of air from the large trough, I place them
+in <i>pots</i> or <i>dishes</i>, of various sizes, to hold more or less water,
+according to the time that I have occasion to keep the air, as fig. 2.
+These I plunge in water, and slide the jars into them; after which they
+may be taken out together, and be set wherever it shall be most
+convenient. For the purpose of merely removing a jar of air from one
+place to another, where it is not to stand longer than a few days, I
+make use of common <i>tea-dishes</i>, which will hold water enough for that
+time, unless the air be in a state of diminution, by means of any
+process that is going on in it.</p>
+
+<p>If I want to try whether an animal will live in any kind of air, I first
+put the air into a small vessel, just large enough to give it room to
+stretch itself; and as I generally make use of <i>mice</i> for this purpose,
+I have found it very convenient to use the hollow part of a tall
+beer-glass, <i>d</i> fig. 1, which contains between two and<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span> three ounce
+measures of air. In this vessel a mouse will live twenty minutes, or
+half an hour.</p>
+
+<p>For the purpose of these experiments it is most convenient to catch the
+mice in small wire traps, out of which it is easy to take them, and
+holding them by the back of the neck, to pass them through the water
+into the vessel which contains the air. If I expect that the mouse will
+live a considerable time, I take care to put into the vessel something
+on which it may conveniently sit, out of the reach of the water. If the
+air be good, the mouse will soon be perfectly at its ease, having
+suffered nothing by its passing through the water. If the air be
+supposed to be noxious, it will be proper (if the operator be desirous
+of preserving the mice for farther use) to keep hold of their tails,
+that they may be withdrawn as soon as they begin to shew signs of
+uneasiness; but if the air be thoroughly noxious, and the mouse happens
+to get a full inspiration, it will be impossible to do this before it be
+absolutely irrecoverable.</p>
+
+<p>In order to <i>keep</i> the mice, I put them into receivers open at the top
+and bottom, standing upon plates of tin perforated with many holes, and
+covered with other plates of the same kind, held down by sufficient
+weights, as fig. 3. These<span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span> receivers stand upon <i>a frame of wood</i>, that
+the fresh air may have an opportunity of getting to the bottoms of them,
+and circulating through them. In the inside I put a quantity of paper or
+tow, which must be changed, and the vessel washed and dried, every two
+or three days. This is most conveniently done by having another
+receiver, ready cleaned and prepared, into which the mice may be
+transferred till the other shall be cleaned.</p>
+
+<p>Mice must be kept in a pretty exact temperature, for either much heat or
+much cold kills them presently. The place in which I have generally kept
+them is a shelf over the kitchen fire-place where, as it is usual in
+Yorkshire, the fire never goes out; so that the heat varies very little,
+and I find it to be, at a medium, about 70 degrees of Fahrenheit's
+thermometer. When they had been made to pass through the water, as they
+necessarily must be in order to a change of air, they require, and will
+bear a very considerable degree of heat, to warm and dry them.</p>
+
+<p>I found, to my great surprize, in the course of these experiments, that
+mice will live intirely without water; for though I have kept them for
+three or four months, and have offered them water several times, they
+would never taste it;<span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span> and yet they continued in perfect health and
+vigour. Two or three of them will live very peaceably together in the
+same vessel; though I had one instance of a mouse tearing another almost
+in pieces, and when there was plenty of provisions for both of them.</p>
+
+<p>In the same manner in which a mouse is put into a vessel of any kind of
+air, a <i>plant</i>, or any thing else, may be put into it, viz. by passing
+it through the water; and if the plant be of a kind that will grow in
+water only, there will be no occasion to set it in a pot of earth, which
+will otherwise be necessary.</p>
+
+<p>There may appear, at first sight, some difficulty in opening the mouth
+of a phial, containing any substance, solid or liquid, to which water
+must not be admitted, in a jar of any kind of air, which is an operation
+that I have sometimes had recourse to; but this I easily effect by means
+of <i>a cork cut tapering</i>, and a strong, wire thrust through it, as in
+fig. 4, for in this form it will sufficiently fit the mouth of any
+phial, and by holding the phial in one hand, and the wire in the other,
+and plunging both my hands into the trough of water, I can easily convey
+the phial through the water into the jar; which must either be held by
+an assistant, or be fastened by strings, with its mouth projecting<span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span> over
+the shelf. When the phial is thus conveyed into the jar, the cork may
+easily be removed, and may also be put into it again at pleasure, and
+conveyed the same way out again.</p>
+
+<p>When any thing, as a gallipot, &amp;c. is to be supported at a considerable
+height within a jar, it is convenient to have such <i>wire stands</i> as are
+represented fig. 5. They answer better than any other, because they take
+up but little room, and may be easily bended to any shape or height.</p>
+
+<p>If I have occasion to pour air from a vessel with a wide mouth into
+another with a very narrow one, I am obliged to make use of a funnel,
+fig. 6, but by this means the operation is exceedingly easy; first
+filling the vessel into which the air is to be conveyed with water, and
+holding the mouth of it, together with the funnel, both under water with
+one hand, while the other is employed in pouring the air; which,
+ascending through the funnel up into the vessel, makes the water
+descend, and takes its place. These funnels are best made of glass,
+because the air being visible through them, the quantity of it may be
+more easily estimated by the eye.<span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span> It will be convenient to have several
+of these funnels of different sizes.</p>
+
+<p>In order to expel air from solid substances by means of heat, I
+sometimes put them into a <i>gun-barrel</i>, fig. 7, and filling it up with
+dry sand, that has been well burned, so that no air can come from it, I
+lute to the open end the stem of a tobacco pipe, or a small glass tube.
+Then having put the closed end of the barrel, which contains the
+materials, into the fire, the generated air, issuing through the tube,
+may be received in a vessel of quicksilver, with its mouth immersed in a
+bason of the same, suspended all together in wires, in the manner
+described in the figure: or any other fluid substance may be used
+instead of quicksilver.</p>
+
+<p>But the most accurate method of procuring air from several substances,
+by means of heat, is to put them, if they will bear it, into phials full
+of quicksilver, with the mouths immersed in the same, and then throw the
+focus of a burning mirror upon them. For this purpose the phials should
+be made with their bottoms round, and very thin, that they may not be
+liable to break with a pretty sudden application of heat.<span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span></p>
+
+<p>If I want to expel air from any liquid, I nearly fill a phial with it,
+and having a cork perforated, I put through it, and secure with cement,
+a glass tube, bended in the manner represented at <i>e</i> fig. 1. I then put
+the phial into a kettle of water, which I set upon the fire and make to
+boil. The air expelled by the heat, from the liquor contained in the
+phial, issues through the tube, and is received in the bason of
+quicksilver, fig. 7. Instead of this suspended bason, I sometimes
+content myself with tying a flaccid bladder to the end of the tube, in
+both these processes, that it may receive the newly generated air.</p>
+
+<p>In experiments on those kinds of air which are readily imbibed by water,
+I always make use of quicksilver, in the manner represented fig. 8, in
+which <i>a</i> is the bason of quicksilver, <i>b</i> a glass vessel containing
+quicksilver, with its mouth immersed in it, <i>c</i> a phial containing the
+ingredients from which the air is to be produced; and <i>d</i> is a small
+recipient, or glass vessel designed to receive and intercept any liquor
+that may be discharged along with the air, which is to be transmitted
+free from any moisture into the vessel <i>b</i>. If there be no apprehension
+of moisture, I make use of the glass tube only, without any recipient,
+in the manner represented <i>e</i> fig. 1. In order to invert the vessel <i>b</i>,
+I first<span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span> fill it with quicksilver, and then carefully cover the mouth of
+it with a piece of soft leather; after which it may be turned upside
+down without any danger of admitting the air, and the leather may be
+withdrawn when it is plunged in the quicksilver.</p>
+
+<p>In order to generate air by the solution of metals, or any process of a
+similar nature, I put the materials into a phial, prepared in the manner
+represented at <i>e</i> fig. 1, and put the end of the glass tube under the
+mouth of any vessel into which I want to convey the air. If heat be
+necessary I can easily apply to it a candle, or a red hot poker while it
+hangs in this position.</p>
+
+<p>When I have occasion to transfer air from a jar standing in the trough
+of water to a vessel standing in quicksilver, or in any other situation
+whatever, I make use of the contrivance represented fig. 9, which
+consists of a bladder, furnished at one end with a small glass tube
+bended, and at the other with a cork, perforated so as just to admit the
+small end of a funnel. When the common air is carefully pressed out of
+this bladder, and the funnel is thrust tightly into the cork, it may be
+filled with any kind of air as easily as a glass jar; and then a string
+being tied above the cork in which the funnel is inserted,<span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span> and the
+orifice in the other cork closed, by pressing the bladder against it, it
+may be carried to any place, and if the tube be carefully wiped, the air
+may be conveyed quite free from moisture through a body of quicksilver,
+or any thing else. A little practice will make this very useful
+man&oelig;uvre perfectly easy and accurate.</p>
+
+<p>In order to impregnate fluids with any kind of air, as water with fixed
+air, I fill a phial with the fluid larger or less as I have occasion (as
+<i>a</i> fig. 10;) and then inverting it, place it with its mouth downwards,
+in a bowl <i>b</i>, containing a quantity of the same fluid; and having
+filled the bladder, fig. 9, with the air, I throw as much of it as I
+think proper into the phial, in the manner described above. To
+accelerate the impregnation, I lay my hand on the top of the phial, and
+shake it as much as I think proper.</p>
+
+<p>If, without having any air previously generated, I would convey it into
+the fluid immediately as it arises from the proper materials, I keep the
+same bladder in connection with a phial <i>c</i> fig. 10, containing the same
+materials (as chalk, salt of tartar, or pearl ashes in diluted oil of
+vitriol, for the generation of fixed air) and taking care, lest, in the
+act of effervescence, any of the materials in the phial <i>c</i><span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span> should get
+into the vessel <i>a</i>, to place this phial on a stand lower than that on
+which the bason was placed, I press out the newly generated air, and
+make it ascend directly into the fluid. For this purpose, and that I may
+more conveniently shake the phial <i>c</i>, which is necessary in some
+processes, especially with chalk and oil of vitriol, I sometimes make
+use of a flexible leathern tube <i>d</i>, and sometimes only a glass tube.
+For if the bladder be of a sufficient length, it will give room for the
+agitation of the phial; or if not, it is easy to connect two bladders
+together by means of a perforated cork, to which they may both be
+fastened.</p>
+
+<p>When I want to try whether any kind of air will admit a candle to burn
+in it, I make use of a cylindrical glass vessel, fig. 11. and a bit of
+wax candle <i>a</i> fig. 12, fastened to the end of a wire <i>b</i>, and turned
+up, in such a manner as to be let down into the vessel with the flame
+upwards. The vessel should be kept carefully covered till the moment
+that the candle is admitted. In this manner I have frequently
+extinguished a candle more than twenty times successively, in a vessel
+of this kind, though it is impossible to dip the candle into it without
+giving the external air an opportunity of mixing with the air in the
+inside more or less. The candle <i>c</i>, at the other end of the wire is<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span>
+very convenient for holding under a jar standing in water, in order to
+burn as long as the inclosed air can supply it; for the moment that it
+is extinguished, it may be drawn through the water before any smoke can
+have mixed with the air.</p>
+
+<p>In order to draw air out of a vessel which has its mouth immersed in
+water, and thereby to raise the water to whatever height may be
+necessary, it is very convenient to make use of a glass <i>syphon</i>, fig.
+13, putting one of the legs up into the vessel, and drawing the air out
+at the other end by the mouth. If the air be of a noxious quality, it
+may be necessary to have a syringe fastened to the syphon, the manner of
+which needs no explanation. I have not thought it safe to depend upon a
+valve at the top of the vessel, which Dr. Hales sometimes made use of.</p>
+
+<p>If, however, a very small hole be made at the top of a glass vessel, it
+may be filled to any height by holding it under water, while the air is
+issuing out at the hole, which may then be closed with wax or cement.</p>
+
+<p>If the generated air will neither be absorbed by water, nor diminish
+common air, it may be convenient to put part of the materials into a
+cup, supported by a stand, and the other part<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span> into a small glass
+vessel, placed on the edge of it, as at <i>f</i>, fig. 1. Then having, by
+means of a syphon, drawn the air to at convenient height, the small
+glass vessel may be easily pushed into the cup, by a wire introduced
+through the water; or it may be contrived, in a variety of ways, only to
+discharge the contents of the small vessel into the larger. The distance
+between the boundary of air and water, before and after the operation,
+will shew the quantity of the generated air. The effect of processes
+that <i>diminish</i> air may also be tried by the same apparatus.</p>
+
+<p>When I want to admit a particular kind of air to any thing that will not
+bear wetting, and yet cannot be conveniently put into a phial, and
+especially if it be in the form of a powder, and must be placed upon a
+stand (as in those experiments in which the focus of a burning mirror is
+to be thrown upon it) I first exhaust a receiver, in which it is
+previously placed; and having a glass tube, bended for the purpose, as
+in fig. 14, I screw it to the stem of a transfer of the air pump on
+which the receiver had been exhausted, and introducing it through the
+water into a jar of that kind of air with which I would fill the
+receiver, I only turn the cock, and I gain my purpose. In this method,
+however, unless the pump be very<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span> good, and several contrivances, too
+minute to be particularly described, be made use of a good deal of
+common air will get into the receiver.</p>
+
+<p>When I want to measure the goodness of any kind of air, I put two
+measures of it into a jar standing in water; and when I have marked upon
+the glass the exact place of the boundary of air and water, I put to it
+one measure of nitrous air; and after waiting a proper time, note the
+quantity of its diminution. If I be comparing two kinds of air that are
+nearly alike, after mixing them in a large jar, I transfer the mixture
+into a long glass tube, by which I can lengthen my scale to what degree
+I please.</p>
+
+<p>If the quantity of the air, the goodness of which I want to ascertain,
+be exceedingly small, so as to be contained in a part of a glass tube,
+out of which water will not run spontaneously, as <i>a</i> fig. 15; I first
+measure with a pair of compasses the length of the column of air in the
+tube, the remaining part being filled with water, and lay it down upon a
+scale; and then, thrusting a wire of a proper thickness, <i>b</i>, into the
+tube, I contrive, by means of a thin plate of iron, bent to a sharp
+angle <i>c</i>, to draw it out again, when the whole<span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span> of this little
+apparatus has been introduced through the water into a jar of nitrous
+air; and the wire being drawn out, the air from the jar must supply its
+place. I then measure the length of this column of nitrous air which I
+have got into the tube, and lay it also down upon the scale, so as to
+know the exact length of both the columns. After this, holding the tube
+under water, with a small wire I force the two separate columns of air
+into contact, and when they have been a sufficient time together, I
+measure the length of the whole, and compare it with the length of both
+the columns taken before. A little experience will teach the operator
+how far to thrust the wire into the tube, in order to admit as much air
+as he wants and no more.</p>
+
+<p>In order to take the electric spark in a quantity of any kind of air,
+which must be very small, to produce a sensible effect upon it, in a
+short time, by means of a common machine, I put a piece of wire into the
+end of a small tube, and fasten it with hot cement, as in fig. 16; and
+having got the air I want into the tube by means of the apparatus fig.
+15, I place it inverted in a bason containing either quicksilver, or any
+other fluid substance by which I chuse to have the air confined. I then,
+by the help of the air pump, drive out as much of the air as I think
+convenient, admitting the<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span> quicksilver, &amp;c. to it, as at <i>a</i>, and
+putting a brass ball on the end of the wire, I take the sparks or shocks
+upon it, and thereby transmit them through the air to the liquor in the
+tube.</p>
+
+<p>To take the electric sparks in any kind of fluid, as oil, &amp;c. I use the
+same apparatus described above, and having poured into the tube as much
+of the fluid as I conjecture I can make the electric spark pass through,
+I fill the rest with quicksilver; and placing it inverted in a bason of
+quicksilver, I take the sparks as before.</p>
+
+<p>If air be generated very fast by this process, I use a tube that is
+narrow at the top, and grows wider below, as fig. 17, that the
+quicksilver may not recede too soon beyond the striking distance.</p>
+
+<p>Sometimes I have used a different apparatus for this purpose,
+represented fig. 18. Taking a pretty wide glass tube, hermetically
+sealed at the upper-end, and open below, at about an inch, or at what
+distance I think convenient from the top, I get two holes made in it,
+opposite to each other. Through these I put two wires, and fastening
+them with warm cement, I fix them at what distance I please from each
+other. Between these wires I take the sparks, and the bubbles of air
+rise, as they are formed, to the top of the tube.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span></p>
+<h2>PART I.</h2>
+
+<h3><i>Experiments and Observations made in, and before the year 1772.</i></h3>
+
+
+<p>In writing upon the subject of <i>different kinds of air</i>, I find myself
+at a loss for proper <i>terms</i>, by which to distinguish them, those which
+have hitherto obtained being by no means sufficiently characteristic, or
+distinct. The only terms in common use are, <i>fixed air</i>, <i>mephitic</i>, and
+<i>inflammable</i>. The last, indeed, sufficiently characterizes and
+distinguishes that kind of air which takes fire, and explodes on the
+approach of flame; but it might have been termed <i>fixed</i> with as much
+propriety as that to which Dr. Black and others have given that
+denomination, since it is originally part of some solid substance, and
+exists in an unelastic state.<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span></p>
+
+<p>All these newly discovered kinds of air may also be called <i>factitious</i>;
+and if, with others, we use the term <i>fixable</i>, it is still obvious to
+remark, that it is applicable to them all; since they are all capable of
+being imbibed by some substance or other, and consequently of being
+<i>fixed</i> in them, after they have been in an elastic state.</p>
+
+<p>The term <i>mephitic</i> is equally applicable to what is called <i>fixed air</i>,
+to that which is <i>inflammable</i>, and to many other kinds; since they are
+equally noxious, when breathed by animals. Rather, however, than either
+introduce new terms, or change the signification of old ones, I shall
+use the term <i>fixed air</i>, in the sense in which it is now commonly used,
+and distinguish the other kinds by their properties, or some other
+periphrasis. I shall be under a necessity, however, of giving names to
+those kinds of air, to which no names had been given by others, as
+<i>nitrous</i>, <i>acid</i>, and <i>alkaline</i>.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span></p>
+<h2>SECTION I.</h2>
+
+<h3><i>Of <span class="smcap">Fixed Air</span>.</i></h3>
+
+
+<p>It was in consequence of living for some time in the neighbourhood of a
+public brewery, that I was induced to make experiments on fixed air, of
+which there is always a large body, ready formed, upon the surface of
+the fermenting liquor, generally about nine inches, or a foot in depth,
+within which any kind of substance may be very conveniently placed; and
+though, in these circumstances, the fixed air must be continually mixing
+with the common air, and is therefore far from being perfectly pure, yet
+there is a constant fresh supply from the fermenting liquor, and it is
+pure enough for many purposes.</p>
+
+<p>A person, who is quite a stranger to the properties of this kind of air,
+would be agreeably amused with extinguishing lighted candles, or chips
+of wood in it, as it lies upon the surface of the fermenting liquor; for
+the smoke readily unites with this kind of air, probably by means of the
+water which it contains; so that very little or none of the smoke will
+escape into the open air, which is incumbent upon it. It is remarkable,
+that the upper surface of this<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span> smoke, floating in the fixed air, is
+smooth, and well defined; whereas the lower surface is exceedingly
+ragged, several parts hanging down to a considerable distance within the
+body of the fixed air, and sometimes in the form of balls, connected to
+the upper stratum by slender threads, as if they were suspended. The
+smoke is also apt to form itself into broad flakes, parallel to the
+surface of the liquor, and at different distances from it, exactly like
+clouds. These appearances will sometimes continue above an hour, with
+very little variation. When this fixed air is very strong, the smoke of
+a small quantity of gunpowder fired in it will be wholly retained by it,
+no part escaping into the common air.</p>
+
+<p>Making an agitation in this air, the surface of it, (which still
+continues to be exactly defined) is thrown into the form of waves, which
+it is very amusing to look upon; and if, by this agitation, any of the
+fixed air be thrown over the side of the vessel, the smoke, which is
+mixed with it, will fall to the ground, as if it was so much water, the
+fixed air being heavier than common air.</p>
+
+<p>The red part of burning wood was extinguished in this air, but I could
+not perceive that a red-hot poker was sooner cooled in it.<span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span></p>
+
+<p>Fixed air does not instantly mix with common air. Indeed if it did, it
+could not be caught upon the surface of the fermenting liquor. A candle
+put under a large receiver, and immediately plunged very deep below the
+surface of the fixed air, will burn some time. But vessels with the
+smallest orifices, hanging with their mouths downwards in the fixed air,
+will <i>in time</i> have the common air, which they contain, perfectly mixed
+with it. When the fermenting liquor is contained in vessels close
+covered up, the fixed air, on removing the cover, readily affects the
+common air which is contiguous to it; so that, candles held at a
+considerable distance above the surface will instantly go out. I have
+been told by the workmen, that this will sometimes be the case, when the
+candles are held two feet above the mouth of the vessel.</p>
+
+<p>Fixed air unites with the smoke of rosin, sulphur, and other electrical
+substances, as well as with the vapour of water; and yet, by holding the
+wire of a charged phial among these fumes, I could not make any
+electrical atmosphere, which surprized me a good deal, as there was a
+large body of this smoke, and it was so confined, that it could not
+escape me.</p>
+
+<p>I also held some oil of vitriol in a glass vessel within the fixed air,
+and by plunging a<span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span> piece of red-hot glass into it, raised a copious and
+thick fume. This floated upon the surface of the fixed air like other
+fumes, and continued as long.</p>
+
+<p>Considering the near affinity between water and fixed air, I concluded
+that if a quantity of water was placed near the yeast of the fermenting
+liquor, it could not fail to imbibe that air, and thereby acquire the
+principal properties of Pyrmont, and some other medicinal mineral
+waters. Accordingly, I found, that when the surface of the water was
+considerable, it always acquired the pleasant acidulous taste that
+Pyrmont water has. The readiest way of impregnating water with this
+virtue, in these circumstances, is to take two vessels, and to keep
+pouring the water from one into the other, when they are both of them
+held as near the yeast as possible; for by this means a great quantity
+of surface is exposed to the air, and the surface is also continually
+changing. In this manner, I have sometimes, in the space of two or three
+minutes, made a glass of exceedingly pleasant sparkling water, which
+could hardly be distinguished from very good Pyrmont, or rather Seltzer
+water.</p>
+
+<p>But the <i>most effectual</i> way of impregnating water with fixed air is to
+put the vessels which contain the water into glass jars, filled with
+the<span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span> purest fixed air made by the solution of chalk in diluted oil of
+vitriol, standing in quicksilver. In this manner I have, in about two
+days, made a quantity of water to imbibe more than an equal bulk of
+fixed air, so that, according to Dr. Brownrigg's experiments, it must
+have been much stronger than the best imported Pyrmont; for though he
+made his experiments at the spring-head, he never found that it
+contained quite so much as half its bulk of this air. If a sufficient
+quantity of quicksilver cannot be procured, <i>oil</i> may be used with
+sufficient advantage, for this purpose, as it imbibes the fixed air very
+slowly. Fixed air may be kept in vessels standing in water for a long
+time, if they be separated by a partition of oil, about half an inch
+thick. Pyrmont water made in these circumstances, is little or nothing
+inferior to that which has stood in quicksilver.</p>
+
+<p>The <i>readiest</i> method of preparing this water for use is to agitate it
+strongly with a large surface exposed to the fixed air. By this means
+more than an equal bulk of air may be communicated to a large quantity
+of water in the space of a few minutes. But since agitation promotes the
+dissipation of fixed air from water, it cannot be made to imbibe so
+great a quantity in this method as in the former, where more time is
+taken.<span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span></p>
+
+<p>Easy directions for impregnating water with fixed air I have published
+in a small pamphlet, designed originally for the use of seamen in long
+voyages, on the presumption that it might be of use for preventing or
+curing the sea scurvy, equally with wort, which was recommended by Dr.
+Macbride for this purpose, on no other account than its property of
+generating fixed air, by its fermentation in the stomach.</p>
+
+<p>Water thus impregnated with fixed air readily dissolves iron, as Mr.
+Lane has discovered; so that if a quantity of iron filings be put to it,
+it presently becomes a strong chalybeate, and of the mildest and most
+agreeable kind.</p>
+
+<p>I have recommended the use of <i>chalk</i> and oil of vitriol as the
+cheapest, and, upon the whole, the best materials for this purpose. But
+some persons prefer <i>pearl ashes</i>, <i>pounded marble</i>, or other calcareous
+or <i>alkaline substances</i>; and perhaps with reason. My own experience has
+not been sufficient to enable me to decide in this case.</p>
+
+<p>Whereas some persons had suspected that a quantity of the oil of vitriol
+was rendered volatile by this process, I examined it, by all the
+chemical methods that are in use; but could<span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span> not find that water thus
+impregnated contained the least perceivable quantity of that acid.</p>
+
+<p>Mr. Hey, indeed, who assisted me in this examination, found that
+distilled water, impregnated with fixed air, did not mix so readily with
+soap as the distilled water itself; but this was also the case when the
+fixed air had passed through a long glass tube filled with alkaline
+salts, which, it may be supposed, would have imbibed any of the oil of
+vitriol that might have been contained in that air<a name="FNanchor_2_2" id="FNanchor_2_2"></a><a href="#Footnote_2_2" class="fnanchor">[2]</a>.</p>
+
+<p>Fixed air itself may be said to be of the nature of an acid, though of a
+weak and peculiar sort.&mdash;&mdash;Mr. Bergman of Upsal, who honoured me with a
+letter upon the subject, calls it the <i>a&euml;rial acid</i>, and, among other
+experiments to prove it to be an acid, he says that it changes the blue
+juice of tournesole into red. This Mr. Hey found to be true, and he
+moreover discovered that when water tinged blue with the juice of
+tournesole, and then red with fixed air, has been exposed to the open
+air, it recovers its blue colour again.</p>
+
+<p>The heat of boiling water will expel all the fixed air, if a phial
+containing the impregnated<span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span> water be held in it; but it will often
+require above half an hour to do it completely.</p>
+
+<p>Dr. Percival, who is particularly attentive to every improvement in the
+medical art, and who has thought so well of this impregnation as to
+prescribe it in several cases, informs me that it seems to be much
+stronger, and sparkles more, like the true Pyrmont water, after it has
+been kept some time. This circumstance, however, shews that, in time,
+the fixed air is more easily disengaged from the water; and though, in
+this state, it may affect the taste more sensibly, it cannot be of so
+much use in the stomach and bowels, as when the air is more firmly
+retained by the water.</p>
+
+<p>By the process described in my pamphlet, fixed air may be readily
+incorporated with wine, beer, and almost any other liquor whatever; and
+when beer, wine, or cyder, is become flat or dead (which is the
+consequence of the escape of the fixed air they contained) they may be
+revived by this means; but the delicate and agreeable flavour, or
+acidulous taste, communicated by fixed air, and which is very manifest
+in water, can hardly be perceived in wine, or any liquors which have
+much taste of their own.<span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span></p>
+
+<p>I should think that there can be no doubt, but that water thus
+impregnated with fixed air must have all the medicinal virtues of
+genuine Pyrmont or Seltzer water; since these depend upon the fixed air
+they contain. If the genuine Pyrmont water derives any advantage from
+its being a natural chalybeate, this may also be obtained by providing a
+common chalybeate water, and using it in these processes, instead of
+common water.</p>
+
+<p>Having succeeded so well with this artificial Pyrmont water, I imagined
+that it might be possible to give <i>ice</i> the same virtue, especially as
+cold is known to promote the absorption of fixed air by water; but in
+this I found myself quite mistaken. I put several pieces of ice into a
+quantity of fixed air, confined by quicksilver, but no part of the air
+was absorbed in two days and two nights; but upon bringing it into a
+place where the ice melted, the air was absorbed as usual.</p>
+
+<p>I then took a quantity of strong artificial Pyrmont water, and putting
+it into a thin glass phial, I set it in a pot that was filled with snow
+and salt. This mixture instantly freezing the water that was contiguous
+to the sides of the glass, the air was discharged plentifully, so<span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span> that
+I catched a considerable quantity, in a bladder tied to the mouth of the
+phial.</p>
+
+<p>I also took two quantities of the same Pyrmont water, and placed one of
+them where it might freeze, keeping the other in a cold place, but where
+it would not freeze. This retained its acidulous taste, though the phial
+which contained it was not corked; whereas the other being brought into
+the same place, where the ice melted very slowly, had at the same time
+the taste of common water only. That quantity of water which had been
+frozen by the mixture of snow and salt, was almost as much like snow as
+ice, such a quantity of air-bubbles were contained in it, by which it
+was prodigiously increased in bulk.</p>
+
+<p>The pressure of the atmosphere assists very considerably in keeping
+fixed air confined in water; for in an exhausted receiver, Pyrmont water
+will absolutely boil, by the copious discharge of its air. This is also
+the reason why beer and ale froth so much <i>in vacuo</i>. I do not doubt,
+therefore, but that, by the help of a condensing engine, water might be
+much more highly impregnated with the virtues of the Pyrmont spring; and
+it would not be difficult to contrive a method of doing it.<span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span></p>
+
+<p>The manner in which I made several experiments to ascertain the
+absorption of fixed air by different fluid substances, was to put the
+liquid into a dish, and holding it within the body of the fixed air at
+the brewery, to set a glass vessel into it, with its mouth inverted.
+This glass being necessarily filled with the fixed air, the liquor would
+rise into it when they were both taken into the common air, if the fixed
+air was absorbed at all.</p>
+
+<p>Making use of <i>ether</i> in this manner, there was a constant bubbling from
+under the glass, occasioned by this fluid easily rising in vapour, so
+that I could not, in this method, determine whether it imbibed the air
+or not. I concluded however, that they did incorporate, from a very
+disagreeable circumstance, which made me desist from making any more
+experiments of the kind. For all the beer, over which this experiment
+was made, contracted a peculiar taste; the fixed air impregnated with
+the ether being, I suppose, again absorbed by the beer. I have also
+observed, that water which remained a long time within this air has
+sometimes acquired a very disagreeable taste. At one time it was like
+tar-water. How this was acquired, I was very desirous of making some
+experiments to ascertain, but I was discouraged<span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span> by the fear of injuring
+the fermenting liquor. It could not come from the fixed air only.</p>
+
+<p>Insects and animals which breathe very little are stifled in fixed air,
+but are not soon quite killed in it. Butterflies and flies of other
+kinds will generally become torpid, and seemingly dead, after being held
+a few minutes over the fermenting liquor; but they revive again after
+being brought into the fresh air. But there are very great varieties
+with respect to the time in which different kinds of flies will either
+become torpid in the fixed air, or die in it. A large strong frog was
+much swelled, and seemed to be nearly dead, after being held about six
+minutes over the fermenting liquor; but it recovered upon being brought
+into the common air. A snail treated in the same manner died presently.</p>
+
+<p>Fixed air is presently fatal to vegetable life. At least sprigs of mint
+growing in water, and placed over the fermenting liquor, will often
+become quite dead in one day, or even in a less space of time; nor do
+they recover when they are afterwards brought into the common air. I am
+told, however, that some other plants are much more hardy in this
+respect.<span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span></p>
+
+<p>A red rose, fresh gathered, lost its redness, and became of a purple
+colour, after being held over the fermenting liquor about twenty-four
+hours; but the tips of each leaf were much more affected than the rest
+of it. Another red rose turned perfectly white in this situation; but
+various other flowers of different colours were very little affected.
+These experiments were not repeated, as I wish they might be done, in
+pure fixed air, extracted from chalk by means of oil of vitriol.</p>
+
+<p>For every purpose, in which it was necessary that the fixed air should
+be as unmixed as possible, I generally made it by pouring oil of vitriol
+upon chalk and water, catching it in a bladder fastened to the neck of
+the phial in which they were contained, taking care to press out all the
+common air, and also the first, and sometimes the second, produce of
+fixed air; and also, by agitation, making it as quickly as I possibly
+could. At other times, I made it pass from the phial in which it was
+generated through a glass tube, without the intervention of any bladder,
+which, as I found by experience, will not long make a sufficient
+separation between several kinds of air and common air.</p>
+
+<p>I had once thought that the readiest method of procuring fixed air, and
+in sufficient purity,<span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span> would be by the simple process of burning chalk,
+or pounded lime-stone in a gun-barrel, making it pass through the stem
+of a tobacco-pipe, or a glass tube carefully luted to the orifice of it.
+In this manner I found that air is produced in great plenty; but, upon
+examining it, I found, to my very great surprise, that little more than
+one half of it was fixed air, capable of being absorbed by water; and
+that the rest was inflammable, sometimes very weakly, but sometimes
+pretty highly so.</p>
+
+<p>Whence this inflammability proceeds, I am not able to determine, the
+lime or chalk not being supposed to contain any other than fixed air. I
+conjecture, however, that it must proceed from the iron, and the
+separation of it from the calx may be promoted by that small quantity of
+oil of vitriol, which I am informed is contained in chalk, if not in
+lime-stone also.</p>
+
+<p>But it is an objection to this hypothesis, that the inflammable air
+produced in this manner burns blue, and not at all like that which is
+produced from iron, or any other metal, by means of an acid. It also has
+not the smell of that kind of inflammable air which is produced from
+mineral substances. Besides, oil of vitriol without water, will not
+dissolve iron; nor can inflammable air be got from it, unless the acid
+be<span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span> considerably diluted; and when I mixed brimstone with the chalk,
+neither the quality nor the quantity of the air was changed by it.
+Indeed no air, or permanently elastic vapour, can be got from brimstone,
+or any oil.</p>
+
+<p>Perhaps this inflammable principle may come from some remains of the
+animals, from which it is thought that all calcareous matter proceeds.</p>
+
+<p>In the method in which I generally made the fixed air (and indeed
+always, unless the contrary be particularly mentioned, viz. by diluted
+oil of vitriol and chalk) I found by experiment that it was as pure as
+Mr. Cavendish made it. For after it had patted through a large body of
+water in small bubbles, still 1/50 or 1/60 part only was not absorbed by
+water. In order to try this as expeditiously as possible, I kept pouring
+the air from one glass vessel into another, immersed in a quantity of
+cold water, in which manner I found by experience, that almost any
+quantity may be reduced as far as possible in a very short time. But the
+most expeditious method of making water imbibe any kind of air, is to
+confine it in a jar; and agitate it strongly, in the manner described in
+my pamphlet on the impregnation of water with fixed air, and represented
+fig. 10.<span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span></p>
+
+<p>At the same time that I was trying the purity of my fixed air, I had the
+curiosity to endeavour to ascertain whether that part of it which is not
+miscible in water, be equally diffused through the whole mass; and, for
+this purpose, I divided a quantity of about a gallon into three parts,
+the first consisting of that which was uppermost, and the last of that
+which was the lowest, contiguous to the water; but all these parts were
+reduced in about an equal proportion, by passing through the water, so
+that the whole mass had been of an uniform composition. This I have also
+found to be the case with several kinds of air, which will, not properly
+incorporate.</p>
+
+<p>A mouse will live very well, though a candle will not burn in the
+residuum of the purest fixed air that I can make; and I once made a very
+large quantity for the sole purpose of this experiment. This, therefore,
+seems to be one instance of the generation of genuine common air, though
+vitiated in some degree. It is also another proof of the residuum of
+fixed air being, in part at least, common air, that it becomes turbid,
+and is diminished by the mixture of nitrous air, as will be explained
+hereafter.</p>
+
+<p>That fixed air only wants some addition to make it permanent, and
+immiscible with water<span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span> if not in all respects, common air, I have been
+led to conclude, from several attempts which I once made to mix it with
+air in which a quantity of iron filings and brimstone, made into a paste
+with water, had stood; for, in several mixtures of this kind, I imagined
+that not much more than half of the fixed air could be imbibed by water;
+but, not being able to repeat the experiment, I conclude that I either
+deceived myself in it, or that I overlooked some circumstance on which
+the success of it depended.</p>
+
+<p>These experiments, however, whether they were fallacious or otherwise,
+induced me to try whether any alteration would be made in the
+constitution of fixed air, by this mixture of iron filings and
+brimstone. I therefore put a mixture of this kind into a quantity of as
+pure fixed air as I could make, and confined the whole in quicksilver,
+lest the water should absorb it before the effects of the mixture could
+take place. The consequence was, that the fixed air was diminished, and
+the quicksilver rose in the vessel, till about the fifth part was
+occupied by it; and, as near as I could judge, the process went on, in
+all respects, as if the air in the inside had been common air.<span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span></p>
+
+<p>What is most remarkable, in the result of this experiment, is, that the
+fixed air, into which this mixture had been put, and which had been in
+part diminished by it, was in part also rendered insoluble in water by
+this means. I made this experiment four times, with the greatest care,
+and observed, that in two of them about one sixth, and in the other two
+about one fourteenth, of the original quantity, was such as could not be
+absorbed by water, but continued permanently elastic. Lest I should have
+made any mistake with respect to the purity of the fixed air, the last
+time that I made the experiment, I set part of the fixed air, which I
+made use of, in a separate vessel, and found it to be exceedingly pure,
+so as to be almost wholly absorbed by water; whereas the other part, to
+which I had put the mixture, was far from being so.</p>
+
+<p>In one of these cases, in which fixed air was made immiscible with
+water, it appeared to be not very noxious to animals; but in another
+case, a mouse died in it pretty soon. This difference probably arose
+from my having inadvertently agitated the air in water rather more in
+one case than in the other.</p>
+
+<p>As the iron is reduced to a calx by this process, I once concluded, that
+it is phlogiston that<span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span> fixed air wants, to make it common air; and, for
+any thing I yet know this may be the case, though I am ignorant of the
+method of combining them; and when I calcined a quantity of lead in
+fixed air, in the manner which will be described hereafter, it did not
+seem to have been less soluble in water than it was before.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_2_2" id="Footnote_2_2"></a><a href="#FNanchor_2_2"><span class="label">[2]</span></a> An account of Mr. Hey's experiments will be found in the
+Appendix to these papers.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>SECTION II.</h2>
+
+<h3><i>Of <span class="smcap">Air</span> in which a <span class="smcap">Candle</span>, or <span class="smcap">Brimstone</span>, has burned out.</i></h3>
+
+
+<p>It is well known that flame cannot subsist long without change of air,
+so that the common air is necessary to it, except in the case of
+substances, into the composition of which nitre enters, for these will
+burn <i>in vacuo</i>, in fixed air, and even under water, as is evident in
+some rockets, which are made for this purpose. The quantity of air which
+even a small flame requires to keep it burning is prodigious. It is
+generally said, that an ordinary candle <i>consumes</i>, as it is called,
+about a gallon in a minute. Considering this amazing consumption of air,
+by fires of all kinds, volcanos, &amp;c. it becomes a great object of
+philosophical inquiry, to ascertain what change is made in the
+constitution of the air by flame, and to discover what provision<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span> there
+is in nature for remedying the injury which the atmosphere receives by
+this means. Some of the following experiments will, perhaps, be thought
+to throw light upon the subject.</p>
+
+<p>The diminution of the quantity of air in which a candle, or brimstone,
+has burned out, is various; But I imagine that, at a medium, it may be
+about one fifteenth, or one sixteenth of the whole; which is one third
+as much as by animal or vegetable substances putrefying in it, by the
+calcination of metals, or by any of the other causes of the complete
+diminution of air, which will be mentioned hereafter.</p>
+
+<p>I have sometimes thought, that flame disposes the common air to deposit
+the fixed air it contains; for if any lime-water be exposed to it, it
+immediately becomes turbid. This is the case, when wax candles, tallow
+candles, chips of wood, spirit of wine, ether, and every other substance
+which I have yet tried, except brimstone, is burned in a close glass
+vessel, standing in lime-water. This precipitation of fixed air (if this
+be the case) may be owing to something emitted from the burning bodies,
+which has a stronger affinity with the other constituent parts of the
+atmosphere<a name="FNanchor_3_3" id="FNanchor_3_3"></a><a href="#Footnote_3_3" class="fnanchor">[3]</a>.</p>
+<p><span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span></p>
+<p>If brimstone be burned in the same circumstances, the lime-water
+continues transparent, but still there may have been the same
+precipitation of the fixed part of the air; but that, uniting with the
+lime and the vitriolic acid, it forms a selenetic salt, which is soluble
+in water. Having evaporated a quantity of water thus impregnated, by
+burning brimstone a great number of times over it, a whitish powder
+remained, which had an acid taste; but repeating the experiment with a
+quicker evaporation, the powder had no acidity, but was very much like
+chalk. The burning of brimstone but once over a quantity of lime-water,
+will affect it in such a manner, that breathing into it will not make it
+turbid, which otherwise it always presently does.</p>
+
+<p>Dr. Hales supposed, that by burning brimstone repeatedly in the same
+quantity of air, the diminution would continue without end. But this I
+have frequently tried, and not found to be the case. Indeed, when the
+ignition has been imperfect in the first instance, a second firing of
+the same substance will increase the effect of the first, &amp;c. but this
+progress soon ceases.<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span></p>
+
+<p>In many cases of the diminution of air, the effect is not immediately
+apparent, even when it stands in water; for sometimes the bulk of air
+will not be much reduced, till it has passed several times through a
+quantity of water, which has thereby a better opportunity of absorbing
+that part of the air, which had not been perfectly detatched from the
+rest. I have sometimes found a very great reduction of a mass of air, in
+consequence of passing but once through cold water. If the air has stood
+in quicksilver, the diminution is generally inconsiderable, till it has
+undergone this operation, there not being any substance exposed to the
+air that could absorb any part of it.</p>
+
+<p>I could not find any considerable alteration in the specific gravity of
+the air, in which candles, or brimstone, had burned out. I am satisfied,
+however, that it is not heavier than common air, which must have been
+manifest, if so great a diminution of the quantity had been owing, as
+Dr. Hales and others supposed, to the elasticity of the whole mass being
+impaired. After making several trials for this purpose, I concluded that
+air, thus diminished in bulk, is rather lighter than common air, which
+favours the supposition of the fixed, or heavier part of the common air,
+having been precipitated.<span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span></p>
+
+<p>An animal will live nearly, if not quite as long, in air in which
+candles have burned out, as in common air. This fact surprized me very
+greatly, having imagined that what is called the <i>consumption</i> of air by
+flame, or respiration, to have been of the same nature, and in the same
+degree; but I have since found, that this fact has been observed by many
+persons, and even so early as by Mr. Boyle. I have also observed, that
+air, in which brimstone has burned, is not in the least injurious to
+animals, after the fumes, which at first make it very cloudy, have
+intirely subsided.</p>
+
+<p>I must, in this place, admonish my reader not to confound the simple
+<i>burning of brimstone</i>, or of matches (<i>i. e.</i> bits of wood dipped in
+it) and the burning of brimstone with a burning mirror, or any <i>foreign
+heat</i>. The effect of the former is nothing more than that of any other
+<i>flame</i>, or <i>ignited vapour</i>, which will not burn, unless the air with
+which it is surrounded be in a very pure state, and which is therefore
+extinguished when the air begins to be much vitiated. Lighted brimstone,
+therefore reduces the air to the same state as lighted wood. But the
+focus of a burning mirror thrown for a sufficient time either upon
+brimstone, or wood, after it has ceased to burn of its own accord, and
+has become <i>charcoal</i>, will have a much<span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span> greater effect: of the same
+kind, diminishing the air to its utmost extent, and making it thoroughly
+noxious. In fact, as will be seen hereafter, more phlogiston is expelled
+from these substances in the latter case than in the former. I never,
+indeed, actually carried this experiment so far with brimstone; but from
+the diminution of air that I did produce by this means, I concluded
+that, by continuing the process some time longer, it would have been
+effected.</p>
+
+<p>Having read, in the Memoirs of the Philosophical Society at Turin, vol.
+I. p. 41. that air in which candles had burned out was perfectly
+restored, so that other candles would burn in it again as well as ever,
+after having been exposed to a considerable degree of <i>cold</i>, and
+likewise after having been compressed in bladders, (for the cold had
+been supposed to have produced this effect by nothing but
+<i>condensation</i>) I repeated those experiments, and did, indeed, find,
+that when I compressed the air in <i>bladders</i>, as the Count de Saluce,
+who made the observation, had done, the experiment succeeded: but having
+had sufficient reason to distrust bladders, I compressed the air in a
+glass vessel standing in water; and then I found, that this process is
+altogether ineffectual for the purpose. I kept the air compressed much
+more, and much longer, than the<span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span> Count had done, but without producing
+any alteration in it. I also find, that a greater degree of cold than
+that which he applied, and of longer continuance, did by no means
+restore this kind of air: for when I had exposed the phials which
+contained it a whole night, in which the frost was very intense; and
+also when I kept it surrounded with a mixture of snow and salt, I found
+it, in all respects, the same as before.</p>
+
+<p>It is also advanced, in the same Memoir, p. 41. that <i>heat</i> only, as the
+reverse of <i>cold</i>, renders air unfit for candles burning in it. But I
+repeated the experiment of the Count for that purpose, without finding
+any such effect from it. I also remember that, many years ago, I filled
+an exhausted receiver with air, which had passed through a glass tube
+made red-hot, and found that a candle would burn in it perfectly well.
+Also, rarefaction by the air-pump does not injure air in the least
+degree.</p>
+
+<p>Though this experiment failed, I have been so happy, as by accident to
+have hit upon a method of restoring air, which has been injured by the
+burning of candles, and to have discovered at least one of the
+restoratives which nature employs for this purpose. It is <i>vegetation</i>.
+This restoration of vitiated air, I conjecture, is<span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span> effected by plants
+imbibing the phlogistic matter with which it is overloaded by the
+burning of inflammable bodies. But whether there be any foundation for
+this conjecture or not, the fact is, I think, indisputable. I shall
+introduce the account of my experiments on this subject, by reciting
+some of the observations which I made on the growing of plants in
+confined air, which led to this discovery.</p>
+
+<p>One might have imagined that, since common air is necessary to
+vegetable, as well as to animal life, both plants and animals had
+affected it in the same manner; and I own I had that expectation, when I
+first put a sprig of mint into a glass jar, standing inverted in a
+vessel of water: but when it had continued growing there for some
+months, I found that the air would neither extinguish a candle, nor was
+it at all inconvenient to a mouse, which I put into it.</p>
+
+<p>The plant was not affected any otherwise than was the necessary
+consequence of its confined situation; for plants growing in several
+other kinds of air, were all affected in the very same manner. Every
+succession of leaves was more diminished in size than the preceding,
+till, at length, they came to be no bigger than the heads of pretty
+small pins. The root decayed, and the stalk also, beginning from the
+root;<span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span> and yet the plant continued to grow upwards, drawing its
+nourishment through a black and rotten stem. In the third or fourth set
+of leaves, long and white hairy filaments grew from the insertion of
+each leaf and sometimes from the body of the stem, shooting out as far
+as the vessel in which it grew would permit, which, in my experiments,
+was about two inches. In this manner a sprig of mint lived, the old
+plant decaying, and new ones shooting up in its place, but less and less
+continually, all the summer season.</p>
+
+<p>In repeating this experiment, care must be taken to draw away all the
+dead leaves from about the plant, lest they should putrefy, and affect
+the air. I have found that a fresh cabbage leaf, put under a glass
+vessel filled with common air, for the space of one night only, has so
+affected the air, that a candle would not burn in it the next morning,
+and yet the leaf had not acquired any smell of putrefaction.</p>
+
+<p>Finding that candles would burn very well in air in which plants had
+grown a long time, and having had some reason to think, that there was
+something attending vegetation, which restored air that had been injured
+by respiration, I thought it was possible that the same process<span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span> might
+also restore the air that had been injured by the burning of candles.</p>
+
+<p>Accordingly, on the 17th of August 1771, I put a sprig of mint into a
+quantity of air, in which a wax candle had burned out, and found that,
+on the 27th of the same month, another candle burned perfectly well in
+it. This experiment I repeated, without the least variation in the
+event, not less than eight or ten times in the remainder of the summer.</p>
+
+<p>Several times I divided the quantity of air in which the candle had
+burned out, into two parts, and putting the plant into one of them, left
+the other in the same exposure, contained, also, in a glass vessel
+immersed in water, but without any plant; and never failed to find, that
+a candle would burn in the former, but not in the latter.</p>
+
+<p>I generally found that five or six days were sufficient to restore this
+air, when the plant was in its vigour; whereas I have kept this kind of
+air in glass vessels, immersed in water many months, without being able
+to perceive that the least alteration had been made in it. I have also
+tried a great variety of experiments upon it, as by condensing,
+rarefying, exposing to the light and heat, &amp;c. and throwing into it the<span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span>
+effluvia of many different substances, but without any effect.</p>
+
+<p>Experiments made in the year 1772, abundantly confirmed my conclusion
+concerning the restoration of air, in which candles had burned out by
+plants growing in it. The first of these experiments was made in the
+month of May; and they were frequently repeated in that and the two
+following months, without a single failure.</p>
+
+<p>For this purpose I used the flames of different substances, though I
+generally used wax or tallow candles. On the 24th of June the experiment
+succeeded perfectly well with air in which spirit of wine had burned
+out, and on the 27th of the same month it succeeded equally well with
+air in which brimstone matches had burned out, an effect of which I had
+despaired the preceding year.</p>
+
+<p>This restoration of air, I found, depended upon the <i>vegetating state</i>
+of the plant; for though I kept a great number of the fresh leaves of
+mint in a small quantity of air in which candles had burned out, and
+changed them frequently, for a long space of time, I could perceive no
+melioration in the state of the air.<span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span></p>
+
+<p>This remarkable effect does not depend upon any thing peculiar to
+<i>mint</i>, which was the plant that I always made use of till July 1772;
+for on the 16th of that month, I found a quantity of this kind of air to
+be perfectly restored by sprigs of <i>balm</i>, which had grown in it from
+the 7th of the same month.</p>
+
+<p>That this restoration of air was not owing to any <i>aromatic effluvia</i> of
+these two plants, not only appeared by the <i>essential oil of mint</i>
+having no sensible effect of this kind; but from the equally complete
+restoration of this vitiated air by the plant called <i>groundsel</i>, which
+is usually ranked among the weeds, and has an offensive smell. This was
+the result of an experiment made the 16th of July, when the plant had
+been growing in the burned air from the 8th of the same month. Besides,
+the plant which I have found to be the most effectual of any that I have
+tried for this purpose is <i>spinach</i>, which is of quick growth, but will
+seldom thrive long in water. One jar of burned air was perfectly
+restored by this plant in four days, and another in two days. This last
+was observed on the 22d of July.</p>
+
+<p>In general, this effect may be presumed to have taken place in much less
+time than I have mentioned; because I never chose to make a<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span> trial of
+the air, till I was pretty sure, from preceding observations, that the
+event which I had expected must have taken place, if it would succeed at
+all; lest, returning back that part of the air on which I made the
+trial, and which would thereby necessarily receive a small mixture of
+common air, the experiment might not be judged to be quite fair; though
+I myself might be sufficiently satisfied with respect to the allowance
+that was to be made for that small imperfection.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_3_3" id="Footnote_3_3"></a><a href="#FNanchor_3_3"><span class="label">[3]</span></a> The supposition, mentioned in this and other passages of
+the first part of this publication, viz. that the diminution of common
+air, by this and other processes is, in part at least, owing to the
+precipitation of the fixed air from it, the reader will find confirmed
+by the experiments and observations in the second part.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>SECTION III.</h2>
+
+<h3><i>Of <span class="smcap">inflammable Air</span>.</i></h3>
+
+
+<p>I have generally made inflammable air in the manner described by Mr.
+Cavendish, in the Philosophical Transactions, from iron, zinc, or tin;
+but chiefly from the two former metals, on account of the process being
+the least troublesome: but when I extracted it from vegetable or animal
+substances, or from coals, I put them into a gun-barrel, to the orifice
+of which I luted a glass tube, or the stem of a tobacco-pipe, and to the
+end of this I tied a flaccid bladder in order to catch the generated
+air; or I received the air in a vessel of quicksilver, in the manner
+represented Fig. 7.<span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span></p>
+
+<p>There is not, I believe, any vegetable or animal substance whatever, nor
+any mineral substance, that is inflammable, but what will yield great
+plenty of inflammable air, when they are treated in this manner, and
+urged with a strong heat; but, in order to get the most air, the heat
+must be applied as suddenly, and as vehemently, as possible. For,
+notwithstanding the same care be taken in luting, and in every other
+respect, six or even ten times more air may be got by a sudden heat than
+by a slow one, though the heat that is last applied be as intense as
+that which was applied suddenly. A bit of dry oak, weighing about twelve
+grains, will generally yield about a sheep's bladder full of inflammable
+air with a brisk heat, when it will only give about two or three ounce
+measures, if the same heat be applied to it very gradually. To what this
+difference is owing, I cannot tell. Perhaps the phlogiston being
+extricated more slowly may not be intirely expelled, but form another
+kind of union with its base; so that charcoal made with a heat slowly
+applied shall contain more phlogiston than that which is made with a
+sudden heat. It may be worth while to examine the properties of the
+charcoal with this view.</p>
+
+<p>Inflammable air, when it is made by a quick process, has a very strong
+and offensive smell,<span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span> from whatever substance it be generated; but this
+smell is of three different kinds, according as the air is extracted
+from mineral, vegetable, or animal substances. The last is exceedingly
+fetid; and it makes no difference, whether it be extracted from a bone,
+or even an old and dry tooth, from soft muscular flesh; or any other
+part of the animal. The burning of any substance occasions the same
+smell: for the gross fume which arises from them, before they flame, is
+the inflammable air they contain, which is expelled by heat, and then
+readily ignited. The smell of inflammable air is the very same, as far
+as I am able to perceive, from whatever substance of the same kingdom it
+be extracted. Thus it makes no difference whether it be got from iron,
+zinc, or tin, from any kind of wood, or, as was observed before, from
+any part of an animal.</p>
+
+<p>If a quantity of inflammable air be contained in a glass vessel standing
+in water, and have been generated very fast, it will smell even through
+the water, and this water will also soon become covered with a thin
+film, assuming all the different colours. If the inflammable air have
+been generated from iron, this matter will appear to be a red okre, or
+the earth of iron, as I have found by collecting a considerable quantity
+of it; and if it have been generated<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span> from zinc, it is a whitish
+substance, which I suppose to be the calx of the metal. It likewise
+settles to the bottom of the vessel, and when the water is stirred, it
+has very much the appearance of wool. When water is once impregnated in
+this manner, it will continue to yield this scum for a considerable time
+after the air is removed from it. This I have often observed with
+respect to iron.</p>
+
+<p>Inflammable air, made by a violent effervescence, I have observed to be
+much more inflammable than that which is made by a weak effervescence,
+whether the water or the oil of vitriol prevailed in the mixture. Also
+the offensive smell was much stronger in the former case than in the
+latter. The greater degree of inflammability appeared by the greater
+number of successive explosions, when a candle was presented to the neck
+of a phial filled with it.<a name="FNanchor_4_4" id="FNanchor_4_4"></a><a href="#Footnote_4_4" class="fnanchor">[4]</a> It is possible, however, that this
+diminution of inflammability may, in some measure, arise from the air
+continuing so much longer in the bladder when it is made very slowly;
+though<span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span> I think the difference is too great for this cause to have
+produced the whole of it. It may, perhaps, deserve to be tried by a
+different process, without a bladder.</p>
+
+<p>Inflammable air is not thought to be miscible with water, and when kept
+many months, seems, in general, to be as inflammable as ever. Indeed,
+when it is extracted from vegetable or animal substances, a part of it
+will be imbibed by the water in which it stands; but it may be presumed,
+that in this case, there was a mixture of fixed air extracted from the
+substance along with it. I have indisputable evidence, however, that
+inflammable air, standing long in water, has actually lost all its
+inflammability, and even come to extinguish flame much more than that
+air in which candles have burned out. After this change it appears to be
+greatly diminished in quantity, and it still continues to kill animals
+the moment they are put into it.</p>
+
+<p>This very remarkable fact first occurred to my observation on the
+twenty-fifth of May 1771, when I was examining a quantity of inflammable
+air, which had been made from zinc, near three years before. Upon this,
+I immediately set by a common quart-bottle filled with inflammable air
+from iron, and another equal quantity from zinc; and examining them in<span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span>
+the beginning of December following, that from the iron was reduced near
+one half in quantity, if I be not greatly mistaken; for I found the
+bottle half full of water, and I am pretty clear that it was full of air
+when it was set by. That which had been produced from zinc was not
+altered, and filled the bottle as at first.</p>
+
+<p>Another instance of this kind occurred to my observation on the 19th of
+June 1772, when a quantity of air, half of which had been inflammable
+air from zinc, and half air in which mice had died, and which had been
+put together the 30th of July 1771, appeared not to be in the least
+inflammable, but extinguished flame, as much as any kind of air that I
+had ever tried. I think that, in all, I have had four instances of
+inflammable air losing its inflammability, while it stood in water.</p>
+
+<p>Though air tainted with putrefaction extinguishes flame, I have not
+found that animals or vegetables putrefying in inflammable air render it
+less inflammable. But one quantity of inflammable air, which I had set
+by in May 1771, along with the others above mentioned, had had some
+putrid flesh in it; and this air had lost its inflammability, when it
+was examined at the same time with the other in the December<span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span> following.
+The bottle in which this air had been kept, smelled exactly like very
+strong Harrogate water. I do not think that any person could have
+distinguished them.</p>
+
+<p>I have made plants grow for several months in inflammable air made from
+zinc, and also from oak; but, though the plants grew pretty well, the
+air still continued inflammable. The former, indeed, was not so highly
+inflammable as when it was fresh made, but the latter was quite as much
+so; and the diminution of inflammability in the former case, I attribute
+to some other cause than the growth of the plant.</p>
+
+<p>No kind of air, on which I have yet made the experiment, will conduct
+electricity; but the colour of an electric spark is remarkably different
+in some different kinds of air, which seems to shew that they are not
+equally good non-conductors. In fixed air, the electric spark is
+exceedingly white; but in inflammable air it is of a purple, or red
+colour. Now, since the most vigorous sparks are always the whitest, and,
+in other cases, when the spark is red, there is reason to think that the
+electric matter passes with difficulty, and with less rapidity: it is
+possible that the inflammable air may contain particles which conduct
+electricity, though very imperfectly; and that the whiteness of the
+spark in the fixed air, may be<span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span> owing to its meeting with no conducting
+particles at all. When an explosion was made in a quantity of
+inflammable air, it was a little white in the center, but the edges of
+it were still tinged with a beautiful purple. The degree of whiteness in
+this case was probably owing to the electric matter rushing with more
+violence in an explosion than in a common spark.</p>
+
+<p>Inflammable air kills animals as suddenly as fixed air, and, as far as
+can be perceived, in the same manner, throwing them into convulsions,
+and thereby occasioning present death. I had imagined that, by animals
+dying in a quantity of inflammable air, it would in time become less
+noxious; but this did not appear to be the case; for I killed great
+number of mice in a small quantity of this air; which I kept several
+months for this purpose, without its being at all sensibly mended; the
+last, as well as the first mouse, dying the moment it was put into it.</p>
+
+<p>I once imagined that, since fixed and inflammable air are the reverse of
+one another, in several remarkable properties, a mixture of them would
+make common air; and while I made the mixtures in bladders, I imagined
+that I had succeeded in my attempt; but I have since found that thin
+bladders do not sufficiently prevent<span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span> the air that is contained in them
+from mixing with the external air. Also corks will not sufficiently
+confine different kinds of air, unless the phials in which they are
+confined be set with their mouths downwards, and a little water lie in
+the necks of them, which, indeed, is equivalent to the air standing in
+vessels immersed in water. In this manner, however, I have kept
+different kinds of air for several years.</p>
+
+<p>Whatever methods I took to promote the mixture of fixed and inflammable
+air, they were all ineffectual. I think it my duty, however, to recite
+the issue of an experiment or two of this kind, in which equal mixtures
+of these two kinds of air had stood near three years, as they seem to
+shew that they had in part affected one another, in that long space of
+time. These mixtures I examined April 27, 1771. One of them had stood in
+quicksilver, and the other in a corked phial, with a little water in it.
+On opening the latter in water, the water instantly rushed in, and
+filled almost half of the phial, and very little more was absorbed
+afterwards. In this case the water in the phial had probably absorbed a
+considerable part of the fixed air, so that the inflammable air was
+exceedingly rarefied; and yet the whole quantity that must have been
+rendered non-elastic was ten times more than the bulk of the water, and
+it has not<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span> been found that water can contain much more than its own
+bulk of fixed air. But in other cases I have found the diminution of a
+quantity of air, and especially of fixed air, to be much greater than I
+could well account for by any kind of absorption.</p>
+
+<p>The phial which had stood immersed in quicksilver had lost very little
+of its original quantity of air; and being now opened in water, and left
+there, along with another phial, which was just then filled, as this had
+been three years before, viz. with air half inflammable and half fixed,
+I observed that the quantity of both was diminished, by the absorption
+of the water, in the same proportion.</p>
+
+<p>Upon applying a candle to the mouths of the phials which had been kept
+three years, that which had stood in quicksilver went off at one
+explosion, exactly as it would have done if there had been a mixture of
+common air with the inflammable. As a good deal depends upon the
+apertures of the vessels in which the inflammable air is mixed, I mixed
+the two kinds of air in equal proportions in the same phial, and after
+letting the phial stand some days in water, that the fixed air might be
+absorbed, I applied a candle to it, but it made ten or twelve explosions
+(stopping the phial<span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span> after each of them) before the inflammable matter
+was exhausted.</p>
+
+<p>The air which had been confined in the corked phial exploded in the very
+same manner as an equal and fresh mixture of the two kinds of air in the
+same phial, the experiment being made as soon as the fixed air was
+absorbed, as before; so that in this case, the two kinds of air did not
+seem to have affected one another at all.</p>
+
+<p>Considering inflammable air as air united to, or loaded with phlogiston,
+I exposed to it several substances, which are said to have a near
+affinity with phlogiston, as oil of vitriol, and spirit of nitre (the
+former for above a month), but without making any sensible alteration in
+it.</p>
+
+<p>I observed, however, that inflammable air, mixed with the fumes of
+smoking spirit of nitre, goes off at one explosion, exactly like a
+mixture of half common and half inflammable air. This I tried several
+times, by throwing the inflammable air into a phial full of spirit of
+nitre, with its mouth immersed in a bason containing some of the same
+spirit, and then applying the flame of a candle to the mouth of the
+phial, the moment that it was uncovered, after it had been taken out of
+the bason.<span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span></p>
+
+<p>This remarkable effect I hastily concluded to have arisen from the
+inflammable air having been in part deprived of its inflammability, by
+means of the stronger affinity, which the spirit of nitre had with
+phlogiston, and therefore I imagined that by letting them stand longer
+in contact, and especially by agitating them strongly together, I should
+deprive the air of all its inflammability; but neither of these
+operations succeeded, for still the air was only exploded at once, as
+before.</p>
+
+<p>And lastly, when I passed a quantity of inflammable air, which had been
+mixed with the fumes of spirit of nitre, through a body of water, and
+received it in another vessel, it appeared not to have undergone any
+change at all, for it went off in several successive explosions, like
+the purest inflammable air. The effect above-mentioned must, therefore,
+have been owing to the fumes of the spirit of nitre supplying the place
+of common air for the purpose of ignition, which is analogous to other
+experiments with nitre.</p>
+
+<p>Having had the curiosity, on the 25th of July 1772, to expose a great
+variety of different kinds of air to water out of which the air it
+contained had been boiled, without any particular view; the result was,
+in several respects, altogether<span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span> unexpected, and led to a variety of new
+observations on the properties and affinities of several kinds of air
+with respect to water. Among the rest three fourths of that which was
+inflammable was absorbed by the water in about two days, and the
+remainder was inflammable, but weakly so.</p>
+
+<p>Upon this, I began to agitate a quantity of strong inflammable air in a
+glass jar, standing in a pretty large trough of water, the surface of
+which was exposed to the common air, and I found that when I had
+continued the operation about ten minutes, near one fourth of the
+quantity of air had disappeared; and finding that the remainder made an
+effervescence with nitrous air, I concluded that it must have become fit
+for respiration, whereas this kind of air is, at the first, as noxious
+as any other kind whatever. To ascertain this, I put a mouse into a
+vessel containing 2-1/2 ounce measures of it, and observed that it lived
+in it twenty minutes, which is as long as a mouse will generally live in
+the same quantity of common air. This mouse was even taken out alive,
+and recovered very well. Still also the air in which it had breathed so
+long was inflammable, though very weakly so. I have even found it to be
+so when a mouse has actually died in it. Inflammable air thus diminished
+by agitation in<span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span> water, makes but one explosion on the approach of a
+candle, exactly like a mixture of inflammable air with common air.</p>
+
+<p>From this experiment I concluded that, by continuing the same process, I
+should deprive inflammable air of all its inflammability, and this I
+found to be the case; for, after a longer agitation, it admitted a
+candle to burn in it, like common air, only more faintly; and indeed by
+the test of nitrous air it did not appear to be near so good as common
+air. Continuing the same process still farther, the air which had been
+most strongly inflammable a little before, came to extinguish a candle,
+exactly like air in which a candle had burned out, nor could they be
+distinguished by the test of nitrous air.</p>
+
+<p>I found, by repeated trials, that it was difficult to catch the time in
+which inflammable air obtained from metals, in coming to extinguish
+flame, was in the state of common air, so that the transition from the
+one to the other must be very short. Indeed I think that in many,
+perhaps in most cases, there may be no proper medium at all, the
+phlogiston passing at once from that mode of union with its base which
+constitutes inflammable air, to that which constitutes an air that
+extinguishes flame, being so much overloaded as to admit of no more. I
+readily,<span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span> however, found this middle state in a quantity of inflammable
+air extracted from oak, which air I had kept a year, and in which a
+plant had grown, though very poorly, for some part of the time. A
+quantity of this air, after being agitated in water till it was
+diminished about one half, admitted a candle to burn in it exceedingly
+well, and was even hardly to be distinguished from common air by the
+test of nitrous air.</p>
+
+<p>I took some pains to ascertain the quantity of diminution, in fresh made
+and very highly-inflammable air from iron, at which it ceased to be
+inflammable, and, upon the whole, I concluded that it was so when it was
+diminished a little more than one half; for a quantity which was
+diminished exactly one half had something inflammable in it, but in the
+slightest degree imaginable. It is not improbable, however, but there
+may be great differences in the result of this experiment.</p>
+
+<p>Finding that water would imbibe inflammable air, I endeavoured to
+impregnate water with it, by the same process by which I had made water
+imbibe fixed air; but though I found that distilled water would imbibe
+about one fourteenth of its bulk of inflammable air, I could not
+perceive that the taste of it was sensibly altered.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_4_4" id="Footnote_4_4"></a><a href="#FNanchor_4_4"><span class="label">[4]</span></a> To try this, after every explosion, which immediately
+follows the presenting of the flame, the mouth of the phial should be
+closed (I generally do it with a finger of the hand in which I hold the
+phial) for otherwise the inflammable air will continue burning, though
+invisibly in the day time, till the whole be consumed.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span></p>
+<h2>SECTION IV.</h2>
+
+<h3><i>Of <span class="smcap">Air</span> infected with <span class="smcap">animal respiration</span>, or <span class="smcap">Putrefaction</span>.</i></h3>
+
+<p>That candles will burn only a certain time, in a given quantity of air
+is a fact not better known, than it is that animals can live only a
+certain time in it; but the cause of the death of the animal is not
+better known than that of the extinction of flame in the same
+circumstances; and when once any quantity of air has been rendered
+noxious by animals breathing in it as long as they could, I do not know
+that any methods have been discovered of rendering it fit for breathing
+again. It is evident, however, that there must be some provision in
+nature for this purpose, as well as for that of rendering the air fit
+for sustaining flame; for without it the whole mass of the atmosphere
+would, in time, become unfit for the purpose of animal life; and yet
+there is no reason to think that it is, at present, at all less fit for
+respiration than it has ever been. I flatter myself, however, that I
+have hit upon two of the methods employed by nature for this great
+purpose. How many others there may be, I cannot tell.<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span></p>
+
+<p>When animals die upon being put into air in which other animals have
+died, after breathing in it as long as they could, it is plain that the
+cause of their death is not the want of any <i>pabulum vit&aelig;,</i> which has
+been supposed to be contained in the air, but on account of the air
+being impregnated with something stimulating to their lungs; for they
+almost always die in convulsions, and are sometimes affected so
+suddenly, that they are irrecoverable after a single inspiration, though
+they be withdrawn immediately, and every method has been taken to bring
+them to life again. They are affected in the same manner, when they are
+killed in any other kind of noxious air that I have tried, viz. fixed
+air, inflammable air, air filled with the fumes of brimstone, infected
+with putrid matter, in which a mixture of iron filings and brimstone has
+stood, or in which charcoal has been burned, or metals calcined, or in
+nitrous air, &amp;c.</p>
+
+<p>As it is known that <i>convulsions</i> weaken, and exhaust the vital powers,
+much more than the most vigorous <i>voluntary</i> action of the muscles,
+perhaps these universal convulsions may exhaust the whole of what we may
+call the <i>vis vit&aelig;</i> at once, at least that the lungs may be rendered
+absolutely incapable of action, till the animal be<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span> suffocated, or be
+irrecoverable for want of respiration.</p>
+
+<p>If a mouse (which is an animal that I have commonly made use of for the
+purpose of these experiments) can stand the first shock of this
+stimulus, or has been habituated to it by degrees, it will live a
+considerable time in air in which other mice will die instantaneously. I
+have frequently found that when a number of mice have been confined in a
+given quantity of air, less than half the time that they have actually
+lived in it, a fresh mouse being introduced to them has been instantly
+thrown into convulsions, and died. It is evident, therefore, that if the
+experiment of the Black Hole were to be repeated, a man would stand the
+better chance of surviving it, who should enter at the first, than at
+the last hour.</p>
+
+<p>I have also observed, that young mice will always live much longer than
+old ones, or than those which are full grown, when they are confined in
+the same quantity of air. I have sometimes known a young mouse to live
+six hours in the same circumstances in which an old mouse has not lived
+one. On these accounts, experiments with mice, and, for the same reason,
+no doubt, with other animals also, have a considerable degree of
+uncertainty attending them; and<span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span> therefore, it is necessary to repeat
+them frequently, before the result can be absolutely depended upon. But
+every person of feeling will rejoice with me in the discovery of
+<i>nitrous air</i>, to be mentioned hereafter, which supersedes many
+experiments with the respiration of animals, being a much more accurate
+test of the purity of air.</p>
+
+<p>The discovery of the provision in nature for restoring air, which has
+been injured by the respiration of animals, having long appeared to me
+to be one of the most important problems in natural philosophy, I have
+tried a great variety of schemes in order to effect it. In these my
+guide has generally been to consider the influences to which the
+atmosphere is, in fact, exposed; and, as some of my unsuccessful trials
+may be of use to those who are disposed to take pains in the farther
+investigation of this subject, I shall mention the principal of them.</p>
+
+<p>The noxious effluvium with which air is loaded by animal respiration, is
+not absorbed by standing, without agitation; in fresh or salt water. I
+have kept it many months in fresh water, when, instead of being
+meliorated, it has seemed to become even more deadly, so as to require
+more time to restore it, by the methods which will be explained
+hereafter, than air which has<span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span> been lately made noxious. I have even
+spent several hours in pouring this air from one glass vessel into
+another, in water, sometimes as cold, and sometimes as warm, as my hands
+could bear it, and have sometimes also wiped the vessels many times,
+during the course of the experiment, in order to take off that part of
+the noxious matter, which might adhere to the glass vessels, and which
+evidently gave them an offensive smell; but all these methods were
+generally without any sensible effect. The <i>motion</i>, also, which the air
+received in these circumstances, it is very evident, was of no use for
+this purpose. I had not then thought of the simple, but most effectual
+method of agitating air in water, by putting it into a tall jar and
+shaking it with my hand.</p>
+
+<p>This kind of air is not restored by being exposed to the <i>light</i>, or by
+any other influence to which it is exposed, when confined in a thin
+phial, in the open air, for some months.</p>
+
+<p>Among other experiments, I tried a great variety of different
+<i>effluvia</i>, which are continually exhaling into the air, especially of
+those substances which are known to resist putrefaction; but I could not
+by these means effect any melioration of the noxious quality of this
+kind of air.<span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span></p>
+
+<p>Having read, in the memoirs of the Imperial Society, of a plague not
+affecting a particular village, in which there was a large sulphur-work,
+I immediately fumigated a quantity of this kind of air; or (which will
+hereafter appear to be the very same thing) air tainted with
+putrefaction, with the fumes of burning brimstone, but without any
+effect.</p>
+
+<p>I once imagined, that the <i>nitrous acid</i> in the air might be the general
+restorative which I was in quest of; and the conjecture was favoured, by
+finding that candles would burn in air extracted from saltpetre. I
+therefore spent a good deal of time in attempting, by a burning glass,
+and other means, to impregnate this noxious air, with some effluvium of
+saltpetre, and, with the same view, introduced into it the fumes of the
+smoaking spirit of nitre; but both these methods were altogether
+ineffectual.</p>
+
+<p>In order to try the effect of <i>heat</i>, I put a quantity of air, in which
+mice had died, into a bladder, tied to the end of the stem of a
+tobacco-pipe, at the other end of which was another bladder, out of
+which the air was carefully pressed. I then put the middle part of the
+stem into a chafing-dish of hot coals, strongly urged with a pair of
+bellows; and, pressing the bladders alternately, I made the air pass
+several<span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span> times through the heated part of the pipe. I have also made
+this kind of air very hot, standing in water before the fire. But
+neither of these methods were of any use.</p>
+
+<p><i>Rarefaction</i> and <i>condensation</i> by instruments were also tried, but in
+vain.</p>
+
+<p>Thinking it possible that the <i>earth</i> might imbibe the noxious quality
+of the air, and thence supply the roots of plants with such putrescent
+matter as is known to be nutritive to them, I kept a quantity of air, in
+which mice had died, in a phial, one half of which was filled with fine
+garden-mould; but, though it stood two months in these circumstances, it
+was not the better for it.</p>
+
+<p>I once imagined that, since several kinds of air cannot be long
+separated from common air, by being confined in bladders, in bottles
+well corked; or even closed with ground stopples, the affinity between
+this noxious air and the common air might be so great, that they would
+mix through a body of water interposed between them; the water
+continually receiving from the one, and giving to the other, especially
+as water receives some kind of impregnation from, I believe, every kind
+of air to which it is contiguous;<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span> but I have seen no reason to
+conclude, that a mixture of any kind of air with the common air can be
+produced in this manner.</p>
+
+<p>I have kept air in which mice have died, air in which candles have
+burned out, and inflammable air, separated from the common air, by the
+slightest partition of water that I could well make, so that it might
+not evaporate in a day or two, if I should happen not to attend to them;
+but I found no change in them after a month or six weeks. The
+inflammable air was still inflammable, mice died instantly in the air in
+which other mice had died before, and candles would not burn where they
+had burned out before.</p>
+
+<p>Since air tainted with animal or vegetable putrefaction is the same
+thing with air rendered noxious by animal respiration, I shall now
+recite the observations which I have made upon this kind of air, before
+I treat of the method of restoring them.</p>
+
+<p>That these two kinds of air are, in fact, the same thing, I conclude
+from their having several remarkable common properties, and from their
+differing in nothing that I have been able to observe. They equally
+extinguish flame, they are equally noxious to animals, they are<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span>
+equally, and in the same way, offensive to the smell, and they are
+restored by the same means.</p>
+
+<p>Since air which has passed through the lungs is the same thing with air
+tainted with animal putrefaction, it is probable that one use of the
+lungs is to carry off a <i>putrid effluvium</i>, without which, perhaps, a
+living body might putrefy as soon as a dead one.</p>
+
+<p>When a mouse putrefies in any given quantity of air, the bulk of it is
+generally increased for a few days; but in a few days more it begins to
+shrink up, and in about eight or ten days, if the weather be pretty
+warm, it will be found to be diminished 1/6, or 1/5 of its bulk. If it
+do not appear to be diminished after this time, it only requires to be
+passed through water, and the diminution will not fail to be sensible. I
+have sometimes known almost the whole diminution to take place, upon
+once or twice passing through the water. The same is the case with air,
+in which animals have breathed as long as they could. Also, air in which
+candles have burned out may almost always be farther reduced by this
+means.</p>
+
+<p>All these processes, as I observed before, seem to dispose the compound
+mass of air to part with<span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span> some constituent part belonging to it (which
+appears to be the <i>fixed air</i> that enters into its constitution) and
+this being miscible with water, must be brought into contact with it, in
+order to mix with it to the most advantage, especially when its union
+with the other constituent principles of the air is but partially
+broken.</p>
+
+<p>I have put mice into vessels which had their mouths immersed in
+quicksilver, and observed that the air was not much contracted after
+they were dead or cold; but upon withdrawing the mice, and admitting
+lime water to the air, it immediately became turbid, and was contracted
+in its dimensions as usual.</p>
+
+<p>I tried the same thing with air tainted with putrefaction, putting a
+dead mouse to a quantity of common air, in a vessel which had its mouth
+immersed in quicksilver, and after a week I took the mouse out, drawing
+it through the quicksilver, and observed that, for some time, there was
+an apparent increase of the air perhaps about 1/20. After this, it stood
+two days in the quicksilver, without any sensible alteration; and then
+admitting water to it, it began to be absorbed, and continued so, till
+the original quantity was diminished about 1/6. If, instead of common
+water, I had made use of lime-water<span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span> in this experiment, I make no doubt
+but it would have become turbid.</p>
+
+<p>If a quantity of lime-water in a phial be put under a glass vessel
+standing in water, it will not become turbid, and provided the access of
+the common air be prevented, it will continue lime-water, I do not know
+how long; but if a mouse be left to putrefy in the vessel, the water
+will deposit all its lime in a few days. This is owing to the fixed air
+deposited by the common air, and perhaps also from more fixed air
+discharged from the putrefying substances in some part of the process of
+putrefaction.</p>
+
+<p>The air that is discharged from putrefying substances seems, in some
+cases, to be chiefly fixed air, with the addition of some other
+effluvium, which has the power of diminishing common air. The
+resemblance between the true putrid effluvium and fixed air in the
+following experiment, which is as decisive as I can possibly contrive
+it, appeared to be very great; indeed much greater than I had expected.
+I put a dead mouse into a tall glass vessel, and having filled the
+remainder with quicksilver, and set it, inverted, in a pot of
+quicksilver, I let it stand about two months, in which time the putrid
+effluvium issuing from the mouse had filled the whole vessel, and part
+of the dissolved<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span> blood, which lodged upon the surface of the
+quicksilver, began to be thrown out. I then filled another glass vessel,
+of the same size and shape, with as pure fixed air as I could make, and
+exposed them both, at the same time, to a quantity of lime-water. In
+both cases the water grew turbid alike, it rose equally fast in both the
+vessels, and likewise equally high; so that about the same quantity
+remained unabsorbed by the water. One of these kinds of air, however,
+was exceedingly sweet and pleasant, and the other insufferably
+offensive; one of them also would have made an addition to any quantity
+of common air, with which it had been mixed, and the other would have
+diminished it. This, at least, would have been the consequence, if the
+mouse itself had putrefied in any quantity of common air.</p>
+
+<p>It seems to depend, in some measure, upon the <i>time</i>, and other
+circumstances, in the dissolution of animal or vegetable substances,
+whether they yield the proper putrid effluvium, or fixed, or inflammable
+air; but the experiments which I have made upon this subject, have not
+been numerous enough to enable me to decide with certainty concerning
+those circumstances.</p>
+
+<p>Putrid cabbage, green or boiled, infects the air in the very same manner
+as putrid<span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span> animal substances. Air thus tainted is equally contracted in
+its dimensions, it equally extinguishes flame, and is equally noxious to
+animals; but they affect the air very differently, if the heat that is
+applied to them be considerable.</p>
+
+<p>If beef or mutton, raw or boiled, be placed so near to the fire, that
+the heat to which it is exposed shall equal, or rather exceed, that of
+the blood, a considerable quantity of air will be generated in a day or
+two, about 1/7th of which I have generally found to be absorbed by
+water, while all the rest was inflammable; but air generated from
+vegetables, in the same circumstances, will be almost all fixed air, and
+no part of it inflammable. This I have repeated again and again, the
+whole process being in quicksilver; so that neither common air nor
+water, had any access to the substance on which the experiment was made;
+and the generation of air, or effluvium of any kind, except what might
+be absorbed by quicksilver, or resorbed by the substance itself, might
+be distinctly noted.</p>
+
+<p>A vegetable substance, after standing a day or two in these
+circumstances, will yield nearly all the air that can be extracted from
+it, in that degree of heat; whereas an animal substance<span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span> will continue
+to give more air, or effluvium, of some kind or other, with very little
+alteration, for many weeks. It is remarkable, however, that though a
+piece of beef or mutton, plunged in quicksilver, and kept in this degree
+of heat, yield air, the bulk of which is inflammable, and contracts no
+putrid smell (at least, in a day or two) a mouse treated in the same
+manner, yields the proper putrid effluvium, as indeed the smell
+sufficiently indicates.</p>
+
+<p>That the putrid effluvium will mix with water seems to be evident from
+the following experiment. If a mouse be put into a jar full of water,
+standing with its mouth inverted in another vessel of water, a
+considerable quantity of elastic matter (and which may, therefore, be
+called <i>air</i>) will soon be generated, unless the weather be so cold as
+to check all putrefaction. After a short time, the water contracts an
+extremely fetid and offensive smell, which seems to indicate that the
+putrid effluvium pervades the water, and affects the neighbouring air;
+and since, after this, there is often no increase of the air, that seems
+to be the very substance which is carried off through the water, as fast
+as it is generated; and the offensive smell is a sufficient proof that
+it is not fixed air. For this has a very agreeable flavour, whether it
+be produced by fermentation, or extracted from<span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span> chalk by oil of vitriol;
+affecting not only the mouth, but even the nostrils; with a pungency
+which is peculiarly pleasing to a certain degree, as any person may
+easily satisfy himself, who will chuse to make the experiment.</p>
+
+<p>If the water in which the mouse was immersed, and which is saturated
+with the putrid air, be changed, the greater part of the putrid air,
+will, in a day or two, be absorbed, though the mouse continues to yield
+the putrid effluvium as before; for as soon as this fresh water becomes
+saturated with it, it begins to be offensive to the smell, and the
+quantity of the putrid air upon its surface increases as before. I kept
+a mouse producing putrid air in this manner for the space of several
+months.</p>
+
+<p>Six ounce measures of air not readily absorbed by water, appeared to
+have been generated from one mouse, which had been putrefying eleven
+days in confined air, before it was put into a jar which was quite
+filled with water, for the purpose of this observation.</p>
+
+<p>Air thus generated from putrid mice standing in water, without any
+mixture of common air, extinguishes flame, and is noxious to animals,
+but not more so than common air only tainted with putrefaction. It is
+exceedingly difficult<span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span> and tedious to collect a quantity of this putrid
+air, not miscible in water, so very great a proportion of what is
+collected being absorbed by the water in which it is kept; but what that
+proportion is, I have not endeavoured to ascertain. It is probably the
+same proportion that that part of fixed air, which is not readily
+absorbed by water, bears to the rest; and therefore this air, which I at
+first distinguished by the name of <i>the putrid effluvium</i>, is probably
+the same with fixed air, mixed with the phlogistic matter, which, in
+this and other processes, diminishes common air.</p>
+
+<p>Though a quantity of common air be diminished by any substance
+putrefying in it, I have not yet found the same effect to be produced by
+a mixture of putrid air with common air; but, in the manner in which I
+have hitherto made the experiment, I was obliged to let the putrid air
+pass through a body of water, which might instantly absorb the
+phlogistic matter that diminished the common air.</p>
+
+<p>Insects of various kinds live perfectly well in air tainted with animal
+or vegetable putrefaction, when a single inspiration of it would have
+instantly killed any other animal. I have frequently tried the
+experiment with flies and butterflies. The <i>aphides</i> also will thrive as
+well<span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span> upon plants growing in this kind of air, as in the open air. I
+have even been frequently obliged to take plants out of the putrid air
+in which they were growing, on purpose to brush away the swarms of these
+insects which infected them; and yet so effectually did some of them
+conceal themselves, and so fast did they multiply, in these
+circumstances, that I could seldom keep the plants quite clear of them.</p>
+
+<p>When air has been freshly and strongly tainted with putrefaction, so as
+to smell through the water, sprigs of mint have presently died, upon
+being put into it, their leaves turning black; but if they do not die
+presently, they thrive in a most surprizing manner. In no other
+circumstances have I ever seen vegetation so vigorous as in this kind of
+air, which is immediately fatal to animal life. Though these plants have
+been crouded in jars filled with this air, every leaf has been full of
+life; fresh shoots have branched out in various directions, and have
+grown much faster than other similar plants, growing in the same
+exposure in common air.</p>
+
+<p>This observation led me to conclude, that plants, instead of affecting
+the air in the same manner with animal respiration, reverse the effects
+of breathing, and tend to keep the atmosphere sweet and wholesome, when
+it is become<span class='pagenum'><a name="Page_87" id="Page_87">[Pg 87]</a></span> noxious, in consequence of animals either living and
+breathing, or dying and putrefying in it.</p>
+
+<p>In order to ascertain this, I took a quantity of air, made thoroughly
+noxious, by mice breathing and dying in it, and divided it into two
+parts; one of which I put into a phial immersed in water; and to the
+other (which was contained in a glass jar, standing in water) I put a
+sprig of mint. This was about the beginning of August 1771, and after
+eight or nine days, I found that a mouse lived perfectly well in that
+part of the air, in which the sprig of mint had grown, but died the
+moment it was put into the other part of the same original quantity of
+air; and which I had kept in the very same exposure, but without any
+plant growing in it.</p>
+
+<p>This experiment I have several times repeated; sometimes using air in
+which animals had breathed and died, and at other times using air,
+tainted with vegetable or animal putrefaction; and generally with the
+same success.</p>
+
+<p>Once, I let a mouse live and die in a quantity of air which had been
+noxious, but which had been restored by this process, and it lived
+nearly as long as I conjectured it might have done in an equal quantity
+of fresh air; but this is so exceedingly various, that it is not easy to
+form<span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span> any judgment from it; and in this case the symptom of <i>difficult
+respiration</i> seemed to begin earlier than it would have done in common
+air.</p>
+
+<p>Since the plants that I made use of manifestly grow and thrive in putrid
+air; since putrid matter is well known to afford proper nourishment for
+the roots of plants; and since it is likewise certain that they receive
+nourishment by their leaves as well as by their roots, it seems to be
+exceedingly probable, that the putrid effluvium is in some measure
+extracted from the air, by means of the leaves of plants, and therefore
+that they render the remainder more fit for respiration.</p>
+
+<p>Towards the end of the year some experiments of this kind did not answer
+so well as they had done before, and I had instances of the relapsing of
+this restored air to its former noxious state. I therefore suspended my
+judgment concerning the efficacy of plants to restore this kind of
+noxious air, till I should have an opportunity of repeating my
+experiments, and giving more attention to them. Accordingly I resumed
+the experiments in the summer of the year 1772, when I presently had the
+most indisputable proof of the restoration of putrid air by vegetation;
+and as the fact is of some importance, and the subsequent variation in
+the state of this<span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span> kind of air is a little remarkable, I think it
+necessary to relate some of the facts pretty circumstantially.</p>
+
+<p>The air, on which I made the first experiments, was rendered exceedingly
+noxious by mice dying in it on the 20th of June. Into a jar nearly
+filled with one part of this air, I put a sprig of mint, while I kept
+another part of it in a phial, in the same exposure; and on the 27th of
+the same month, and not before, I made a trial of them, by introducing a
+mouse into a glass vessel, containing 2-1/2 ounce measures filled with
+each kind of air; and I noted the following facts.</p>
+
+<p>When the vessel was filled with the air in which the mint had grown, a
+very large mouse lived five minutes in it, before it began to shew any
+sign of uneasiness. I then took it out, and found it to be as strong and
+vigorous as when it was first put in; whereas in that air which had been
+kept in the phial only, without a plant growing in it, a younger mouse
+continued not longer than two or three seconds, and was taken out quite
+dead. It never breathed after, and was immediately motionless. After
+half an hour, in which time the larger mouse (which I had kept alive,
+that the experiment might be made on both the kinds of air with the very
+same animal) would have been sufficiently<span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span> recruited, supposing it to
+have received any injury by the former experiment, was put into the same
+vessel of air; but though it was withdrawn again, after being in it
+hardly one second, it was recovered with difficulty, not being able to
+stir from the place for near a minute. After two days, I put the same
+mouse into an equal quantity of common air, and observed that it
+continued seven minutes without any sign of uneasiness; and being very
+uneasy after three minutes longer, I took it out. Upon the whole, I
+concluded that the restored air wanted about one fourth of being as
+wholesome as common air. The same thing also appeared when I applied the
+test of nitrous air.</p>
+
+<p>In the seven days, in which the mint was growing in this jar of noxious
+air, three old shoots had extended themselves about three inches, and
+several new ones had made their appearance in the same time. Dr.
+Franklin and Sir John Pringle happened to be with me, when the plant had
+been three or four days in this state, and took notice of its vigorous
+vegetation, and remarkably healthy appearance in that confinement.</p>
+
+<p>On the 30th of the same month, a mouse lived fourteen minutes, breathing
+naturally all the time, and without appearing to be much<span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span> uneasy, till
+the last two minutes, in the vessel containing two ounce measures and a
+half of air which had been rendered noxious, by mice breathing in it
+almost a year before, and which, I had found to be most highly noxious
+on the 19th of this month, a plant having grown in it, but not
+exceedingly well, these eleven days; on which account I had deferred
+making the trial so long. The restored air was affected by a mixture of
+nitrous air, almost as much as common air.</p>
+
+<p>As this putrid air was thus easily restored to a considerable degree of
+fitness for respiration, by plants growing in it, I was in hopes that by
+the same means it might in time be so much more perfectly restored, that
+a candle would burn in it; and for this purpose I kept plants growing in
+the jars which contained this air till the middle of August following,
+but did not take sufficient care to pull out all the old and rotten
+leaves. The plants, however, had grown, and looked so well upon the
+whole, that I had no doubt but that the air must constantly have been in
+a mending state; when I was exceedingly surprized to find, on the 24th
+of that month, that though the air in one of the jars had not grown
+worse, it was no better; and that the air in the other jar was so much
+worse than it had been, that a mouse would have died in it in a<span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span> few
+seconds. It also made no effervescence with nitrous air, as it had done
+before.</p>
+
+<p>Suspecting that the same plant might be capable of restoring putrid air
+to a certain degree only, or that plants might have a contrary tendency
+in some stages of their growth, I withdrew the old plant, and put a
+fresh one in its place; and found that, after seven days, the air was
+restored to its former wholesome state. This fact I consider as a very
+remarkable one, and well deserving of a farther investigation, as it may
+throw more light upon the principles of vegetation. It is not, however,
+a single fact; for I had several instances of the same kind in the
+preceding year; but it seemed so very extraordinary, that air should
+grow worse by the continuance of the same treatment by which it had
+grown better, that, whenever I observed it, I concluded that I had not
+taken sufficient care to satisfy myself of its previous restoration.</p>
+
+<p>That plants are capable of perfectly restoring air injured by
+respiration, may, I think, be inferred with certainty from the perfect
+restoration, by this means, of air which had passed through my lungs, so
+that a candle would burn in it again, though it had extinguished flame
+before, and apart of the same original quantity<span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span> of air still continued
+to do so. Of this one instance occurred in the year 1771, a sprig of
+mint having grown in a jar of this kind of air, from the 25th of July to
+the 17th of August following; and another trial I made, with the same
+success, the 7th of July 1772, the plant having grown in it from the
+29th of June preceding. In this case also I found that the effect was
+not owing to any virtue in the leaves of mint; for I kept them
+constantly changed in a quantity of this kind of air, for a considerable
+time, without making any sensible alteration in it.</p>
+
+<p>These proofs of a partial restoration of air by plants in a state of
+vegetation, though in a confined and unnatural situation, cannot but
+render it highly probable, that the injury which is continually done to
+the atmosphere by the respiration of such a number of animals, and the
+putrefaction of such masses of both vegetable and animal matter, is, in
+part at least, repaired by the vegetable creation. And, notwithstanding
+the prodigious mass of air that is corrupted daily by the
+above-mentioned causes; yet, if we consider the immense profusion of
+vegetables upon the face of the earth, growing in places, suited to
+their nature, and consequently at full liberty to exert all their
+powers, both inhaling and exhaling, it can hardly be thought, but<span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span> that
+it may be a sufficient counterbalance to it, and that the remedy is
+adequate to the evil.</p>
+
+<p>Dr. Franklin, who, as I have already observed, saw some of my plants in
+a very flourishing state, in highly noxious air, was pleased to express
+very great satisfaction with the result of the experiments. In his
+answer to the letter in which I informed him of it, he says,</p>
+
+<p>"That the vegetable creation should restore the air which is spoiled by
+the animal part of it, looks like a rational system, and seems to be of
+a piece with the rest. Thus fire purifies water all the world over. It
+purifies it by distillation, when it raises it in vapours, and lets it
+fall in rain; and farther still by filtration, when, keeping it fluid,
+it suffers that rain to percolate the earth. We knew before that putrid
+animal substances were converted into sweet vegetables, when mixed with
+the earth, and applied as manure; and now, it seems, that the same
+putrid substances, mixed with the air, have a similar effect. The strong
+thriving state of your mint in putrid air seems to shew that the air is
+mended by taking something from it, and not by adding to it." He adds,
+"I hope this will give some check to the rage of destroying trees that
+grow near houses, which has<span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span> accompanied our late improvements in
+gardening, from an opinion of their being unwholesome. I am certain,
+from long observation, that there is nothing unhealthy in the air of
+woods; for we Americans have every where our country habitations in the
+midst of woods, and no people on earth enjoy better health, or are more
+prolific."</p>
+
+<p>Having rendered inflammable air perfectly innoxious by continued
+<i>agitation in a trough of water</i>, deprived of its air, I concluded that
+other kinds of noxious air might be restored by the same means; and I
+presently found that this was the case with putrid air, even of more
+than a year's standing. I shall observe once for all, that this process
+has never failed to restore any kind of noxious air on which I have
+tried it, viz. air injured by respiration or putrefaction, air infected
+with the fumes of burning charcoal, and of calcined metals, air in which
+a mixture of iron filings and brimstone, that in which paint made of
+white lead and oil has stood, or air which has been diminished by a
+mixture of nitrous air. Of the remarkable effect which this process has
+on nitrous air itself, an account will be given in its proper place.</p>
+
+<p>If this process be made in water deprived of air, either by the
+air-pump, by boiling, or by distillation,<span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span> or if fresh rain-water be
+used, the air will always be diminished by the agitation; and this is
+certainly the fairest method of making the experiment. If the water be
+fresh pump-water, there will always be an increase of the air by
+agitation, the air contained in the water being set loose, and joining
+that which is in the jar. In this case, also, the air has never failed
+to be restored; but then it might be suspected that the melioration was
+produced by the addition of some more wholesome ingredient. As these
+agitations were made in jars with wide mouths, and in a trough which had
+a large surface exposed to the common air, I take it for granted that
+the noxious effluvia, whatever they be, were first imbibed by the water,
+and thereby transmitted to the common atmosphere. In some cases this was
+sufficiently indicated by the disagreeable smell which attended the
+operation.</p>
+
+<p>After I had made these experiments, I was informed that an ingenious
+physician and philosopher had kept a fowl alive twenty-four hours, in a
+quantity of air in which another fowl of the same size had not been able
+to live longer than an hour, by contriving to make the air, which it
+breathed, pass through no very large quantity of acidulated water, the
+surface of which was not exposed to the common air; and that<span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span> even when
+the water was not acidulated, the fowl lived much longer than it could
+have done, if the air which it breathed had not been drawn through the
+water.</p>
+
+<p>As I should not have concluded that this experiment would have succeeded
+so well, from any observations that I had made upon the subject, I took
+a quantity of air in which mice had died, and agitated it very strongly,
+first in about five times its own quantity of distilled water, in the
+manner in which I had impregnated water with fixed air; but though the
+operation was continued a long time, it made no sensible change in the
+properties of the air. I also repeated the operation with pump-water,
+but with as little effect. In this case, however, though the air was
+agitated in a phial, which had a narrow neck, the surface of the water
+in the bason was considerably large, and exposed to the common
+atmosphere, which must have tended a little to favour the experiment.</p>
+
+<p>In order to judge more precisely of the effect of these different
+methods of agitating air, I transferred the very noxious air, which I
+had hot been able to amend in the least degree by the former method,
+into an open jar, standing in a trough of water; and when I had agitated
+it till it was diminished about one third, I found<span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span> it to be better than
+air in which candles had burned out, as appeared by the test of the
+nitrous air; and a mouse lived in 2-1/2 ounce measures of it a quarter
+of an hour, and was not sensibly affected the first ten or twelve
+minutes.</p>
+
+<p>In order to determine whether the addition of any <i>acid</i> to the water,
+would make it more capable of restoring putrid air, I agitated a
+quantity of it in a phial containing very strong vinegar; and after that
+in <i>aqua fortis</i>, only half diluted with water; but by neither of these
+processes was the air at all mended, though the agitation was repeated,
+at intervals, during a whole day, and it was moreover allowed to stand
+in that situation all night.</p>
+
+<p>Since, however, water in these experiments must have imbibed and
+retained a certain portion of the noxious effluvia, before they could be
+transmitted to the external air, I do not think it improbable but that
+the agitation of the sea and large lakes may be of some use for the
+purification of the atmosphere, and the putrid matter contained in water
+may be imbibed by aquatic plants, or be deposited in some other manner.</p>
+
+<p>Having found, by several experiments above-mentioned that the proper
+putrid effluvium<span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span> is something quite distinct from fixed air, and
+finding, by the experiments of Dr. Macbride, that fixed air corrects
+putrefaction; it occured to me, that fixed air, and air tainted with
+putrefaction, though equally, noxious when separate, might make a
+wholesome mixture, the one, correcting the other; and I was confirmed in
+this opinion by, I believe, not less than fifty or sixty instances, in
+which air, that had been made in the highest degree noxious, by
+respiration or putrefaction, was so far sweetened, by a mixture of about
+four times as much fixed air, that afterwards mice lived in it
+exceedingly well, and in some cases almost as long as in common air. I
+found it, indeed, to be more difficult to restore <i>old</i> putrid air by
+this means; but I hardly ever failed to do it, when the two kinds of air
+had stood a long time together; by which I mean about a fortnight or
+three weeks.</p>
+
+<p>The reason why I do not absolutely conclude that the restoration of air
+in these cases was the effect of fixed air, is that, when I made a trial
+of the mixture, I sometimes agitated the two kinds of air pretty
+strongly together, in a trough of water, or at least passed it several
+times through water, from one jar to another, that the superfluous fixed
+air might be absorbed, not suspecting at that time that the agitation
+could have any other effect. But<span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span> having since found that very violent,
+and especially long-continued agitation in water, without any mixture of
+fixed air, never failed to render any kind of noxious air in some
+measure fit for respiration (and in one particular instance the mere
+transferring of the air from one vessel to another through the water,
+though for a much longer time than I ever used for the mixtures of air,
+was of considerable use for the same purpose) I began to entertain some
+doubt of the efficacy of fixed air in this case. In some cases also the
+mixture of fixed air had by no means so much effect on the putrid air
+as, from the generality of my observations, I should have expected.</p>
+
+<p>I was always aware, indeed, that it might be said, that, the residuum of
+fixed air not being very noxious, such an addition must contribute to
+mend the putrid air; but, in order to obviate this objection, I once
+mixed the residuum of as much fixed air as I had found, by a variety of
+trials, to be sufficient to restore a given quantity of putrid air, with
+an equal quantity of that air, without making any sensible melioration
+of it.</p>
+
+<p>Upon the whole, I am inclined to think that this process could hardly
+have succeeded so well as it did with me, and in so great a number<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span> of
+trials, unless fixed air have some tendency to correct air tainted with
+respiration or putrefaction; and it is perfectly agreeable to the
+analogy of Dr. Macbride's discoveries, and may naturally be expected
+from them, that it should have such an effect.</p>
+
+<p>By a mixture of fixed air I have made wholesome the residuum of air
+generated by putrefaction only, from mice plunged in water. This, one
+would imagine, <i>&agrave; priori</i>, to be the most noxious of all kinds of air.
+For if common air only tainted with putrefaction be so deadly, much more
+might one expect that air to be so, which was generated from
+putrefaction only; but it seems to be nothing more than common air (or
+at least that kind of fixed air which is not absorbed by water) tainted
+with putrefaction, and therefore requires no other process to sweeten
+it. In this case, however, we seem to have an instance of the generation
+of genuine common air, though mixed with something that is foreign to
+it. Perhaps the residuum of fixed air may be another instance of the
+same nature, and also the residuum of inflammable air, and of nitrous
+air, especially nitrous air loaded with phlogiston, after long agitation
+in water.<span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span></p>
+
+<p>Fixed air is equally diffused through the whole mass of any quantity of
+putrid air with which it is mixed: for dividing the mixture into two
+equal parts, they were reduced in the same proportion by passing through
+water. But this is also the case with some of the kinds of air which
+will not incorporate, as inflammable air, and air in which brimstone has
+burned.</p>
+
+<p>If fixed air tend to correct air which has been injured by animal
+respiration or putrefaction, <i>lime kilns</i>, which discharge great
+quantities of fixed air, may be wholesome in the neighbourhood of
+populous cities, the atmosphere of which must abound with putrid
+effluvia. I should think also that physicians might avail themselves of
+the application of fixed air in many putrid disorders, especially as it
+may be so easily administered by way of <i>clyster</i>, where it would often
+find its way to much of the putrid matter. Nothing is to be apprehended
+from the distention of the bowels by this kind of air, since it is so
+readily absorbed by any fluid or moist substance.</p>
+
+<p>Since fixed air is not noxious <i>per se</i>, but, like fire, only in excess,
+I do not think it at all hazardous to attempt to <i>breathe</i> it. It is
+however easily conveyed into the <i>stomach</i>, in natural or artificial
+Pyrmont water, in briskly-fermenting<span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span> liquors, or a vegetable diet. It
+is even possible, that a considerable quantity of fixed air might be
+imbibed by the absorbing vessels of the skin, if the whole body, except
+the head, should be suspended over a vessel of strongly-fermenting
+liquor; and in some putrid disorders this treatment might be very
+salutary. If the body was exposed quite naked, there would be very
+little danger from the cold in this situation, and the air having freer
+access to the skin might produce a greater effect. Being no physician, I
+run no risk by throwing out these random, and perhaps whimsical
+proposals.<a name="FNanchor_5_5" id="FNanchor_5_5"></a><a href="#Footnote_5_5" class="fnanchor">[5]</a></p>
+
+<p>Having communicated my observations on fixed air, and especially my
+scheme of applying it by way of <i>clyster</i> in putrid disorders, to Mr.
+Hey, an ingenious surgeon in Leeds a case presently occurred, in which
+he had an opportunity of giving it a trial; and mentioning it to Dr.
+Hird and Dr. Crowther, two physicians who attended the patient, they
+approved the scheme, and it was put in execution; both by applying the
+fixed air by way of clyster, and at the same time making the patient
+drink plentifully of liquors strongly impregnated with<span class='pagenum'><a name="Page_104" id="Page_104">[Pg 104]</a></span> it. The event
+was such, that I requested Mr. Hey to draw up a particular account of
+the case, describing the whole of the treatment, that the public might
+be satisfied that this new application of fixed air is perfectly safe,
+and also, have an opportunity of judging how far it had the effect which
+I expected from it; and as the application is new, and not unpromising,
+I shall subjoin his letter to me on the subject, by way of <i>Appendix</i> to
+these papers.</p>
+
+<p>When I began my inquires into the properties of different kinds of air,
+I engaged my friend Dr. Percival to attend to the <i>medicinal uses</i> of
+them, being sensible that his knowledge of philosophy as well as of
+medicine would give him a singular advantage for this purpose. The
+result of his observations I shall also insert in the Appendix.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_5_5" id="Footnote_5_5"></a><a href="#FNanchor_5_5"><span class="label">[5]</span></a> Some time after these papers were first printed, I was
+pleased to find the same proposal in <i>Dr. Alexander's Experimental
+Essays</i>.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_105" id="Page_105">[Pg 105]</a></span></p>
+<h2>SECTION V.</h2>
+
+<h3><i>Of <span class="smcap">Air</span> in which a mixture of <span class="smcap">Brimstone</span> and <span class="smcap">Filings</span> of <span class="smcap">Iron</span> has stood.</i></h3>
+
+
+<p>Reading in Dr. Hales's account of his experiments, that there was a
+great diminution of the quantity of air in which <i>a mixture of powdered
+brimstone and filings of iron, made into a paste with water</i>, had stood,
+I repeated the experiment, and found the diminution greater than I had
+expected. This diminution of air is made as effectually, and as
+expeditiously, in quicksilver as in water; and it may be measured with
+the greatest accuracy, because there is neither any previous expansion
+or increase of the quantity of air, and because it is some time before
+this process begins to have any sensible effect. This diminution of air
+is various; but I have generally found it to be between one fifth and
+one fourth of the whole.</p>
+
+<p>Air thus diminished is not heavier, but rather lighter than common air;
+and though lime-water does not become turbid when it is exposed to this
+air, it is probably owing to the formation of a selenitic salt, as was
+the case with the simple burning of brimstone above-mentioned.<span class='pagenum'><a name="Page_106" id="Page_106">[Pg 106]</a></span> That
+something proceeding from the brimstone strongly affects the water which
+is confined in the same place with this mixture, is manifest from the
+very strong smell that it has of the volatile spirit of vitriol.</p>
+
+<p>I conclude that the diminution of air by this, process is of the same
+kind with the diminution of it in the other cases, because when this
+mixture is put into air which has been previously diminished, either by
+the burning of candles, by respiration, or putrefaction, though it never
+fails to diminish it something more, it is, however, no farther than
+this process alone would have done it. If a fresh mixture be introduced
+into a quantity of air which had been reduced by a former mixture, it
+has little or no farther effect.</p>
+
+<p>I once observed, that when a mixture of this kind was taken out of a
+quantity of air in which a candle had before burned out, and in which it
+had stood for several days, it was quite cold and black, as it always
+becomes in a confined place; but it presently grew very hot, smoaked
+copously, and smelled very offensively; and when it was cold, it was
+brown, like the rust of iron.<span class='pagenum'><a name="Page_107" id="Page_107">[Pg 107]</a></span></p>
+
+<p>I once put a mixture of this kind to a quantity of inflammable air, made
+from iron, by which means it was diminished 1/9 or 1/10 in its bulk;
+but, as far as I could judge, it was still as inflammable as ever.
+Another quantity of inflammable air was also reduced in the same
+proportion, by a mouse putrefying in it; but its inflammability was not
+seemingly lessened.</p>
+
+<p>Air diminished by this mixture of iron filings and brimstone, is
+exceedingly noxious to animals, and I have not perceived that it grows
+any better by keeping in water. The smell of it is very pungent and
+offensive.</p>
+
+<p>The quantity of this mixture which I made use of in the preceding
+experiments, was from two to four ounce measures; but I did not
+perceive, but that the diminution of the quantity of air (which was
+generally about twenty ounce measures) was as great with the smallest,
+as with the largest quantity. How small a quantity is necessary to
+diminish a given quantity of air to a <i>maximum</i>, I have made no
+experiments to ascertain.</p>
+
+<p>As soon as this mixture of iron filings with, brimstone and water,
+begins to ferment, it also turns black, and begins to swell, and it
+continues<span class='pagenum'><a name="Page_108" id="Page_108">[Pg 108]</a></span> to do so, till it occupies twice as much space as it did at
+first. The force with which it expands is great; but how great it is I
+have not endeavoured to determine.</p>
+
+<p>When this mixture is immersed in water, it generates no air, though it
+becomes black, and swells.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2>SECTION VI.</h2>
+
+<h3><i>Of<span class="smcap"> nitrous Air</span>.</i></h3>
+
+
+<p>Ever since I first read Dr. Hales's most excellent <i>Statical Essays</i>, I
+was particularly struck with that experiment of his, of which an account
+is given, VOL. I, p. 224. and VOL. II, p. 280. in which common air, and
+air generated from the Walton pyrites, by spirit of nitre, made a turbid
+red mixture, and in which part of the common air was absorbed; but I
+never expected to have the satisfaction of seeing this remarkable
+appearance, supposing it to be peculiar to that particular mineral.
+Happening to mention this subject to the Hon. Mr. Cavendish, when I was
+in London, in the spring of the year 1772, he said that he did not
+imagine but that other kinds of pyrites, or the metals might answer as
+well, and that<span class='pagenum'><a name="Page_109" id="Page_109">[Pg 109]</a></span> probably the red appearance of the mixture depended upon
+the spirit of nitre only. This encouraged me to attend to the subject;
+and having no pyrites, I began with the solution of the different metals
+in spirit of nitre, and catching the air which was generated in the
+solution, I presently found what I wanted, and a good deal more.</p>
+
+<p>Beginning with the solution of brass, on the 4th of June 1772, I first
+found this remarkable species of air, only one effect of which, was
+casually observed by Dr. Hales; and he gave so little attention to it,
+and it has been so much unnoticed since his time, that, as far as I
+know, no name has been given to it. I therefore found myself, contrary
+to my first resolution, under an absolute necessity of giving a name to
+this kind of air myself. When I first began to speak and write of it to
+my friends, I happened to distinguish it by the name of <i>nitrous air</i>,
+because I had procured it by means of spirit of nitre only; and though I
+cannot say that I altogether like the term, neither myself nor any of my
+friends, to whom I have applied for the purpose, have been able to hit
+upon a better; so that I am obliged, after all, to content myself with
+it.<span class='pagenum'><a name="Page_110" id="Page_110">[Pg 110]</a></span></p>
+
+<p>I have found that this kind of air is readily procured from iron,
+copper, brass, tin, silver, quicksilver, bismuth, and nickel, by the
+nitrous acid only, and from gold and the regulus of antimony by <i>aqua
+regia</i>. The circumstances attending the solution of each of these metals
+are various, but hardly worth mentioning, in treating of the properties
+of the <i>air</i> which they yield; which, from what metal soever it is
+extracted, has, as far as I have been able to observe, the very same
+properties.</p>
+
+<p>One of the most conspicuous properties of this kind of air is the great
+diminution of any quantity of common air with which it is mixed,
+attended with a turbid red, or deep orange colour, and a considerable
+heat. The <i>smell</i> of it, also, is very strong, and remarkable, but very
+much resembling that of smoking spirit of nitre.</p>
+
+<p>The diminution of a mixture of this and common air is not an equal
+diminution of both the kinds, which is all that Dr. Hales could observe,
+but of about one fifth of the common air, and as much of the nitrous air
+as is necessary to produce that effect; which, as I have found by many
+trials, is about one half as much as the original quantity of common
+air. For if one measure of nitrous air be put to two<span class='pagenum'><a name="Page_111" id="Page_111">[Pg 111]</a></span> measures of common
+air, in a few minutes (by which time the effervescence will be over, and
+the mixture will have recovered its transparency) there will want about
+one ninth of the original two measures; and if both the kinds of air be
+very pure, the diminution will still go on slowly, till in a day or two,
+the whole will be reduced to one fifth less than the original quantity
+of common air. This farther diminution, by long standing, I had not
+observed at the time of the first publication of these papers.</p>
+
+<p>I hardly know any experiment that is more adapted to amaze and surprize
+than this is, which exhibits a quantity of air, which, as it were,
+devours a quantity of another kind of air half as large as itself, and
+yet is so far from gaining any addition to its bulk, that it is
+considerably diminished by it. If, after this full saturation of common
+air with nitrous air, more nitrous air be put to it, it makes an
+addition equal to its own bulk, without producing the least redness, or
+any other visible effect.</p>
+
+<p>If the smallest quantity of common air be put to any larger quantity of
+nitrous air, though the two together will not occupy so much space as
+they did separately, yet the quantity will still be larger than that of
+the nitrous air only. One ounce measure of common<span class='pagenum'><a name="Page_112" id="Page_112">[Pg 112]</a></span> air being put to near
+twenty ounce measures of nitrous air, made an addition to it of about
+half an ounce measure. This being a much greater proportion than the
+diminution of common air, in the former experiment, proves that part of
+the diminution in the former case is in the nitrous air. Besides, it
+will presently appear, that nitrous air is subject to a most remarkable
+diminution; and as common air, in a variety of other cases, suffers a
+diminution from one fifth to one fourth, I conclude, that in this case
+also it does not exceed that proportion, and therefore that the
+remainder of the diminution respects the nitrous air.</p>
+
+<p>In order to judge whether the <i>water</i> contributed to the diminution of
+this mixture of nitrous and common air, I made the whole process several
+times in quicksilver, using one third of nitrous, and two thirds of
+common air, as before. In this case the redness continued a very long
+time, and the diminution was not so great as when the mixtures had been
+made in water, there remaining one seventh more than the original
+quantity of common air.</p>
+
+<p>This mixture stood all night upon the quicksilver; and the next morning
+I observed that it was no farther diminished upon the admission<span class='pagenum'><a name="Page_113" id="Page_113">[Pg 113]</a></span> of
+water to it, nor by pouring it several times through the water, and
+letting it stand in water two days.</p>
+
+<p>Another mixture, which had stood about six hours on the quicksilver, was
+diminished a little more upon the admission of water, but was never less
+than the original quantity of common air. In another case however, in
+which the mixture had stood but a very short time in quicksilver, the
+farther diminution, which took place upon the admission of water, was
+much more considerable; so that the diminution, upon the whole, was very
+nearly as great as if the process had been intirely in water.</p>
+
+<p>It is evident from these experiments, that the diminution is in part
+owing to the absorption by the water; but that when the mixture is kept
+a long time, in a situation in which there is no water to absorb any
+part of it, it acquires a constitution, by which it is afterwards
+incapable of being absorbed by water, or rather, there is an addition to
+the quantity of air by nitrous air produced by the solution of the
+quicksilver.</p>
+
+<p>It will be seen, in the second part of this work, that, in the
+decomposition of nitrous air by its mixture with common air, there is<span class='pagenum'><a name="Page_114" id="Page_114">[Pg 114]</a></span>
+nothing at hand when the process is made in quicksilver, with which the
+acid that entered into its composition can readily unite.</p>
+
+<p>In order to determine whether the fixed part of common air was deposited
+in the diminution of it by nitrous air, I inclosed a vessel full of
+lime-water in the jar in which the process was made, but it occasioned
+no precipitation of the lime; and when the vessel was taken out, after
+it had been in that situation a whole day, the lime was easily
+precipitated by breathing into it as usual.</p>
+
+<p>But though the precipitation of the lime was not sensible in this method
+of making the experiment, it is sufficiently so when the whole process
+is made in lime-water, as will be seen in the second part of this work;
+so that we have here another evidence of the deposition of fixed air
+from common air. I have made no alteration, however, in the preceding
+paragraph, because it may not be unuseful, as a caution to future
+experimenters.</p>
+
+<p>It is exceedingly remarkable that this effervescence and diminution,
+occasioned by the mixture of nitrous air, is peculiar to common air, or
+<i>air fit for respiration</i>; and, as far as I can judge, from a great
+number of observations,<span class='pagenum'><a name="Page_115" id="Page_115">[Pg 115]</a></span> is at least very nearly, if not exactly, in
+proportion to its fitness for this purpose; so that by this means the
+goodness of air may be distinguished much more accurately than it can be
+done by putting mice, or any other animals, to breathe in it.</p>
+
+<p>This was a most agreeable discovery to me, as I hope it may be an useful
+one to the public; especially as, from this time, I had no occasion for
+so large a stock of mice as I had been used to keep for the purpose of
+these experiments, using them only in those which required to be very
+decisive; and in these cases I have seldom failed to know beforehand in
+what manner they would be affected.</p>
+
+<p>It is also remarkable that, on whatever account air is unfit for
+respiration, this same test is equally applicable. Thus there is not the
+least effervescence between nitrous and fixed air, or inflammable air,
+or any species of diminished air. Also the degree of diminution being
+from nothing at all to more than one third of the whole of any quantity
+of air, we are, by this means, in possession of a prodigiously large
+<i>scale</i>, by which we may distinguish very small degrees of difference in
+the goodness of air.</p>
+
+<p>I have not attended much to this circumstance, having used this test
+chiefly for greater<span class='pagenum'><a name="Page_116" id="Page_116">[Pg 116]</a></span> differences; but, if I did not deceive myself, I
+have perceived a real difference in the air of my study, after a few
+persons have been with me in it, and the air on the outside of the
+house. Also a phial of air having been sent me, from the neighbourhood
+of York, it appeared not to be so good as the air near Leeds; that is,
+it was not diminished so much by an equal mixture of nitrous air, every
+other circumstance being as nearly the same as I could contrive. It may
+perhaps be possible, but I have not yet attempted it, to distinguish
+some of the different winds, or the air of different times of the year,
+&amp;c. &amp;c. by this test.</p>
+
+<p>By means of this test I was able to determine what I was before in doubt
+about, viz. the <i>kind</i> as well as the <i>degree</i> of injury done to air by
+candles burning in it. I could not tell with certainty, by means of
+mice, whether it was at all injured with respect to respiration; and yet
+if nitrous air may be depended upon for furnishing an accurate test, it
+must be rather more than one third worse than common air, and have been
+diminished by the same general cause of the other diminutions of air.
+For when, after many trials, I put one measure of thoroughly putrid and
+highly noxious air, into the same vessel with two measures of good
+wholesome air, and into another vessel an equal quantity,<span class='pagenum'><a name="Page_117" id="Page_117">[Pg 117]</a></span> viz. three
+measures of air in which a candle had burned out; and then put equal
+quantities of nitrous air to each of them, the latter was diminished
+rather more than the former.</p>
+
+<p>It agrees with this observation, that <i>burned air</i> is farther diminished
+both by putrefaction, and a mixture of iron filings and brimstone; and I
+therefore take it for granted by every other cause of the diminution of
+air. It is probable, therefore, that burned air is air so far loaded
+with phlogiston, as to be able to extinguish a candle, which it may do
+long before it is fully saturated.</p>
+
+<p>Inflammable air with a mixture of nitrous air burns with a green flame.
+This makes a very pleasing experiment when it is properly conducted. As,
+for some time, I chiefly made use of <i>copper</i> for the generation of
+nitrous air, I first ascribed this circumstance to that property of this
+metal, by which it burns with a green flame; but I was presently
+satisfied that it must arise from the spirit of nitre, for the effect is
+the very same from which ever of the metals the nitrous air is
+extracted, all of which I tried for this purpose, even silver and gold.<span class='pagenum'><a name="Page_118" id="Page_118">[Pg 118]</a></span></p>
+
+<p>A mixture of oil of vitriol and spirit of nitre in equal proportions
+dissolved iron, and the produce was nitrous air; but a less degree of
+spirit of nitre in the mixture produced air that was inflammable, and
+which burned with a green flame. It also tinged common air a little red,
+and diminished it, though not much.</p>
+
+<p>The diminution of common air by a mixture of nitrous air, is not so
+extraordinary as the diminution which nitrous air itself is subject to
+from a mixture of iron filings and brimstone, made into a paste with
+water. This mixture, as I have already observed, diminishes common air
+between one fifth and one fourth, but has no such effect upon any kind
+of air that has been diminished, and rendered noxious by any other
+process; but when it is put to a quantity of nitrous air, it diminishes
+it so much, that no more than one fourth of the original quantity will
+be left.</p>
+
+<p>The effect of this process is generally perceived in five or six hours,
+about which time the visible effervesence of the mixture begins; and in
+a very short time it advances so rapidly, that in about an hour almost
+the whole effect will have taken place. If it be suffered to stand a day
+or two longer, the air will still be diminished farther, but only a very
+little farther,<span class='pagenum'><a name="Page_119" id="Page_119">[Pg 119]</a></span> in proportion to the first diminution. The glass jar,
+in which the air and this mixture have been confined, has generally been
+so much heated in this process, that I have not been able to touch it.</p>
+
+<p>Nitrous air thus diminished has not so strong a smell as nitrous air
+itself, but smells just like common air in which the same mixture has
+stood; and it is not capable of being diminished any farther, by a fresh
+mixture of iron and brimstone.</p>
+
+<p>Common air saturated with nitrous air is also no farther diminished by
+this mixture of iron filings and brimstone, though the mixture ferments
+with great heat, and swells very much in it.</p>
+
+<p>Plants die very soon, both in nitrous air, and also in common air
+saturated with nitrous air, but especially in the former.</p>
+
+<p>Neither nitrous air, nor common air saturated with nitrous air, differ
+in specific gravity from common air. At least, the difference is so
+small, that I could not be sure there was any; sometimes about three
+pints of it seeming to be about half a grain heavier, and at other times
+as much lighter than common air.<span class='pagenum'><a name="Page_120" id="Page_120">[Pg 120]</a></span></p>
+
+<p>Having, among other kinds of air, exposed a quantity of nitrous air to
+water out of which the air had been well boiled, in the experiment to
+which I have more than once referred (as having been the occasion of
+several new and important observations) I found that 19/20 of the whole
+was absorbed. Perceiving, to my great surprize, that so very great a
+proportion of this kind of air was miscible with water, I immediately
+began to agitate a considerable quantity of it, in a jar standing in a
+trough of the same kind of water; and, with about four times as much
+agitation as fixed air requires, it was so far absorbed by the water,
+that only about one fifth remained. This remainder extinguished flame,
+and was noxious to animals.</p>
+
+<p>Afterwards I diminished a pretty large quantity of nitrous air to one
+eighth of its original bulk, and the remainder still retained much of
+its peculiar smell, and diminished common air a little. A mouse also
+died in it, but not so suddenly as it would have done in pure nitrous
+air. In this operation the peculiar smell of nitrous air is very
+manifest, the water being first impregnated with the air, and then
+transmitting it to the common atmosphere.</p>
+
+<p>This experiment gave me the hint of impregnating water with nitrous air,
+in the manner<span class='pagenum'><a name="Page_121" id="Page_121">[Pg 121]</a></span> in which I had before done it with fixed air; and I
+presently found that distilled water would imbibe about one tenth of its
+bulk of this kind of air, and that it acquired a remarkably acid and
+astringent taste from it. The smell of water thus impregnated is at
+first peculiarly pungent. I did not chuse to swallow any of it, though,
+for any thing that I know, it may be perfectly innocent, and perhaps, in
+some cases, salutary.</p>
+
+<p>This kind of air is retained very obstinately by water. In an exhausted
+receiver a quantity of water thus saturated emitted a whitish fume, such
+as sometimes issues from bubbles of this air when it is first generated,
+and also some air-bubbles; but though it was suffered to stand a long
+time in this situation, it still retained its peculiar taste; but when
+it had stood all night pretty near the fire, the water was become quite
+vapid, and had deposited a filmy kind of matter, of which I had often
+collected a considerable quantity from the trough in which jars
+containing this air had stood. This I suppose to be a precipitate of the
+metal, by the solution of which the nitrous air was generated. I have
+not given so much attention to it as to know, with certainty, in what
+circumstances this <i>deposit</i> is made, any more than I do the matter
+deposited from inflammable air above-mentioned;<span class='pagenum'><a name="Page_122" id="Page_122">[Pg 122]</a></span> for I cannot get it, at
+least in any considerable quantity, when I please; whereas I have often
+found abundance of it, when I did not expect it at all.</p>
+
+<p>The nitrous air with which I made the first impregnation of water was
+extracted from copper; but when I made the impregnation with air from
+quicksilver, the water had the very same taste, though the matter
+deposited from it seemed to be of a different kind; for it was whitish,
+whereas the other had a yellowish tinge. Except the first quantity of
+this impregnated water, I could never deprive any more that I made of
+its peculiar taste. I have even let some of it stand more than a week,
+in phials with their mouths open, and sometimes very near the fire,
+without producing any alteration in it<a name="FNanchor_6_6" id="FNanchor_6_6"></a><a href="#Footnote_6_6" class="fnanchor">[6]</a>.</p>
+
+<p>Whether any of the spirit of nitre contained in the nitrous air be mixed
+with the water in this operation, I have not yet endeavoured to
+determine. This, however, may probably be the case, as the spirit of
+nitre is, in a considerable degree, volatile<a name="FNanchor_7_7" id="FNanchor_7_7"></a><a href="#Footnote_7_7" class="fnanchor">[7]</a>.</p>
+
+<p><span class='pagenum'><a name="Page_123" id="Page_123">[Pg 123]</a></span></p><p>It will perhaps be thought, that the most <i>useful</i>, if not the most
+remarkable, of all the properties of this extraordinary kind of air, is
+its power of preserving animal substances from putrefaction, and of
+restoring those that are already putrid, which it possesses in a far
+greater degree than fixed air. My first observation of this was
+altogether casual. Having found nitrous air to suffer so great a
+diminution as I have already mentioned by a mixture of iron filings and
+brimstone, I was willing to try whether it would be equally diminished
+by other causes of the diminution of common air, especially by
+putrefaction; and for this purpose I put a dead mouse into a quantity of
+it, and placed it near the fire, where the tendency to putrefaction was
+very great. In this case there was a considerable diminution, viz. from
+5-1/4 to 3-1/4; but not so great as I had expected, the antiseptic power
+of the nitrous air having checked the tendency to putrefaction; for
+when, after a week, I took the mouse out, I<span class='pagenum'><a name="Page_124" id="Page_124">[Pg 124]</a></span> perceived, to my very great
+surprize, that it had no offensive smell.</p>
+
+<p>Upon this I took two other mice, one of them just killed, and the other
+soft and putrid, and put them both into the same jar of nitrous air,
+standing in the usual temperature of the weather, in the months of July
+and August of 1772; and after twenty-five days, having observed that
+there was little or no change in the quantity of the air, I took the
+mice out; and, examining them, found them both perfectly sweet, even
+when cut through in several places. That which had been put into the air
+when just dead was quite firm; and the flesh of the other, which had
+been putrid and soft, was still soft, but perfectly sweet.</p>
+
+<p>In order to compare the antiseptic power of this kind of air with that
+of fixed air, I examined a mouse which I had inclosed in a phial full of
+fixed air, as pure as I could make it, and which I had corked very
+close; but upon opening this phial in water about a month after, I
+perceived that a large quantity of putrid effluvium had been generated;
+for it rushed with violence out of the phial; and the smell that came
+from it, the moment the cork was taken out, was insufferably offensive.
+Indeed Dr. Macbride says, that he could only restore very thin pieces<span class='pagenum'><a name="Page_125" id="Page_125">[Pg 125]</a></span>
+of putrid flesh by means of fixed air. Perhaps the antiseptic power of
+these kinds of air may be in proportion to their acidity.</p>
+
+<p>If a little pains were taken with this subject, this remarkable
+antiseptic power of nitrous air might possibly be applied to various
+uses, perhaps to the preservation of the more delicate birds, fishes,
+fruits, &amp;c. mixing it in different proportions with common or fixed air.
+Of this property of nitrous air anatomists may perhaps avail themselves,
+as animal substances may by this means be preserved in their natural
+soft state; but how long it will answer for this purpose, experience
+only can shew.</p>
+
+<p>I calcined lead and tin in the manner hereafter described in a quantity
+of nitrous air, but with very little sensible effect; which rather
+surprized me; as, from the result of the experiment with the iron
+filings and brimstone, I had expected a very great diminution of the
+nitrous air by this process; the mixture of iron filings and brimstone,
+and the calcination of metals, having the same effect upon common air,
+both of them diminishing it in nearly the same proportion. But though I
+made the metals <i>fume</i> copiously in nitrous air, there might be no real
+<i>calcination</i>, the phlogiston not being separated, and the proper
+calcination prevented by there being no <i>fixed</i><span class='pagenum'><a name="Page_126" id="Page_126">[Pg 126]</a></span> <i>air</i>, which is
+necessary to the formation of the calx, to unite with it.</p>
+
+<p>Nitrous air is procured from all the proper metals by spirit of nitre,
+except lead, and from all the semi-metals that I have tried, except
+zinc. For this purpose I have used bismuth and nickel, with spirit of
+nitre only, and regulus of antimony and platina, with <i>aqua regia</i>.</p>
+
+<p>I got little or no air from lead by spirit of nitre, and have not yet
+made any experiments to ascertain the nature of this solution. With zinc
+I have taken a little pains.</p>
+
+<p>Four penny-weights and seventeen grains of zinc dissolved in spirit of
+nitre, to which as much water was added, yielded about twelve ounce
+measures of air, which had, in some degree, the properties of nitrous
+air, making a slight effervescence with common air, and diminishing it
+about as much as nitrous air, which had been itself diminished one half
+by washing in water. The smell of them both was also the same; so that I
+concluded it to be the same thing, that part of the nitrous air, which
+is imbibed by water, being retained in this solution.</p>
+
+<p>In order to discover whether this was the case, I made the solution boil
+in a sand-heat. Some<span class='pagenum'><a name="Page_127" id="Page_127">[Pg 127]</a></span> air came from it in this state, which seemed to be
+the same thing, with nitrous air diminished about one sixth, or one
+eighth, by washing in water. When the fluid part was evaporated, there
+remained a brown fixed substance, which was observed by Mr. Hellot, who
+describes it, Ac. Par. 1735, M. p. 35. A part of this I threw into a
+small red-hot crucible; and covering it immediately with a receiver,
+standing in water, I observed that very dense red fumes rose from it,
+and filled the receiver. This redness continued about as long as that
+which is occasioned by a mixture of nitrous and common air; the air was
+also considerably diminished within the receiver. This substance,
+therefore, must certainly have contained within it the very same thing,
+or principle, on which the peculiar properties of nitrous air depend.</p>
+
+<p>It is remarkable, however, that though the air within the receiver was
+diminished about one fifth by this process, it was itself as much
+affected with a mixture of nitrous air, as common air is, and a candle
+burned in it very well. This may perhaps be attributed to some effect of
+the spirit of nitre, in the composition of that brown substance.</p>
+
+<p>Nitrous air, I find, will be considerably diminished in its bulk by
+standing a long time in water, about as much as inflammable air is<span class='pagenum'><a name="Page_128" id="Page_128">[Pg 128]</a></span>
+diminished in the same circumstances. For this purpose I kept for some
+months a quart-bottle full of each of these kinds of air; but as
+different quantities of inflammable air vary very much in this respect,
+it is not improbable but that nitrous air may vary also.</p>
+
+<p>From one trial that I made, I conclude that nitrous air may be kept in a
+bladder much better than most other kinds of air. The air to which I
+refer was kept about a fortnight in a bladder, through which the
+peculiar smell of the nitrous air was very sensible for several days. In
+a day or two the bladder became red, and was much contracted in its
+dimensions. The air within it had lost very little of its peculiar
+property of diminishing common air.</p>
+
+<p>I did not endeavour to ascertain the exact quantity of nitrous air
+produced from given quantities, of all the metals which yield it; but
+the few observations which I did make for this purpose I shall recite in
+this place:</p>
+
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='left'>dwt.</td><td align='left'>gr.</td></tr>
+<tr><td align='left'>6</td><td align='left'>0</td><td align='left'>of silver</td><td align='left'>yielded</td><td align='left'>17-1/2</td><td align='left'>ounce measures.</td></tr>
+<tr><td align='left'>5</td><td align='left'>19</td><td align='left'>of quicksilver</td><td align='left'>&nbsp;</td><td align='left'>4-1/2</td></tr>
+<tr><td align='left'>1</td><td align='left'>2-1/2</td><td align='left'>of copper</td><td align='left'>&nbsp;</td><td align='left'>14-1/2</td></tr>
+<tr><td align='left'>2</td><td align='left'>0</td><td align='left'>of brass</td><td align='left'>&nbsp;</td><td align='left'>21</td></tr>
+<tr><td align='left'>0</td><td align='left'>20</td><td align='left'>of iron</td><td align='left'>&nbsp;</td><td align='left'>16</td></tr>
+<tr><td align='left'>1</td><td align='left'>5</td><td align='left'>of bismuth</td><td align='left'>&nbsp;</td><td align='left'>6</td></tr>
+<tr><td align='left'>0</td><td align='left'>12</td><td align='left'>of nickel</td><td align='left'>&nbsp;</td><td align='left'>4</td></tr>
+</table></div>
+
+
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_6_6" id="Footnote_6_6"></a><a href="#FNanchor_6_6"><span class="label">[6]</span></a> I have since found, that nitrous air has never failed to
+escape from the water, which has been impregnated with it, by long
+exposure to the open air.</p></div>
+
+<div class="footnote"><p><a name="Footnote_7_7" id="Footnote_7_7"></a><a href="#FNanchor_7_7"><span class="label">[7]</span></a> This suspicion has been confirmed by the ingenious Mr.
+Bewley, of Great Massingham in Norfolk, who has discovered that the acid
+taste of this water is not the necessary consequence of its impregnation
+with nitrous air, but is the effect of the <i>acid vapour</i>, into which
+part of this air is resolved, when it is decomposed by a mixture with
+common air. This, it will be seen, exactly agrees with my own
+observation on the constitution of nitrous air, in the second part of
+this work. A more particular account of Mr. Bewley's observation will be
+given in the <i>Appendix</i>.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_129" id="Page_129">[Pg 129]</a></span></p>
+<h2>SECTION VII.</h2>
+
+<h3><i>Of <span class="smcap">Air</span> infected with the <span class="smcap">fumes</span> of <span class="smcap">burning Charcoal</span>.</i></h3>
+
+
+
+<p>Air infected with the fumes of burning charcoal is well known to be
+noxious; and the Honourable Mr. Cavendish favoured me with an account of
+some experiments of his, in which a quantity of common air was reduced
+from 180 to 162 ounce measures, by passing through a red-hot iron tube
+filled with the dust of charcoal. This diminution he ascribed to such a
+<i>destruction</i> of common air as Dr. Hales imagined to be the consequence
+of burning. Mr. Cavendish also observed, that there had been a
+generation of fixed air in this process, but that it was absorbed by
+sope leys. This experiment I also repeated, with a small variation of
+circumstances, and with nearly the same result.</p>
+
+<p>Afterwards, I endeavoured to ascertain, by what appears to me to be an
+easier and more certain method, in what manner air is affected with the
+fumes of charcoal, viz. by suspending bits of charcoal within glass
+vessels, filled to a certain height with water, and standing inverted<span class='pagenum'><a name="Page_130" id="Page_130">[Pg 130]</a></span>
+in another vessel of water, while I threw the focus of a burning mirror,
+or lens, upon them. In this manner I diminished a given quantity of air
+one fifth, which is nearly in the same proportion with other diminutions
+of air.</p>
+
+<p>If, instead of pure water, I used <i>lime-water</i> in this process, it never
+failed to become turbid by the precipitation of the lime, which could
+only be occasioned by fixed air, either discharged from the charcoal, or
+deposited by the common air. At first I concluded that it came from the
+charcoal; but considering that it is not probable that fixed air,
+confined in any substance, can bear so great a degree of heat as is
+necessary to make charcoal, without being wholly expelled; and that in
+other diminutions of common air, by phlogiston only, there appears to be
+a deposition of fixed air, I have now no doubt but that, in this case
+also, it is supplied from the same source.</p>
+
+<p>This opinion is the more probable, from there being the same
+precipitation of lime, in this process, with whatever degree of heat the
+charcoal had been made. If, however, the charcoal had not been made with
+a very considerable degree of heat, there never failed to be a permanent
+addition of inflammable air produced; which agrees with what I observed
+before, that,<span class='pagenum'><a name="Page_131" id="Page_131">[Pg 131]</a></span> in converting dry wood into charcoal, the greatest part
+is changed into inflammable air.</p>
+
+<p>I have sometimes found, that charcoal which was made with the most
+intense heat of a smith's fire, which vitrified part of a common
+crucible in which the charcoal was confined, and which had been
+continued above half an hour, did not diminish the air in which the
+focus of a burning mirror was thrown upon it; a quantity of inflammable
+air equal to the diminution of the common air being generated in the
+process: whereas, at other times, I have not perceived that there was
+any generation of inflammable air, but a simple diminution of common
+air, when the charcoal had been made with a much less degree of heat.
+This subject deserves to be farther investigated.</p>
+
+<p>To make the preceding experiment with still more accuracy, I repeated it
+in quicksilver; when I perceived that there was a small increase of the
+quantity of air, probably from a generation of inflammable air. Thus it
+stood without any alteration a whole night, and part of the following
+day; when lime-water, being admitted to it, it presently became turbid,
+and, after some time, the whole quantity of air, which was about four
+ounce measures, was diminished one fifth, as before. In this case, I
+carefully<span class='pagenum'><a name="Page_132" id="Page_132">[Pg 132]</a></span> weighed the piece of charcoal, which was exactly two grains,
+and could not find that it was sensibly diminished in weight by the
+operation.</p>
+
+<p>Air thus diminished by the fumes of burning charcoal not only
+extinguishes flame, but is in the highest degree noxious to animals; it
+makes no effervescence with nitrous air, and is incapable of being
+diminished any farther by the fumes of more charcoal, by a mixture of
+iron filings and brimstone, or by any other cause of the diminution of
+air that I am acquainted with.</p>
+
+<p>This observation, which respects all other kinds of diminished air,
+proves that Dr. Hales was mistaken in his notion of the <i>absorption</i> of
+air in those circumstances in which he observed it. For he supposed that
+the remainder was, in all cases, of the same nature with that which had
+been absorbed, and that the operation of the same cause would not have
+failed to produce a farther diminution; whereas all my observations shew
+that air, which has once been fully diminished by any cause whatever, is
+not only incapable of any farther diminution, either from the same or
+from any other cause, but that it has likewise acquired <i>new
+properties</i>, most remarkably different from those which it had before,
+and that they are, in a great measure, the<span class='pagenum'><a name="Page_133" id="Page_133">[Pg 133]</a></span> same in all the cases. These
+circumstances give reason to suspect, that the cause of diminution is,
+in reality, the same in all the cases. What this cause is, may, perhaps,
+appear in the next course of observations.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2>SECTION VIII.</h2>
+
+<h3><i>Of the effect of the <span class="smcap">calcination</span> of <span class="smcap">Metals</span>, and of the <span class="smcap">effluvia</span> of
+<span class="smcap">Paint</span> made with <span class="smcap">White-Lead</span> and <span class="smcap">Oil</span>, on <span class="smcap">Air</span>.</i>
+</h3>
+
+<p>Having been led to suspect, from the experiments which I had made with
+charcoal, that the diminution of air in that case, and perhaps in other
+cases also, was, in some way or other the consequence of its having more
+than its usual quantity of phlogiston, it occurred to me, that the
+calcination of metals, which are generally supposed to consist of
+nothing but a metallic earth united to phlogiston, would tend to
+ascertain the fact, and be a kind of <i>experimentum crucis</i> in the case.</p>
+
+<p>Accordingly, I suspended pieces of lead and tin in given quantities of
+air, in the same manner as I had before treated the charcoal; and
+throwing the focus of a burning mirror or lens upon them, so as to make
+them fume<span class='pagenum'><a name="Page_134" id="Page_134">[Pg 134]</a></span> copiously. I presently perceived a diminution of the air. In
+the first trial that I made, I reduced four ounce measures of air to
+three, which is the greatest diminution of common air that I had ever
+observed before, and which I account for, by supposing that, in other
+cases, there was not only a cause of diminution, but causes of addition
+also, either of fixed or inflammable air, or some other permanently
+elastic matter, but that the effect of the calcination of metals being
+simply the escape of phlogiston, the cause of diminution was alone and
+uncontrouled.</p>
+
+<p>The air, which I had thus diminished by calcination of lead, I
+transferred into another clean phial, but found that the calcination of
+more lead in it (or at least the attempt to make a farther calcination)
+had no farther effect upon it. This air also, like that which had been
+infected with the fumes of charcoal, was in the highest degree noxious,
+made no effervescence with nitrous air, was no farther diminished by the
+mixture of iron filings and brimstone, and was not only rendered
+innoxious, but also recovered, in a great measure, the other properties
+of common air, by washing in water.</p>
+
+<p>It might be suspected that the noxious quality of air in which <i>lead</i>
+was calcined, might<span class='pagenum'><a name="Page_135" id="Page_135">[Pg 135]</a></span> be owing to some fumes peculiar to that metal; but
+I found no sensible difference between the properties of this air, and
+that in which <i>tin</i> was calcined.</p>
+
+<p>The <i>water</i> over which metals are calcined acquires a yellowish tinge,
+and an exceedingly pungent smell and taste, pretty much (as near as I
+can recollect, for I did not compare them together) like that over which
+brimstone has been frequently burned. Also a thin and whitish pellicle
+covered both the surface of the water, and likewise the sides of the
+phial in which the calcination was made; insomuch that, without
+frequently agitating the water, it grew so opaque by this constantly
+accumulating incrustation, that the sun-beams could not be transmitted
+through it in a quantity sufficient to produce the calcination.</p>
+
+<p>I imagined, however, that, even when this air was transferred into a
+clean phial, the metals were not so easily melted or calcined as they
+were in fresh air; for the air being once fully saturated with
+phlogiston, may not so readily admit any more, though it be only to
+transmit it to the water. I also suspected that metals were not easily
+melted or calcined in inflammable, fixed, or nitrous air, or any kind
+of<span class='pagenum'><a name="Page_136" id="Page_136">[Pg 136]</a></span> diminished air.<a name="FNanchor_8_8" id="FNanchor_8_8"></a><a href="#Footnote_8_8" class="fnanchor">[8]</a> None of these kinds of air suffered any change by
+this operation; nor was there any precipitation of lime, when charcoal
+was heated in any of these kinds of air standing in lime-water. This
+furnishes another, and I think a pretty decisive proof, that, in the
+precipitation of lime by charcoal, the fixed air does not come from the
+charcoal, but from the common air. Otherwise it is hard to assign a
+reason, why the same degree of heat (or at least a much greater) should
+not expel the fixed air from this substance, though surrounded by these
+different kinds of air, and why the fixed air might not be transmitted
+through them to the lime-water.</p>
+
+<p>Query. May not water impregnated with phlogiston from calcined metals,
+or by any other method, be of some use in medicine? The effect of this
+impregnation is exceedingly remarkable; but the principle with which it
+is impregnated is volatile, and intirely escapes in a day or two, if the
+surface of the water be exposed to the common atmosphere.</p>
+<p><span class='pagenum'><a name="Page_137" id="Page_137">[Pg 137]</a></span></p>
+<p>It should seem that phlogiston is retained more obstinately by charcoal
+than it is by lead or tin; for when any given quantity of air is fully
+saturated with phlogiston from charcoal, no heat that I have yet applied
+has been able to produce any more effect upon it; whereas, in the same
+circumstances, lead and tin may still be calcined, at least be made to
+emit a copious fume, in which some part of the phlogiston may be set
+loose. The air indeed, can take no more; but the water receives it, and
+the sides of the phial also receive an addition of incrustation. This is
+a white powdery substance, and well deserves to be examined. I shall
+endeavour to do it at my leisure.</p>
+
+<p>Lime-water never became turbid by the calcination of metals over it, the
+calx immediately seizing the precipitated fixed air, in preference to
+the lime in the water; but the colour, smell, and taste of the water was
+always changed and the surface of it became covered with a yellow
+pellicle, as before.</p>
+
+<p>When this process was made in quicksilver, the air was diminished only
+one fifth; and upon water being admitted to it, no more was absorbed;
+which is an effect similar to that of a mixture of nitrous and common
+air, which was mentioned before.<span class='pagenum'><a name="Page_138" id="Page_138">[Pg 138]</a></span></p>
+
+<p>The preceding experiments on the calcination of metals suggested to me a
+method of explaining the cause of the mischief which is known to arise
+from fresh <i>paint</i>, made with white-lead (which I suppose is an
+imperfect calx of lead) and oil.</p>
+
+<p>To verify my hypothesis, I first put a small pot full of this kind of
+paint, and afterwards (which answered much better, by exposing a greater
+surface of the paint) I daubed several pieces of paper with it, and put
+them under a receiver, and observed, that in about twenty-four hours,
+the air was diminished between one fifth and one fourth, for I did not
+measure it very exactly. This air also was, as I expected to find, in
+the highest degree noxious; it did not effervesce with nitrous air, it
+was no farther diminished by a mixture of iron filings and brimstone,
+and was made wholesome by agitation in water deprived of all air.</p>
+
+<p>I think it appears pretty evident, from the preceding experiments on the
+calcination of metals that air is, some way or other, diminished in
+consequence of being highly charged with phlogiston; and that agitation
+in water restores it, by imbibing a great part of the phlogistic
+matter.<span class='pagenum'><a name="Page_139" id="Page_139">[Pg 139]</a></span></p>
+
+<p>That water has a considerable affinity with phlogiston, is evident from
+the strong impregnation which it receives from it. May not plants also
+restore air diminished by putrefaction by absorbing part of the
+phlogiston with which it is loaded? The greater part of a dry plant, as
+well as of a dry animal substance, consists of inflammable air, or
+something that is capable of being converted into inflammable air; and
+it seems to be as probable that this phlogistic matter may have been
+imbibed by the roots and leaves of plants, and afterwards incorporated
+into their substance, as that it is altogether produced by the power of
+vegetation. May not this phlogistic matter be even the most essential
+part of the food and support of both vegetable and animal bodies?</p>
+
+<p>In the experiments with metals, the diminution of air seems to be the
+consequence of nothing but a saturation with phlogiston; and in all the
+other cases of the diminution of air, I do not see but that it may be
+effected by the same means. When a vegetable or animal substance is
+dissolved by putrefaction, the escape of the phlogistic matter (which,
+together with all its other constituent parts, is then let loose from
+it) may be the circumstance that produces the diminution of the air in
+which it putrefies. It is highly improbable that what remains after an<span class='pagenum'><a name="Page_140" id="Page_140">[Pg 140]</a></span>
+animal body has been thoroughly dissolved by putrefaction, should yield
+so great a quantity of inflammable air, as the dried animal substance
+would have done. Of this I have not made an actual trial, though I have
+often thought of doing it, and still intend to do it; but I think there
+can be no doubt of the result.</p>
+
+<p>Again, iron, by its fermentation with brimstone and water, is evidently
+reduced to a calx, so that phlogiston must have escaped from it.
+Phlogiston also must evidently be set loose by the ignition of charcoal,
+and is not improbably the matter which flies off from paint, composed of
+white-lead and oil. Lastly, since spirit of nitre is known to have a
+very remarkable affinity with phlogiston, it is far from being
+improbable that nitrous air may also produce the same effect by the same
+means.</p>
+
+<p>To this hypothesis it may be objected, that, if diminished air be air
+saturated with phlogiston, it ought to be inflammable. But this by no
+means follows; since its inflammability may depend upon some particular
+<i>mode of combination</i>, or degree of affinity, with which we are not
+acquainted. Besides, inflammable air seems to consist of some other
+principle, or to have some other constituent part, besides phlogiston<span class='pagenum'><a name="Page_141" id="Page_141">[Pg 141]</a></span>
+and common air, as is probable from that remarkable deposit, which, as I
+have observed, is made by inflammable air, both from iron and zinc.</p>
+
+<p>It is not improbable, however, but that a greater degree of heat may
+inflame that air which extinguishes a common candle, if it could be
+conveniently applied. Air that is inflammable, I observe, extinguishes
+red-hot wood; and indeed inflammable substances can only be those which,
+in a certain degree of heat, have a less affinity with the phlogiston
+they contain, than the air, or some other contiguous substance, has with
+it; so that the phlogiston only quits one substance, with which it was
+before combined, and enters another, with which it may be combined in a
+very different manner. This substance, however, whether it be air or any
+thing else, being now fully saturated with phlogiston, and not being
+able to take any more, in the same circumstances, must necessarily
+extinguish fire, and put a stop to the ignition of all other bodies,
+that is, to the farther escape of phlogiston from them.</p>
+
+<p>That plants restore noxious air, by imbibing the phlogiston with which
+it is loaded, is very agreeable to the conjectures of Dr. Franklin,<span class='pagenum'><a name="Page_142" id="Page_142">[Pg 142]</a></span>
+made many years ago, and expressed in the following extract from the
+last edition of his Letters, p. 346.</p>
+
+<p>"I have been inclined to think that the fluid <i>fire</i>, as well as the
+fluid <i>air</i>, is attracted by plants in their growth, and becomes
+consolidated with the other materials of which they are formed, and
+makes a great part of their substance; that, when they come to be
+digested, and to suffer in the vessels a kind of fermentation, part of
+the fire, as well as part of the air, recovers its fluid active state
+again, and diffuses itself in the body, digesting and separating it;
+that the fire so re-produced, by digestion and separation, continually
+leaving the body, its place is supplied by fresh quantities, arising
+from the continual separation; that whatever quickens the motion of the
+fluids in an animal, quickens the separation, and re-produces more of
+the fire, as exercise; that all the fire emitted by wood, and other
+combustibles, when burning, existed in them before in a solid state,
+being only discovered when separating; that some fossils, as sulphur,
+sea-coal, &amp;c. contain a great deal of solid fire; and that, in short,
+what escapes and is dissipated in the burning of bodies, besides water
+and earth, is generally the air and fire, that before made parts of the
+solid."</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_8_8" id="Footnote_8_8"></a><a href="#FNanchor_8_8"><span class="label">[8]</span></a> I conclude from the experiments of M. Lavoisier, which were
+made with a much better burning lens than I had an opportunity of making
+use of, that there was no <i>real calcination</i> of the metals, though they
+were made to <i>fume</i> in inflammable or nitrous air; because he was not
+able to produce more than a slight degree of calcination in any given
+quantity of common air.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_143" id="Page_143">[Pg 143]</a></span></p>
+<h2>SECTION IX.</h2>
+
+<h3><i>Of <span class="smcap">Marine Acid Air</span>.</i></h3>
+
+
+<p>Being very much struck with the result of an experiment of the Hon. Mr.
+Cavendish, related Phil. Trans. Vol. LVI. p. 157, by which, though, he
+says, he was not able to get any inflammable air from copper, by means
+of spirit of salt, he got a much more remarkable kind of air, viz. one
+that lost its elasticity by coming into contact with water, I was
+exceedingly desirous of making myself acquainted with it. On this
+account, I began with making the experiment in quicksilver, which I
+never failed to do in any case in which I suspected that air might
+either be absorbed by water, or be in any other manner affected by it;
+and by this means I presently got a much more distinct idea of the
+nature and effects of this curious solution.</p>
+
+<p>Having put some copper filings into a small phial, with a quantity of
+spirit of salt; and making the air (which was generated in great plenty,
+on the application of heat) ascend into<span class='pagenum'><a name="Page_144" id="Page_144">[Pg 144]</a></span> a tall glass vessel full of
+quicksilver, and standing in quicksilver, the whole produce continued a
+considerable time without any change of dimensions. I then introduced a
+small quantity of water to it; when about three fourths of it (the whole
+being about four ounce measures) presently, but gradually, disappeared,
+the quicksilver rising in the vessel. I then introduced a considerable
+quantity of water; but there was no farther diminution of the air, and
+the remainder I found to be inflammable.</p>
+
+<p>Having frequently continued this process a long time after the admission
+of the water, I was much amused with observing the large bubbles of the
+newly generated air, which came through the quicksilver, the sudden
+diminution of them when they came to the water, and the very small
+bubbles which went through the water. They made, however, a continual,
+though slow, increase of inflammable air.</p>
+
+<p>Fixed air, being admitted to the whole produce of this air from copper,
+had no sensible effect upon it. Upon the admission of water, a great
+part of the mixture presently disappeared; another part, which I suppose
+to have been the fixed air, was absorbed slowly; and in this particular
+case the very small permanent<span class='pagenum'><a name="Page_145" id="Page_145">[Pg 145]</a></span> residuum did not take fire; but it is
+very possible that it might have done so, if the quantity had been
+greater.</p>
+
+<p>The solution of <i>lead</i> in the marine acid is attended with the very same
+ph&aelig;nomena as the solution of copper in the same acid; about three
+fourths of the generated air disappearing on the admission of water; and
+the remainder being inflammable.</p>
+
+<p>The solutions of iron, tin, and zinc, in the marine acid, were all
+attended with the same ph&aelig;nomena as the solutions of copper and lead,
+but in a less degree; for in iron one eighth, in tin one sixth, and in
+zinc one tenth of the generated air disappeared on the admission of
+water. The remainder of the air from iron, in this case, burned with a
+green, or very light blue flame.</p>
+
+<p>I had always thought it something extraordinary that a species of air
+should <i>lose its elasticity</i> by the mere <i>contact</i> of any thing, and
+from the first suspected that it must have been <i>imbibed</i> by the water
+that was admitted to it; but so very great a quantity of this air
+disappeared upon the admission of a very small quantity of water, that
+at first I could not help concluding that appearances favoured the
+former<span class='pagenum'><a name="Page_146" id="Page_146">[Pg 146]</a></span> hypothesis. I found, however, that when I admitted a much
+smaller quantity of water, confined in a narrow glass tube, a part only
+of the air disappeared, and that very slowly, and that more of it
+vanished upon the admission of more water. This observation put it
+beyond a doubt, that this air was properly <i>imbibed</i> by the water,
+which, being once fully saturated with it, was not capable of receiving
+any more.</p>
+
+<p>The water thus impregnated tasted very acid, even when it was much
+diluted with other water, through which the tube containing it was
+drawn. It even dissolved iron very fast, and generated inflammable air.
+This last observation, together with another which immediately follows,
+led me to the discovery of the true nature of this remarkable kind of
+air.</p>
+
+<p>Happening, at one time, to use a good deal of copper and a small
+quantity of spirit of salt, in the generation of this kind of air, I was
+surprized to find that air was produced long after, I could not but
+think that the acid must have been saturated with the metal; and I also
+found that the proportion of inflammable air to that which was absorbed
+by the water continually diminished, till, instead of being<span class='pagenum'><a name="Page_147" id="Page_147">[Pg 147]</a></span> one fourth
+of the whole, as I had first observed, it was not so much as one
+twentieth. Upon this, I concluded that this subtle air did not arise
+from the copper, but from the spirit of salt; and presently making the
+experiment with the acid only, without any copper, or metal of any kind,
+this air was immediately produced in as great plenty as before; so that
+this remarkable kind of air is, in fact, nothing more than the vapour,
+or fumes of spirit of salt, which appear to be of such a nature, that
+they are not liable to be condensed by cold, like the vapour of water,
+and other fluids, and therefore may be very properly called an <i>acid
+air</i>, or more restrictively, the <i>marine acid air</i>.</p>
+
+<p>This elastic acid vapour, or acid air, extinguishes flame, and is much
+heavier than common air; but how much heavier, will not be easy to
+ascertain. A cylindrical glass vessel, about three fourths of an inch in
+diameter, and four inches deep, being filled with it, and turned upside
+down, a lighted candle may be let down into it more than twenty times
+before it will burn at the bottom. It is pleasing to observe the colour
+of the flame in this experiment; for both before the candle goes out,
+and also when it is first lighted again, it burns with a beautiful
+green, or rather light-blue flame, such as is seen when common salt is
+thrown into the fire.<span class='pagenum'><a name="Page_148" id="Page_148">[Pg 148]</a></span></p>
+
+<p>When this air is all expelled from any quantity of spirit of salt, which
+is easily perceived by the subsequent vapour being condensed by cold,
+the remainder is a very weak acid, barely capable of dissolving iron.</p>
+
+<p>Being now in the possession of a new subject of experiments, viz. an
+elastic acid vapour, in the form of a permanent air, easily procured,
+and effectually confined by glass and quicksilver, with which it did not
+seem to have any affinity; I immediately began to introduce a variety of
+substances to it; in order to ascertain its peculiar properties and
+affinities, and also the properties of those other bodies with respect
+to it.</p>
+
+<p>Beginning with <i>water</i>, which, from preceding observations, I knew would
+imbibe it, and become impregnated with it; I found that 2-1/2 grains of
+rain-water absorbed three ounce measures of this air, after which it was
+increased one third in its bulk, and weighed twice as much as before; so
+that this concentrated vapour seems to be twice as heavy as rain-water:
+Water impregnated with it makes the strongest spirit of salt that I have
+seen, dissolving iron with the most rapidity. Consequently, two thirds
+of the best spirit of salt is nothing more than mere phlegm or water.<span class='pagenum'><a name="Page_149" id="Page_149">[Pg 149]</a></span></p>
+
+<p>Iron filings, being admitted to this air, were dissolved by it pretty
+fast, half of the air disappearing, and the other half becoming
+inflammable air, not absorbed by water. Putting chalk to it, fixed air
+was produced.</p>
+
+<p>I had not introduced many substances to this air, before I discovered
+that it had an affinity with <i>phlogiston</i>, so that it would deprive
+other substances of it, and form with it such an union as constitutes
+inflammable air; which seems to shew, that inflammable air universally
+consists of the union of some acid vapour with phlogiston.</p>
+
+<p>Inflammable air was produced, when to this acid air I put spirit of
+wine, oil of olives, oil of turpentine, charcoal, phosphorus, bees-wax,
+and even sulphur. This last observation, I own, surprized me; for, the
+marine acid being reckoned the weakest of the three mineral acids, I did
+not think that it had been capable of dislodging the oil of vitriol from
+this substance; but I found that it had the very same effect both upon
+alum and nitre; the vitriolic acid in the former case, and the nitrous
+in the latter, giving place to the stronger vapour of spirit of salt.<span class='pagenum'><a name="Page_150" id="Page_150">[Pg 150]</a></span></p>
+
+<p>The rust of iron, and the precipitate of nitrous air made from copper,
+also imbibed this air very fast, and the little that remained of it was
+inflammable air; which proves, that these calces contain phlogiston. It
+seems also to be pretty evident, from this experiment, that the
+precipitate above mentioned is a real calx of the metal, by the solution
+of which the nitrous air is generated.</p>
+
+<p>As some remarkable circumstances attend the absorption of this acid air,
+by the substances above-mentioned, I shall briefly mention them.</p>
+
+<p>Spirit of wine absorbs this air as readily as water itself, and is
+increased in bulk by that means. Also, when it is saturated, it
+dissolves iron with as much rapidity, and still continues inflammable.</p>
+
+<p>Oil of olives absorbs this air very slowly, and at the same time, it
+turns almost black, and becomes glutinous. It is also less miscible with
+water, and acquires a very disagreeable smell. By continuing upon the
+surface of the water, it became white, and its offensive smell went off
+in a few days.</p>
+
+<p>Oil of turpentine absorbed this air very fast, turning brown, and almost
+black. No inflammable<span class='pagenum'><a name="Page_151" id="Page_151">[Pg 151]</a></span> air was formed, till I raised more of the acid
+air than the oil was able to absorb, and let it stand a considerable
+time; and still the air was but weakly inflammable. The same was the
+case with the oil of olives, in the last mentioned experiment; and it
+seems to be probable, that, the longer this acid air had continued in
+contact with the oil, the more phlogiston it would have extracted from
+it. It is not wholly improbable, but that, in the intermediate state,
+before it becomes inflammable air, it may be nearly of the nature of
+common air.</p>
+
+<p>Bees-wax absorbed this air very slowly. About the bigness of a hazel-nut
+of the wax being put to three ounce measures of the acid air, the air
+was diminished one half in two days, and, upon the admission of water,
+half of the remainder also disappeared. This air was strongly
+inflammable.</p>
+
+<p>Charcoal absorbed this air very fast. About one fourth of it was
+rendered immiscible in water, and was but weakly inflammable.</p>
+
+<p>A small bit of <i>phosphorus</i>, perhaps about half a grain, smoked, and
+gave light in the acid air, just as it would have done in common air
+confined. It was not sensibly wasted after<span class='pagenum'><a name="Page_152" id="Page_152">[Pg 152]</a></span> continuing about twelve
+hours in that state, and the bulk of the air was very little diminished.
+Water being admitted to it absorbed it as before, except about one fifth
+of the whole. It was but weakly inflammable.</p>
+
+<p>Putting several pieces of <i>sulphur</i> to this air, it was absorbed but
+slowly. In about twenty-four hours about one fifth of the quantity had
+disappeared; and water being admitted to the remainder, very little more
+was absorbed. The remainder was inflammable, and burned with a blue
+flame.</p>
+
+<p>Notwithstanding the affinity which this acid air appears to have with
+phlogiston, it is not capable of depriving all bodies of it. I found
+that dry wood, crusts of bread, and raw flesh, very readily imbibed this
+air, but did not part with any of their phlogiston to it. All these
+substances turned very brown, after they had been some time exposed to
+this air, and tasted very strongly of the acid when they were taken out;
+but the flesh, when washed in water, became very white, and the fibres
+easily separated from one another, even more than they would have done
+if it had been boiled or roasted<a name="FNanchor_9_9" id="FNanchor_9_9"></a><a href="#Footnote_9_9" class="fnanchor">[9]</a>.</p>
+<p><span class='pagenum'><a name="Page_153" id="Page_153">[Pg 153]</a></span></p>
+<p>When I put a piece of <i>saltpetre</i> to this air it was presently
+surrounded with a white fume, which soon filled the whole vessel,
+exactly like the fume which bursts from the bubbles of nitrous air, when
+it is generated by a vigorous fermentation, and such as is seen when
+nitrous air is mixed with this acid air. In about a minute, the whole
+quantity of air was absorbed, except a very little, which might be the
+common air that had lodged upon the surface of the spirit of salt within
+the phial.</p>
+
+<p>A piece of <i>alum</i> exposed to this air turned yellow, absorbed it as fast
+as the saltpetre had done, and was reduced by it to the form of a
+powder. Common salt, as might be expected, had no effect whatever on
+this marine acid air.</p>
+
+<p>I had also imagined, that if air diminished by the processes
+above-mentioned was affected in this manner, in consequence of its being
+saturated with phlogiston, a mixture of this acid air might imbibe that
+phlogiston, and render it wholesome again; but I put about one fourth of
+this air to a quantity of air in which metals had been calcined, without
+making any sensible alteration in it. I do not, however, infer from
+this, that air is not diminished by means of phlogiston, since the
+common air, like some other substances, may hold<span class='pagenum'><a name="Page_154" id="Page_154">[Pg 154]</a></span> the phlogiston too
+fast, to be deprived of it by this acid air.</p>
+
+<p>I shall conclude my account of these experiments with observing, that
+the electric spark is visible in acid air, exactly as it is in common
+air; and though I kept making this spark a considerable time in a
+quantity of it, I did not perceive that any sensible alteration was made
+in it. A little inflammable air was produced, but not more than might
+have come from the two iron nails which I made use of in taking the
+sparks.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_9_9" id="Footnote_9_9"></a><a href="#FNanchor_9_9"><span class="label">[9]</span></a> It will be seen, in the second part of this work, that, in
+some of these processes, I had afterwards more success.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>SECTION X.</h2>
+
+<h3><span class="smcap">Miscellaneous Observations.</span></h3>
+
+
+<p>1. As many of the preceding observations relate to the <i>vinous</i> and
+<i>putrefactive</i> fermentations, I had the curiosity to endeavour to
+ascertain in what manner the air would be affected by the <i>acetous</i>
+fermentation. For this purpose I inclosed a phial full of small beer in
+a jar standing in water; and observed that, during the first two or
+three days, there was an increase of the air in the jar, but from that
+time it gradually decreased, till at length there appeared to be a
+diminution of about one tenth of the whole quantity.<span class='pagenum'><a name="Page_155" id="Page_155">[Pg 155]</a></span></p>
+
+<p>During this time the whole surface of it was gradually covered with a
+scum, beautifully corrugated. After this there was an increase of the
+air till there was more than the original quantity; but this must have
+been fixed air, not incorporated with the rest of the mass; for,
+withdrawing the beer, which I found to be sour, after it had stood 18 or
+20 days under the jar, and passing the air several times through cold
+water, the original quantity was diminished about one ninth. In the
+remainder a candle would not burn, and a mouse would have died
+presently.</p>
+
+<p>The smell of this air was exceedingly pungent, but different from that
+of the putrid effluvium. A mouse lived perfectly well in this air, thus
+affected with the acetous fermentation; after it had stood several days
+mixed with four times the quantity of fixed air.</p>
+
+<p>2. All the kinds of factitious air on which I have yet made the
+experiment are highly noxious, except that which is extracted from
+saltpetre, or alum; but in this even a candle burned just as in common
+air<a name="FNanchor_10_10" id="FNanchor_10_10"></a><a href="#Footnote_10_10" class="fnanchor">[10]</a>. In one quantity which<span class='pagenum'><a name="Page_156" id="Page_156">[Pg 156]</a></span> I got from saltpetre a candle not only
+burned, but the flame was increased, and something was heard like a
+hissing, similar to the decrepitation of nitre in an open fire. This
+experiment was made when the air was fresh made, and while it probably
+contained some particles of nitre, which would have been deposited
+afterwards. The air was extracted from these substances by heating them
+in a gun-barrel, which was much corroded and soon spoiled by the
+experiment. What effect this circumstance may have had upon the air I
+have not considered.</p>
+
+<p>November 6, 1772, I had the curiosity to examine the state of a quantity
+of this air which had been extracted from saltpetre above a year, and
+which at first was perfectly wholesome; when, to my very great surprize,
+I found that it was become, in the highest degree, noxious. It made no
+effervescence with nitrous air, and a mouse died the moment it was put
+into it. I had not, however, washed it in rain-water quite ten minutes
+(and perhaps less time would have been sufficient) when I found, upon
+trial, that it was restored to its former perfectly wholesome state. It
+effervesced with nitrous air as much as the best common air ever does;
+and<span class='pagenum'><a name="Page_157" id="Page_157">[Pg 157]</a></span> even a candle burned in it very well, which I had never before
+observed of any kind of noxious air meliorated by agitation in water.
+This series of facts, relating to air extracted from nitre, appear to me
+to be very extraordinary and important, and, in able hands, may lead to
+considerable discoveries.</p>
+
+<p>3. There are many substances which impregnate common air in a very
+remarkable manner, but without making it noxious to animals. Among other
+things I tried volatile alkaline salts, and camphor; the latter of which
+I melted with a burning-glass, in air inclosed in a phial. The mouse,
+which was put into this air, sneezed and coughed very much, especially
+after it was taken out; but it presently recovered, and did not appear
+to have been sensibly injured.</p>
+
+<p>4. Having made several experiments with a mixture of iron filings and
+brimstone, kneaded to a paste with water, I had the curiosity to try
+what would be the effect of substituting <i>brass dust</i> in the place of
+the iron filings. The result was, that when this mixture had stood about
+three weeks, in a given quantity of air, it had turned black, but was
+not increased in bulk. The air also was neither sensibly increased nor
+decreased, but the nature of it was changed; for it extinguished flame,
+it would have<span class='pagenum'><a name="Page_158" id="Page_158">[Pg 158]</a></span> killed a mouse presently, and was not restored by fixed
+air, which had been mixed with it several days.</p>
+
+<p>5. I have frequently mentioned my having, at one time, exposed equal
+quantities of different kinds of air in jars standing in boiled water.
+<i>Common air</i> in this experiment was diminished four sevenths, and the
+remainder extinguished flame. This experiment demonstrates that water
+does not absorb air equally, but that it decomposes it, taking one part,
+and leaving the rest. To be quite sure of this fact, I agitated a
+quantity of common air in boiled water, and when I had reduced it from
+eleven ounce measures to seven, I found that it extinguished a candle,
+but a mouse lived in it very well. At another time a candle barely went
+out when the air was diminished one third, and at other times I have
+found this effect lake place at other very different degrees of
+diminution.</p>
+
+<p>This difference I attribute to the differences in the state of the water
+with respect to the air contained in it; for sometimes it had stood
+longer than at other times before I made use of it. I also used
+distilled-water, rain-water, and water out of which the air had been
+pumped, promiscuously with rain water. I even doubt, not but that, in a
+certain state of the water,<span class='pagenum'><a name="Page_159" id="Page_159">[Pg 159]</a></span> there might be no sensible difference in
+the bulk of the agitated air, and yet at the end of the process it would
+extinguish a candle, air being supplied from the water in the place of
+that part of the common air which had been absorbed.</p>
+
+<p>It is certainly a little extraordinary that the very same process should
+so far mend putrid air, as to reduce it to the standard of air in which
+candles have burned out; and yet that it should so far injure common and
+wholesome air as to reduce it to about the same standard: but so the
+fact certainly is. If air extinguish flame in consequence of its being
+previously saturated with phlogiston, it must, in this case, have been
+transferred from the water to the air, and it is by no means
+inconsistent with this hypothesis to suppose, that, if the air be over
+saturated with phlogiston, the water will imbibe it, till it be reduced
+to the same proportion that agitation in water would have communicated
+to it.</p>
+
+<p>To a quantity of common air, thus diminished by agitation in water, till
+it extinguished a candle, I put a plant, but it did not so far restore
+it as that a candle would burn in it again; which to me appeared not a
+little extraordinary, as it did not seem to be in a worse state than air
+in which candles had burned out, and<span class='pagenum'><a name="Page_160" id="Page_160">[Pg 160]</a></span> which had never failed to be
+restored by the same means.</p>
+
+<p>I had no better success with a quantity of permanent air which I had
+collected from my pump-water. Indeed these experiments were begun before
+I was acquainted with that property of nitrous air, which makes it so
+accurate a measure of the goodness of other kinds of air; and it might
+perhaps be rather too late in the year when I made the experiments.
+Having neglected these two jars of air, the plants died and putrefied in
+both of them; and then I found the air in them both to be highly
+noxious, and to make no effervescence with nitrous air.</p>
+
+<p>I found that a pint of my pump-water contained about one fourth of an
+ounce measure of air, one half of which was afterwards absorbed by
+standing in fresh pump-water. A candle would not burn in this air, but a
+mouse lived in it very well. Upon the whole, it seemed to be in about
+the same state as air in which a candle had burned out.</p>
+
+<p>6. I once imagined that, by mere <i>stagnation</i>, air might become unfit
+for respiration, or at least<span class='pagenum'><a name="Page_161" id="Page_161">[Pg 161]</a></span> the burning of candles; but if this be the
+case, and the change be produced gradually, it must require a long time
+for the purpose. For on the 22d of September 1772, I examined a quantity
+of common air, which had been kept in a phial, without agitation, from
+May 1771, and found it to be in no respect worse than fresh air, even by
+the test of the nitrous air.</p>
+
+<p>7. The crystallization of nitre makes no sensible alteration in the air
+in which the process is made. For this purpose I dissolved as much nitre
+as a quantity of hot water would contain, and let it cool under a
+receiver, standing in water.</p>
+
+<p>8. November 6, 1772, a quantity of inflammable air, which, by long
+keeping, had come to extinguish flame, I observed to smell very much
+like common air in which a mixture of iron filings and brimstone had
+stood. It was not, however, quite so strong, but it was equally noxious.</p>
+
+<p>9. Bismuth and nickel are dissolved in the marine acid with the
+application of a considerable degree of heat; but little or no air is
+got from either of them; but, what I thought a little remarkable,<span class='pagenum'><a name="Page_162" id="Page_162">[Pg 162]</a></span> both
+of them smelled very much like Harrowgate water, or liver of sulphur.
+This smell I have met with several times in the course of my
+experiments, and in processes very different from one another.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_10_10" id="Footnote_10_10"></a><a href="#FNanchor_10_10"><span class="label">[10]</span></a> Experiments, of which an account will be given in the
+second part of this work, make it probable, that though a candle burned
+even <i>more than well</i> in this air, an animal would not have lived in it.
+At the time of this first publication, however, I had no idea of this
+being possible in nature.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_163" id="Page_163">[Pg 163]</a></span></p>
+<h2>PART II.</h2>
+
+<h3><i>Experiments and Observations made in the Year 1773, and the Beginning
+of 1774.</i></h3>
+
+
+
+<hr style="width: 65%;" />
+<h2>SECTION I.</h2>
+
+<h3><i>Observations on <span class="smcap">Alkaline Air</span>.</i></h3>
+
+
+<p>After I had made the discovery of the <i>marine acid air</i>, which the
+vapour of spirit of salt may properly enough be called, and had made
+those experiments upon it, of which I have given an account in the
+former part of this work, and others which I propose to recite in this
+part; it occurred to me, that, by a process similar to that by which
+this <i>acid</i> air is expelled from the spirit of salt, an <i>alkaline</i> air
+might be expelled from substances containing volatile alkali.<span class='pagenum'><a name="Page_164" id="Page_164">[Pg 164]</a></span></p>
+
+<p>Accordingly I procured some volatile spirit of sal ammoniac, and having
+put it into a thin phial, and heated it with the flame of a candle, I
+presently found that a great quantity of vapour was discharged from it;
+and being received in a vessel of quicksilver, standing in a bason of
+quicksilver, it continued in the form of a transparent and permanent
+air, not at all condensed by cold; so that I had the same opportunity of
+making experiments upon it, as I had before on the acid air, being in
+the same favourable circumstances.</p>
+
+<p>With the same ease I also procured this air from <i>spirit of hartshorn</i>,
+and <i>sal volatile</i> either in a fluid or solid form, i. e. from those
+volatile alkaline salts which are produced by the distillation of sal
+ammoniac with fixed alkalis. But in this case I soon found that the
+alkaline air I procured was not pure; for the fixed air, which entered
+into the composition of my materials, was expelled along with it. Also,
+uniting again with the alkaline air, in the glass tube through which
+they were conveyed, they stopped it up, and were often the means of
+bursting my vessels.</p>
+
+<p>While these experiments were new to me, I imagined that I was able to
+procure this air with peculiar advantage and in the greatest<span class='pagenum'><a name="Page_165" id="Page_165">[Pg 165]</a></span> abundance,
+either from the salts in a dry state, when they were just covered with
+water, or in a perfectly fluid state; for, upon applying a candle to the
+phials in which they were contained, there was a most astonishing
+production of air; but having examined it, I found it to be chiefly
+fixed air, especially after the first or second produce from the same
+materials; and removing my apparatus to a trough of water and using the
+water instead of quicksilver, I found that it was not presently absorbed
+by it.</p>
+
+<p>This, however, appears to be an easy and elegant method of procuring
+fixed air, from a small quantity of materials, though there must be a
+mixture of alkaline air along with it; as it is by means of its
+combination with this principle only, that it is possible, that so much
+fixed air should be retained in any liquid. Water, at least, we know,
+cannot be made to contain much more than its own bulk of fixed air.</p>
+
+<p>After this disappointment, I confined myself to the use of that volatile
+spirit of sal ammoniac which is procured by a distillation with slaked
+lime, which contains no fixed air; and which seems, in a general state,
+to contain about as much alkaline air, as an equal quantity of spirit of
+salt contains of the acid air.<span class='pagenum'><a name="Page_166" id="Page_166">[Pg 166]</a></span></p>
+
+<p>Wanting, however, to procure this air in greater quantities, and this
+method being rather expensive, it occurred to me, that alkaline air
+might, probably, be procured, with the most ease and convenience, from
+the original materials, mixed in the same proportions that chemists had
+found by experience to answer the best for the production of the
+volatile spirit of sal ammoniac. Accordingly I mixed one fourth of
+pounded sal ammoniac, with three fourths of slaked lime; and filling a
+phial with the mixture, I presently found it completely answered my
+purpose. The heat of a candle expelled from this mixture a prodigious
+quantity of alkaline air; and the same materials (as much as filled an
+ounce phial) would serve me a considerable time, without changing;
+especially when, instead of a glass phial, I made use of a small iron
+tube, which I find much more convenient for the purpose.</p>
+
+<p>As water soon begins to rise in this process, it is necessary, if the
+air is intended to be conveyed perfectly <i>dry</i> into the vessel of
+quicksilver, to have a small vessel in which this water (which is the
+common volatile spirit of sal ammoniac) may be received. This small
+vessel must be interposed between the vessel which contains the
+materials for the generation of the air, and that in which it is to be
+received, as <i>d</i> fig. 8.<span class='pagenum'><a name="Page_167" id="Page_167">[Pg 167]</a></span></p>
+
+<p>This <i>alkaline</i> air being perfectly analogous to the <i>acid</i> air, I was
+naturally led to investigate the properties of it in the same manner,
+and nearly in the same order. From this analogy I concluded, as I
+presently found to be the fact, that this alkaline air would be readily
+imbibed by water, and, by its union with it, would form a volatile
+spirit of sal ammoniac. And as the water, when admitted to the air in
+this manner, confined by quicksilver, has an opportunity of fully
+saturating itself with the alkaline vapour, it is made prodigiously
+stronger than any volatile spirit of sal ammoniac that I have ever seen;
+and I believe stronger than it can be made in the common way.</p>
+
+<p>In order to ascertain what addition, with respect to quantity and
+weight, water would acquire by being saturated with alkaline air, I put
+1-1/4 grains of rain-water into a small glass tube, closed at one end
+with cement, and open at the other, the column of water measuring 7/10
+of an inch; and having introduced it through the quicksilver into a
+vessel containing alkaline air, observed that it absorbed 7/8 of an
+ounce measure of the <i>air</i>, and had then gained about half a grain in
+weight, and was increased to 8-1/2 tenths of an inch in length. I did
+not make a second experiment of this kind, and therefore will not answer
+for the exactness of these proportions in<span class='pagenum'><a name="Page_168" id="Page_168">[Pg 168]</a></span> future trials. What I did
+sufficiently answered my purpose, in a general view of the subject.</p>
+
+<p>When I had, at one time, saturated a quantity of distilled water with
+alkaline air, so that a good deal of the air remained unabsorbed on the
+surface of the water, I observed that, as I continued to throw up more
+air, a considerable proportion of it was imbibed, but not the whole; and
+when I had let the apparatus stand a day, much more of the air that lay
+on the surface was imbibed. And after the water would imbibe no more of
+the <i>old</i> air, it imbibed <i>new</i>. This shews that water requires a
+considerable time to saturate itself with this kind of air, and that
+part of it more readily unites with water than the rest.</p>
+
+<p>The same is also, probably, the case with all the kinds of air with
+which water can be impregnated. Mr. Cavendish made this observation with
+respect to fixed air, and I repeated the whole process above-mentioned
+with acid air, and had precisely the same result. The alkaline water
+which I procured in this experiment was, beyond comparison, stronger to
+the smell, than any spirit of sal ammoniac that I had seen.<span class='pagenum'><a name="Page_169" id="Page_169">[Pg 169]</a></span></p>
+
+<p>This experiment led me to attempt the making of spirit of sal ammoniac
+in a larger quantity, by impregnating distilled water with this alkaline
+air. For this purpose I filled a piece of a gun-barrel with the
+materials above-mentioned, and luted to the open end of it a small glass
+tube, one end of which was bent, and put within the mouth of a glass
+vessel, containing a quantity of distilled water upon quicksilver,
+standing in a bason of quicksilver, as in fig. 7. In these circumstances
+the heat of the fire, applied gradually, expelled the alkaline air,
+which, passing through the tube, and the quicksilver, came at last to
+the water, which, in time, became fully saturated with it.</p>
+
+<p>By this means I got a very strong alkaline liquor, from which I could
+again expel the alkaline air which I had put into it, whenever it
+happened to be more convenient to me to get it in that manner. This
+process may easily be performed in a still larger way; and by this means
+a liquor of the same nature with the volatile spirit of sal ammoniac,
+might be made much stronger, and much cheaper, than it is now made.</p>
+
+<p>Having satisfied myself with respect to the relation that alkaline air
+bears to water, I was impatient to find what would be the consequence<span class='pagenum'><a name="Page_170" id="Page_170">[Pg 170]</a></span>
+of mixing this new air with the other kinds with which I was acquainted
+before, and especially with <i>acid</i> air; having a notion that these two
+airs, being of opposite natures, might compose a <i>neutral air</i>, and
+perhaps the very same thing with common air. But the moment that these
+two kinds of air came into contact, a beautiful white cloud was formed,
+and presently filled the whole vessel in which they were contained. At
+the same time the quantity of air began to diminish, and, at length,
+when the cloud was subsided, there appeared to be formed a solid <i>while
+salt</i>, which was found to be the common <i>sal ammoniac</i>, or the marine
+acid united to the volatile alkali.</p>
+
+<p>The first quantity that I produced immediately deliquesced, upon being
+exposed to the common air; but if it was exposed in a very dry and warm
+place, it almost all evaporated, in a white cloud. I have, however,
+since, from the same materials, produced the salt above-mentioned in a
+state not subject to deliquesce or evaporate. This difference, I find,
+is owing to the proportion of the two kinds of air in the compound. It
+is only volatile when there is more than a due proportion of either of
+the constituent parts. In these cases the smell of the salts is
+extremely pungent, but very different from one another; being manifestly
+acid, or alkaline,<span class='pagenum'><a name="Page_171" id="Page_171">[Pg 171]</a></span> according to the prevalence of each of these airs
+respectively.</p>
+
+<p><i>Nitrous air</i> admitted to alkaline air likewise occasioned a whitish
+cloud, and part of the air was absorbed; but it presently grew clear
+again; leaving only a little dimness on the sides of the vessel. This,
+however, might be a kind of salt, formed by the union of the two kinds
+of air. There was no other salt formed that I could perceive. Water
+being admitted to this mixture of nitrous and alkaline air presently
+absorbed the latter, and left the former possessed of its peculiar
+properties.</p>
+
+<p><i>Fixed air</i> admitted to alkaline air formed oblong and slender crystals,
+which crossed one another, and covered the sides of the vessel in the
+form of net-work. These crystals must be the same thing with the
+volatile alkalis which chemists get in a solid form, by the distillation
+of sal ammoniac with fixed alkaline salts.</p>
+
+<p><i>Inflammable air</i> admitted to alkaline air exhibited no particular
+appearance. Water, as in the former experiment, absorbed the alkaline
+air, and left the inflammable air as it was before. It was remarkable,
+however, that the water which was admitted to them became<span class='pagenum'><a name="Page_172" id="Page_172">[Pg 172]</a></span> whitish, and
+that this white cloud settled, in the form of a white powder, to the
+bottom of the vessel.</p>
+
+<p>Alkaline air mixed with <i>common air</i>, and standing together several
+days, first in quicksilver, and then in water (which absorbed the
+alkaline air) it did not appear that there was any change produced in
+the common air: at least it was as much diminished by nitrous air as
+before. The same was the case with a mixture of acid air and common air.</p>
+
+<p>Having mixed air that had been diminished by the fermentation of a
+mixture of iron filings and brimstone with alkaline air, the water
+absorbed the latter, but left the former, with respect to the test of
+nitrous air (and therefore, as I conclude, with respect to all its
+properties) the same that it was before.</p>
+
+<p><i>Spirit of wine</i> imbibes alkaline air as readily as water, and seems to
+be as inflammable afterwards as before.</p>
+
+<p>Alkaline air contracts no union with <i>olive oil</i>. They were in contact
+almost two days, without any diminution of the air. Oil of turpentine,
+and essential oil of mint, absorbed a very small<span class='pagenum'><a name="Page_173" id="Page_173">[Pg 173]</a></span> quantity of alkaline
+air, but were not sensibly changed by it.</p>
+
+<p><i>Ether</i>, however, imbibed alkaline air pretty freely; but it was
+afterwards as inflammable as before, and the colour was not changed. It
+also evaporated as before, but I did not attend to this last
+circumstance very accurately.</p>
+
+<p><i>Sulphur</i>, <i>nitre</i>, <i>common salt</i>, and <i>flints</i>, were put to alkaline
+air without imbibing any part of it; but <i>charcoal</i>, <i>spunge</i>, bits of
+<i>linen cloth</i>, and other substances of that nature, seemed to condense
+this air upon their surfaces; for it began to diminish immediately upon
+their being put to it; and when they were taken out the alkaline smell
+they had contracted was so pungent as to be almost intolerable,
+especially that of the spunge. Perhaps it might be of use to recover
+persons from swooning. A bit of spunge, about as big as a hazel nut,
+presently imbibed an ounce measure of alkaline air.</p>
+
+<p>A piece of the inspissated juice of <i>turnsole</i> was made very dry and
+warm, and yet it imbibed a great quantity of the air; by which it
+contracted a most pungent smell, but the colour of it was not changed.<span class='pagenum'><a name="Page_174" id="Page_174">[Pg 174]</a></span></p>
+
+<p><i>Alum</i> undergoes a very remarkable change by the action of alkaline air.
+The outward shape and size remain the same, but the internal structure
+is quite changed, becoming opaque, beautifully white, and, to
+appearance, in all respects, like alum which had been roasted; and so as
+not to be at all affected by a degree of heat that would have reduced it
+to that state by roasting. This effect is produced slowly; and if a
+piece of alum be taken out of alkaline air before the operation is over,
+the inside will be transparent, and the outside, to an equal thickness,
+will be a white crust.</p>
+
+<p>I imagine that the alkaline vapour seizes upon the water that enters
+into the constitution of crude alum, and which would have been expelled
+by heat. Roasted alum also imbibes alkaline air, and, like the raw alum
+that has been exposed to it, acquires a taste that is peculiarly
+disagreeable.</p>
+
+<p><i>Phosphorus</i> gave no light in alkaline air, and made no lasting change
+in its dimensions. It varied, indeed, a little, being sometimes
+increased and sometimes diminished, but after a day and a night, it was
+in the same state as at the first. Water absorbed this air just as if
+nothing had been put to it.<span class='pagenum'><a name="Page_175" id="Page_175">[Pg 175]</a></span></p>
+
+<p>Having put some <i>spirit of salt</i> to alkaline air, the air was presently
+absorbed, and a little of the white salt above-mentioned was formed. A
+little remained unabsorbed, and transparent, but upon the admission of
+common air to it, it instantly became white.</p>
+
+<p><i>Oil of vitriol</i>, also formed a white salt with alkaline air, and this
+did not rise in white fumes.</p>
+
+<p>Acid air, as I have observed in my former papers, extinguishes a candle.
+Alkaline air, on the contrary, I was surprized to find, is slightly
+inflammable; which, however, seems to confirm the opinion of chemists,
+that the volatile alkali contains phlogiston.</p>
+
+<p>I dipped a lighted candle into a tall cylindrical vessel, filled with
+alkaline air, when it went out three or four times successively; but at
+each time the flame was considerably enlarged, by the addition of
+another flame, of a pale yellow colour; and at the last time this light
+flame descended from the top of the vessel to the bottom. At another
+time, upon presenting a lighted candle to the mouth of the same vessel,
+filled with the same kind of air, the yellowish flame ascended two
+inches higher than the flame of the candle. The electric spark taken in
+alkaline<span class='pagenum'><a name="Page_176" id="Page_176">[Pg 176]</a></span> air is red, as it is in common inflammable air.</p>
+
+<p>Though alkaline air be inflammable, it appeared, by the following
+experiment, to be heavier than the common inflammable air, as well as to
+contract no union with it. Into a vessel containing a quantity of
+inflammable air, I put half as much alkaline air, and then about the
+same quantity of acid air. These immediately formed a white cloud, but
+it did not rise within the space that was occupied by the inflammable
+air; so that this latter had kept its place above the alkaline air, and
+had not mixed with it.</p>
+
+<p>That alkaline air is lighter than acid air is evident from the
+appearances that attend the mixture, which are indeed very beautiful.
+When acid air is introduced into a vessel containing alkaline air, the
+white cloud which they form appears at the bottom only, and ascends
+gradually. But when the alkaline air is put to the acid, the whole
+becomes immediately cloudy, quite to the top of the vessel.</p>
+
+<p>In the last place, I shall observe that alkaline air, as well as acid,
+dissolves <i>ice</i> as fast as a hot fire can do it. This was tried when
+both the kinds of air, and every instrument made use of<span class='pagenum'><a name="Page_177" id="Page_177">[Pg 177]</a></span> in the
+experiment, had been exposed to a pretty intense frost several hours. In
+both cases, also, the water into which the ice was melted dissolved more
+ice, to a considerable quantity.</p>
+
+
+
+<hr style="width: 65%;" />
+<h2>SECTION II.</h2>
+
+<h3><i>Of <span class="smcap">common Air</span> diminished and made noxious by various processes.</i></h3>
+
+
+<p>It will have been observed that, in the first publication of my papers,
+I confined myself chiefly to the narration of the new <i>facts</i> which I
+had discovered, barely mentioning any <i>hypotheses</i> that occurred to me,
+and never seeming to lay much stress upon them. The reason why I was so
+much upon my guard in this respect was, left, in consequence of
+attaching myself to any hypothesis too soon, the success of my future
+inquiries might be obstructed. But subsequent experiments having thrown
+great light upon the preceding ones and having confirmed the few
+conjectures I then advanced, I may now venture to speak of my hypotheses
+with a little less diffidence. Still, however, I shall be ready to
+relinquish any notions I may now entertain, if new facts should
+hereafter appear not to favour them.<span class='pagenum'><a name="Page_178" id="Page_178">[Pg 178]</a></span></p>
+
+<p>In a great variety of cases I have observed that there is a remarkable
+<i>diminution</i> of common, or respirable air, in proportion to which it is
+always rendered unfit for respiration, indisposed to effervesce with
+nitrous air, and incapable of farther diminution from any other cause.
+The circumstances which produce this effect I had then observed to be
+the burning of candles, the respiration of animals, the putrefaction of
+vegetables or animal substances, the effervescence of iron filings and
+brimstone, the calcination of metals, the fumes of charcoal, the
+effluvia of paint made of white-lead and oil, and a mixture of nitrous
+air.</p>
+
+<p>All these processes, I observed, agree in this one circumstance, and I
+believe in no other, that the principle which the chemists call
+<i>phlogiston</i> is set loose; and therefore I concluded that the diminution
+of the air was, in some way or other, the consequence of the air
+becoming overcharged with phlogiston,<a name="FNanchor_11_11" id="FNanchor_11_11"></a><a href="#Footnote_11_11" class="fnanchor">[11]</a> and that water, and growing
+vegetables, tend to restore<span class='pagenum'><a name="Page_179" id="Page_179">[Pg 179]</a></span> this air to a state fit for respiration, by
+imbibing the superfluous phlogiston. Several experiments which I have
+since made tend to confirm this supposition.</p>
+
+<p>Common air, I find, is diminished, and rendered noxious, by <i>liver of
+sulphur</i>, which the chemists say exhales phlogiston, and nothing else.
+The diminution in this case was one fifth of the whole, and afterwards,
+as in other similar cases, it made no effervescence with nitrous air.</p>
+
+<p>I found also, after Dr. Hales, that air is diminished by <i>Homberg's
+pyrophorus</i>.</p>
+
+<p>The same effect is produced by firing <i>gunpowder</i> in air. This I tried
+by firing the gunpowder in a receiver half exhausted, by which the air
+was rather more injured than it would have been by candles burning in
+it.</p>
+
+<p>Air is diminished by a cement made with one half common coarse
+turpentine and half bees-wax. This was the result of a very casual
+observation.<span class='pagenum'><a name="Page_180" id="Page_180">[Pg 180]</a></span> Having, in an air-pump of Mr. Smeaton's construction,
+closed that end of the syphon-gage, which is exposed to the outward air,
+with this cement (which I knew would make it perfectly air-light)
+instead of sealing it hermetically; I observed that, in a course of
+time, the quicksilver in that leg kept continually rising, so that the
+measures I marked upon it were of no use to me; and when I opened that
+end of the tube, and closed it again, the same consequence always took
+place. At length, suspecting that this effect must have arisen from the
+bit of <i>cement</i> diminishing the air to which it was exposed, I covered
+all the inside of a glass tube with it, and one end of it being quite
+closed with the cement, I set it perpendicular, with its open end
+immersed in a bason of quicksilver; and was presently satisfied that my
+conjecture was well founded: for, in a few days, the quicksilver rose so
+much within the tube, that the air in the inside appeared to be
+diminished about one sixth.</p>
+
+<p>To change this air I filled the tube with quicksilver, and pouring it
+out again, I replaced the tube in its former situation; when the air was
+diminished again, but not so fast as before. The same lining of cement
+diminished the air a third time. How long it will retain this power I
+cannot tell. This cement had<span class='pagenum'><a name="Page_181" id="Page_181">[Pg 181]</a></span> been made several months before I made
+this experiment with it. I must observe, however, that another quantity
+of this kind of cement, made with a finer and more liquid turpentine,
+had not the power of diminishing air, except in a very small proportion.
+Also the common red cement has this property in the same small degree.
+Common air, however, which had been confined in a glass vessel lined
+with this cement about a month, was so far injured that a candle would
+not burn in it. In a longer time it would, I doubt not, have become
+thoroughly noxious.</p>
+
+<p>Iron that has been suffered to rust in nitrous air diminishes common air
+very fast, as I shall have occasion to mention when I give a
+continuation of my experiments on nitrous air.</p>
+
+<p>Lastly, the same effect, I find, is produced by the <i>electric spark</i>,
+though I had no expectation of this event when I made the experiment.</p>
+
+<p>This experiment, however, and those which I have made in pursuance of
+it, has fully confirmed another of my conjectures, which relates to the
+<i>manner</i> in which air is diminished by being overcharged with
+phlogiston, viz. the phlogiston having a nearer affinity with some of
+the constituent parts of the air than the fixed<span class='pagenum'><a name="Page_182" id="Page_182">[Pg 182]</a></span> air which enters into
+the composition of it, in consequence of which the fixed air is
+precipitated.</p>
+
+<p>This I first imagined from perceiving that lime-water became turbid by
+burning candles over it, p. 44. This was also the case with lime-water
+confined in air in which an animal substance was putrefying, or in which
+an animal died, p. 79. and that in which charcoal was burned, p. 81.
+But, in all these cases, there was a possibility of the fixed air being
+discharged from the candle, the putrefying substance, the lungs of the
+animal, or the charcoal. That there is a precipitation of lime when
+nitrous air is mixed with common air, I had not then observed, but I
+have since found it to be the case.</p>
+
+<p>That there was no precipitation of lime when brimstone was burned, I
+observed, p. 45. might be owing to the fixed air and the lime uniting
+with the vitriolic acid, and making a salt, which was soluble in water;
+which salt I, indeed, discovered by the evaporation of the water.</p>
+
+<p>I also observed, p. 46, 105. that diminished air being rather lighter
+than common air is a circumstance in favour of the fixed, or the<span class='pagenum'><a name="Page_183" id="Page_183">[Pg 183]</a></span>
+heavier part of the common air, having been precipitated.</p>
+
+<p>It was upon this idea, together with others similar to it, that I took
+so much pains to mix fixed air with air diminished by respiration or
+putrefaction, in order to make it fit for respiration again; and I
+thought that I had, in general, succeeded to a considerable degree, p.
+99, &amp;c. I will add, also, what I did not mention before, that I once
+endeavoured, but without effect, to preserve mice alive in the same
+unchanged air, by supplying them with fixed air, when the air in which
+they were confined began to be injured by their respiration. Without
+effect, also, I confined for some months, a quantity of quick lime in a
+given quantity of common air, thinking it might extract the fixed air
+from it.</p>
+
+<p>The experiments which I made with electricity were solely intended to
+ascertain what has often been attempted, but, as far as I know, had
+never been fully accomplished, viz. to change the blue colour of
+liquors, tinged with vegetable juices, red.</p>
+
+<p>For this purpose I made use of a glass tube, about one tenth of an inch
+diameter in the inside, as in fig. 16. In one end of this I cemented<span class='pagenum'><a name="Page_184" id="Page_184">[Pg 184]</a></span> a
+piece of wire <i>b</i>, on which I put a brass ball. The lower part from <i>a</i>
+was filled with water tinged blue, or rather purple, with the juice of
+turnsole, or archil. This is easily done by an air-pump, the tube being
+set in a vessel of the tinged water.</p>
+
+<p>Things being thus prepared, I perceived that, after I had taken the
+electric spark, between the wire <i>b</i>, and the liquor at <i>a</i>, about a
+minute, the upper part of it began to look red, and in about two minutes
+it was very manifestly so; and the red part, which was about a quarter
+of an inch in length, did not readily mix with the rest of the liquor. I
+observed also, that if the tube lay inclined while I took the sparks,
+the redness extended twice as far on the lower side as on the upper.</p>
+
+<p>The most important, though the least expected observation, however, was
+that, in proportion as the liquor became red, it advanced nearer to the
+wire, so that the space of air in which the sparks were taken was
+diminished; and at length I found that the diminution was about one
+fifth of the whole space; after which more electrifying produced no
+sensible effect.</p>
+
+<p>To determine whether the cause of the change of colour was in the <i>air</i>,
+or in the <span class='pagenum'><a name="Page_185" id="Page_185">[Pg 185]</a></span><i>electric matter</i>, I expanded the air which had been
+diminished in the tube by means of an air-pump, till it expelled all the
+liquor, and admitted fresh blue liquor into its place; but after that,
+electricity produced no sensible effect, either on the air, or on the
+liquor; so that it was evident that the electric matter had decomposed
+the air, and had made it deposite something that was of an acid nature.</p>
+
+<p>In order to determine whether the <i>wire</i> had contributed any thing to
+this effect, I used wires of different metals, iron, copper, brass, and
+silver; but the result was the very same with them all.</p>
+
+<p>It was also the same when, by means of a bent glass tube, I made the
+electric spark without any wire at all, in the following manner. Each
+leg of the tube, fig. 19. stood in a bason of quicksilver; which, by
+means of an air-pump, was made to ascend as high as <i>a, a</i>, in each leg,
+while the space between <i>a</i> and <i>b</i> in each contained the blue liquor,
+and the space between <i>b</i> and <i>b</i> contained common air. Things being
+thus disposed, I made the electric spark perform the circuit from one
+leg to the other, passing from the liquor in one leg of the tube to the
+liquor in the other leg, through the space of air. The effect was, that
+the liquor, in<span class='pagenum'><a name="Page_186" id="Page_186">[Pg 186]</a></span> both the legs, became red, and the space of air between
+them was contracted, as before.</p>
+
+<p>Air thus diminished by electricity makes no effervescence with, and is
+no farther diminished by a mixture of nitrous air; so that it must have
+been in the highest degree noxious, exactly like air diminished by any
+other process.</p>
+
+<p>In order to determine what the <i>acid</i> was, which was deposited by the
+air, and which changed the colour of the blue liquor, I exposed a small
+quantity of the liquor so changed to the common air, and found that it
+recovered its blue colour, exactly as water, tinged with the same blue,
+and impregnated with fixed air, will do. But the following experiment
+was still more decisive to this purpose. Taking the electric spark upon
+<i>lime-water</i>, instead of the blue liquor, the lime was precipitated as
+the air diminished.</p>
+
+<p>From these experiments it pretty clearly follows, that the electric
+matter either is, or contains phlogiston; since it does the very same
+thing that phlogiston does. It is also probable, from these experiments,
+that the sulphureous smell, which is occasioned by electricity, being
+very different from that of fixed air, the phlogiston<span class='pagenum'><a name="Page_187" id="Page_187">[Pg 187]</a></span> in the electric
+matter itself may contribute to it.</p>
+
+<p>It was now evident that common air diminished by any one of the
+processes above-mentioned being the same thing, as I have observed, with
+air diminished by any other of them (since it is not liable to be
+farther diminished by any other) the loss which it sustains, in all the
+cases, is, in part, that of the <i>fixed air</i> which entered into its
+constitution. The fixed air thus precipitated from common air by means
+of phlogiston unites with lime, if any lime water be ready to receive
+it, unless there be some other substance at hand, with which it has a
+greater affinity, as the <i>calces of metals</i>.</p>
+
+<p>If the whole of the diminution of common air was produced by the
+deposition of fixed air, it would be easy to ascertain the quantity of
+fixed air that is contained in any given quantity of common air. But it
+is evident that the whole of the diminution of common air by phlogiston
+is not owing to the precipitation of fixed air, because a mixture of
+nitrous air will make a great diminution in all kinds of air that are
+fit for respiration, even though they never were common air, and though
+nothing was used in the process for generating them that can be supposed
+to yield fixed air.<span class='pagenum'><a name="Page_188" id="Page_188">[Pg 188]</a></span></p>
+
+<p>Indeed, it appears, from some of the experiments, that the diminution of
+some of these kinds of air by nitrous air is so great, and approaches so
+nearly to the quantity of the diminution of common air by the same
+process, as to shew that, unless they be very differently affected by
+phlogiston, very little is to be allowed to the loss of fixed air in the
+diminution of common air by nitrous air.</p>
+
+<p>The kinds of air on which this experiment was made were inflammable air,
+nitrous air diminished by iron filings and brimstone, and nitrous air
+itself; all of which are produced by the solution of metals in acids;
+and also on common air diminished and made noxious, and therefore
+deprived of its fixed air by phlogistic processes; and they were
+restored to a great degree of purity by agitation in water, out of which
+its own air had been carefully boiled.</p>
+
+<p>To five parts of inflammable air, which had been agitated in water till
+it was diminished about one half (at which time part of it fired with a
+weak explosion) I put one part of nitrous air, which diminished it one
+eighth of the whole. This was done in lime-water, without any
+precipitation of lime. To compare this with common air, I mixed the same
+quantity, viz. five parts of this, and one part of nitrous air: when<span class='pagenum'><a name="Page_189" id="Page_189">[Pg 189]</a></span>
+considerable crust of lime was formed upon the surface of the lime
+water, though the diminution was very little more than in the former
+process. It is possible, however, that the common air might have taken
+more nitrous air before it was fully saturated, so as to begin to
+receive an addition to its bulk.</p>
+
+<p>I agitated in water a quantity of nitrous air phlogisticated with iron
+filings and brimstone, and found it to be so far restored, that three
+fourths of an ounce measure of nitrous air being put to two ounce
+measures of it, made no addition to it.</p>
+
+<p>But the most remarkable of these experiments is that which I made with
+<i>nitrous air</i> itself which I had no idea of the possibility of reducing
+to a state fit for respiration by any process whatever, at the time of
+my former publication on this subject. This air, however, itself,
+without any previous phlogistication, is purified by agitation in water
+till it is diminished by fresh nitrous air, and to a very considerable
+degree.</p>
+
+<p>In a pretty long time I agitated nitrous air in water, supplying it from
+time to time with more, as the former quantity diminished, till only one
+eighteenth of the whole quantity remained; in which state it was so
+wholesome,<span class='pagenum'><a name="Page_190" id="Page_190">[Pg 190]</a></span> that a mouse lived in two ounce measures of it more than ten
+minutes, without shewing any sign of uneasiness; so that I concluded it
+must have been about as good as air in which candles had burned out.
+After agitating it again in water, I put one part of fresh nitrous air
+to five parts of this air, and it was diminished one ninth part. I then
+agitated it a third time, and putting more nitrous air to it, it was
+diminished again in the same proportion, and so a fourth time; so that,
+by continually repeating the process, it would, I doubt not, have been
+all absorbed. These processes were made in lime-water, without forming
+any incrustation on the surface of it.</p>
+
+<p>Lastly, I took a quantity of common air, which had been diminished and
+made noxious by phlogistic processes; and when it had been agitated in
+water, I found that it was diminished by nitrous air, though not so much
+as it would have been at the first. After cleansing it a second time, it
+was diminished again by the same means; and, after that, a third time;
+and thus there can be no doubt but that, in time, the whole quantity
+would have disappeared. For I have never found that agitation in water,
+deprived of its own air, made any addition to a quantity of noxious air;
+though, <i>a priori</i>, it might have been imagined that, as a saturation<span class='pagenum'><a name="Page_191" id="Page_191">[Pg 191]</a></span>
+with phlogiston diminishes air, the extraction of phlogiston would
+increase the bulk of it. On the contrary, agitation in water always
+diminished noxious air a little; indeed, if water be deprived of all its
+own air, it is impossible to agitate any kind of air in it without some
+loss. Also, when noxious air has been restored by plants, I never
+perceived that it gained any addition to its bulk by that means. There
+was no incrustation of the lime-water in the above-mentioned experiment.</p>
+
+<p>It is not a little remarkable, that those kinds of air which never had
+been common air, as inflammable air, phlogisticated nitrous air, and
+nitrous air itself, when rendered wholesome by agitation in water,
+should be more diminished by fresh nitrous air, than common air which
+had been made noxious, and restored by the same process; and yet, from
+the few trials that I have made, I could not help concluding that this
+is the case.</p>
+
+<p>In this course of experiments I was very near deceiving myself, in
+consequence of transferring the nitrous air which I made use of in a
+bladder, in the manner described, p. 15. fig. 9. so as to conclude that
+there was a precipitation of lime in all the above-mentioned cases, and
+that even nitrous air itself produced that effect. But<span class='pagenum'><a name="Page_192" id="Page_192">[Pg 192]</a></span> after repeated
+trials, I found that there was no precipitation of lime, except, in the
+first diminution of common air, when the nitrous air was transferred in
+a glass vessel.</p>
+
+<p>That the calces of metals contain air, of some kind or other, and that
+this air contributes to the additional weight of the calces, above that
+of the metals from which they are made, had been observed by Dr. Hales;
+and Mr. Hartley had informed me, that when red-lead is boiled in linseed
+oil, there is a prodigious discharge of air before they incorporate. I
+had likewise found, that no weight is either gained or lost by the
+calcination of tin in a close glass vessel; but I purposely deferred
+making any more experiments on the subject, till we should have some
+weather in which I could make use of a large burning lens, which I had
+provided for that and other purposes; but, in the mean time, I was led
+to the discovery in a different manner.</p>
+
+<p>Having, by the last-recited experiments, been led to consider the
+electric matter as phlogiston, or something containing phlogiston, I was
+endeavouring to revivify the calx of lead with it; when I was surprized
+to perceive a considerable generation of air. It occurred to me, that
+possibly this effect might arise from the <i>heat</i> communicated<span class='pagenum'><a name="Page_193" id="Page_193">[Pg 193]</a></span> to the
+red-lead by the electric sparks, and therefore I immediately filled a
+small phial with the red-lead, and heating it with a candle, I presently
+expelled from it a quantity of air about four or five times the bulk of
+the lead, the air being received in a vessel of quicksilver. How much
+more air it would have yielded, I did not try.</p>
+
+<p>Along with the air, a small quantity of <i>water</i> was likewise thrown out;
+and it immediately occurred to me, that this water and air together must
+certainly be the cause of the addition of weight in the calx. It still
+remained to examine what kind of air this was; but admitting water to
+it, I found that it was imbibed by it, exactly like <i>fixed air</i>, which I
+therefore immediately concluded it must be<a name="FNanchor_12_12" id="FNanchor_12_12"></a><a href="#Footnote_12_12" class="fnanchor">[12]</a>.</p>
+
+<p>After this, I found that Mr. Lavoisier had completely discovered the
+same thing, though his apparatus being more complex, and less<span class='pagenum'><a name="Page_194" id="Page_194">[Pg 194]</a></span> accurate
+than mine, he concluded that more of the air discharged from the calces
+of metals was immiscible with water than I found it to be. It appeared
+to me that I had never obtained fixed air more pure.</p>
+
+<p>It being now pretty clearly determined, that common air is made to
+deposit the fixed air which entered into the constitution of it, by
+means of phlogiston, in all the cases of diminished air, it will follow,
+that in the precipitation of lime, by breathing into lime-water the
+fixed air, which incorporates with lime, comes not from the lungs, but
+from the common air, decomposed by the phlogiston exhaled from them, and
+discharged, after having been taken in with the aliment, and having
+performed its function in the animal system.</p>
+
+<p>Thus my conjecture is more confirmed, that the cause of the death of
+animals in confined air is not owing to the want of any <i>pabulum vit&aelig;</i>,
+which the air had been supposed to contain, but to the want of a
+discharge of the phlogistic matter, with which the system was loaded;
+the air, when once saturated with it, being no sufficient <i>menstruum</i> to
+take it up.</p>
+
+<p>The instantaneous death of animals put into air so vitiated, I still
+think is owing to some<span class='pagenum'><a name="Page_195" id="Page_195">[Pg 195]</a></span> <i>stimulus</i>, which, by causing immediate,
+universal and violent convulsions, exhausts the whole of the <i>vis vit&aelig;</i>
+at once; because, as I have observed, the manner of their death is the
+very same in all the different kinds of noxious air.</p>
+
+<p>To this section on the subject of diminished, and noxious air, or as it
+might have been called <i>phlogisticated air</i>, I shall subjoin a letter
+which I addressed to Sir John Pringle, on the noxious quality of the
+effluvia of putrid marshes, and which was read at a meeting of the Royal
+Society, December 16, 1773.</p>
+
+<p>This letter which is printed in the Philosophical Transactions, Vol. 74,
+p. 90. is immediately followed by another paper, to which I would refer
+my reader. It was written by Dr. Price, who has so greatly distinguished
+himself, and done such eminent service to his country, and to mankind,
+by his calculations relating to the probabilities of human life, and was
+suggested by his hearing this letter read at the Royal Society. It
+contains a confirmation of my observations on the noxious effects of
+stagnant waters by deductions from Mr. Muret's account of the Bills of
+Mortality for a parish situated among marshes, in the district of Vaud,
+belonging to the Canton of Bern in Switzerland.<span class='pagenum'><a name="Page_196" id="Page_196">[Pg 196]</a></span></p>
+
+<p>
+<span style="margin-left: 2.5em;">To Sir JOHN PRINGLE, Baronet.</span><br />
+<br />
+<span style="margin-left: 2.5em;">DEAR SIR,</span><br />
+</p>
+
+<p>Having pursued my experiments on different kinds of air considerably
+farther, in several respects, than I had done when I presented the last
+account of them to the Royal Society; and being encouraged by the
+favourable notice which the Society has been pleased to take of them, I
+shall continue my communications on this subject; but, without waiting
+for the result of a variety of processes, which I have now going on, or
+of other experiments, which I propose to make, I shall, from time to
+time, communicate such detached articles, as I shall have given the most
+attention to, and with respect to which, I shall have been the most
+successful in my inquiries.</p>
+
+<p>Since the publication of my papers, I have read two treatises, written
+by Dr. Alexander, of Edinburgh, and am exceedingly pleased with the
+spirit of philosophical inquiry, which they discover. They appear to me
+to contain many new, curious, and valuable observations; but one of the
+<i>conclusions</i>, which he draws from his experiments, I am satisfied, from
+my<span class='pagenum'><a name="Page_197" id="Page_197">[Pg 197]</a></span> own observations, is ill founded, and from the nature of it, must be
+dangerous. I mean his maintaining, that there is nothing to be
+apprehended from the neighbourhood of putrid marshes.</p>
+
+<p>I was particularly surprised, to meet with such an opinion as this, in a
+book inscribed to yourself, who have so clearly explained the great
+mischief of such a situation, in your excellent treatise <i>on the
+diseases of the army</i>. On this account, I have thought it not improper,
+to address to you the following observations and experiments, which I
+think clearly demonstrate the fallacy of Dr. Alexander's reasoning,
+indisputably establish your doctrine, and indeed justify the
+apprehensions of all mankind in this case.</p>
+
+<p>I think it probable enough, that putrid matter, as Dr. Alexander has
+endeavoured to prove, will preserve other substances from putrefaction;
+because, being already saturated with the putrid effluvium, it cannot
+readily take any more; but Dr. Alexander was not aware, that air thus
+loaded with putrid effluvium is exceedingly noxious when taken into the
+lungs. I have lately, however, had an opportunity of fully ascertaining
+how very noxious such air is.<span class='pagenum'><a name="Page_198" id="Page_198">[Pg 198]</a></span></p>
+
+<p>Happening to use at Calne, a much larger trough of water, for the
+purpose of my experiments, than I had done at Leeds, and not having
+fresh water so near at hand as I had there, I neglected to change it,
+till it turned black, and became offensive, but by no means to such a
+degree, as to deter me from making use of it. In this state of the
+water, I observed bubbles of air to rise from it, and especially in one
+place, to which some shelves, that I had in it, directed them; and
+having set an inverted glass vessel to catch them, in a few days I
+collected, a considerable quantity of this air, which issued
+spontaneously from the putrid water; and putting nitrous air to it, I
+found that no change of colour or diminution ensued, so that it must
+have been, in the highest degree, noxious. I repeated the same
+experiment several times afterwards, and always with the same result.</p>
+
+<p>After this, I had the curiosity to try how wholesome air would be
+affected by this water; when, to my real surprise, I found, that after
+only one minute's agitation in it, a candle would not burn in it; and,
+after three or four minutes, it was in the same state with the air,
+which had issued spontaneously from the same water.<span class='pagenum'><a name="Page_199" id="Page_199">[Pg 199]</a></span></p>
+
+<p>I also found, that common air, confined in a glass vessel, in <i>contact</i>
+only with this water, and without any agitation, would not admit a
+candle to burn in it after two days.</p>
+
+<p>These facts certainly demonstrate, that air which either arises from
+stagnant and putrid water, or which has been for some time in contact
+with it, must be very unfit for respiration; and yet Dr. Alexander's
+opinion is rendered so plausible by his experiments, that it is very
+possible that many persons may be rendered secure, and thoughtless of
+danger, in a situation in which they must necessarily breathe it. On
+this account, I have thought it right to make this communication as
+early as I conveniently could; and as Dr. Alexander appears to be an
+ingenuous and benevolent man, I doubt not but he will thank me for it.</p>
+
+<p>That air issuing from water, or rather from the soft earth, or mud, at
+the bottom of pits containing water, is not always unwholesome, I have
+also had an opportunity of ascertaining. Taking a walk, about two years
+ago, in the neighbourhood of Wakefield, in Yorkshire, I observed bubbles
+of air to arise, in remarkably great plenty, from a small pool of water,
+which, upon inquiry, I was informed had been the place, where some
+persons had been boring the<span class='pagenum'><a name="Page_200" id="Page_200">[Pg 200]</a></span> ground, in order to find coal. These
+bubbles of air having excited my curiosity, I presently returned, with a
+bason, and other vessels proper for my purpose, and having stirred the
+mud with a long stick, I soon got about a pint of this air; and,
+examining it, found it to be good, common air; at least a candle burned
+in it very well. I had not then discovered the method of ascertaining
+the goodness of common air, by a mixture of nitrous air. Previous to the
+trial, I had suspected that this air would have been found to be
+inflammable.</p>
+
+<p>I shall conclude this letter with observing, that I have found a
+remarkable difference in different kinds of water, with respect to their
+effect on common air agitated in them, and which I am not yet able to
+account for. If I agitate common air in the water of a deep well, near
+my house in Calne, which is hard, but clear and sweet, a candle will not
+burn in it after three minutes. The same is the case with the
+rain-water, which I get from the roof of my house. But in distilled
+water, or the water of a spring-well near the house, I must agitate the
+air about twenty minutes, before it will be so much injured. It may be
+worth while, to make farther experiments with respect to this property
+of water.<span class='pagenum'><a name="Page_201" id="Page_201">[Pg 201]</a></span></p>
+
+<p>In consequence of using the rain-water, and the well-water above
+mentioned, I was very near concluding, contrary to what I have asserted
+in this treatise, that common air suffers a decomposition by great
+rarefaction. For when I had collected a considerable quantity of air,
+which had been rarefied about four hundred times, by an excellent pump
+made for me by Mr. Smeaton, I always found, that if I filled my
+receivers with the water above mentioned, though I did it so gradually
+as to occasion as little agitation as possible, a candle would not burn
+in the air that remained in them. But when I used distilled water, or
+fresh spring-water, I undeceived myself.</p>
+
+<p>I think myself honoured by the attention, which, from the first, you
+have given to my experiments, and am, with the greatest respect,</p>
+
+<p>
+<span style="margin-left: 5em;">Dear Sir,</span><br />
+<br />
+<span style="margin-left: 7em;">Your most obliged</span><br />
+<br />
+<span style="margin-left: 9em;">Humble Servant,</span><br />
+<br />
+<span style="margin-left: 2.5em;">London, 7 Dec. 1773.</span><br />
+<br />
+<span style="margin-left: 5em;">J. PRIESTLEY.</span><br />
+</p>
+
+
+<h3>POSTSCRIPT.</h3><p><span class='pagenum'><a name="Page_202" id="Page_202">[Pg 202]</a></span></p>
+
+<p>I cannot help expressing my surprize, that so clear and intelligible an
+account, of Mr. <span class="smcap">Smeaton's</span> air-pump, should have been before the public
+so long, as ever since the publication of the forty-seventh volume of
+the Philosophical Transactions, printed in 1752, and yet that none of
+our philosophical instrument-makers should use the construction. The
+superiority of this pump, to any that are made upon the common plan, is,
+indeed, prodigious. Few of them will rarefy more than 100 times, and, in
+a general way, not more than 60 or 70 times; whereas this instrument
+must be in a poor state indeed, if it does not rarefy 200 or 300 times;
+and when it is in good order, it will go as far as 1000 times, and
+sometimes even much farther than that; besides, this instrument is
+worked with much more ease, than a common air-pump, and either exhausts
+or condenses at pleasure. In short, to a person engaged in philosophical
+pursuits, this instrument is an invaluable acquisition. I shall have
+occasion to recite some experiments, which I could not have made, and
+which, indeed, I should hardly have dared to attempt, if I had not been
+possessed of such an air-pump as this. It is much to be wished, that
+some person of spirit in the trade would attempt<span class='pagenum'><a name="Page_203" id="Page_203">[Pg 203]</a></span> the construction of an
+instrument, which would do great credit to himself, as well as be of
+eminent service to philosophy.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_11_11" id="Footnote_11_11"></a><a href="#FNanchor_11_11"><span class="label">[11]</span></a> On this account, if it was thought convenient to introduce
+a new term (or rather make a new application of a term already in use
+among chemists) it might not be amiss to call air that has been
+diminished, and made noxious by any of the processes above mentioned, or
+others similar to them, by the common appellation of <i>phlogisticated
+air</i>; and, if it was necessary, the particular process by which it was
+phlogisticated might be added; as common air phlogisticated by charcoal,
+air phlogisticated by the calcination of metals, nitrous air
+phlogisticated with the liver of sulphur, &amp;c.</p></div>
+
+<div class="footnote"><p><a name="Footnote_12_12" id="Footnote_12_12"></a><a href="#FNanchor_12_12"><span class="label">[12]</span></a> Here it becomes me to ask pardon of that excellent
+philosopher Father Beccaria of Turin, for conjecturing that the
+phlogiston, with which he revivified metals, did not come from the
+electric matter itself, but from what was discharged from other pieces
+of metal with which he made the experiment. See History of Electricity,
+p. 277, &amp;c. This <i>revivification of metals</i> by electricity completes the
+proof of the electric matter being, or containing phlogiston.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>SECTION III.</h2>
+
+<h3><i>Of <span class="smcap">Nitrous Air</span>.</i></h3>
+
+
+<p>Since the publication of my former papers I have given more attention to
+the subject of nitrous air than to any other species of air; and having
+been pretty fortunate in my inquiries, I shall be able to lay before my
+reader a more satisfactory account of the curious phenomena occasioned
+by it, and also of its nature and constitution, than I could do before,
+though much still remains to be investigated concerning it, and many new
+objects of inquiry are started.</p>
+
+<p>With a view to discover where the power of nitrous air to diminish
+common air lay, I evaporated to dryness a quantity of the solution of
+copper in diluted spirit of nitre; and having procured from it a
+quantity of a <i>green precipitate</i>, I threw the focus of a burning-glass
+upon it, when it was put into a vessel of quicksilver, standing inverted
+in a bason of quicksilver. In this manner I procured air from it,<span class='pagenum'><a name="Page_204" id="Page_204">[Pg 204]</a></span> which
+appeared to be, in all respects, nitrous air; so that part of the same
+principle which had escaped during the solution, in the form of <i>air</i>,
+had likewise been retained in it, and had not left it in the evaporation
+of the water.</p>
+
+<p>With great difficulty I also procured a small quantity of the same kind
+of air from a solution of <i>iron</i> in spirit of nitre, by the same
+process.</p>
+
+<p>Having, for a different purpose, fired some paper, which had been dipped
+in a solution of copper in diluted spirit of nitre, in nitrous air, I
+found there was a considerable addition to the quantity of it; upon
+which I fired some of the same kind of paper in quicksilver and
+presently observed that air was produced from it in great plenty. This
+air, at the first, seemed to have some singular properties, but
+afterwards I found that it was nothing more than a mixture of nitrous
+air, from the precipitate of the solution, and of inflammable air, from
+the paper; but that the former was predominant.</p>
+
+<p>In the mixture of this kind of air with common air, in a trough of water
+which had been putrid, but which at that time seemed to have recovered
+its former sweetness (for it was not in the least degree offensive to
+the smell) a phenomenon<span class='pagenum'><a name="Page_205" id="Page_205">[Pg 205]</a></span> sometimes occurred, which for a long time
+exceedingly delighted and puzzled me; but which was afterwards the means
+of letting me see much farther into the constitution of nitrous air than
+I had been able to see before.</p>
+
+<p>When the diminution of the air was nearly completed, the vessel in which
+the mixture was made began to be filled with the most beautiful <i>white
+fumes</i>, exactly resembling the precipitation of some white substance in
+a transparent menstruum, or the falling of very fine snow; except that
+it was much thicker below than above, as indeed is the case in all
+chemical precipitations. This appearance continued two or three minutes.</p>
+
+<p>At other times I went over the same process, as nearly as possible in
+the same manner, but without getting this remarkable appearance, and was
+several times greatly disappointed and chagrined, when I baulked the
+expectations of my friends, to whom I had described, and meant to have
+shewn it. This made me give all the attention I possibly could to this
+experiment, endeavouring to recollect every circumstance, which, though
+unsuspected at the time, might have contributed to produce this new
+appearance; and I took a great deal of pains to procure a quantity of
+this air from the paper<span class='pagenum'><a name="Page_206" id="Page_206">[Pg 206]</a></span> above mentioned for the purpose, which, with a
+small burning lens, and an uncertain sun, is not a little troublesome.
+But all that I observed for some time was, that I stood the best chance
+of succeeding when I <i>warmed</i> the vessel in which the mixture was made,
+and <i>agitated</i> the air during the effervescence.</p>
+
+<p>Finding, at length, that, with the same preparation and attentions, I
+got the same appearance from a mixture of nitrous and common air in the
+same trough of water, I concluded that it could not depend upon any
+thing peculiar to the precipitate of the <i>copper</i> contained in the
+<i>paper</i> from which the air was procured, as I had at first imagined, but
+upon what was common to it, and pure nitrous air.</p>
+
+<p>Afterwards, having, (with a view to observe whether any crystals would
+be formed by the union of volatile alkali, and nitrous air, similar to
+those formed by it and fixed air, as described by Mr. Smeth in his
+<i>Dissertation on fixed Air</i>) opened the mouth of a phial which was half
+filled with a volatile alkaline liquor, in a jar of nitrous air (in the
+manner described p. 11. fig. 4.) I had an appearance which perfectly
+explained the preceding. All that part of the phial which was above the
+liquor, and which<span class='pagenum'><a name="Page_207" id="Page_207">[Pg 207]</a></span> contained common air, was filled with beautiful
+<i>white clouds</i>, as if some fine white powder had been instantly thrown
+into it, and some of these clouds rose within the jar of nitrous air.
+This appearance continued about a minute, and then intirely disappeared,
+the air becoming transparent.</p>
+
+<p>Withdrawing the phial, and exposing it to the common air, it there also
+became turbid, and soon after the transparency returned. Introducing it
+again into the nitrous air, the clouds appeared as before. In this
+manner the white fumes, and transparency, succeeded each other
+alternately, as often as I chose to repeat the experiment, and would no
+doubt have continued till the air in the jar had been thoroughly diluted
+with common air. These appearances were the same with any substance that
+contained <i>volatile alkali</i>, fluid or solid.</p>
+
+<p>When, instead of the small phial, I used a large and tall glass jar,
+this appearance was truly fine and striking, especially when the water
+in the trough was very transparent. For I had only to put the smallest
+drop of a volatile alkaline liquor, or the smallest bit of the solid
+salt, into the jar, and the moment that the mouth of it was opened in a
+jar of nitrous air, the white clouds above mentioned began to<span class='pagenum'><a name="Page_208" id="Page_208">[Pg 208]</a></span> be formed
+at the mouth, and presently descended to the bottom, so as to fill the
+whole, were it ever so large, as with fine snow.</p>
+
+<p>In considering this experiment, I soon perceived that this curious
+appearance must have been occasioned by the mixture of the nitrous and
+common air, and therefore that the white clouds must be <i>nitrous
+ammoniac</i>, formed by the acid of the nitrous air, set loose in the
+decomposition of it by common air, while the phlogiston, which must be
+another constituent part of nitrous air, entering the common air, is the
+cause of the diminution it suffers in this process; as it is the cause
+of a similar diminution, in a variety of other processes.</p>
+
+<p>I would observe, that it is not peculiar to nitrous air to be a test of
+the fitness of air for respiration. Any other process by which air is
+diminished and made noxious answers the same purpose. Liver of sulphur
+for instance, the calcination of metals, or a mixture of iron filings
+and brimstone will do just the same thing; but the application of them
+is not so easy, or elegant, and the effect is not so soon perceived. In
+fact, it is <i>phlogiston</i> that is the test. If the air be so loaded with
+this principle that it can take no more, which is seen by its not being
+diminished in any of the processes<span class='pagenum'><a name="Page_209" id="Page_209">[Pg 209]</a></span> above mentioned, it is noxious; and
+it is wholesome in proportion to the quantity of phlogiston that it is
+able to take.</p>
+
+<p>This, I have no doubt, is the true theory of the diminution of common
+air by nitrous air, the redness of the appearance being nothing more
+than the usual colour of the fumes, of spirit of nitre, which is now
+disengaged from the superabundant phlogiston with which it was combined
+in the nitrous air, and ready to form another union with any thing that
+is at hand, and capable of it.</p>
+
+<p>With the volatile alkali it forms nitrous ammoniac, water imbibes it
+like any other acid, even quicksilver is corroded by it; but this action
+being slow, the redness in this mixture of nitrous and common air
+continues much longer when the process is made in quicksilver, than when
+it is made in water, and the diminution, as I have also observed; is by
+no means so great.</p>
+
+<p>I was confirmed in this opinion when I put a bit of volatile alkaline
+salt into the jar of quicksilver in which I made the mixture of nitrous
+and common air. In these circumstances, the vessel being previously
+filled with the alkaline fumes, the acid immediately joined them, formed
+the white clouds above mentioned,<span class='pagenum'><a name="Page_210" id="Page_210">[Pg 210]</a></span> and the diminution proceeded almost
+as far as when the process was made in water. That it did not proceed
+quite so far, I attribute chiefly to the small quantity of calx formed
+by the slight solution of mercury with the acid fumes not being able to
+absorb all the fixed air that is precipitated from the common air by the
+phlogiston.</p>
+
+<p>In part, also, it may be owing to the small quantify of surface in the
+quicksilver in the vessels that I made use of; in consequence of which
+the acid fumes could act upon it only in a slow succession, so that part
+of them, as well as of the fixed air, had an opportunity of forming
+another union with the diminished air.</p>
+
+<p>This, as I have observed before, was so much the case when the process
+was made in quicksilver, without any volatile alkali, that when water
+was admitted to it, after some time, it was not capable of dissolving
+that union, tho' it would not have taken place if the process had been
+in water from the first.</p>
+
+<p>In diversifying this experiment, I found that it appeared to very great
+advantage when I suspended a piece of volatile salt in the common air,
+previous to the admission of nitrous<span class='pagenum'><a name="Page_211" id="Page_211">[Pg 211]</a></span> air to it, inclosing it in a bit
+of gauze, muslin, or a small net of wire. For, presently after the
+redness of the mixture begins to go off, the white cloud, like snow,
+begins to descend from the salt, as if a white powder was shaken out of
+the bag that contains it. This white cloud presently fills the whole
+vessel, and the appearance will last about five minutes.</p>
+
+<p>If the salt be not put to the mixture of these two kinds of air till it
+has perfectly recovered its transparency, the effervescence being
+completely over, no white cloud will be formed; and, what is rather more
+remarkable, there is nothing of this appearance when the salt is put
+into the nitrous air itself. The reason of this must be, that the acid
+of the nitrous air has a nearer affinity with its phlogiston than with
+the volatile alkali; though the phlogiston having a nearer affinity with
+something in the common air, the acid being thereby set loose, will
+unite with the alkaline vapour, if it be at hand to unite with it.</p>
+
+<p>There is also very little, if any white cloud formed upon holding a
+piece of the volatile salt within the mouth of a phial containing
+smoking spirit of nitre. Also when I threw the focus of a burning mirror
+upon some sal ammoniac in nitrous air, and filled the whole<span class='pagenum'><a name="Page_212" id="Page_212">[Pg 212]</a></span> vessel with
+white fumes which arose from it, they were soon dispersed, and the air
+was neither diminished nor altered.</p>
+
+<p>I was now fully convinced, that the white cloud which I casually
+observed, in the first of these experiments, was occasioned by the
+volatile alkali emitted from the water, which was in a slight degree
+putrid; and that the warming, and agitation of the vessels, had promoted
+the emission of the putrid, or alkaline effluvium.</p>
+
+<p>I could not perceive that the diminution of common air by the mixture of
+nitrous air was sensibly increased by the presence of the volatile
+alkali. It is possible, however, that, by assisting the water to take up
+the acid, something less of it may be incorporated with the remaining
+diminished air than would otherwise have been; but I did not give much
+attention to this circumstance.</p>
+
+<p>When the phial in which I put the alkaline salts contained any kind of
+noxious air, the opening of it in nitrous air was not followed by any
+thing of the appearance above mentioned. This was the case with
+inflammable air. But when, after agitating the inflammable air in water,
+I had brought it to a state in which it<span class='pagenum'><a name="Page_213" id="Page_213">[Pg 213]</a></span> was diminished a little by the
+mixture of nitrous air, the cloudy appearance was in the same
+proportion; so that this appearance seems to be equally a test of the
+fitness of air for respiration, with the redness which attends the
+mixture of it with nitrous air only.</p>
+
+<p>Having generally fastened the small bag which contained the volatile
+salt to a piece of brass wire in the preceding experiment, I commonly
+found the end of it corroded, and covered with a blue substance. Also
+the salt itself, and sometimes the bag was died blue. But finding that
+this was not the case when I used an iron wire in the same
+circumstances, but that it became <i>red</i>, I was satisfied that both the
+metals had been dissolved by the volatile alkali. At first I had a
+suspicion that the blue might have come from the copper, out of which
+the nitrous air had been made. But when the nitrous air was made from
+iron, the appearances were, in all respects, the same.</p>
+
+<p>I have observed, in the preceding section, that if nitrous air be mixed
+with common air in <i>lime-water</i>, the surface of the water, where it is
+contiguous to that mixture, will be covered with an incrustation of
+lime, shewing that some fixed air had been deposited in the process. It
+is remarkable, however, as I there also just<span class='pagenum'><a name="Page_214" id="Page_214">[Pg 214]</a></span> mentioned, that this is
+the case when nitrous air alone is put to a vessel of lime-water, after
+it has been kept in a <i>bladder</i>, or only transferred from one vessel to
+another by a bladder, in the manner described, p. 15. fig. 9.</p>
+
+<p>As I had used the same bladder for transferring various kinds of air,
+and among the rest <i>fixed air</i>, I first imagined that this effect might
+have been occasioned by a mixture of this fixed air with the nitrous
+air, and therefore took a fresh bladder; but still the effect was the
+same. To satisfy myself farther, that the bladder had produced this
+effect, I put one into a jar of nitrous air, and after it had continued
+there a day and a night, I found that the nitrous air in this jar,
+though it was transferred in a glass vessel, made lime-water turbid.</p>
+
+<p>Whether there was any thing in the preparation of these bladders that
+occasioned their producing this effect, I cannot tell. They were such as
+I procure from the apothecaries. The thing seems to deserve farther
+examination, as there seems, in this case, to be the peculiar effect of
+fixed air from other causes, or else a production of fixed air from
+materials that have not been supposed to yield it, at least not in
+circumstances similar to these.<span class='pagenum'><a name="Page_215" id="Page_215">[Pg 215]</a></span></p>
+
+<p>As fixed air united to water dissolves iron, I had the curiosity to try
+whether fixed air alone would do it; and as nitrous air is of an <i>acid</i>
+nature, as well as fixed air, I, at the same time, exposed a large
+surface of iron to both the kinds; first filling two eight ounce phials
+with nails, and then with quicksilver, and after that displacing the
+quicksilver in one of the phials by fixed air, and in the other by
+nitrous air; then inverting them, and leaving them with their mouths
+immersed in basons of quicksilver.</p>
+
+<p>In these circumstances the two phials stood about two months, when no
+sensible change at all was produced in the fixed air, or in the iron
+which had been exposed to it, but a most remarkable, and most unexpected
+change was made in the nitrous air; and in pursuing the experiment, it
+was transformed into a species of air, with properties which, at the
+time of my first publication on this subject, I should not have
+hesitated to pronounce impossible, viz. air in which a candle burns
+quite naturally and freely, and which is yet in the highest degree
+noxious to animals, insomuch that they die the moment they are put into
+it; whereas, in general, animals live with little sensible inconvenience
+in air in which candles have burned out. Such, however, is nitrous air,
+after it has been long exposed to a large surface of iron.<span class='pagenum'><a name="Page_216" id="Page_216">[Pg 216]</a></span></p>
+
+<p>It is not less extraordinary, that a still longer continuance of nitrous
+air in these circumstances (but <i>how long</i> depends upon too many, and
+too minute circumstances to be ascertained with exactness) makes it not
+only to admit a candle to burn in it, but enables it to burn with an
+<i>enlarged flame</i>, by another flame (extending every where to an equal
+distance from that of the candle, and often plainly distinguishable from
+it) adhering to it. Sometimes I have perceived the flame of the candle,
+in these circumstances, to be twice as large as it is naturally, and
+sometimes not less than five or six times larger; and yet without any
+thing like an <i>explosion</i>, as in the firing of the weakest inflammable
+air.</p>
+
+<p>Nor is the farther progress in the transmutation of nitrous air, in
+these circumstances, less remarkable. For when it has been brought to
+the state last mentioned, the agitation of it in fresh water almost
+instantly takes off that peculiar kind of inflammability, so that it
+extinguishes a candle, retaining its noxious quality. It also retains
+its power of diminishing common air in a very great degree.</p>
+
+<p>But this noxious quality, like the noxious quality of all other kinds of
+air that will bear agitation in water, is taken out of it by this
+operation, continued about five minutes; in<span class='pagenum'><a name="Page_217" id="Page_217">[Pg 217]</a></span> which process it suffers a
+farther and very considerable diminution. It is then itself diminished
+by fresh nitrous air, and animals live in it very well, about as well as
+in air in which candles have burned out.</p>
+
+<p>Lastly, One quantity of nitrous air, which had been exposed to iron in
+quicksilver, from December 18 to January 20, and which happened to stand
+in water till January 31 (the iron still continuing in the phial) was
+fired with an explosion, exactly like a weak inflammable air. At the
+same time another quantity of nitrous air, which had likewise been
+exposed to iron, standing in quicksilver, till about the same time, and
+had then stood in water only, without iron, only admitted a candle to
+burn in it with an enlarged flame, as in the cases above mentioned. But
+whether the difference I have mentioned in the circumstances of these
+experiments contributed to this difference in the result, I cannot tell.</p>
+
+<p>Nitrous air treated in the manner above mentioned is diminished about
+one fourth by standing in quicksilver; and water admitted to it will
+absorb about half the remainder; but if water only, and no quicksilver,
+be used from the beginning, the nitrous air will be diminished much
+faster and farther; so that not more than one<span class='pagenum'><a name="Page_218" id="Page_218">[Pg 218]</a></span> fourth, one sixth, or one
+tenth of the original quantity will remain. But I do not know that there
+is any difference in the constitution of the air which remains in these
+two cases.</p>
+
+<p>The water which has imbibed this nitrous air exposed to iron is
+remarkably green, also the phial containing it becomes deeply, and, I
+believe, indelibly tinged with green; and if the water be put into
+another vessel, it presently deposits a considerable quantity of matter,
+which when dry appears to be the earth or ochre of iron; from which it
+is evident, that the acid of the nitrous air dissolves the iron; while
+the phlogiston, being set loose, diminishes nitrous air, as in the
+process of the iron filings and brimstone.</p>
+
+<p>Upon this hint, instead of using <i>iron</i>, I introduced a pot of <i>liver of
+sulphur</i> into a jar of nitrous air, and presently found, that what I had
+before done by means of iron in six weeks, or two months, I could do by
+liver of sulphur (in consequence, no doubt, of its giving its phlogiston
+more freely) in less than twenty-four hours, especially when the process
+was kept warm.</p>
+
+<p>It is remarkable, however, that if the process with liver of sulphur be
+suffered to proceed,<span class='pagenum'><a name="Page_219" id="Page_219">[Pg 219]</a></span> the nitrous air will be diminished much farther.
+At one time not more than one twentieth of the original quantity
+remained, and how much farther it right have been diminished, I cannot
+tell. In this great diminution, it does not admit a candle to burn in it
+at all; and I generally found this to be the case whenever the
+diminution had proceeded beyond three fourths of the original
+quantity<a name="FNanchor_13_13" id="FNanchor_13_13"></a><a href="#Footnote_13_13" class="fnanchor">[13]</a>.</p>
+
+<p>It is something remarkable, that though the diminution of nitrous air by
+iron filings and brimstone very much resembles the diminution of it by
+iron only, or by liver of sulphur, yet the iron filings and brimstone
+never bring it to such a state as that a candle will burn in it; and
+also that, after this process, it is never capable of diminishing common
+air. But when it is considered that these properties are destroyed by
+agitation in water, this difference in the result of processes, in other
+respects similar, will appear less extraordinary; and they agree in
+this, that long agitation in water makes both these kinds of nitrous air
+equally fit for respiration, being equally diminished by fresh nitrous
+air. It is possible that there would have been<span class='pagenum'><a name="Page_220" id="Page_220">[Pg 220]</a></span> a more exact agreement
+in the result of these processes, if they had been made in equal degrees
+of <i>heat</i>; but the process with iron was made in the usual temperature
+of the atmosphere, and that with liver of sulphur generally near a fire.</p>
+
+<p>It may clearly, I think, be inferred from these experiments, that all
+the difference between fresh nitrous air, that state of it in which it
+is partially inflammable, or wholly so, that in which it again
+extinguishes candles, and that in which it finally becomes fit for
+respiration, depends upon some difference in the <i>mode of the
+combination</i> of its acid with phlogiston, or on the <i>proportion</i> between
+these two ingredients in its composition; and it is not improbable but
+that, by a little more attention to these experiments, the whole mystery
+of this proportion and combination may be explained.</p>
+
+<p>I must not omit to observe that there was something peculiar in the
+result of the first experiment which I made with nitrous air exposed to
+iron; which was that, without any agitation in water, it was diminished
+by fresh nitrous air, and that a candle burned in it quite naturally. To
+what this difference was owing I cannot tell. This air, indeed, had been
+exposed to the iron a week or two longer than in<span class='pagenum'><a name="Page_221" id="Page_221">[Pg 221]</a></span> any of the other
+cases, but I do not imagine that this circumstance could have produced
+that difference.</p>
+
+<p>When the process is in water with iron, the time in which the diminution
+is accomplished is exceedingly various; being sometimes completed in a
+few days, whereas at other times it has required a week or a fortnight.
+Some kinds of iron also produced this effect much sooner than others,
+but on what circumstances this difference depends I do not know. What
+are the varieties in the result of this experiment when it is made in
+quicksilver I cannot tell, because, on account of its requiring more
+time, I have not repeated it so often; but I once found that nitrous air
+was not sensibly changed by having been exposed to iron in quicksilver
+nine days; whereas in water a very considerable alteration was always
+made in much less than half that time.</p>
+
+<p>It may just deserve to be mentioned, that nitrous air extremely rarified
+in an air-pump dissolves iron, and is diminished by it as much as when
+it is in its native state of condensation.</p>
+
+<p>It is something remarkable, though I never attended to it particularly
+before I made these last experiments, and it may tend to throw some<span class='pagenum'><a name="Page_222" id="Page_222">[Pg 222]</a></span>
+light upon them, that when a candle is extinguished, as it never fails
+to be, in nitrous air, the flame seems to be a little enlarged at its
+edges, by another bluish flame added to it, just before its extinction.</p>
+
+<p>It is proper to observe in this place, that the electric spark taken in
+nitrous air diminishes it to one fourth of its original quantity, which
+is about the quantity of its diminution by iron filings and brimstone,
+and also by liver of sulphur without heat. The air is also brought by
+electricity to the same state as it is by iron filings and brimstone,
+not diminishing common air. If the electric spark be taken in it when it
+is confined by water tinged with archil, it is presently changed from
+blue to red, and that to a very great degree.</p>
+
+<p>When the iron nails or wires, which I have used to diminish nitrous air,
+had done their office, I laid them aside, not suspecting that they could
+be of any other philosophical use; but after having lain exposed to the
+open air almost a fortnight; having, for some other purpose, put some of
+them into a vessel containing common air, standing inverted, and
+immersed in water, I was surprized to observe that the air in which they
+were confined was diminished. The diminution proceeded so fast,<span class='pagenum'><a name="Page_223" id="Page_223">[Pg 223]</a></span> that
+the process was completed in about twenty-four hours; for in that time
+the air was diminished about one fifth, so that it made no effervescence
+with nitrous air, and was, therefore, no doubt, highly noxious, like air
+diminished by any other process.</p>
+
+<p>This experiment I have repeated a great number of times, with the same
+phials, filled with nails or wires that have been suffered to rust in
+nitrous air, but their power of diminishing common air grows less and
+less continually. How long it will be before it is quite exhausted I
+cannot tell. This diminution of air I conclude must arise from the
+phlogiston, either of the nitrous air or the iron, being some way
+entangled in the rust, in which the wires were encrusted, and afterwards
+getting loose from it.</p>
+
+<p>To the experiments upon iron filings and brimstone in nitrous air, I
+must add, that when a pot full of this mixture had absorbed as much as
+it could of a jar of nitrous air (which is about three fourths of the
+whole) I put fresh nitrous air to it, and it continued to absorb, till
+three or four jars full of it disappeared; but the absorption was
+exceedingly slow at the last. Also when I drew this pot through the
+water, and admitted fresh nitrous air to it, it absorbed another<span class='pagenum'><a name="Page_224" id="Page_224">[Pg 224]</a></span> jar
+full, and then ceased. But when I scraped off the outer surface of this
+mixture, which had been so long exposed to the nitrous air, the
+remainder absorbed more of the air.</p>
+
+<p>When I took the top of the mixture which I had scraped off and threw
+upon it the focus of a burning-glass, the air in which it was confined
+was diminished, and became quite noxious; yet when I endeavoured to get
+air from this matter in a jar full of quicksilver, I was able to procure
+little or nothing.</p>
+
+<p>It is not a little remarkable that nitrous air diminished by iron
+filings and brimstone, which is about one fourth, cannot, by agitation
+in water, be diminished much farther; whereas pure nitrous air may, by
+the same process, be diminished to one twentieth of its whole bulk, and
+perhaps much more. This is similar to the effect of the same mixture,
+and of phlogiston in other cases, on fixed air; for it so far changes
+its constitution, that it is afterwards incapable of mixing with water.
+It is similar also to the effect of phlogiston in acid air, which of
+itself is almost instantly absorbed by water; but by this addition it is
+first converted into inflammable air, which does not readily mix with
+water, and which, by long agitation<span class='pagenum'><a name="Page_225" id="Page_225">[Pg 225]</a></span> in water, becomes of another
+constitution, still less miscible with water.</p>
+
+<p>I shall close this section with a few other observations of a
+miscellaneous nature.</p>
+
+<p>Nitrous air is as much diminished both by iron filings, and also by
+liver of sulphur, when confined in quicksilver, as when it is exposed to
+water.</p>
+
+<p>Distilled water tinged blue with the juice of turnsole becomes red on
+being impregnated with nitrous air; but by being exposed a week or a
+fortnight to the common atmosphere, in open and shallow vessels, it
+recovers its blue colour; though, in that time, the greater part of the
+water will be evaporated. This shews that in time nitrous air escapes
+from the water with which it is combined, just as fixed air does, though
+by no means so readily<a name="FNanchor_14_14" id="FNanchor_14_14"></a><a href="#Footnote_14_14" class="fnanchor">[14]</a>.</p>
+
+<p>Having dissolved silver, copper, and iron in equal quantities of spirit
+of nitre diluted with water, the quantities of nitrous air produced from
+them were in the following proportion; from iron 8, from copper 6-1/4,
+from silver 6. In<span class='pagenum'><a name="Page_226" id="Page_226">[Pg 226]</a></span> about the same proportion also it was necessary to
+mix water with the spirit of nitre in each case, in order to make it
+dissolve these metals with equal rapidity, silver requiring the least
+water, and iron the most.</p>
+
+<p>Phosphorus gave no light in nitrous air, and did not take away from its
+power of diminishing common air; only when the redness of the mixture
+went off, the vessel in which it was made was filled with white fumes,
+as if there had been some volatile alkali in it. The phosphorus itself
+was unchanged.</p>
+
+<p>There is something remarkable in the effect of nitrous air on <i>insects</i>
+that are put into it. I observed before that this kind of air is as
+noxious as any whatever, a mouse dying the moment it is put into it; but
+frogs and snails (and therefore, probably, other animals whose
+respiration is not frequent) will bear being exposed to it a
+considerable time, though they die at length. A frog put into nitrous
+air struggled much for two or three minutes, and moved now and then for
+a quarter of an hour, after which it was taken out, but did not recover.
+<i>Wasps</i> always died the moment they were put into the nitrous air. I
+could never observe that they made the least motion in it, nor could
+they be recovered to life afterwards.<span class='pagenum'><a name="Page_227" id="Page_227">[Pg 227]</a></span> This was also the case in general
+with <i>spiders</i>, <i>flies</i>, and <i>butterflies</i>. Sometimes, however, spiders
+would recover after being exposed about a minute to this kind of air.</p>
+
+<p>Considering how fatal nitrous air is to insects, and likewise its great
+antiseptic power, I conceived that considerable use might be made of it
+in medicine, especially in the form of <i>clysters</i>, in which fixed air
+had been applied with some success; and in order to try whether the
+bowels of an animal would bear the injection of it, I contrived, with
+the help of Mr. Hey, to convey a quantity of it up the anus of a dog.
+But he gave manifest signs of uneasiness, as long as he retained it,
+which was a considerable time, though in a few hours afterwards he was
+as lively as ever, and seemed to have suffered nothing from the
+operation.</p>
+
+<p>Perhaps if nitrous air was diluted either with common air, or fixed air,
+the bowels might bear it better, and still it might be destructive to
+<i>worms</i> of all kinds, and be of use to check or correct putrefaction in
+the intestinal canal, or other parts of the system. I repeat it once
+more that, being no physician, I run no risk by such proposals as these;
+and I cannot help flattering myself that, in time, very great medicinal
+use will be made of the application<span class='pagenum'><a name="Page_228" id="Page_228">[Pg 228]</a></span> of these different kinds of air to
+the animal system. Let ingenious physicians attend to this subject, and
+endeavour to lay hold of the new <i>handle</i> which is now presented them,
+before it be seized by rash empiricks; who, by an indiscriminate and
+injudicious application, often ruin the credit of things and processes
+which might otherwise make an useful addition to the <i>materia</i> and <i>ars
+medica</i>.</p>
+
+<p>In the first publication of my papers, having experienced the remarkable
+antiseptic power of nitrous air, I proposed an attempt to preserve
+anatomical preparations, &amp;c. by means of it; but Mr. Hey, who made the
+trial, found that, after some months, various animal substances were
+shriveled, and did not preserve their natural forms in this kind of
+air.</p>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_13_13" id="Footnote_13_13"></a><a href="#FNanchor_13_13"><span class="label">[13]</span></a> The result of several of these experiments I had the
+pleasure of trying in the presence of the celebrated Mr. De Luc of
+Geneva, when he was upon a visit to Lord Shelburne in Wiltshire.</p></div>
+
+<div class="footnote"><p><a name="Footnote_14_14" id="Footnote_14_14"></a><a href="#FNanchor_14_14"><span class="label">[14]</span></a> I have not repeated this experiment with that variation of
+circumstances which an attention to Mr. Bewley's observation will
+suggest.</p></div>
+</div>
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_229" id="Page_229">[Pg 229]</a></span></p>
+<h2>SECTION IV.</h2>
+
+<h3><i>Of <span class="smcap">Marine Acid Air</span>.</i></h3>
+
+
+<p>In my former experiments on this species of air I procured it from
+spirit of salt, but I have since hit upon a much less expensive method
+of getting it, by having recourse to the process by which the spirit of
+salt is itself originally made. For this purpose I fill a small phial
+with common salt, pour upon it a small quantity of concentrated oil of
+vitriol, and receive the fumes emitted by it in a vessel previously
+filled with quicksilver, and standing in a bason of quicksilver, in
+which it appears in the form of a perfectly <i>transparent air</i>, being
+precisely the same thing with that which I had before expelled from the
+spirit of salt.</p>
+
+<p>This method of procuring acid air is the more convenient, as a phial,
+once prepared in this manner, will suffice, for common experiments, many
+weeks; especially if a little more oil of vitriol be occasionally put to
+it. It only requires a little more heat at the last than at the first.
+Indeed, at the first, the heat of a person's hand will often be
+sufficient to make it<span class='pagenum'><a name="Page_230" id="Page_230">[Pg 230]</a></span> throw out the vapour. In warm weather it will
+even keep smoking many days without the application of any other heat.</p>
+
+<p>On this account, it should be placed where there are no instruments, or
+any thing of metal, that can be corroded by this acid vapour. It is from
+dear-bought experience that I give this advice. It may easily be
+perceived when this phial is throwing out this acid vapour, as it always
+appears, in the open air, in the form of a light cloud; owing, I
+suppose, to the acid attracting to itself, and uniting with, the
+moisture that is in the common atmosphere.</p>
+
+<p>By this process I even made a stronger spirit of salt than can be
+procured in any other way. For having a little water in the vessel which
+contains the quicksilver, it imbibes the acid vapour, and at length
+becomes truly saturated with it. Having, in this manner, impregnated
+pure water with acid air, I could afterwards expel the same air from it,
+as from common spirit of salt.</p>
+
+<p>I observed before that this acid vapour, or air, has a strong affinity
+with <i>phlogiston</i>, so that it decomposes many substances which contain
+it, and with them forms a permanently inflammable air, no more liable to
+be imbibed<span class='pagenum'><a name="Page_231" id="Page_231">[Pg 231]</a></span> by water than inflammable air procured by any other process,
+being in fact the very same thing; and that, in some cases, it even
+dislodges spirit of nitre and oil of vitriol, which in general appear to
+be stronger acids than itself. I have since observed that, by giving it
+more time, it will extract phlogiston from substances from which I at
+first concluded that it was not able to do it, as from dry wood, crusts
+of bread not burnt, dry flesh, and what is more extraordinary from
+flints. As there was something peculiar to itself in the process or
+result of each of these experiments, it may not be improper to mention
+them distinctly.</p>
+
+<p>Pieces of dry <i>cork wood</i> being put to the acid air, a small quantity
+remained not imbibed by water, and was inflammable.</p>
+
+<p>Very dry pieces of <i>oak</i>, being exposed to this air a day and a night,
+after imbibing a considerable quantity of it, produced air which was
+inflammable indeed, but in the slightest degree imaginable. It seemed to
+be very nearly in the state of common air.</p>
+
+<p>A piece of <i>ivory</i> imbibed the acid vapour very slowly. In a day and a
+night, however, about half an ounce measure of permanent air was
+produced, and it was pretty strongly inflammable.<span class='pagenum'><a name="Page_232" id="Page_232">[Pg 232]</a></span> The ivory was not
+discoloured, but was rendered superficially soft, and clammy, tasting
+very acid.</p>
+
+<p>Pieces of <i>beef</i>, roasted, and made quite dry, but not burnt, absorbed
+the acid vapour slowly; and when it had continued in this situation all
+night, from five ounce measures of the air, half a measure was
+permanent, and pretty strongly inflammable. This experiment succeeded a
+second time exactly in the same manner; but when I used pieces of white
+dry <i>chicken-flesh</i> though I allowed the same time, and in other
+respects the process seemed to go on in the same manner, I could not
+perceive that any part of the remaining air was inflammable.</p>
+
+<p>Some pieces of a whitish kind of <i>flint</i>, being put into a quantity of
+acid air, imbibed but a very little of it in a day and a night; but of
+2-1/2 ounce measures of it, about half a measure remained unabsorbed by
+water, and this was strongly inflammable, taking fire just like an equal
+mixture of inflammable and common air. At another time, however, I could
+not procure any inflammable air by this means, but to what circumstance
+these different results were owing I cannot tell.<span class='pagenum'><a name="Page_233" id="Page_233">[Pg 233]</a></span></p>
+
+<p>That inflammable air is produced from <i>charcoal</i> in acid air I observed
+before. I have since found that it may likewise be procured from <i>pit
+coal</i>, without being charred.</p>
+
+<p>Inflammable air I had also observed to arise from the exposure of spirit
+of wine, and various <i>oily</i> substances, to the vapour of spirit of salt.
+I have since made others of a similar nature, and as peculiar
+circumstances attended some of these experiments, I shall recite them
+more at large.</p>
+
+<p><i>Essential oil of mint</i> absorbed this air pretty fast, and presently
+became of a deep brown colour. When it was taken out of this air it was
+of the consistence of treacle, and sunk in water, smelling differently
+from what it did before; but still the smell of the mint was
+predominant. Very little or none of the air was fixed, so as to become
+inflammable; but more time would probably have produced this effect.</p>
+
+<p><i>Oil of turpentine</i> was also much thickened, and became of a deep brown
+colour, by being saturated with acid air.</p>
+
+<p><i>Ether</i> absorbed acid air very fast, and became first of a turbid white,
+and then of a yellow<span class='pagenum'><a name="Page_234" id="Page_234">[Pg 234]</a></span> and brown colour. In one night a considerable
+quantity of permanent air was produced, and it was strongly inflammable.</p>
+
+<p>Having, at one time, fully saturated a quantity of ether with acid air,
+I admitted bubbles of common air to it, through the quicksilver, by
+which it was confined, and observed that white fumes were made in it, at
+the entrance of every bubble, for a considerable time.</p>
+
+<p>At another time, having fully saturated a small quantity of ether with
+acid air, and having left the phial in which it was contained nearly
+full of the air, and inverted, it was by some accident overturned; when,
+instantly, the whole room was filled with a visible fume, like a white
+cloud, which had very much the smell of ether, but peculiarly offensive.
+Opening the door and window of the room, this light cloud filled a long
+passage, and another room. In the mean time the ether was seemingly all
+vanished, but some time after the surface of the quicksilver in which
+the experiment had been made was covered with a liquor that tasted very
+acid; arising, probably, from the moisture in the atmosphere attracted
+by the acid vapour with which the ether had been impregnated.<span class='pagenum'><a name="Page_235" id="Page_235">[Pg 235]</a></span></p>
+
+<p>This visible cloud I attribute to the union of the moisture in the
+atmosphere with the compound of the acid air and ether. I have since
+saturated other quantities of ether with acid air, and found it to be
+exceedingly volatile, and inflammable. Its exhalation was also visible,
+but not in so great a degree as in the case above mentioned.</p>
+
+<p><i>Camphor</i> was presently reduced into a fluid state by imbibing acid air,
+but there seemed to be something of a whitish sediment in it. After
+continuing two days in this situation I admitted water to it;
+immediately upon which the camphor resumed its former solid state, and,
+to appearance, was the very same substance that it had been before; but
+the taste of it was acid, and a very small part of the air was
+permanent, and slightly inflammable.</p>
+
+<p>The acid air seemed to make no impression upon a piece of Derbyshire
+<i>spar</i>, of a very dark colour, and which, therefore, seemed to contain a
+good deal of phlogiston.</p>
+
+<p>As the acid air has so near an affinity with phlogiston, I expected that
+the fumes of <i>liver of sulphur</i>, which chemists agree to be phlogistic,
+would have united with it, so as to form inflammable air; but I was
+disappointed in that expectation.<span class='pagenum'><a name="Page_236" id="Page_236">[Pg 236]</a></span> This substance imbibed half of the
+acid air to which it was introduced: one fourth of the remainder, after
+standing one day in quicksilver, was imbibed by water, and what was left
+extinguished a candle. This experiment, however, seems to prove that
+acid air and phlogiston may form a permanent kind of air that is not
+inflammable. Perhaps it may be air in such a state as common air loaded
+with phlogiston, and from which the fixed air has been precipitated. Or
+rather, it may be the same thing with inflammable air, that has lost its
+inflammability by long standing in water. It well deserves a farther
+examination.</p>
+
+<p>The following experiments are those in which the <i>stronger acids</i> were
+made use of, and therefore they may assist us farther to ascertain their
+affinities with certain substances, with respect to this marine acid in
+the form of air.</p>
+
+<p>I put a quantity of strong concentrated <i>oil of vitriol</i> to acid air,
+but it was not at all affected by it in a day and a night. In order to
+try whether it would not have more power in a more condensed state, I
+compressed it with an additional atmosphere; but upon taking off this
+pressure, the air expanded again, and appeared to be not at all
+diminished. I also put a quantity of strong <i>spirit of nitre</i> to it
+without any<span class='pagenum'><a name="Page_237" id="Page_237">[Pg 237]</a></span> sensible effect. We may conclude, therefore, that the
+marine acid, in this form of air, is not able to dislodge the other
+acids from their union with water.</p>
+
+<p><i>Blue vitriol</i>, which is formed by the union of the vitriolic acid with
+copper, turned to a dark green the moment that it was put to the acid
+air, which it absorbed, though slowly. Two pieces, as big as small nuts,
+absorbed three ounce measures of the air in about half an hour. The
+green colour was very superficial; for it was easily wiped or washed
+off.</p>
+
+<p><i>Green copperas</i> turned to a deeper green upon being put into acid air,
+which it absorbed slowly. <i>White copperas</i> absorbed this air very fast,
+and was dissolved in it.</p>
+
+<p><i>Sal ammoniac</i>, being the union of spirit of salt with volatile alkali,
+was no more affected with the acid air than, as I have observed before,
+common salt was.</p>
+
+<p>I also introduced to the acid air various other substances, without any
+particular expectation; and it may be worth while to give an account of
+the results, that the reader may draw from them such conclusions as he
+shall think reasonable.<span class='pagenum'><a name="Page_238" id="Page_238">[Pg 238]</a></span></p>
+
+<p><i>Borax</i> absorbed acid air about as fast as blue vitriol, but without any
+thing else that was observable.</p>
+
+<p>Fine white <i>sugar</i> absorbed this air slowly, was thoroughly penetrated
+with it, became of a deep brown colour, and acquired a smell that was
+peculiarly pungent.</p>
+
+<p>A piece of <i>quick lime</i> being put to about twelve or fourteen ounce
+measures of acid air, and continuing in that situation about two days,
+there remained one ounce measure of air that was not absorbed by water,
+and it was very strongly inflammable, as much so as a mixture of half
+inflammable and half common air. Very particular care was taken that no
+common air mixed with the acid air in this process. At another time,
+from about half the quantity of acid air above mentioned, with much less
+quick-lime, and in the space of one day, I got half an ounce measure of
+air that was inflammable in a slight degree only. This experiment proves
+that some part of the phlogiston which escapes from the fuel, in contact
+with which the lime is burned, adheres to it. But I am very far from
+thinking that the causticity of quick-lime is at all owing to this
+circumstance.<span class='pagenum'><a name="Page_239" id="Page_239">[Pg 239]</a></span></p>
+
+<p>I have made a few more experiments on the mixture of acid air with
+<i>other kinds of air</i>, and think that it may be worth while to mention
+them, though nothing of consequence, at least nothing but negative
+conclusions, can be drawn from them.</p>
+
+<p>A quantity of common air saturated with nitrous air was put to a
+quantity of acid air, and they continued together all night, without any
+sensible effect. The quantity of both remained the same, and water being
+admitted to them, it absorbed all the acid air, and left the other just
+as before.</p>
+
+<p>A mixture of two thirds of air diminished by iron filings and brimstone,
+and one third acid air, were mixed together, and left to stand four
+weeks in quicksilver. But when the mixture was examined, water presently
+imbibed all the acid air, and the diminished air was found to be just
+the same that it was before. I had imagined that the acid air might have
+united with the phlogiston with which the diminished air was
+overcharged, so as to render it wholsome; and I had read an account of
+the stench arising from putrid bodies being corrected by acid fumes.<span class='pagenum'><a name="Page_240" id="Page_240">[Pg 240]</a></span></p>
+
+<p>The remaining experiments, in which the acid air was principally
+concerned, are of a miscellaneous nature.</p>
+
+<p>I put a piece of dry <i>ice</i> to a quantity of acid air (as was observed in
+the section concerning <i>alkaline</i> air) taking it with a forceps, which,
+as well as the air itself, and the quicksilver by which it had been
+confined; had been exposed to the open air for an hour, in a pretty
+strong frost. The moment it touched the air it was dissolved as fast as
+it would have been by being thrown into a hot fire, and the air was
+presently imbibed. Putting fresh pieces of ice to that which was
+dissolved before, they were also dissolved immediately, and the water
+thus procured did not freeze again, though it was exposed a whole night,
+in a very intense frost.</p>
+
+<p>Flies and spiders die in acid air, but not so quickly as in nitrous air.
+This surprized me very much; as I had imagined that nothing could be
+more speedily fatal to all animal life than this pure acid vapour.</p>
+
+<p>As inflammable air, I have observed, fires at one explosion in the
+vapour of smoking spirit of nitre, just like an equal mixture of
+inflammable and common air, I thought it was possible that the fume
+which naturally rises from common<span class='pagenum'><a name="Page_241" id="Page_241">[Pg 241]</a></span> spirit of salt might have the same
+effect, but it had not. For this purpose I treated the spirit of salt,
+as I had before done the smoking spirit of nitre; first filling a phial
+with it, then inverting it in a vessel containing a quantity of the same
+acid; and having thrown the inflammable air into it, and thereby driven
+out all the acid, turning it with its mouth upwards, and immediately
+applying a candle to it.</p>
+
+<p>Acid air not being so manageable as most of the other kinds of air, I
+had recourse to the following peculiar method, in order to ascertain its
+<i>specific gravity</i>. Having filled an eight ounce phial with this air,
+and corked it up, I weighed it very accurately; and then, taking out the
+cork, I blew very strongly into it with a pair of bellows, that the
+common air might take place of the acid; and after this I weighed it
+again, together with the cork, but I could not perceive the least
+difference in the weight. I conclude, however, from this experiment,
+that the acid air is heavier than the common air, because the mouth of
+the phial and the inside of it were evidently moistened by the water
+which the acid vapour had attracted from the air, which moisture must
+have added to the weight of the phial.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_242" id="Page_242">[Pg 242]</a></span></p>
+<h2>SECTION V.</h2>
+
+<h3><i>Of <span class="smcap">Inflammable Air</span>.</i></h3>
+
+
+<p>It will have appeared from my former experiments, that inflammable air
+consists chiefly, if not wholly, of the union of an acid vapour with
+phlogiston; that as much of the phlogiston as contributes to make air
+inflammable is imbibed by the water in which it is agitated; that in
+this process it soon becomes fit for respiration, and by the continuance
+of it comes at length to extinguish flame. These observations, and
+others which I have made upon this kind of air, have been confirmed by
+my later experiments, especially those in which I have connected
+<i>electrical experiments</i> with those on air.</p>
+
+<p>The electric spark taken in any kind of <i>oil</i> produces inflammable air,
+as I was led to observe in the following manner. Having found, as will
+be mentioned hereafter, that ether doubles the quantity of any kind of
+air to which it is admitted; and being at that time engaged in a course
+of experiments to ascertain the effect of the electric matter on all the
+different kinds of air, I had the curiosity to try what it would do with
+<i>common air</i>, thus increased<span class='pagenum'><a name="Page_243" id="Page_243">[Pg 243]</a></span> by means of ether. The very first spark, I
+observed, increased the quantity of this air very considerably, so that
+I had very soon six or eight times as much as I began with; and whereas
+water imbibes all the ether that is put to any kind of air, and leaves
+it without any visible change, with respect to quantity or quality, this
+air, on the contrary, was not imbibed by water. It was also very little
+diminished by the mixture of nitrous air. From whence it was evident,
+that it had received an addition of some other kind of air, of which it
+now principally consisted.</p>
+
+<p>In order to determine whether this effect was produced by the <i>wire</i>, or
+the <i>cement</i> by which the air was confined (as I thought it possible
+that phlogiston might be discharged from them) I made the experiment in
+a glass syphon, fig. 19, and by that means I contrived to make the
+electric spark pass from quicksilver through the air on which I made the
+experiment, and the effect was the same as before. At one time there
+happened to be a bubble of common air, without any ether, in one part of
+the syphon, and another bubble with ether in another part of it; and it
+was very amusing to observe how the same electric sparks diminished the
+former of these bubbles, and increased the latter.<span class='pagenum'><a name="Page_244" id="Page_244">[Pg 244]</a></span></p>
+
+<p>It being evident that the <i>ether</i> occasioned the difference that was
+observable in these two cases, I next proceeded to take the electric
+spark in a quantity of ether only, without any air whatever; and
+observed that every spark produced a small bubble; and though, while the
+sparks were taken in the ether itself, the generation of air was slow,
+yet when so much air was collected, that the sparks were obliged to pass
+through it, in order, to come to the ether and the quicksilver on which
+it rested, the increase was exceedingly rapid; so that, making the
+experiment in small tubes, as fig. 16, the quicksilver soon receded
+beyond the striking distance. This air, by passing through water, was
+diminished to about one third, and was inflammable.</p>
+
+<p>One quantity of air produced in this manner from ether I suffered to
+stand two days in water, and after that I transferred it several times
+through the water, from one vessel to another, and still found that it
+was very strongly inflammable; so that I have no doubt of its being
+genuine inflammable air, like that which is produced from metals by
+acids, or by any other chemical process.</p>
+
+<p>Air produced from ether, mixed both with common and nitrous air, was
+likewise inflammable;<span class='pagenum'><a name="Page_245" id="Page_245">[Pg 245]</a></span> but in the case of the nitrous air, the original
+quantity bore a very small proportion to the quantity generated.</p>
+
+<p>Concluding that the inflammable matter in this air came from the ether,
+as being of the class of <i>oils</i>, I tried other kinds of oil, as <i>oil of
+olives</i>, <i>oil of turpentine</i>, and <i>essential oil of mint</i>, taking the
+electric spark in them, without any air to begin with, and found that
+inflammable air was produced in this manner from them all. The
+generation of air from oil of turpentine was the quickest, and from the
+oil of olives the slowest in these three cases.</p>
+
+<p>By the same process I got inflammable air from <i>spirit of wine</i>, and
+about as copiously as from the essential oil of mint. This air continued
+in water a whole night, and when it was transferred into another vessel
+was strongly inflammable.</p>
+
+<p>In all these cases the inflammable matter might be supposed to arise
+from the inflammable substances on which the experiments were made. But
+finding that, by the same process I could get inflammable air from the
+<i>volatile spirit of sal ammoniac</i>, I conclude that the phlogiston was in
+part supplied by the electric matter itself. For though, as I have
+observed before,<span class='pagenum'><a name="Page_246" id="Page_246">[Pg 246]</a></span> the alkaline air which is expelled from the spirit of
+sal ammoniac be inflammable, it is so in a very slight degree, and can
+only be perceived to be so when there is a considerable quantity of it.</p>
+
+<p>Endeavouring to procure air from a caustic alkaline liquor, accurately
+made for me by Mr. Lane, and also from spirit of salt, I found that the
+electric spark could not be made visible in either of them; so that they
+must be much more perfect conductors of electricity than water, or other
+fluid substances. This experiment well deserves to be prosecuted.</p>
+
+<p>I observed before that inflammable air, by standing long in water, and
+especially by agitation in water, loses its inflammability; and that in
+the latter case, after passing through a state in which it makes some
+approach to common air (just admitting a candle to burn in it) it comes
+to extinguish a candle. I have since made another observation of this
+kind, which well deserves to be recited. It relates to the inflammable
+air generated from oak the 27th of July 1771, of which I have made
+mention before.</p>
+
+<p>This air I have observed to have been but weakly inflammable some months
+after it was generated, and to have been converted into<span class='pagenum'><a name="Page_247" id="Page_247">[Pg 247]</a></span> pretty good or
+wholesome air by no great degree of agitation in water; but on the 27th
+of March 1773, I found the remainder of it to be exceedingly good air. A
+candle burned in it perfectly well, and it was diminished by nitrous air
+almost as much as common air.</p>
+
+<p>I shall conclude this section with a few miscellaneous observations of
+no great importance.</p>
+
+<p>Inflammable air is not changed by being made to pass many times through
+a red-hot iron tube. It is also no more diminished or changed by the
+fumes of liver of sulphur, or by the electric spark, than I have before
+observed it to have been by a mixture of iron filings and brimstone.
+When the electric spark was taken in it, it was confined by a quantity
+of water tinged blue with the juice of archil, but the colour remained
+unchanged.</p>
+
+<p>I put two <i>wasps</i> into inflammable air, and let them remain there a
+considerable time, one of them near an hour. They presently ceased to
+move, and seemed to be quite dead for about half an hour after they were
+taken into the open air; but then they came to life again, and presently
+after seemed to be as well as ever they had been.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_248" id="Page_248">[Pg 248]</a></span></p>
+<h2>SECTION VI.</h2>
+
+<h3><i>Of <span class="smcap">Fixed Air</span>.</i></h3>
+
+
+<p>The additions I have made to my observations on <i>fixed air</i> are neither
+numerous nor considerable.</p>
+
+<p>The most important of them is a confirmation of my conjecture, that
+fixed air is capable of forming an union with phlogiston, and thereby
+becoming a kind of air that is not miscible with water. I had produced
+this effect before by means of iron filings and brimstone, fermenting in
+this kind of air; but I have since had a much more decisive and elegant
+proof of it by <i>electricity</i>. For after taking a small electric
+explosion, for about an hour, in the space of an inch of fixed air,
+confined in a glass tube one tenth of an inch in diameter, fig. 16, I
+found that when water was admitted to it, only one fourth of the air was
+imbibed. Probably the whole of it would have been rendered immiscible in
+water, if the electrical operation had been continued a sufficient time.
+This air continued several days in water, and was even agitated in water
+without any farther diminution.<span class='pagenum'><a name="Page_249" id="Page_249">[Pg 249]</a></span> It was not, however, common air, for it
+was not diminished by nitrous air.</p>
+
+<p>By means of iron filings and brimstone I have, since my former
+experiments, procured a considerable quantity of this kind of air in a
+method something different from that which I used before. For having
+placed a pot of this mixture under a receiver, and exhausted it with a
+pump of Mr. Smeaton's construction, I filled it with fixed air, and then
+left it plunged under water; so that no common air could have access to
+it. In this manner, and in about a week, there was, as near as I can
+recollect, one sixth, or at least one eighth of the whole converted into
+a permanent air, not imbibed by water.</p>
+
+<p>From this experiment I expected that the same effect would have been
+produced on fixed air by the fumes of <i>liver of sulphur</i>; but I was
+disappointed in that expectation, which surprised me not a little;
+though this corresponds in some measure, to the effect of phlogiston
+exhaled from this substance on acid air. Perhaps more time may be
+requisite for this purpose, for this process was not continued more than
+a day and a night.<span class='pagenum'><a name="Page_250" id="Page_250">[Pg 250]</a></span></p>
+
+<p>Iron filings and brimstone, I have observed, ferment with great heat in
+nitrous air, and I have since observed that this process is attended
+with greater heat in fixed air than in common air.</p>
+
+<p>Though fixed air incorporated with water dissolves iron, fixed air
+without water has no such power, as I observed before. I imagined that,
+if it could have dissolved iron, the phlogiston would have united with
+the air, and have made it immiscible with water, as in the former
+instances; but after being confined in a phial full of nails from the
+15th of December to the 4th of October following, neither the iron nor
+the air appeared to have been affected by their mutual contact.</p>
+
+<p>Having exposed equal quantities of common and fixed air, in equal and
+similar cylindrical glass vessels, to equal degrees of heat, by placing
+them before a fire, and frequently changing their situations, I observed
+that they were expanded exactly alike, and when removed from the fire
+they both recovered their former dimensions.</p>
+
+<p>Having had some small suspicion that liver of sulphur, besides emitting
+phlogiston, might<span class='pagenum'><a name="Page_251" id="Page_251">[Pg 251]</a></span> also yield some fixed air (which is known to be
+contained in the salt of tartar from which it is made) I mixed the two
+ingredients, viz. salt of tartar and brimstone, and putting them into a
+thin phial, and applying the flame of a candle to it, so as to form the
+liver of sulphur, I received the air that came from it in this process
+in a vessel of quicksilver. In this manner I procured a very
+considerable quantity of fixed air, so that I judged it was all
+discharged from the tartar. But though it is possible that a small
+quantity of it may remain in liver of sulphur, when it is made in the
+most perfect manner, it is not probable that it can be expelled without
+heat.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_252" id="Page_252">[Pg 252]</a></span></p>
+<h2>SECTION VII.</h2>
+
+<h3><span class="smcap">Miscellaneous Experiments.</span></h3>
+
+
+<p>1. It is something extraordinary that, though ether, as I found, cannot
+be made to assume the form of air (the vapour arising from it by heat,
+being soon condensed by cold, even in quicksilver) yet that a very small
+quantity of ether put to any kind of air, except the acid, and alkaline,
+which it imbibes, almost instantly doubles the apparent quantity of it;
+but upon passing this air through water, it is presently reduced to its
+original quantity again, with little or no change of quality.</p>
+
+<p>I put about the quantity of half a nut-shell full of ether, inclosed in
+a glass tube, through a body of quicksilver, into an ounce measure of
+common air, confined by quicksilver; upon which it presently began to
+expand, till it occupied the space of two ounce measures. It then
+gradually contracted about one sixth of an ounce measure. Putting more
+ether to it, it again expanded to two ounce measures; but no more
+addition of ether would make it expand any farther. Withdrawing the
+quicksilver, and admitting water to this air, without any agitation,<span class='pagenum'><a name="Page_253" id="Page_253">[Pg 253]</a></span> it
+began to be absorbed; but only about half an ounce measure had
+disappeared after it had stood an hour in the water. But by once passing
+it through water the air was reduced to its original dimensions. Being
+tried by a mixture of nitrous air, it appeared not to be so good as
+fresh air, though the injury it had received was not considerable.</p>
+
+<p>All the phenomena of dilatation and contraction were nearly the same,
+when, instead of common air, I used nitrous air, fixed air, inflammable
+air, or any species of phlogisticated common air. The quantity of each
+of these kinds of air was nearly doubled while they were kept in
+quicksilver, but fixed air was not so much increased as the rest, and
+phlogisticated air less; but after passing through the water, they
+appeared not to have been sensibly changed by the process.</p>
+
+<p>2. Spirit of wine yields no air by means of heat, the vapours being soon
+condensed by cold, like the vapour of water; yet when, in endeavouring
+to procure air from it, I made it boil, and catched the air which had
+rested on the surface of the spirit, and which had been expelled by the
+heat together with the vapour, in a vessel of quicksilver, and
+afterwards admitted acid air to it, the vessel was filled with white
+fumes,<span class='pagenum'><a name="Page_254" id="Page_254">[Pg 254]</a></span> as if there had been a mixture of alkaline air along with it. To
+what this appearance was owing I cannot tell, and indeed I did not
+examine into it.</p>
+
+<p>3. Having been informed by Dr. Small and Mr. Bolton of Birmingham, that
+paper dipped in a solution of copper in spirit of nitre would take fire
+with a moderate heat (a fact which I afterwards found mentioned in the
+Philosophical Transactions) it occurred to me that this would be very
+convenient for experiments relating to <i>ignition</i> in different kinds of
+air; and indeed I found that it was easily fired, either by a burning
+lens, or the approach of red-hot iron on the outside of the phial in
+which it was contained, and that any part of it being once fired, the
+whole was presently reduced to ashes; provided it was previously made
+thoroughly dry, which, however, it is not very easy to do.</p>
+
+<p>With this preparation, I found that this paper burned freely in all
+kinds of air, but not in <i>vacuo</i>, which is also the case with gunpowder;
+and, as I have in effect observed before, all the kinds of air in which
+this paper was burned received an addition to their bulk, which
+consisted partly of nitrous air, from the nitrous precipitate, and
+partly of inflammable air, from the paper. As some of the circumstances<span class='pagenum'><a name="Page_255" id="Page_255">[Pg 255]</a></span>
+attending the ignition of this paper in some of the kinds of air were a
+little remarkable, I shall just recite them.</p>
+
+<p>Firing this paper in <i>inflammable</i> air, which it did without any
+ignition of the inflammable air itself, the quantity increased
+regularly, till the phial in which the process was made was nearly full;
+but then it began to decrease, till one third of the whole quantity
+disappeared.</p>
+
+<p>A piece of this paper being put to three ounce measures of <i>acid</i> air, a
+great part of it presently turned yellow, and the air was reduced to one
+third of the original quantity, at the same time becoming reddish,
+exactly like common air in a phial containing smoking spirit of nitre.
+After this, by the approach of hot iron, I set fire to the paper;
+immediately upon which there was a production of air which more than
+filled the phial. This air appeared, upon examination, to be very little
+different from pure nitrous air. I repeated this experiment with the
+same event.</p>
+
+<p>Paper dipped in a solution of mercury, zinc, or iron, in nitrous acid,
+has, in a small degree, the same property with paper dipped in a
+solution of copper in the same acid.<span class='pagenum'><a name="Page_256" id="Page_256">[Pg 256]</a></span></p>
+
+<p>4. Gunpowder is also fired in all kinds of air, and, in the quantity in
+which I tried it, did not make any sensible change in them, except that
+the common air in which it was fired would not afterwards admit a candle
+to burn in it. In order to try this experiment I half exhausted a
+receiver, and then with a burning-glass fired the gunpowder which had
+been previously put into it. By this means I could fire a greater
+quantity of gunpowder in a small quantity of air, and avoid the hazard
+of blowing up, and breaking my receiver.</p>
+
+<p>I own that I was rather afraid of firing gunpowder in inflammable air,
+but there was no reason for my fear; for it exploded quite freely in
+this air, leaving it, in all respects, just as it was before.</p>
+
+<p>In order to make this experiment, and indeed almost all the experiments
+of firing gunpowder in different kinds of air, I placed the powder upon
+a convenient stand within my receiver, and having carefully exhausted it
+by a pump of Mr. Smeaton's construction, I filled the receiver with any
+kind of air by the apparatus described, p. 19, fig. 14, taking the
+greatest care that the tubes, &amp;c. which conveyed the air should contain
+little or no common air. In the experiment with inflammable air a<span class='pagenum'><a name="Page_257" id="Page_257">[Pg 257]</a></span>
+considerable mixture of common air would have been exceedingly
+hazardous: for, by that assistance, the inflammable air might have
+exploded in such a manner, as to have been dangerous to the operator.
+Indeed, I believe I should not have ventured to have made the experiment
+at all with any other pump besides Mr. Smeaton's.</p>
+
+<p>Sometimes, I filled a glass vessel with quicksilver, and introduced the
+air to it, when it was inverted in a bason of quicksilver. By this means
+I intirely avoided any mixture of common air; but then it was not easy
+to convey the gunpowder into it, in the exact quantity that was
+requisite for my purpose. This, however, was the only method by which I
+could contrive to fire gunpowder in acid or alkaline air, in which it
+exploded just as it did in nitrous or fixed air.</p>
+
+<p>I burned a considerable quantity of gunpowder in an exhausted receiver
+(for it is well known that it will not explode in it) but the air I got
+from it was very inconsiderable, and in these circumstances was
+necessarily mixed with common air. A candle would not burn in it.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_258" id="Page_258">[Pg 258]</a></span></p>
+<h2>SECTION VIII.</h2>
+
+<h3><i><span class="smcap">Queries</span>, <span class="smcap">Speculations</span>, and <span class="smcap">Hints</span>.</i>
+</h3>
+
+<p>I begin to be apprehensive lest, after being considered as a <i>dry
+experimenter</i>, I should pass, with many of my readers, into the opposite
+character of a <i>visionary theorist</i>. A good deal of theory has been
+interspersed in the course of this work, but, not content with this, I
+am now entering upon a long section, which contains nothing else.</p>
+
+<p>The conjectures that I have ventured to advance in the body of the work
+will, I hope, be found to be pretty well supported by facts; but the
+present section will, I acknowledge, contain many <i>random thoughts</i>. I
+have, however, thrown them together by themselves, that readers of less
+imagination, and who care not to advance beyond the regions of plain
+fact, may, if they please, proceed no farther, that their delicacy be
+not offended.</p>
+
+<p>In extenuation of my offence, let it, however, be considered, that
+<i>theory</i> and <i>experiment</i><span class='pagenum'><a name="Page_259" id="Page_259">[Pg 259]</a></span> necessarily go hand in hand, every process
+being intended to ascertain some particular <i>hypothesis</i>, which, in
+fact, is only a conjecture concerning the circumstances or the cause of
+some natural operation; consequently that the boldest and most original
+experimenters are those, who, giving free scope to their imaginations,
+admit the combination of the most distant ideas; and that though many of
+these associations of ideas, will be wild and chimerical, yet that
+others will have the chance of giving rise to the greatest and most
+capital discoveries; such as very cautious, timid, sober, and
+slow-thinking people would never have come at.</p>
+
+<p>Sir Isaac Newton himself, notwithstanding the great advantage which he
+derived from a habit of <i>patient thinking</i>, indulged bold and excentric
+thoughts, of which his Queries at the end of his book of Optics are a
+sufficient evidence. And a quick conception of distant analogies, which
+is the great key to unlock the secret of nature, is by no means
+incompatible with the spirit of <i>perseverance</i>, in investigations
+calculated to ascertain and pursue those analogies.<span class='pagenum'><a name="Page_260" id="Page_260">[Pg 260]</a></span></p>
+
+
+<p>&sect; 1. <i>Speculations concerning the <span class="smcap">constituent</span> <span class="smcap">principles</span> of the
+different kinds of <span class="smcap">air</span>, and the <span class="smcap">constitution</span> and <span class="smcap">origin</span> of the
+<span class="smcap">atmosphere</span>, &amp;c.</i></p>
+
+<p>All the kinds of air that appear to me to be essentially distinct from
+each other are <i>fixed air</i>, <i>acid</i> and <i>alkaline</i>; for these, and
+another principle, called <i>phlogiston</i>, which I have not been able to
+exhibit in the form of <i>air</i>, and which has never yet been exhibited by
+itself in <i>any form</i>, seem to constitute all the kinds of air that I am
+acquainted with.</p>
+
+<p>Acid air and phlogiston constitute an air which either extinguishes
+flame, or is itself inflammable, according, probably, to the quantity of
+phlogiston combined in it, or the mode of combination. When it
+extinguishes flame, it is probably so much charged with the phlogistic
+matter, as to take no more from a burning candle, which must, therefore,
+necessarily go out in it. When it is inflammable, it is probably so much
+charged with phlogiston, that the heat communicated by a burning candle
+makes it immediately separate itself from the other principle with which
+it was united, in which separation <i>heat</i> is produced, as in other cases
+of ignition; the action and reaction, which necessarily attends the
+separation of the constituent principles,<span class='pagenum'><a name="Page_261" id="Page_261">[Pg 261]</a></span> exciting probably a vibratory
+motion in them.</p>
+
+<p>Since inflammable, air, by agitation in water, first comes to lose its
+inflammability, so as to be fit for respiration, and even to admit a
+candle to burn in it, and then comes to extinguish a candle; it seems
+probable that water imbibes a great part of this extraordinary charge of
+phlogiston. And that water <i>can</i> be impregnated with phlogiston, is
+evident from many of my experiments, especially those in which metals
+were calcined over it.</p>
+
+<p>Water having this affinity with phlogiston, it is probable that it
+always contains a considerable portion of it; which phlogiston having a
+stronger affinity with the acid air, which is perhaps the basis of
+common air, may by long agitation be communicated to it, so as to leave
+it over saturated, in consequence of which it will extinguish a candle.</p>
+
+<p>It is possible, however, that inflammable air and air which extinguishes
+a candle may differ from one another in the <i>mode</i> of the combination of
+these two constituent principles, as well as in the proportional
+quantity of each; and by agitation in water, or long standing, that mode
+of combination may change. This we<span class='pagenum'><a name="Page_262" id="Page_262">[Pg 262]</a></span> know to be the case with other
+substances, as with <i>milk</i>, from which, by standing only, <i>cream</i> is
+separated; which by agitation becomes <i>butter</i>. Also many substances,
+being at rest, putrefy, and thereby become quite different from what
+they were before. If this be the case with inflammable air, the water
+may imbibe either of the constituent parts, whenever any proportion of
+it is spontaneously separated from the rest; and should this ever be
+that phlogiston, with which air is but slightly overcharged, as by the
+burning of a candle, it will be recovered to a state in which a candle
+may burn in it again.</p>
+
+<p>It will be observed, however, that it was only in one instance that I
+found that strong inflammable air, in its transition to a state in which
+it extinguishes a candle, would admit a candle to burn in it, and that
+was very faintly; that then the air was far from being pure, as appeared
+by the test of nitrous air; and that it was only from a particular
+quantity of inflammable air which I got from oak, and which had stood a
+long time in water, that I ever got air which was as pure as common air.
+Indeed, it is much more easy to account for the passing of inflammable
+air into a state in which it extinguishes candles, without any
+intermediate state, in which it will admit a candle to burn in it, than
+otherwise. This subject requires and deserves farther investigation.<span class='pagenum'><a name="Page_263" id="Page_263">[Pg 263]</a></span> It
+will also be well worth while to examine what difference the agitation
+of air in natural or artificial <i>sea-water</i> will occasion.</p>
+
+<p>Since acid air and phlogiston make inflammable air, and since
+inflammable air is convertible into air fit for respiration, it seems
+not to be improbable, that these two ingredients are the only essential
+principles of common air. For this change is produced by agitation in
+water only, without the addition of any fixed air, though this kind of
+air, like various other things of a foreign nature, may be combined with
+it.</p>
+
+<p>Considering also what prodigious quantities of inflammable air are
+produced by the burning of small pieces of wood or pit-coal, it may not
+be improbable but that the <i>volcanos</i>, with which there are evident
+traces of almost the whole surface of the earth having been overspread,
+may have been the origin of our atmosphere, as well as (according to the
+opinion of some) of all the solid land.</p>
+
+<p>The superfluous phlogiston of the air, in the state in which it issues
+from volcanos, may have been imbibed by the waters of the sea, which it
+is probable originally covered the surface of the earth, though part of
+it might have united with the acid vapour exhaled from the sea, and<span class='pagenum'><a name="Page_264" id="Page_264">[Pg 264]</a></span> by
+this union have made a considerable and valuable addition to the common
+mass of air; and the remainder of this over-charge of phlogiston may
+have been imbibed by plants as soon as the earth was furnished with
+them.</p>
+
+<p>That an acid vapour is really exhaled from the sea, by the heat of the
+sun, seems to be evident from the remarkably different states of the
+atmosphere, in this respect, in hot and cold climates. In Hudson's bay,
+and also in Russia, it is said, that metals hardly ever rust, whereas
+they are remarkably liable to rust in Barbadoes, and other islands
+between the tropics. See Ellis's Voyage, p. 288. This is also the case
+in places abounding with salt-springs, as Nantwich in Cheshire.</p>
+
+<p>That mild air should consist of parts of so very different a nature as
+an acid vapour and phlogiston, one of which is so exceedingly corrosive,
+will not appear surprising to a chemist, who considers the very strong
+affinity which these two principles are known to have with each other,
+and the exceedingly different properties which substances composed by
+them possess. This is exemplified in common <i>sulphur</i>, which is as mild
+as air, and may be taken into the stomach with the utmost safety, though
+nothing can be more destructive than one of its<span class='pagenum'><a name="Page_265" id="Page_265">[Pg 265]</a></span> constituent parts,
+separately taken, viz. oil of vitriol. Common air, therefore,
+notwithstanding its mildness, may be composed of similar principles, and
+be a real <i>sulphur</i>.</p>
+
+<p>That the fixed air which makes part of the atmosphere is not presently
+imbibed by the waters of the sea, on which it rests, may be owing to the
+union which this kind of air also appears to be capable of forming with
+phlogiston. For fixed air is evidently of the nature of an acid; and it
+appears, in fact, to be capable of being combined with phlogiston, and
+thereby of constituting a species of air not liable to be imbibed by
+water. Phlogiston, however, having a stronger affinity with acid air,
+which I suppose to be the basis of common air, it is not surprising
+that, uniting with this, in preference to the fixed air, the latter
+should be precipitated, whenever a quantity of common air is made
+noxious by an over-charge of phlogiston.</p>
+
+<p>The fixed air with which our atmosphere abounds may also be supplied by
+volcanos, from the vast masses of calcareous matter lodged in the earth,
+together with inflammable air. Also a part of it may be supplied from
+the fermentation of vegetables upon the surface of it. At<span class='pagenum'><a name="Page_266" id="Page_266">[Pg 266]</a></span> present, as
+fast as it is precipitated and imbibed by one process, it may be set
+loose by others.</p>
+
+<p>Whether there be, upon, the whole, an increase or a decrease of the
+general mass of the atmosphere is not easy to conjecture, but I should
+imagine that it rather increases. It is true that many processes
+contribute to a great visible diminution of common air, and that when by
+other processes it is restored to its former wholesomeness, it is not
+increased in its dimensions; but volcanos and fires still supply vast
+quantities of air, though in a state not yet fit for respiration; and it
+will have been seen in my experiments, that vegetable and animal
+substances, dissolved by putrefaction, not only emit phlogiston, but
+likewise yield a considerable quantity of permanent elastic air,
+overloaded indeed with phlogiston, as might be expected, but capable of
+being purified by those processes in nature by which other noxious air
+is purified.</p>
+
+<p>That particles are continually detaching themselves from the surfaces of
+all solid bodies, even the metallic ones, and that these particles
+constitute the most permanent part of the atmosphere, as Sir Isaac
+Newton supposed, does not appear to me to be at all probable.<span class='pagenum'><a name="Page_267" id="Page_267">[Pg 267]</a></span></p>
+
+<p>My readers will have observed, that not only is common air liable to be
+diminished by a mixture of nitrous air, but likewise air originally
+produced from inflammable air, and even from nitrous air itself, which
+never contained any fixed air. From this it may be inferred, that the
+whole of the diminution of common air by phlogiston is not owing to the
+precipitation of fixed air, but from a real contraction of its
+dimensions, in consequence of its union with phlogiston. Perhaps an
+accurate attention to the specific gravity of air procured from these
+different materials, and in these different states, may determine this
+matter, and assist us in investigating the nature of phlogiston.</p>
+
+<p>In what <i>manner</i> air is diminished by phlogiston, independent of the
+precipitation of any of its constituent parts, is not easy to conceive;
+unless air thus diminished be heavier than air not diminished, which I
+did not find to be the case. It deserves, however, to be tried with more
+attention. That phlogiston should communicate absolute <i>levity</i> to the
+bodies with which it is combined, is a supposition that I am not willing
+to have recourse to, though it would afford an easy solution of this
+difficulty.</p>
+
+<p>I have likewise observed, that a mouse will live almost as long in
+inflammable air, when it<span class='pagenum'><a name="Page_268" id="Page_268">[Pg 268]</a></span> has been agitated in water, and even before it
+has been deprived of all its inflammability, as in common air; and yet
+that in this state it is not, perhaps, so much diminished by nitrous air
+as common air is. In this case, therefore, the diminution seems to have
+been occasioned by a contraction of dimensions, and not by a loss of any
+constituent part; so that the air is really better, that is, more fit
+for respiration, than, by the test of nitrous air, it would seem to be.</p>
+
+<p>If this be the case (for it is not easy to judge with accuracy by
+experiments with small animals) nitrous air will be an accurate test of
+the goodness of <i>common air</i> only, that is, air containing a
+considerable proportion of fixed air. But this is the most valuable
+purpose for which a test of the goodness of air can be wanted. It will
+still, indeed, serve for a measure of the goodness of air that does not
+contain fixed air; but, a smaller degree of diminution in this case,
+must be admitted to be equivalent to a greater diminution in the other.</p>
+
+<p>As I could never, by means of growing vegetables, bring air which had
+been thoroughly noxious to so pure a state as that a candle would burn
+in it, it may be suspected that something else besides <i>vegetation</i> is
+necessary to produce this effect. But it should be considered, that<span class='pagenum'><a name="Page_269" id="Page_269">[Pg 269]</a></span> no
+part of the common atmosphere can ever be in this highly noxious state,
+or indeed in a state in which a candle will not burn in it; but that
+even air reduced to this state, either by candles actually burning out
+in it, or by breathing it, has never failed to be perfectly restored by
+vegetation, at least so far that candles would burn in it again, and, to
+all appearance, as well, and as long as ever; so that the growing
+vegetables, with which the surface of the earth is overspread, may, for
+any thing that appears to the contrary, be a cause of the purification
+of the atmosphere sufficiently adequate to the effect.</p>
+
+<p>It may likewise be suspected, that since <i>agitation in water</i> injures
+pure common air, the agitation of the sea may do more harm than good in
+this respect. But it requires a much more violent and longer continued
+agitation of air in water than is ever occasioned by the waves of the
+sea to do the least sensible injury to it. Indeed a light agitation of
+air in <i>putrid water</i> injures it very materially; but if the water be
+sweet, this effect is not produced, except by a long and tedious
+operation, whereas it requires but a very short time, in comparison, to
+restore a quantity of any of the most noxious kinds of air to a very
+great degree of wholesomeness by the same process.<span class='pagenum'><a name="Page_270" id="Page_270">[Pg 270]</a></span></p>
+
+<p>Dr. Hales found that he could breathe the same air much longer when, in
+the course of his respiration, it was made to pass through several folds
+of cloth dipped in vinegar, in a solution of sea-salt, or in salt of
+tartar, especially the last. Statical Essays, vol. 1. p. 266. The
+experiment is valuable, and well deserves to be repeated with a greater
+variety of circumstances. I imagine that the effect was produced by
+those substances, or by the <i>water</i> which they attracted from the air,
+imbibing the phlogistic matter discharged from the lungs. Perhaps the
+phlogiston may unite with the watery part of the atmosphere, in
+preference to any other part of it, and may by that means be more easily
+transferred to such salts as imbibe moisture.</p>
+
+<p>Sir Isaac Newton defines <i>flame</i> to be <i>fumus candens</i>, considering all
+<i>smoke</i> as being of the same nature, and capable of ignition. But the
+smoke of common fuel consists of two very different things. That which
+rises first is mere <i>water</i>, loaded with some of the grosser parts of
+the fuel, and is hardly more capable of becoming red hot than water
+itself; but the other kind of smoke, which alone is capable of ignition,
+is properly <i>inflammable air</i>, which is also loaded with other
+heterogeneous matter, so as to appear like a very dense smoke. A lighted
+candle soon shews them to be essentially different<span class='pagenum'><a name="Page_271" id="Page_271">[Pg 271]</a></span> from each other. For
+one of them instantly takes fire, whereas the other extinguishes a
+candle.</p>
+
+<p>It is remarkable that gunpowder will take fire, and explode in all kinds
+of air, without distinction, and that other substances which contain
+<i>nitre</i> will burn freely in those circumstances. Now since nothing can
+burn, unless there be something at hand to receive the phlogiston, which
+is set loose in the act of ignition, I do not see how this fact can be
+accounted for, but by supposing that the acid of nitre, being peculiarly
+formed to unite with phlogiston, immediately receives it. And if the
+sulphur, which is thereby formed, be instantly decomposed again, as the
+chemists in general say, thence comes the explosion of gunpowder, which,
+however, requires the reaction of some incumbent atmosphere, and without
+which the materials will only <i>melt</i>, and be <i>dispersed</i> without
+explosion.</p>
+
+<p>Nitrous air seems to consist of the nitrous acid vapour united to
+phlogiston, together, perhaps, with some small portion of the metallic
+calx; just as inflammable air consists of the vitriolic or marine acid,
+and the same phlogistic principle. It should seem, however, that
+phlogiston has a stronger affinity with the marine<span class='pagenum'><a name="Page_272" id="Page_272">[Pg 272]</a></span> acid, if that be the
+basis of common air; for nitrous air being admitted to common air, it is
+immediately decomposed; probably by the phlogiston joining with the acid
+principle of the common air, while the fixed air which it contained is
+precipitated, and the acid of the nitrous air is absorbed by the water
+in which the mixture is made, or unites with any volatile alkali that
+happens to be at hand.</p>
+
+<p>This, indeed, is hardly agreeable to the hypothesis of most chemists,
+who suppose that the nitrous acid is stronger than the marine, so as to
+be capable of dislodging it from any base with which it may be combined;
+but it agrees with my own experiments on marine acid air, which shew
+that, in many cases, this <i>weaker acid</i>, as it is called, is capable of
+separating both the vitriolic and the nitrous acids from the phlogiston
+with which they are combined.</p>
+
+<p>On the other hand, the solution of metals in the different acids seems
+to shew, that the nitrous acid forms a closer union with phlogiston than
+the other two; because the air which is formed by the nitrous acid is
+not inflammable, like that which is produced by the oil of vitriol, or
+the spirit of salt. Also, the same weight of iron does not yield half
+the quantity of nitrous air that it does of inflammable.<span class='pagenum'><a name="Page_273" id="Page_273">[Pg 273]</a></span></p>
+
+<p>The great diminution of nitrous air by phlogiston is not easily
+accounted for, unless we suppose that its superabundant acid, uniting
+more intimately with the phlogiston, constitutes a species of <i>sulphur</i>
+that is not easily perceived or catched; though, in the process with
+iron, and also in that with liver of sulphur, part of the redundant
+phlogiston forms such an union with the acid as gives it a kind of
+inflammability.</p>
+
+<p>It appears to me to be very probable, that the spirit of nitre might be
+exhibited in the form of <i>air</i>, if it were possible to find any fluid by
+which it could be confined; but it unites with quicksilver as well as
+with water, so that when, by boiling the spirit of nitre, the fumes are
+driven through the glass tube, fig. 8, they instantly seize upon the
+quicksilver through which they are to be conveyed, and uniting with it,
+form a substance that stops up the tube: a circumstance which has more
+than once exposed me to very disagreeable accidents, in consequence of
+the bursting of the phials.</p>
+
+<p>I do not know any inquiry more promising than the investigation of the
+properties of <i>nitre</i>, the <i>nitrous acid</i>, and <i>nitrous air</i>. Some of
+the most wonderful phenomena in nature are connected<span class='pagenum'><a name="Page_274" id="Page_274">[Pg 274]</a></span> with them, and the
+subject seems to be fully within our reach.</p>
+
+
+<p>&sect; 2. <i>Speculations arising from the consideration of the similarity of
+the <span class="smcap">electric matter</span> and <span class="smcap">phlogiston</span>.</i></p>
+
+<p>There is nothing in the history of philosophy more striking than the
+rapid progress of <i>electricity</i>. Nothing ever appeared more trifling
+than the first effects which were observed of this agent in nature, as
+the attraction and repulsion of straws, and other light substances. It
+excited more attention by the flashes of <i>light</i> which it exhibited. We
+were more seriously alarmed at the electrical <i>shock</i>, and the effects
+of the electrical <i>battery</i>; and we were astonished to the highest
+degree by the discovery of the similarity of electricity with
+<i>lightning</i>, and the <i>aurora borealis</i>, with the connexion it seems to
+have with <i>water-spouts</i>, <i>hurricanes</i>, and <i>earthquakes</i>, and also with
+the part that is probably assigned to it in the system of <i>vegetation</i>,
+and other the most important processes in nature.</p>
+
+<p>Yet, notwithstanding all this, we have been, within a few years, more
+puzzled than ever with the electricity of the <i>torpedo</i>, and of the
+<i>anguille temblante</i> of Surinam, especially since that most curious
+discovery of Mr. Walsh's,<span class='pagenum'><a name="Page_275" id="Page_275">[Pg 275]</a></span> that the former of these wonderful fishes has
+the power of giving a proper electrical shock; the electrical matter
+which proceeds from it performing a real circuit from one part of the
+animal to the other; while both the fish which performs this experiment
+and all its apparatus are plunged in water, which is known to be a
+conducting substance.</p>
+
+<p>Perhaps, however, by considering this fact in connexion with a few
+others, and especially with what I have lately observed concerning the
+identity of electricity and phlogiston, a little light may be thrown
+upon this subject, in consequence of which we may be led to consider
+electricity in a still more important light. Many of my readers, I am
+aware, will smile at what I am going to advance; but the apprehension of
+this shall not interrupt my speculations, how chimerical soever they may
+be thought to be.</p>
+
+<p>The facts, the consideration of which I would combine with that of the
+electricity of the torpedo, are the following.</p>
+
+<p>First, The remarkable electricity of the feathers of a paroquet,
+observed by Mr. Hartmann, an account of which may be seen in Mr.
+Rozier's Journal for Sept. 1771. p. 69. This<span class='pagenum'><a name="Page_276" id="Page_276">[Pg 276]</a></span> bird never drinks, but
+often washes itself; but the person who attended it having neglected to
+supply it with water for this purpose, its feathers appeared to be
+endued with a proper electrical virtue, repelling one another, and
+retaining their electricity a long time after they were plucked from the
+body of the bird, just as they would have done if they had received
+electricity from an excited glass tube.</p>
+
+<p>Secondly, The electric matter directed through the body of any muscle
+forces it to contract. This is known to all persons who attend to what
+is called the electrical shock; which certainly occasions a proper
+<i>convulsion</i>, but has been more fully illustrated by Father Beccaria.
+See my <i>History of Electricity</i>, p. 402.</p>
+
+<p>Lastly, Let it be considered that the proper nourishment of an animal
+body, from which the source and materials of all muscular motion must be
+derived, is probably some modification of phlogiston. Nothing will
+nourish that does not contain phlogiston, and probably in such a state
+as to be easily separated from it by the animal functions.</p>
+
+<p>That the source of muscular motion is phlogiston is still more probable,
+from the consideration of the well known effects of vinous and<span class='pagenum'><a name="Page_277" id="Page_277">[Pg 277]</a></span>
+spirituous liquors, which consist very much of phlogiston, and which
+instantly brace and strengthen the whole nervous and muscular system;
+the phlogiston in this case being, perhaps, more easily extricated, and
+by a less tedious animal process, than in the usual method of extracting
+it from mild aliments. Since, however, the mildest aliments do the same
+thing more slowly and permanently, that spirituous liquors do suddenly
+and transiently, it seems probable that their operation is ultimately
+the same.</p>
+
+<p>This conjecture is likewise favoured by my observation, that respiration
+and putrefaction affect common air in the same manner, and in the same
+manner in which all other processes diminish air and make it noxious,
+and which agree in nothing but the emission of phlogiston. If this be
+the case, it should seem that the phlogiston which we take in with our
+aliment, after having discharged its proper function in the animal
+system (by which it probably undergoes some unknown alteration) is
+discharged as <i>effete</i> by the lungs into the great common <i>menstruum</i>,
+the atmosphere.</p>
+
+<p>My conjecture suggested (whether supported or not) by these facts, is,
+that animals have a power of converting phlogiston, from the state<span class='pagenum'><a name="Page_278" id="Page_278">[Pg 278]</a></span> in
+which they receive it in their nutriment, into that state in which it is
+called the electrical fluid; that the brain, besides its other proper
+uses, is the great laboratory and repository for this purpose; that by
+means of the nerves this great principle, thus exalted, is directed into
+the muscles, and forces them to act, in the same manner as they are
+forced into action when the electric fluid is thrown into them <i>ab
+extra</i>.</p>
+
+<p>I farther suppose, that the generality of animals have no power of
+throwing this generated electricity any farther than the limits of their
+own system; but that the <i>torpedo</i>, and animals of a similar
+construction, have likewise the power, by means of an additional
+apparatus, of throwing it farther, so as to affect other animals, and
+other substances at a distance from them.</p>
+
+<p>In this case, it should seem that the electric matter discharged from
+the animal system (by which it is probably more exhausted and fatigued
+than by ordinary muscular motion) would never return to it, at least so
+as to be capable of being made use of a second time, and yet if the
+structure of these animals be such as that the electric matter shall
+dart from one part of them only, while another part<span class='pagenum'><a name="Page_279" id="Page_279">[Pg 279]</a></span> is left suddenly
+deprived of it, it may make a circuit, as in the Leyden phial.</p>
+
+<p>As to the <i>manner</i> in which the electric matter makes a muscle contract,
+I do not pretend to have any conjecture worth mentioning. I only imagine
+that whatever can make the muscular fibres recede from one another
+farther than the parts of which they consist, must have this effect.</p>
+
+<p>Possibly, the <i>light</i> which is said to proceed from some animals, as
+from cats and wild beasts, when they are in pursuit of their prey in the
+night, may not only arise, as it has hitherto been supposed to do, from
+the friction of their hairs or bristles, &amp;c. but that violent muscular
+exertion may contribute to it. This may assist them occasionally to
+catch their prey; as glow-worms, and other insects, are provided with a
+constant light for that purpose, to the supply of which light their
+nutriment may also contribute.</p>
+
+<p>I would not even say that the light which is said to have proceeded from
+some human bodies, of a particular temperament, and especially on some
+extraordinary occasions, may not have been of the electrical kind, that
+is, produced independently of friction, or with less<span class='pagenum'><a name="Page_280" id="Page_280">[Pg 280]</a></span> friction than
+would have produced it in other persons; as in those cases related by
+Bartholin in his treatice <i>De luce animalium</i>. See particularly what he
+says concerning Theodore king of the Goths, p. 54, concerning Gonzaga
+duke of Mantua, p. 57, and Gothofred Antonius, p. 123: But I would not
+have my readers suppose that I lay much stress upon stories no better
+authenticated than these.</p>
+
+<p>The electric matter in passing through non-conducting substances always
+emits <i>light</i>. This light I have been sometimes inclined to suspect
+might have been supplied from the substance through which it passes. But
+I find that after the electric spark has diminished a quantity of air as
+much as it possibly can, so that it has no more visible effect upon it,
+the electric light in that air is not at all lessened. It is probable,
+therefore, that electric light comes from the electric matter itself;
+and this being a modification of phlogiston, it is probable that <i>all
+light</i> is a modification of phlogiston also. Indeed, since no other
+substances besides such as contain phlogiston are capable of ignition,
+and consequently of becoming luminous, it was on this account pretty
+evident, prior to these deductions from electrical phenomena, that light
+and phlogiston are the same thing, in different forms or states.<span class='pagenum'><a name="Page_281" id="Page_281">[Pg 281]</a></span></p>
+
+<p>It appears to me that <i>heat</i> has no more proper connexion with
+phlogiston than it has with water, or any other constituent part of
+bodies; but that it is a state into which the parts of bodies are thrown
+by their action and reaction with respect to one another; and probably
+(as the English philosophers in general have supposed) the heated state
+of bodies may consist of a subtle vibratory motion of their parts. Since
+the particles which constitute light are thrown from luminous bodies
+with such amazing velocity, it is evident that, whatever be the cause of
+such a projection, the reaction consequent upon it must be considerable.
+This may be sufficient not only to keep up, but also to increase the
+vibration of the parts of those bodies in which the phlogiston is not
+very firmly combined; and the difference between the substances which
+are called <i>inflammable</i> and others which also contain phlogiston may be
+this, that in the former the heat, or the vibration occasioned by the
+emission of their own phlogiston, may be sufficient to occasion the
+emission of more, till the whole be exhausted; that is, till the body be
+reduced to ashes. Whereas in bodies which are not inflammable, the heat
+occasioned by the emission of their own phlogiston may not be sufficient
+for this purpose, but an additional heat <i>ab extra</i> may be necessary.<span class='pagenum'><a name="Page_282" id="Page_282">[Pg 282]</a></span></p>
+
+<p>Some philosophers dislike the term <i>phlogiston</i>; but, for my part, I can
+see no objection to giving that, or any other name, to a <i>real
+something</i>, the presence or absence of which makes so remarkable
+difference in bodies, as that of <i>metallic calces</i> and <i>metals</i>, <i>oil of
+vitriol</i> and <i>brimstone</i>, &amp;c. and which may be transferred from one
+substance to another, according to certain known laws, that is, in
+certain definite circumstances. It is certainly hard to conceive how any
+thing that answers this description can be only a mere <i>quality</i>, or
+mode of bodies, and not <i>substance</i> itself, though incapable of being
+exhibited alone. At least, there can be no harm in giving this name to
+any <i>thing</i>, or any <i>circumstance</i> that is capable of producing these
+effects. If it should hereafter appear not to be a substance, we may
+change our phraseology, if we think proper.</p>
+
+<p>On the other hand I dislike the use of the term <i>fire</i>, as a constituent
+principle of natural bodies, because, in consequence of the use that has
+generally been made of that term, it includes another thing or
+circumstance, viz. <i>heat</i>, and thereby becomes ambiguous, and is in
+danger of misleading us. When I use the term phlogiston, as a principle
+in the constitution of bodies, I cannot mislead myself or others,
+because I use one and the same term to<span class='pagenum'><a name="Page_283" id="Page_283">[Pg 283]</a></span> denote only one and the same
+<i>unknown cause</i> of certain well-known effects. But if I say that <i>fire</i>
+is a principle in the constitution of bodies, I must, at least,
+embarrass myself with the distinction of fire <i>in a state of action</i>,
+and fire <i>inactive</i>, or quiescent. Besides I think the term phlogiston
+preferable to that of fire, because it is not in common use, but
+confined to philosophy; so that the use of it may be more accurately
+ascertained.</p>
+
+<p>Besides, if phlogiston and the electric matter be the same thing, though
+it cannot be exhibited alone, in a <i>quiescent state</i>, it may be
+exhibited alone under one of its modifications, when it is in <i>motion</i>.
+And if light be also phlogiston, or some modification or subdivision of
+phlogiston, the same thing is capable of being exhibited alone in this
+other form also.</p>
+
+<p>In my paper on the <i>conducting power of charcoal</i>, (See Philosophical
+Transactions, vol. 60. p. 221) I observed that there is a remarkable
+resemblance between metals and charcoal; as in both these substances
+there is an intimate union of phlogiston with an earthy base; and I said
+that, had there been any phlogiston in <i>water</i>, I should have concluded,
+that there had been no conducting power in nature, but in consequence of
+an union of this principle with<span class='pagenum'><a name="Page_284" id="Page_284">[Pg 284]</a></span> some base; for while metals have
+phlogiston they conduct electricity, but when they are deprived of it
+they conduct no longer. Now the affinity which I have observed between
+phlogiston and water leads me to conclude that water, in its natural
+state, does contain some portion of phlogiston; and according to the
+hypothesis just now mentioned they must be intimately united, because
+water is not inflammable.</p>
+
+<p>I think, therefore, that after this state of hesitation and suspence, I
+may venture to lay it down as a characteristic distinction between
+conducting and non-conducting substances, that the former contain
+phlogiston intimately united with some base, and that the latter, if
+they contain phlogiston at all, retain it more loosely. In what manner
+this circumstance facilitates the passing of the electric matter through
+one substance, and obstructs its passage through another, I do not
+pretend to say. But it is no inconsiderable thing to have advanced but
+<i>one step</i> nearer to an explanation of so very capital a distinction of
+natural bodies, as that into conductors and non-conductors of
+electricity.</p>
+
+<p>I beg leave to mention in this place, as favourable to this hypothesis,
+a most curious discovery made very lately by Mr. Walsh, who<span class='pagenum'><a name="Page_285" id="Page_285">[Pg 285]</a></span> being
+assisted by Mr. De Luc to make a more perfect vacuum in the double or
+arched barometer, by boiling the quicksilver in the tube, found that the
+electric spark or shock would no more pass through it, than through a
+stick of solid glass. He has also noted several circumstances that
+affect this vacuum in a very extraordinary manner. But supposing that
+vacuum to be perfect, I do not see how we can avoid inferring from the
+fact, that some <i>substance</i> is necessary to conduct electricity; and
+that it is not capable, by its own expansive power, of extending itself
+into spaces void of all matter, as has generally been supposed, on the
+idea of there being nothing to obstruct its passage.</p>
+
+<p>Indeed if this was the case, I do not see how the electric matter could
+be retained within the body of the earth, or any of the planets, or
+solid orbs of any kind. In nature we see it make the most splendid
+appearance in the upper and thinner regions of the atmosphere, just as
+it does in a glass tube nearly exhausted; but if it could expand itself
+beyond that degree of rarity, it would necessarily be diffused into the
+surrounding vacuum, and continue and be condensed there, at least in a
+greater proportion than in or near any solid body, as Newton supposed
+concerning his <i>ether</i>.<span class='pagenum'><a name="Page_286" id="Page_286">[Pg 286]</a></span></p>
+
+<p>If that mode of vibration which constitutes heat be the means of
+converting phlogiston from that state in which it makes a part of solid
+bodies, and eminently contributes to the firmness of their texture into
+that state in which it diminishes common air; may not that peculiar kind
+of vibration by which Dr. Hartley supposes the brain to be affected, and
+by which he endeavours to explain all the phenomena of sensation, ideas,
+and muscular motion, be the means by which the phlogiston, which is
+conveyed into the system by nutriment, is converted into that form or
+modification of it of which the electric fluid consists.</p>
+
+<p>These two states of phlogiston may be conceived to resemble, in some
+measure, the two states of fixed air, viz. elastic, or non-elastic; a
+solid, or a fluid.</p>
+
+
+
+<hr style="width: 65%;" /><p><span class='pagenum'><a name="Page_287" id="Page_287">[Pg 287]</a></span></p>
+<h2>THE APPENDIX.</h2>
+
+
+<p>In this Appendix I shall present the reader with the communications of
+several of my friends on the subject of the preceding work. Among them I
+should with pleasure have inserted some curious experiments, made by Dr.
+Hulme of Halifax, on the air extracted from Buxton water, and on the
+impregnation of several fluids, with different kinds of air; but that he
+informs me he proposes to make a separate publication on the subject.<span class='pagenum'><a name="Page_288" id="Page_288">[Pg 288]</a></span></p>
+
+
+<h3>NUMBER I.</h3>
+
+<div class="blockquot"><p><i><span class="smcap">Experiments</span> made by Mr. Hey to prove that there is no <span class="smcap">Oil</span> of
+<span class="smcap">Vitriol</span> in water impregnated with <span class="smcap">Fixed Air</span>.</i></p></div>
+
+<p>It having been suggested, that air arising from a fermenting mixture of
+chalk and oil of vitriol might carry up with it a small portion of the
+vitriolic acid, rendered volatile by the act of fermentation; I made the
+following experiments, in order to discover whether the acidulous taste,
+which water impregnated with such air affords, was owing to the presence
+of any acid, or only to the fixed air it had absorbed.</p>
+
+<h4><span class="smcap">Experiment I.</span></h4>
+
+<p>I mixed a tea-spoonful of syrup of violets with an ounce of distilled
+water, saturated with fixed air procured from chalk by means of the
+vitriolic acid; but neither upon the first mixture, nor after standing
+24 hours, was the colour of the syrup at all changed, except by its
+simple dilution.</p>
+
+<h4><span class="smcap">Experiment II.</span></h4>
+
+<p>A portion of the same distilled water, unimpregnated with fixed air, was
+mixed with the syrup in the same proportion: not the least difference in
+colour could be perceived betwixt this and the above-mentioned mixture.<span class='pagenum'><a name="Page_289" id="Page_289">[Pg 289]</a></span></p>
+
+<h4><span class="smcap">Experiment III.</span></h4>
+
+<p>One drop of oil of vitriol being mixed with a pint of the same distilled
+water, an ounce of this water was mixed with a tea-spoonful of the
+syrup. This mixture was very distinguishable in colour from the two
+former, having a purplish cast, which the others wanted.</p>
+
+<h4><span class="smcap">Experiment IV.</span></h4>
+
+<p>The distilled water impregnated with so small a quantity of vitriolic
+acid, having a more agreeable taste than when alone, and yet manifesting
+the presence of an acid by means of the syrup of violets; I subjected it
+to some other tests of acidity. It formed curds when agitated with soap,
+lathered with difficulty, and very imperfectly; but not the least
+ebullition could be discovered upon dropping in spirit of sal ammoniac,
+or solution of salt of tartar, though I had taken care to render the
+latter free from causticity by impregnating it with fixed air.</p>
+
+<h4><span class="smcap">Experiment V.</span></h4>
+
+<p>The distilled water saturated with fixed air neither effervesced, nor
+shewed any clouds, when mixed with the fixed or volatile alkali.</p>
+
+<h4><span class="smcap">Experiment VI.</span></h4>
+
+<p>No curd was formed by pouring this water upon an equal quantity of milk,
+and boiling them together.<span class='pagenum'><a name="Page_290" id="Page_290">[Pg 290]</a></span></p>
+
+<h4><span class="smcap">Experiment VII.</span></h4>
+
+<p>When agitated with soap, this water produced curds, and lathered with
+some difficulty; but not so much as the distilled water mixed with
+vitriolic acid in the very small proportion above-mentioned. The same
+distilled water without any impregnation of fixed air lathered with soap
+without the least previous curdling. River-water, and a pleasant
+pump-water not remarkably hard, were compared with these. The former
+produced curds before it lathered, but not quite in so great a quantity
+as the distilled water impregnated with fixed air: the latter caused a
+stronger curd than any of the others above-mentioned.</p>
+
+<h4><span class="smcap">Experiment VIII.</span></h4>
+
+<p>Apprehending that the fixed air in the distilled water occasioned the
+coagulation, or separation of the oily part of the soap, only by
+destroying the causticity of the <i>lixivium</i>, and thereby rendering the
+union less perfect betwixt that and the tallow, and not by the presence
+of any acid; I impregnated a fresh quantity of the same distilled water
+with fixed air, which had passed through half a yard of a wide
+barometer-tube filled with salt of tartar; but this water caused the
+same curdling with soap as the former had done, and appeared in every
+respect to be exactly the same.<span class='pagenum'><a name="Page_291" id="Page_291">[Pg 291]</a></span></p>
+
+<h4><span class="smcap">Experiment IX.</span></h4>
+
+<p>Distilled water saturated with fixed air formed a white cloud and
+precipitation, upon being mixed with a solution of <i>saccharum saturni</i>.
+I found likewise, that fixed air, after passing through the tube filled
+with alkaline salt, upon being let into a phial containing a solution of
+the metalic salt in distilled water, caused a perfect separation of the
+lead, in the form of a white powder; for the water, after this
+precipitation, shewed no cloudiness upon a fresh mixture of the
+substances which had before rendered it opaque.<span class='pagenum'><a name="Page_292" id="Page_292">[Pg 292]</a></span></p>
+
+
+<h3>NUMBER II.</h3>
+
+<div class="blockquot"><p><i>A Letter from Mr. <span class="smcap">Hey</span> to Dr. <span class="smcap">Priestley</span>, concerning the Effects
+of fixed Air applied by way of Clyster.</i></p></div>
+
+
+<p class="right">Leeds, Feb. 15th, 1772.</p>
+
+<p>Reverend Sir,</p>
+
+
+<p>Having lately experienced the good effects of fixed air in a putrid
+fever, applied in a manner, I believe not heretofore made use of, I
+thought it proper to inform you of the agreeable event, as the method of
+applying this powerful corrector of putrefaction took its rise
+principally from your observations and experiments on factitious air;
+and now, at your request, I send the particulars of the case I mentioned
+to you, as far as concerns the administration of this remedy.</p>
+
+<p>January 8, 1772, Mr. Lightbowne, a young gentleman who lives with me,
+was seized with a fever, which, after continuing about ten days, began
+to be attended with those symptoms that indicate a putrescent state of
+the fluids.</p>
+
+<p>18th, His tongue was black in the morning when I first visited him, but
+the blackness went off in the day-time upon drinking: He had begun to
+doze much the preceding day, and now he took little notice of those that
+were about him: His belly was loose, and had been so for some days: his
+pulse beat 110 strokes in a minute, and was rather low: he was ordered
+to take twenty-five grains of Peruvian bark with five of<span class='pagenum'><a name="Page_293" id="Page_293">[Pg 293]</a></span> tormentil-root
+in powder every four hours, and to use red wine and water cold as his
+common drink.</p>
+
+<p>19th, I was called to visit him early in the morning, on account of a
+bleeding at the nose which had come on: he lost about eight ounces of
+blood, which was of a loose texture: the h&aelig;morrhage was suppressed,
+though not without some difficulty, by means of tents made of soft lint,
+dipped in cold water strongly impregnated with tincture of iron, which
+were introduced within the nostrils quite through to their posterior
+apertures; a method which has never yet failed me in like cases. His
+tongue was now covered with a thick black pellicle, which was not
+diminished by drinking: his teeth were furred with the same kind of
+sordid matter, and even the roof of his mouth and sauces were not free
+from it: his looseness and stupor continued, and he was almost
+incessantly muttering to himself: he took this day a scruple of the
+Peruvian bark with ten grains of tormentil every two or three hours: a
+starch clyster, containing a drachm of the compound powder of bole,
+without opium, was given morning and evening: a window was set open in
+his room, though it was a severe frost, and the floor was frequently
+sprinkled with vinegar.</p>
+
+<p>20th, He continued nearly in the same state: when roused from his
+dozing, he generally gave a sensible answer to the questions asked him;
+but he immediately relapsed, and repeated his muttering. His skin was
+dry, and harsh, but without <i>petechi&aelig;</i>. He sometimes voided his urine
+and <i>f&aelig;ces</i> into the bed, but generally had sense enough to ask for the
+bed-pan: as he now<span class='pagenum'><a name="Page_294" id="Page_294">[Pg 294]</a></span> nauseated the bark in substance, it was exchanged
+for Huxham's tincture, of which he took a table spoonful every two hours
+in a cup full of cold water: he drank sometimes a little of the tincture
+of roses, but his common liquors were red wine and water, or rice-water
+and brandy acidulated with elixir of vitriol: before drinking, he was
+commonly requested to rinse his mouth with water to which a little honey
+and vinegar had been added. His looseness rather increased, and the
+stools were watery, black, and f&oelig;tid: It was judged necessary to
+moderate this discharge, which seemed to sink him, by mixing a drachm of
+the <i>theriaca Andromachi</i> with each clyster.</p>
+
+<p>21st. The same putrid symptoms remained, and a <i>subsultus tendinum</i> came
+on: his stools were more f&oelig;tid; and so hot, that the nurse assured me
+she could not apply her hand to the bed-pan, immediately after they were
+discharged, without feeling pain on this account: The medicine and
+clysters were repeated.</p>
+
+<p>Reflecting upon the disagreeable necessity we seemed to lie under of
+confining this putrid matter in the intestines, lest the evacuation
+should destroy the <i>vis vit&aelig;</i> before there was time to correct its bad
+quality, and overcome its bad effects, by the means we were using; I
+considered, that, if this putrid ferment could be more immediately
+corrected, a stop would probably be put to the flux, which seemed to
+arise from, or at least to be encreased by it; and the <i>fomes</i> of the
+disease would likewise be in a great measure removed. I thought nothing
+was so likely to effect this, as the introduction of fixed air into the
+alimentary canal, which, from the experiments of Dr. Macbride, and<span class='pagenum'><a name="Page_295" id="Page_295">[Pg 295]</a></span>
+those you have made since his publication, appears to be the most
+powerful corrector of putrefaction hitherto known. I recollected what
+you had recommended to me as deserving to be tried in putrid diseases, I
+mean, the injection of this kind of air by way of clyster, and judged
+that in the present case such a method was clearly indicated.</p>
+
+<p>The next morning I mentioned my reflections to Dr. Hird and Dr.
+Crowther, who kindly attended this young gentleman at my request, and
+proposed the following method of treatment, which, with their
+approbation, was immediately entered upon. We first gave him five grains
+of ipecacuanha, to evacuate in the most easy manner part of the putrid
+<i>colluvies</i>: he was then allowed to drink freely of brisk orange-wine,
+which contained a good deal of fixed air, yet had not lost its
+sweetness. The tincture of bark was continued as before; and the water
+which he drank along with it, was impregnated with fixed air from the
+atmosphere of a large vat of fermenting wort, in the manner I had
+learned from you. Instead of the astringent clyster, air alone was
+injected, collected from a fermenting mixture of chalk and oil of
+vitriol: he drank a bottle of orange-wine in the course of this day, but
+refused any other liquor except water and his medicine: two bladders
+full of air were thrown up in the afternoon.</p>
+
+<p>23d. His stools were less frequent; their heat likewise and peculiar
+<i>f&oelig;tor</i> were considerably diminished; his muttering was much abated,
+and the <i>subsultus tendinum</i> had left him. Finding that part of the air
+was rejected when given with a bladder in the usual way, I<span class='pagenum'><a name="Page_296" id="Page_296">[Pg 296]</a></span> contrived a
+method of injecting it which was not so liable to this inconvenience. I
+took the flexible tube of that instrument which is used for throwing up
+the fume of tobacco, and tied a small bladder to the end of it that is
+connected with the box made for receiving the tobacco, which I had
+previously taken off from the tube: I then put some bits of chalk into a
+six ounce phial until it was half filled; upon these I poured such a
+quantity of oil of vitriol as I thought capable of saturating the chalk,
+and immediately tied the bladder, which I had fixed to the tube, round
+the neck of the phial: the clyster-pipe, which was fastened to the other
+end of the tube, was introduced into the <i>anus</i> before the oil of
+vitriol was poured upon the chalk. By this method the air passed
+gradually into the intestines as it was generated; the rejection of it
+was in a great measure prevented; and the inconvenience of keeping the
+patient uncovered during the operation was avoided.</p>
+
+<p>24th, He was so much better, that there seemed to be no necessity for
+repeating the clysters: the other means were continued. The window of
+his room was now kept shut.</p>
+
+<p>25th, All the symptoms of putrescency had left him; his tongue and teeth
+were clean; there remained no unnatural blackness or <i>f&oelig;tor</i> in his
+stool, which had now regained their proper consistence; his dozing and
+muttering were gone off; and the disagreeable odour of his breath and
+perspiration was no longer perceived. He took nourishment to-day, with
+pleasure;<span class='pagenum'><a name="Page_297" id="Page_297">[Pg 297]</a></span> and, in the afternoon, sat up an hour in his chair.</p>
+
+<p>His fever, however, did not immediately leave him; but this we
+attributed to his having caught cold from being incautiously uncovered,
+when the window was open, and the weather extremely severe; for a cough,
+which had troubled him in some degree from the beginning, increased, and
+he became likewise very hoarse for several days, his pulse, at the same
+time, growing quicker: but these complaints also went off, and he
+recovered, without any return of the bad symptoms above-mentioned.</p>
+
+<p>
+<span style="margin-left: 2.5em;">I am, Reverend Sir,</span><br />
+<br />
+<span style="margin-left: 5em;">Your obliged humble Servant,</span><br />
+<br />
+<span style="margin-left: 7.5em;"><span class="smcap">Wm. Hey</span>.</span><br />
+</p>
+
+
+<h4>POSTSCRIPT</h4>
+
+<p class="right">
+October 29, 1772.
+</p>
+
+<p>Fevers of the putrid kind have been so rare in this town, and in its
+neighbourhood, since the commencement of the present year, that I have
+not had an opportunity of trying again the effects of fixed air, given
+by way of clyster, in any case exactly similar to Mr. Lightbowne's. I
+have twice given water saturated with fixed air in a fever of the
+putrescent kind, and it agreed very well with the patients. To one of
+them the a&euml;rial clysters were administred, on account of a<span class='pagenum'><a name="Page_298" id="Page_298">[Pg 298]</a></span> looseness,
+which attended the fever, though the stools were not black, nor
+remarkably hot or f&oelig;tid.</p>
+
+<p>These clysters did not remove the looseness, though there was often a
+greater interval than usual betwixt the evacuations, after the injection
+of them. The patient never complained of any uneasy distention of the
+belly from the air thrown up, which, indeed, is not to be wondered at,
+considering how readily this kind of air is absorbed by aqueous and
+other fluids, for which sufficient time was given, by the gradual manner
+of injecting it. Both those patients recovered though the use of fixed
+air did not produce a crisis before the period at which such fevers
+usually terminate. They had neither of them the opportunity of drinking
+such wine as Mr. Lightbowne took, after the use of fixed air was entered
+upon; and this, probably, was some disadvantage to them.</p>
+
+<p>I find the methods of procuring fixed air, and impregnating water with
+it, which you have published, are preferable to those I made use of in
+Mr. Lightbowne's case.</p>
+
+<p>The flexible tube used for conveying the fume of tobacco into the
+intestines, I find to be a very convenient instrument in this case, by
+the method before-mentioned (only adding water to the chalk, before the
+oil of vitriol is instilled, as you direct) the injection of air may be
+continued at pleasure, without any other inconvenience to the patient,
+than what may arise from his continuing in one position during the
+operation, which scarcely deserves to be mentioned, or<span class='pagenum'><a name="Page_299" id="Page_299">[Pg 299]</a></span> from the
+continuance of the clyster-pipe within the anus, which is but trifling,
+if it be not shaken much, or pushed against the rectum.</p>
+
+<p>When I said in my letter, that fixed air appeared to be the greatest
+corrector of putrefaction hitherto known, your philosophical researches
+had not then made you acquainted with that most remarkably antiseptic
+property of nitrous air. Since you favoured me with a view of some
+astonishing proofs of this, I have conceived hopes, that this kind of
+air may likewise be applied medicinally to great advantage.</p>
+
+
+<p class="right">W. H.</p>
+<p><span class='pagenum'><a name="Page_300" id="Page_300">[Pg 300]</a></span></p>
+
+
+<h3>NUMBER III.</h3>
+
+<div class="blockquot"><p><i>Observations on the <span class="smcap">Medicinal Uses</span> of <span class="smcap">Fixed Air</span>. By <span class="smcap">Thomas
+Percival</span>, M. D. Fellow of the <span class="smcap">Royal Society</span>, and of the <span class="smcap">Society</span>
+of <span class="smcap">Antiquaries</span> in <span class="smcap">London</span>.</i></p></div>
+
+<p>These Observations on the <span class="smcap">Medicinal Uses of Fixed Air</span> have been before
+published in the Second Volume of my Essays; but are here reprinted with
+considerable additions. They form a part of an experimental inquiry into
+this interesting and curious branch of Physics; in which the friendship
+of Dr. Priestley first engaged me, in concert with himself.</p>
+
+<p class="right">
+Manchester, March 16, 1774.
+</p>
+
+<p>In a course of Experiments, which is yet unfinished, I have had frequent
+opportunities of observing that <span class="smcap">fixed air</span> may in no inconsiderable
+quantity be breathed without danger or uneasiness. And it is a
+confirmation of this conclusion, that at Bath, where the waters
+copiously exhale this mineral spirit,<a name="FNanchor_15_15" id="FNanchor_15_15"></a><a href="#Footnote_15_15" class="fnanchor">[15]</a> the bathers inspire it with
+impunity. At Buxton also, where the Bath is in a close vault, the
+effects of such <i>effluvia</i>, if noxious, must certainly be perceived.</p>
+<p><span class='pagenum'><a name="Page_301" id="Page_301">[Pg 301]</a></span></p>
+<p>Encouraged by these considerations, and still more by the testimony of a
+very judicious Physician at Stafford, in favour of this powerful
+antiseptic remedy, I have administered fixed air in a considerable
+number of cases of the <span class="smcap">Phthisis Pulmonalis</span>, by directing my patients to
+inspire the steams of an effervescing mixture of chalk and vinegar; or
+what I have lately preferred, of vinegar and potash. The hectic fever
+has in several instances been considerably abated, and the matter
+expectorated has become less offensive, and better digested. I have not
+yet been so fortunate in any one case, as to effect a cure; although the
+use of mephitic air has been accompanied with proper internal medicines.
+But Dr. Withering, the gentleman referred to above, informs me, that he
+has been more successful. One Phthisical patient under his care has by a
+similar course intirely recovered; another was rendered much better; and
+a third, whose case was truly deplorable, seemed to be kept alive by it
+more than two months. It may be proper to observe that fixed air can
+only be employed with any prospect of success, in the latter stages of
+the <i>phthisis pulmonalis</i>, when a purulent expectoration takes place.
+After the rupture and discharge of a <span class="smcap">Vomica</span> also, such a remedy promises
+to be a powerful palliative. Antiseptic fumigations and vapours have
+been long employed, and much extolled in cases of this kind. I made the
+following experiment, to determine whether their efficacy, in any
+degree, depends on the separation of fixed air from their substance.</p>
+
+<p>One end of a bent tube was fixed in a phial full of lime-water; the
+other end in a bottle of the tincture of<span class='pagenum'><a name="Page_302" id="Page_302">[Pg 302]</a></span> myrrh. The junctures were
+carefully luted, and the phial containing the tincture of myrrh was
+placed in water, heated almost to the boiling point, by the lamp of a
+tea-kettle. A number of air-bubbles were separated, but probably not of
+the mephitic kind, for no precipitation ensued in the lime water. This
+experiment was repeated with the <i>tinct. tolutan&aelig;, ph. ed.</i> and with
+<i>sp, vinos. camp.</i> and the result was entirely the same. The medicinal
+action therefore of the vapours raised from such tinctures, cannot be
+ascribed to the extrication of fixed air; of which it is probable bodies
+are deprived by <i>chemical solution</i> as well as by <i>mixture</i>.</p>
+
+<p>If mephitic air be thus capable of correcting purulent matter in the
+lungs, we may reasonably infer it will be equally useful when applied
+externally to foul <span class="smcap">ulcers</span>. And experience confirms the conclusion. Even
+the sanies of a <span class="smcap">cancer</span>, when the carrot poultice failed, has been
+sweetened by it, the pain mitigated, and a better digestion produced.
+The cases I refer to are now in the Manchester infirmary, under the
+direction of my friend Mr. White, whose skill as a surgeon, and
+abilities as a writer are well known to the public.</p>
+
+<p>Two months have elapsed since these observations were written,<a name="FNanchor_16_16" id="FNanchor_16_16"></a><a href="#Footnote_16_16" class="fnanchor">[16]</a> and
+the same remedy, during that period, has been assiduously applied, but
+without any further success. The progress of the cancers seems to be
+checked by the fixed air; but it is to be feared that a cure will not be
+effected. A palliative remedy, however,<span class='pagenum'><a name="Page_303" id="Page_303">[Pg 303]</a></span> in a disease so desperate and
+loathsome, may be considered as a very valuable acquisition. Perhaps
+<span class="smcap">nitrous air</span> might be still more efficacious. This species of factitious
+air is obtained from all the metals except zinc, by means of the nitrous
+acid; and Dr. Priestley informs me, that as a sweetener and antiseptic
+it far surpasses fixed air. He put two mice into a quantity of it, one
+just killed, the other offensively putrid. After twenty-five days they
+were both perfectly sweet.</p>
+
+<p>In the <span class="smcap">ulcerous sore throat</span> much advantage has been experienced from the
+vapours of effervescing mixtures drawn into the <i>fauces</i><a name="FNanchor_17_17" id="FNanchor_17_17"></a><a href="#Footnote_17_17" class="fnanchor">[17]</a>. But this
+remedy should not supersede the use of other antiseptic
+applications.<a name="FNanchor_18_18" id="FNanchor_18_18"></a><a href="#Footnote_18_18" class="fnanchor">[18]</a></p>
+
+<p>A physician<a name="FNanchor_19_19" id="FNanchor_19_19"></a><a href="#Footnote_19_19" class="fnanchor">[19]</a> who had a very painful <span class="smcap">apthous ulcer</span> at the point of his
+tongue, found great relief, when other remedies failed, from the
+application of fixed air to the part affected. He held his tongue over
+an effervescing mixture of potash and vinegar; and as the pain was
+always mitigated, and generally removed by this vaporisation, he
+repeated it, whenever the anguish arising from the ulcer was more than
+usually severe. He tried a combination of potash and oil of vitriol well
+diluted with water; but this proved stimulant and increased his pain;
+probably owing to some<span class='pagenum'><a name="Page_304" id="Page_304">[Pg 304]</a></span> particles of the acid thrown upon the tongue, by
+the violence of the effervescence. For a paper stained with the purple
+juice of radishes, when held at an equal distance over two vessels, the
+one containing potash and vinegar, the other the same alkali and
+<i>Spiritus vitrioli tenuis</i>, was unchanged by the former, but was spotted
+with red, in various parts, by the latter.</p>
+
+<p>In <span class="smcap">malignant fevers</span> wines abounding with fixed air may be administered,
+to check the septic ferment, and sweeten the putrid <i>colluvies</i> in the
+<i>prim&aelig; vi&aelig;</i>. If the laxative quality of such liquors be thought an
+objection to the use of them, wines of a greater age may be given,
+impregnated with mephitic air, by a simple but ingenious contrivance of
+my friend Dr. Priestley.<a name="FNanchor_20_20" id="FNanchor_20_20"></a><a href="#Footnote_20_20" class="fnanchor">[20]</a></p>
+
+<p>The patient's common drink might also be medicated in the same way. A
+putrid <span class="smcap">diarrh&oelig;a</span> frequently occurs in the latter stage of such
+disorder, and it is a most alarming and dangerous symptom. If the
+discharge be stopped by astringents, a putrid <i>fomes</i> is retained in the
+body, which aggravates the delirium and increases the fever. On the
+contrary, if it be suffered to take its course, the strength of the
+patient must soon be exhausted, and death unavoidably ensue. The
+injection of mephitic air into the intestines, under these
+circumstances, bids fair to be highly serviceable. And a case of this
+deplorable kind, has lately been communicated to me, in which the vapour
+of<span class='pagenum'><a name="Page_305" id="Page_305">[Pg 305]</a></span> chalk and oil of vitriol conveyed into the body by the machine
+employed for tobacco clysters, quickly restrained the <i>diarrh&oelig;a</i>,
+corrected the heat and f&oelig;tor of the stools, and in two days removed
+every symptom of danger<a name="FNanchor_21_21" id="FNanchor_21_21"></a><a href="#Footnote_21_21" class="fnanchor">[21]</a>. Two similar instances of the salutary
+effects of mephitic air, thus administered, have occurred also in my own
+practice, the history of which I shall briefly lay before the reader.
+May we not presume that the same remedy would be equally useful in the
+<span class="smcap">Dysentery</span>? The experiment is at least worthy of trial.</p>
+
+<p>Mr. W&mdash;&mdash;, aged forty-four years, corpulent, inactive, with a short
+neck, and addicted to habits of intemperance, was attacked on the 7th of
+July 1772, with symptoms which seemed to threaten an apoplexy. On the
+8th, a bilious looseness succeeded, with a profuse h&oelig;morrhage from
+the nose. On the 9th, I was called to his assistance. His countenance
+was bloated, his eyes heavy, his skin hot, and his pulse hard, full, and
+oppressed. The diarrh&oelig;a continued; his stools were bilious and very
+offensive; and he complained of griping pains in his bowels. He had
+lost, before I saw him, by the direction of Mr. Hall, a surgeon of
+eminence in Manchester, eight ounces of blood from the arm, which was of
+a lax texture; and he had taken a saline mixture every sixth hour. The
+following draught was prescribed, and a dose of rhubarb directed to be
+administered at night.</p>
+
+<p><span class='pagenum'><a name="Page_306" id="Page_306">[Pg 306]</a></span></p>
+<p>
+<span style="margin-left: 2.5em;">&#8478;. <i>Aq. Cinnam. ten.</i> &#8485;j.</span><br />
+<span style="margin-left: 2.5em;"><i>Succ. Limon. recent.</i> &#8485;&szlig;.</span><br />
+<span style="margin-left: 2.5em;"><i>Salis Nitri gr. xij. Syr. &egrave; Succo Limon. &#658;j. M. f. Haust.</i></span><br />
+<span style="margin-left: 2.5em;"><i>4tis horis sumendus.</i></span><br />
+</p>
+
+<p>July 11. The <i>Diarrh&oelig;a</i> was more moderate; his griping pains were
+abated; and he had less stupor and dejection in his countenance. Pulse
+90, not so hard or oppressed. As his stools continued to be f&oelig;tid,
+the dose of rhubarb was repeated; and instead of simple cinnamon-water,
+his draughts were prepared with an infusion of columbo root.</p>
+
+<p>12. The <i>Diarrh&oelig;a</i> continued; his stools were involuntary; and he
+discharged in this way a quantity of black, grumous, and f&oelig;tid blood.
+Pulse hard and quick; skin hot; tongue covered with a dark fur; abdomen
+swelled; great stupor. Ten grains of columbo root, and fifteen of the
+<i>Gummi rubrum astringens</i> were added to each draught. Fixed air, under
+the form of clysters, was injected every second or third hour; and
+directions were given to supply the patient plentifully with water,
+artificially impregnated with mephitic air. A blister was also laid
+between his shoulders.</p>
+
+<p>13. The Diarrh&oelig;a continued, with frequent discharges of blood; but
+the stools had now lost their f&oelig;tor. Pulse 120; great flatulence in
+the bowels, and fulness in the belly. The clysters of fixed air always
+diminished the tension of the <i>Abdomen</i>, abated flatulence, and made the
+patient more easy and composed for some time after their injection. They
+were<span class='pagenum'><a name="Page_307" id="Page_307">[Pg 307]</a></span> directed to be continued, together with the medicated water. The
+nitre was omitted, and a scruple of the <i>Confect. Damocratis</i> was given
+every fourth hour, in an infusion of columbo root.</p>
+
+<p>14. The Diarrh&oelig;a was how checked, His other symptoms continued as
+before. Blisters were applied to the arms; and a drachm and a half of
+the <i>Tinctura Serpentari&aelig;</i> was added to each draught.</p>
+
+<p>15. His pulse was feeble, quicker and more irregular. He dosed much;
+talked incoherently; and laboured under a slight degree of <i>Dyspn&aelig;a</i>.
+His urine, which had hitherto assumed no remarkable appearance, now
+became pale. Though he discharged wind very freely, his belly was much
+swelled, except for a short time after the injection of the
+air-clysters. The following draughts were then prescribed.</p>
+
+<div class="blockquot"><p>&#8478; <i>Camphor&aelig; mucilag. G. Arab, solut&aelig; gr. viij. Infus. Rad.
+Columbo &#8485; Tinct, Serpent. &#658;ij Confect. Card.
+&#8456;Syr. &egrave; Cort. Aurant &#658;i m. f. Haust. 4tis horis
+sumendus.</i></p></div>
+
+<p>Directions were given to foment his feet frequently with vinegar and
+warm water.</p>
+
+<p>16. He has had no stools since the 14th. His <i>Abdomen</i> is tense. No
+change in the other symptoms. The <i>Tinct. Serpent.</i> was omitted in his
+draughts, and an equal quantity of <i>Tinct. Rh&aelig;i Sp.</i> substituted in its
+place.<span class='pagenum'><a name="Page_308" id="Page_308">[Pg 308]</a></span></p>
+
+<p>In the evening he had a motion to stool, of which he was for the first
+time so sensible, as to give notice to his attendants. But the
+discharge, which was considerable and slightly offensive, consisted
+almost entirely of blood, both in a coagulated and in a liquid state.
+His medicines were therefore varied as follows:</p>
+
+<div class="blockquot"><p>&#8478;. <i>Decoct. Cort. Peruv. &#8485;iss
+Tinct. Cort. ejusd. &#658;ij. Confect.
+Card. &#8456;j Gum. Rubr. Astring. gr.
+xv. Pulv. Alnmin. gr. vij. m. f. Haustus 4tis horis
+fumendus.</i></p></div>
+
+<p>Red Port wine was now given more freely in his medicated water; and his
+nourishment consisted of sago and salep.</p>
+
+<p>In this state, with very little variation, he continued for several
+days; at one time ostive, and at another discharging small quantities of
+f&aelig;ces, mixed with grumous blood. The air-clysters were continued, and
+the astringents omitted.</p>
+
+<p>20. His urine was now of an amber colour, and deposited a slight
+sediment. His pulse was more regular, and although still very quick,
+abated in number ten strokes in a minute. His head was less confused,
+and his sleep seemed to be refreshing. No blood appeared in his stools,
+which were frequent, but small in quantity; and his <i>Abdomen</i> was less
+tense than usual. He was extremely deaf; but gave rational answers to
+the few questions which were proposed to him; and said he felt no pain.<span class='pagenum'><a name="Page_309" id="Page_309">[Pg 309]</a></span></p>
+
+<p>21. He passed a very restless night; his delirium recurred; his pulse
+beat 125 strokes in a minute; his urine was of a deep amber colour when
+first voided; but when cold assumed the appearance of cow's whey. The
+<i>Abdomen</i> was not very tense, nor had he any further discharge of blood.</p>
+
+<p>Directions were given to shave his head, and to wash it with a mixture
+of vinegar and brandy; the quantity of wine in his drink was diminished;
+and the frequent use of the pediluvium was enjoined. The air-clysters
+were discontinued, as his stools were not offensive, and his <i>Abdomen</i>
+less distended.</p>
+
+<p>22. His pulse was now small, irregular, and beat 130 strokes in a
+minute. The <i>Dyspn&oelig;a</i> was greatly increased; his skin was hot, and
+bedewed with a clammy moisture; and every symptom seemed to indicate the
+approach of death. In this state he continued till evening, when he
+recruited a little. The next day he had several slight convulsions. His
+urine which was voided plentifully, still put on the appearance of whey
+when cold. Cordial and antispasmodic draughts, composed of camphor,
+tincture of castor, and <i>Sp. vol. aromat.</i> were now directed; and wine
+was liberally administered.</p>
+
+<p>24. He rose from his bed, and by the assistance of his attendants walked
+across the chamber. Soon after he was seized with a violent convulsion,
+in which he expired.</p>
+
+<p>To adduce a case which terminated fatally as a proof of the efficacy of
+any medicine, recommended<span class='pagenum'><a name="Page_310" id="Page_310">[Pg 310]</a></span> to the attention of the public, may perhaps
+appear singular; but cannot be deemed absurd, when that remedy answered
+the purposes for which it was intended. For in the instance before us;
+fixed air was employed, not with an expectation that it would cure the
+fever, but to obviate the symptoms of putrefaction, and to allay the
+uneasy irritation in the bowels. The disease was too malignant, the
+nervous system too violently affected, and the strength of the patient
+too much exhausted by the discharges of blood which he suffered, to
+afford hopes of recovery from the use of the most powerful antiseptics.</p>
+
+<p>But in the succeeding case the event proved more fortunate.</p>
+
+<p>Elizabeth Grundy, aged seventeen, was attacked on the 10th of December
+1772, with the usual symptoms of a continued fever. The common method of
+cure was pursued; but the disease increased, and soon assumed a putrid
+type.</p>
+
+<p>On the 23d I found her in a constant delirium, with a <i>subsultus
+tendinum</i>. Her skin was hot and dry, her tongue black, her thirst
+immoderate, and her stools frequent, extremely offensive, and for the
+most part involuntary. Her pulse beat 130 strokes in a minute; she dosed
+much; and was very deaf. I directed wine to be administered freely; a
+blister to be applied to her back; the <i>pediluvium</i> to be used several
+times in the day; and mephitic air to be injected under the form of a
+clyster every two hours. The next day her stools were less frequent, had
+lost their f&oelig;tor, and were no longer discharged involuntarily; her<span class='pagenum'><a name="Page_311" id="Page_311">[Pg 311]</a></span>
+pulse was reduced to 110 strokes in the minute; and her delirium was
+much abated. Directions were given to repeat the clysters, and to supply
+the patient liberally with wine. These means were assiduously pursued
+several days; and the young woman was so recruited by the 28th, that the
+injections were discontinued. She was now quite rational, and not averse
+to medicine. A decoction of Peruvian bark was therefore prescribed, by
+the use of which she speedily recovered her health.</p>
+
+<p>I might add a third history of a putrid disease, in which the mephitic
+air is now under trial, and which affords the strongest proof both of
+the <i>antiseptic</i>, and of the <i>tonic</i> powers of this remedy; but as the
+issue of the case remains yet undetermined (though it is highly
+probable, alas! that it will be fatal) I shall relate only a few
+particulars of it. Master D. a boy of about twelve years of age, endowed
+with an uncommon capacity, and with the most amiable dispositions, has
+laboured many months under a hectic fever, the consequence of several
+tumours in different parts of his body. Two of these tumours were laid
+open by Mr. White, and a large quantity of purulent matter was
+discharged from them. The wounds were very properly treated by this
+skilful surgeon, and every suitable remedy, which my best judgment could
+suggest, was assiduously administered. But the matter became sanious, of
+a brown colour, and highly putrid. A <i>Diarrh&oelig;a</i> succeeded; the
+patient's stools were intolerably offensive, and voided without his
+knowledge. A black fur collected about his teeth; his tongue was covered
+with <i>Aphth&aelig;</i>; and his breath was so f&oelig;tid, as scarcely to be
+endured. His strength was almost exhausted;<span class='pagenum'><a name="Page_312" id="Page_312">[Pg 312]</a></span> a <i>subsultus tendinum</i> came
+on; and the final period of his sufferings seemed to be rapidly
+approaching. As a last, but almost hopeless, effort, I advised the
+injection of clysters of mephitic air. These soon corrected the f&oelig;tor
+of the patient's stools; restrained his <i>Diarrh&oelig;a</i>; and seemed to
+recruit his strength and spirits. Within the space of twenty-four hours
+his wounds assumed a more favourable appearance; the matter discharged
+from them became of a better colour and consistence; and was no longer
+so offensive to the smell. The use of this remedy has been continued
+several days, but is now laid aside. A large tumour is suddenly formed
+under the right ear; swallowing is rendered difficult and painful; and
+the patient refuses all food and medicine. Nourishing clysters are
+directed; but it is to be feared that these will renew the looseness,
+and that this amiable youth will quickly sink under his disorder<a name="FNanchor_22_22" id="FNanchor_22_22"></a><a href="#Footnote_22_22" class="fnanchor">[22]</a>.</p>
+
+<p>The use of <i>wort</i> from its saccharine quality, and disposition to
+ferment, has lately been proposed as a remedy for the <span class="smcap">Sea Scurvy</span>. Water
+or other liquors, already abounding with fixed air in a separate state,
+should seem to be better adapted to this purpose; as they will more
+quickly correct the putrid disposition of the fluids, and at the same
+time, by their gentle stimulus<a name="FNanchor_23_23" id="FNanchor_23_23"></a><a href="#Footnote_23_23" class="fnanchor">[23]</a> increase the powers of digestion, and
+give new strength to the whole system.</p>
+
+<p><span class='pagenum'><a name="Page_313" id="Page_313">[Pg 313]</a></span></p><p>Dr. Priestley, who suggested both the idea and the means of executing
+it, has under the sanction of the College of Physicians, proposed the
+scheme to the Lords of the Admiralty, who have ordered trial to be made
+of it, on board some of his Majesty's ships of war. Might it not however
+give additional efficacy to this remedy, if instead of simple water, the
+infusion of malt were to be employed?</p>
+
+<p>I am persuaded such a medicinal drink might be prescribed also with
+great advantage in <span class="smcap">scrophulous complaints</span>, when not attended with a
+hectic fever; and in other disorders in which a general acrimony
+prevails, and the crasis of the blood is destroyed. Under such
+circumstances, I have seen <i>vibices</i> which spread over the body,
+disappear in a few days from the use of wort.</p>
+
+<p>A gentleman who is subject to a scorbutic eruption in his face, for
+which he has used a variety of remedies with no very beneficial effect,
+has lately applied the fumes of chalk and oil of vitriol to the parts
+affected. The operation occasions great itching and pricking in the
+skin, and some degree of drowsiness, but evidently abates the serous
+discharge, and diminishes the eruption. This patient has several
+symptoms which indicate a genuine scorbutic <span class="smcap">Diathesis</span>; and it is
+probable that fixed air, taken internally, would be an useful medicine
+in this case.</p>
+
+<p>The saline draughts of Riverius are supposed to owe their antiemetic
+effects to the air, which is separated from the salt of wormwood during
+the act of effervescence. And the tonic powers of many mineral<span class='pagenum'><a name="Page_314" id="Page_314">[Pg 314]</a></span> waters
+seem to depend on this principle. I was lately desired to visit a lady
+who had most severe convulsive <span class="smcap">reachings</span>. Various remedies had been
+administered without effect, before I saw her. She earnestly desired a
+draught of malt liquor, and was indulged with half a pint of Burton beer
+in brisk effervescence. The vomitings ceased immediately, and returned
+no more. Fermenting liquors, it is well known, abound with fixed air. To
+this, and to the cordial quality of the beer, the favourable effect
+which it produced, may justly be ascribed. But I shall exceed my design
+by enlarging further on this subject. What has been advanced it is
+hoped, will suffice to excite the attention of physicians to a remedy
+which is capable of being applied to so many important medicinal
+purposes.</p>
+
+
+<h3>NUMBER IV.</h3>
+
+<h4><i>Extract of a Letter from <span class="smcap">William Falconer</span>, M.D. of <span class="smcap">Bath</span>.</i></h4>
+
+
+<p class="right">Jan 6, 1774,</p>
+
+<p>Reverend Sir,</p>
+
+
+<p>I once observed the same taste you mention (Philosophical Transactions,
+p. 156. of this Volume, p. 35.) viz. like tar water, in some water that
+I impregnated with fixed air about three years ago. I did not then know
+to what to attribute it, but your experiment seems to clear it up. I
+happened to have spent all my acid for raising effervescence, and to
+supply its place I used a bottle of dulcified spirit of nitre, which I
+knew was greatly under-saturated with spirit of wine;<span class='pagenum'><a name="Page_315" id="Page_315">[Pg 315]</a></span> from which, as
+analogous to your observation, I imagine the effect proceeded.</p>
+
+<p>As<a name="FNanchor_24_24" id="FNanchor_24_24"></a><a href="#Footnote_24_24" class="fnanchor">[24]</a> to the coagulation of the blood of animals by fixed Air, I fear
+it will scarce stand the test of experiment, as I this day gave it, I
+think, a fair trial, in the following manner.</p>
+
+<p>A young healthy man, at 20 years old, received a contusion by a fall,
+was instantly carried to a neighbouring surgeon, and, at my request,
+bled in the following manner.</p>
+
+<p>I inserted a glass funnel into the neck of a large clear phial about
+&#8485;x. contents, and bled him into it to about
+&#8485;viii. By these means the blood was exposed to the air as
+little a time as possible, as it flowed into the bottle as it came from
+the orifice.</p>
+
+<p>As soon as the quantity proposed was drawn, the bottle was carefully
+corked, and brought to me. It was then quite fluid, nor was there the
+least separation of its parts.</p>
+
+<p>On the surface of this I conveyed several streams of fixed air (having
+first placed the bottle with the blood in a bowl of water, heated as
+nearly to the human heat as possible) from the mixture of the vitriolic
+acid and lixiv. tartar, which I use preferably to other alkalines,<span class='pagenum'><a name="Page_316" id="Page_316">[Pg 316]</a></span> as
+being (as Dr. Cullen observes) in the mildest state, and therefore most
+likely to generate most air.</p>
+
+<p>I shook the phial often, and threw many streams of air on the blood, as
+I have often practised with success for impregnating water; but could
+not perceive the smallest signs of coagulation, although it stood in an
+atmosphere of fixed air 20 minutes or more. I then uncorked the bottles,
+and poured off about &#8485;ii to which I added about 6
+or 7 gtts of spirit of vitriol, which coagulated it immediately. I set
+the remainder in a cold place and it coagulated, as near as I could
+judge, in the same time that blood would have done newly drawn from the
+vein.</p>
+
+<p>P. 82. Perhaps the circumilance of putrid vegetables yielding all fixed
+and no inflammable air may be the causes of their proving so antiseptic,
+even when putrid, as appears by Mr. Alexander's Experiments.</p>
+
+<p>P. 86. Perhaps the putrid air continually exhaled may be one cause of
+the luxuriancy of plants growing on dunghills or in very rich soils.</p>
+
+<p>P. 146. Your observation that inflammable air consists of the union of
+some acid vapour with phlogiston, puts me in mind of an old observation
+of Dr. Cullen, that the oil separated from soap by an acid was much more
+inflammable than before, resembling essential oil, and soluble in V. sp.</p>
+
+<p>I have tried fixed air as an antiseptic taken in by respiration, but
+with no great success. In one case it seemed to be of service, in two it
+seemed indifferent, and in one was injurious, by exciting a cough.<span class='pagenum'><a name="Page_317" id="Page_317">[Pg 317]</a></span></p>
+
+
+<h3>NUMBER V.</h3>
+
+<h4><i>Extract of a Letter from Mr. <span class="smcap">William Bewley</span>, of <span class="smcap">Great Massingham,
+Norfolk</span>.</i></h4>
+
+
+<p class="right">March 23, 1774.</p>
+
+<p>Dear Sir,</p>
+
+<p>When I first received your paper, I happened to have a process going on
+for the preparation of <i>nitrous ether</i>, without distillation.<a name="FNanchor_25_25" id="FNanchor_25_25"></a><a href="#Footnote_25_25" class="fnanchor">[25]</a> I had
+heretofore always taken for granted that the elastic fluid generated in
+that preparation was <i>fixed</i> air: but on examination I found this
+combination of the nitrous acid with inflammable spirits, produced an
+elastic fluid that had the same general properties with the air that you
+unwillingly, though very properly, in my opinion, term <i>nitrous</i>; as I
+believe it is not to be procured without employing the <i>nitrous</i> acid,
+either in a simple state, or compounded, as in <i>aqua regia</i>. I shall
+suggest, however, by and by some doubts with respect to it's title to
+the appellation of <i>air</i>.</p>
+
+<p>Water impregnated with your nitrous air <i>certainly</i>, as you suspected
+from it's taste, contains the nitrous<span class='pagenum'><a name="Page_318" id="Page_318">[Pg 318]</a></span> acid. On saturating a quantity of
+this water with a fixed alcali, and then evaporating, &amp;c. I have
+procured two chrystals of nitre. But the principal observations that
+have occurred to me on the subject of nitrous air are the following. My
+experiments have been few and made by snatches, under every disadvantage
+as to apparatus, &amp;c. and with frequent interruptions; and yet I think
+they are to be depended upon.</p>
+
+<p>My first remark is, that nitrous air does not give water a sensibly acid
+impregnation, unless it comes into contact, or is mixed with a portion
+of common or atmospherical air: and my second, that nitrous air
+principally consists of the nitrous acid itself, reduced to the state of
+a <i>permanent</i> vapour not condensable by cold, like other vapours, but
+which requires the presence and admixture of common air to restore it to
+its primitive state of a liquid. I am beholden for this idea, you will
+perceive, to your own very curious discovery of the true nature of Mr.
+Cavendish's <i>marine</i> vapour.</p>
+
+<p>When I first repeated your experiment of impregnating water with nitrous
+air, the water, I must own tasted acid; as it did in one, or perhaps two
+trials afterwards; but, to my great astonishment, in all the following
+experiments, though some part of the factitious air, or vapour, was
+visibly absorbed by the water, I could not perceive the latter to have
+acquired any sensible acidity. I at length found, however, that I could
+render this same water <i>very</i> acid, by means only of the nitrous air
+already included in the phial with it. Taking the inverted phial out of
+the water, I remove my finger from the mouth of it, to admit a<span class='pagenum'><a name="Page_319" id="Page_319">[Pg 319]</a></span> little
+of the common air, and instantly replace my finger. The redness,
+effervescence, and diminution take place. Again taking off my finger,
+and instantly replacing it, more common, air rushes in, and the same
+phenomena recur. The process sometimes requires to be seven or eight
+times repeated, before the whole of the nitrous <i>vapour</i> (as I shall
+venture to call it) is condensed into nitrous <i>acid</i>, by the successive
+entrance of fresh parcels of common air after each effervescence; and
+the water becomes evidently more and more acid after every such fresh
+admission of the external air, which at length ceases to enter, when the
+whole of the vapour has been condensed. No agitation of the water is
+requisite, except a gentle motion, just sufficient to rince the sides of
+the phial, in order to wash off the condensed vapour.</p>
+
+<p>The acidity which you (and I likewise, at first) observed in the water
+agitated with nitrous air <i>alone</i>, I account for thus. On bringing the
+phial to the mouth, the common air meeting with the nitrous vapour in
+the neck of the phial, condenses it, and impregnates the water with the
+acid, in the very act of receiving it upon the tongue. On stopping the
+mouth of the phial with my tongue for a short time and afterwards
+withdrawing it a very little, to suffer the common air to rush past it
+into the phial, the sensation of acidity has been sometimes intolerable:
+but taking a large gulph of the water at the same time, it has been
+found very slightly acid.&mdash;The following is one of the methods by which
+I have given water a very strong acid impregnation, by means of a
+mixture of nitrous and common air.<span class='pagenum'><a name="Page_320" id="Page_320">[Pg 320]</a></span></p>
+
+<p>Into a small phial, containing only common air, I force a quantity of
+nitrous air at random, out of a bladder, and instantly clap my finger on
+the mouth of the bottle. I then immerse the neck of it into water, a
+small quantity of which I suffer to enter, which squirts into it with
+violence; and immediately replacing my finger, remove the phial. The
+water contained in it is already <i>very</i> acid, and it becomes more and
+more so (if a sufficient quantity of nitrous air was at first thrown in)
+on alternately stopping the mouth of the phial, and opening it, as often
+as fresh air will enter.</p>
+
+<p>Since I wrote the above, I have frequently converted a small portion of
+water in an ounce phial into a weak <i>Aqua fortis</i>, by repeated mixtures
+of common and nitrous air; throwing in alternately the one or the other,
+according to the circumstances; that is, as long as there was a
+superabundance of nitrous air, suffering the common air to enter and
+condense it; and, when that was effected, forcing in more nitrous air
+from the bladder, to the common air which now predominated in the
+phial&mdash;and so alternately. I have wanted leisure, and conveniences, to
+carry on this process to its <i>maximum</i>, or to execute it in a different
+and better manner; but from what I have done, I think we may conclude
+that nitrous air consists principally of the nitrous acid,
+phlogisticated, or otherwise so modified, by a previous commenstruation
+with metals, inflammable spirits, &amp;c. as to be reduced into a durably
+elastic vapour: and that, in order to deprive it of its elasticity, and
+restore it to its former state, an addition of common air is requisite,
+and, as I suspect, of water likewise, or some other fluid: as in the<span class='pagenum'><a name="Page_321" id="Page_321">[Pg 321]</a></span>
+course of my few trials, I have not yet been able to condense it in a
+perfectly dry bottle.</p>
+
+
+<h3>NUMBER VI.</h3>
+
+<h4><i>A Letter from</i> Dr. <span class="smcap">Franklin</span>.</h4>
+
+
+<p class="right">Craven Street, April 10, 1774.</p>
+
+<p>Dear Sir,</p>
+
+
+<p>In compliance with your request, I have endeavoured to recollect the
+circumstances of the American experiments I formerly mentioned to you,
+of raising a flame on the surface of some waters there.</p>
+
+<p>When I passed through New Jersey in 1764, I heard it several times
+mentioned, that by applying a lighted candle near the surface of some of
+their rivers, a sudden flame Would catch and spread on the water,
+continuing to burn for near half a minute. But the accounts I received
+were so imperfect that I could form no guess at the cause of such an
+effect, and rather doubted the truth of it. I had no opportunity of
+seeing the experiment; but calling to see a friend who happened to be
+just returned home from making it himself, I learned from him the manner
+of it; which was to choose a shallow place, where the bottom could be
+reached by a walking-stick, and was muddy; the mud was first to be
+stirred with the stick, and when a number of small bubbles began to
+arise from it, the candle was applied. The flame was so sudden and so
+strong, that it catched his ruffle and spoiled it, as I saw.<span class='pagenum'><a name="Page_322" id="Page_322">[Pg 322]</a></span> New-Jersey
+having many pine-trees in different parts of it, I then imagined that
+something like a volatile oil of turpentine might be mixed with the
+waters from a pine-swamp, but this supposition did not quite satisfy me.
+I mentioned the fact to some philosophical friends on my return to
+England, but it was not much attended to. I suppose I was thought a
+little too credulous.</p>
+
+<p>In 1765, the Reverend Dr. Chandler received a letter from Dr. Finley,
+President of the College in that province, relating the same experiment.
+It was read at the Royal Society, Nov. 21, of that year, but not printed
+in the Transactions; perhaps because it was thought too strange to be
+true, and some ridicule might be apprehended if any member should
+attempt to repeat it in order to ascertain or refute it. The following
+is a copy of that account.</p>
+
+<p>"A worthy gentleman, who lives at a few miles distance, informed me that
+in a certain small cove of a mill-pond, near his house, he was surprized
+to see the surface of the water blaze like inflamed spirits. I soon
+after went to the place, and made the experiment with the same success.
+The bottom of the creek was muddy, and when stirred up, so as to cause a
+considerable curl on the surface, and a lighted candle held within two
+or three inches of it, the whole surface was in a blaze, as instantly as
+the vapour of warm inflammable spirits, and continued, when strongly
+agitated, for the space of several seconds. It was at first imagined to
+be peculiar to that place; but upon trial it was soon found, that such a
+bottom in other places exhibited the same phenomenon. The discovery<span class='pagenum'><a name="Page_323" id="Page_323">[Pg 323]</a></span> was
+accidentally made by one belonging to the mill."</p>
+
+<p>I have tried the experiment twice here in England, but without success.
+The first was in a slow running water with a muddy bottom. The second in
+a stagnant water at the bottom of a deep ditch. Being some time employed
+in stirring this water, I ascribed an intermitting fever, which seized
+me a few days after, to my breathing too much of that foul air which I
+stirred up from the bottom, and which I could not avoid while I stooped
+in endeavouring to kindle it.&mdash;The discoveries you have lately made of
+the manner in which inflammable air is in some cases produced, may throw
+light on this experiment, and explain its succeeding in some cases, and
+not in others. With the highest esteem and respect,</p>
+
+<p>
+<span style="margin-left: 2.5em;">I am, Dear Sir,</span><br />
+<br />
+<span style="margin-left: 5em;">Your most obedient humble servant,</span><br />
+<br />
+<span style="margin-left: 7.5em;"><span class="smcap">B. Franklin.</span></span><br />
+</p>
+
+
+<h3>NUMBER VII.</h3>
+
+<h4><i>Extract of a Letter from</i> Mr. <span class="smcap">Henry</span> <i>of</i> Manchester.</h4>
+
+<p>It is with great pleasure I hear of your intended publication <i>on air</i>,
+and I beg leave to communicate to you an experiment or two which I
+lately made.</p>
+
+<p>Dr. Percival had tried, without effect, to dissolve lead in water
+impregnated with fixed air. I however<span class='pagenum'><a name="Page_324" id="Page_324">[Pg 324]</a></span> thought it probable, that the
+experiment might succeed with nitrous air. Into a quantity of water
+impregnated with it, I put several pieces of sheet-lead, and suffered
+them, after agitation, to continue immersed about two hours. A few drops
+of vol. tincture of sulphur changed the water to a deep orange colour,
+but not so deep as when the same tincture was added to a glass of the
+same water, into which one drop of a solution of sugar of lead had been
+instilled. The precipitates of both in the morning, were exactly of the
+same kind; and the water in which the lead had been infused all night,
+being again tried by the same test, gave signs of a still stronger
+saturnine impregnation&mdash;Whether the nitrous air acts as an acid on the
+lead, or in the same manner that fixed air dissolves iron, I do not
+pretend to determine. Syrup of violets added to the nitrous water became
+of a pale red, but on standing about an hour, grew of a turbid brown
+cast.</p>
+
+<p>Though the nitrous acid is not often found, except produced by art, yet
+as there is a probability that nitre may be formed in the earth in large
+towns, and indeed fossile nitre has been actually found in such
+situations, it should be an additional caution against the use of leaden
+pumps.</p>
+
+<p>I tried to dissolve mercury by the same means, but without success.</p>
+
+<p>
+<span style="margin-left: 2.5em;">I am, with the most sincere esteem,</span><br />
+<br />
+<span style="margin-left: 5em;">Dear Sir,</span><br />
+<br />
+<span style="margin-left: 5em;">Your obliged and obedient servant,</span><br />
+<br />
+<span style="margin-left: 7.5em;"><span class="smcap">Tho. Henry</span>.</span><br />
+</p>
+
+<h4><i>FINIS.</i></h4>
+
+<div class="footnotes"><h3>FOOTNOTES:</h3>
+
+<div class="footnote"><p><a name="Footnote_15_15" id="Footnote_15_15"></a><a href="#FNanchor_15_15"><span class="label">[15]</span></a> See Dr. Falconer's very useful and ingenious treatise on
+the Bath water, 2d edit. p. 313.</p></div>
+
+<div class="footnote"><p><a name="Footnote_16_16" id="Footnote_16_16"></a><a href="#FNanchor_16_16"><span class="label">[16]</span></a> May, 1772.</p></div>
+
+<div class="footnote"><p><a name="Footnote_17_17" id="Footnote_17_17"></a><a href="#FNanchor_17_17"><span class="label">[17]</span></a> Vid. Mr. White's useful treatise on the management of
+pregnant and lying-in women, p. 279.</p></div>
+
+<div class="footnote"><p><a name="Footnote_18_18" id="Footnote_18_18"></a><a href="#FNanchor_18_18"><span class="label">[18]</span></a> See the author's observations on the efficacy of external
+applications in the ulcerous sore throats, Essays medical and
+experimental, Vol. I. 2d edit. p. 377.</p></div>
+
+<div class="footnote"><p><a name="Footnote_19_19" id="Footnote_19_19"></a><a href="#FNanchor_19_19"><span class="label">[19]</span></a> The author of these observations.</p></div>
+
+<div class="footnote"><p><a name="Footnote_20_20" id="Footnote_20_20"></a><a href="#FNanchor_20_20"><span class="label">[20]</span></a> Directions for impregnating water with fixed air, in order
+to communicate to it the peculiar spirit and virtues of Pyrmont water,
+and other mineral waters of a similar nature.</p></div>
+
+<div class="footnote"><p><a name="Footnote_21_21" id="Footnote_21_21"></a><a href="#FNanchor_21_21"><span class="label">[21]</span></a> Referring to the case communicated by Mr. Hey.</p></div>
+
+<div class="footnote"><p><a name="Footnote_22_22" id="Footnote_22_22"></a><a href="#FNanchor_22_22"><span class="label">[22]</span></a> He languished about a week, and then died.</p></div>
+
+<div class="footnote"><p><a name="Footnote_23_23" id="Footnote_23_23"></a><a href="#FNanchor_23_23"><span class="label">[23]</span></a> The vegetables which are most efficacious in the cure of
+the scurvy, possess some degree of a stimulating power.</p></div>
+
+<div class="footnote"><p><a name="Footnote_24_24" id="Footnote_24_24"></a><a href="#FNanchor_24_24"><span class="label">[24]</span></a> This refers, to an experiment mentioned in the first
+publication of these papers in the Philosophical Transactions, but
+omitted in this volume.</p></div>
+
+<div class="footnote"><p><a name="Footnote_25_25" id="Footnote_25_25"></a><a href="#FNanchor_25_25"><span class="label">[25]</span></a> The first account of this curious process was, I believe,
+given in the Mem. de l'Ac. de Sc. de Paris for 1742. Though seemingly
+less volatile than the vitriolic ether, it boils with a much smaller
+degree of heat. One day last summer, it boiled in the coolest room of my
+house; as it gave me notice by the explosion attending its driving out
+the cork. To save the bottle, and to prevent the total loss of the
+liquor by evaporation, I found myself obliged instantly to carry it down
+to my cellar.</p></div>
+</div>
+
+
+<hr style="width: 65%;" />
+<h2>ERRATA.</h2>
+
+
+
+<div class='center'>
+<table border="0" cellpadding="4" cellspacing="0" summary="">
+<tr><td align='left'>P. 15. l. 13.</td><td align='left'><i>for</i></td><td align='left'>it to</td><td align='left'><i>read</i></td><td align='left'>to it</td></tr>
+<tr><td align='left'>p. 24. l. 20.</td><td align='left'>&mdash;&mdash;</td><td align='left'>has</td><td align='left'>&mdash;&mdash;</td><td align='left'>had</td></tr>
+<tr><td align='left'>p. 60. l. 22.</td><td align='left'>&mdash;&mdash;</td><td align='left'>inflammable</td><td align='left'>&mdash;&mdash;</td><td align='left'>in inflammable</td></tr>
+<tr><td align='left'>p. 84. l. 5.</td><td align='left'>&mdash;&mdash;</td><td align='left'>experiments</td><td align='left'>&mdash;&mdash;</td><td align='left'>experiment</td></tr>
+<tr><td align='left'>p. 145. l. 16.</td><td align='left'>&mdash;&mdash;</td><td align='left'>with</td><td align='left'>&mdash;&mdash;</td><td align='left'>of</td></tr>
+<tr><td align='left'>p. 153. l. 1.</td><td align='left'>&mdash;&mdash;</td><td align='left'>that is</td><td align='left'>&mdash;&mdash;</td><td align='left'>this air</td></tr>
+<tr><td align='left'>p. 199. l. 17.</td><td align='left'>&mdash;&mdash;</td><td align='left'>ingenious</td><td align='left'>&mdash;&mdash;</td><td align='left'>ingenuous</td></tr>
+<tr><td align='left'>p. 211. l. 23.</td><td align='left'>&mdash;&mdash;</td><td align='left'>of</td><td align='left'>&mdash;&mdash;</td><td align='left'>, if</td></tr>
+<tr><td align='left'>p. 243. l. 27.</td><td align='left'>&mdash;&mdash;</td><td align='left'>diminishing</td><td align='left'>&mdash;&mdash;</td><td align='left'>diminished</td></tr>
+<tr><td align='left'>p. 272. l. 21.</td><td align='left'>&mdash;&mdash;</td><td align='left'>seem</td><td align='left'>&mdash;&mdash;</td><td align='left'>seems</td></tr>
+<tr><td align='left'>p. 301. l. 31.</td><td align='left'>&mdash;&mdash;</td><td align='left'>&mdash;&mdash;</td><td align='left'>&mdash;&mdash;</td><td align='left'>one end</td></tr>
+<tr><td align='left'>p. 303. l. 5.</td><td align='left'>&mdash;&mdash;</td><td align='left'>&mdash;&mdash;</td><td align='left'>&mdash;&mdash;</td><td align='left'>the nitrous</td></tr>
+<tr><td align='left'>p. 304. l. 21.</td><td align='left'>&mdash;&mdash;</td><td align='left'>deslrium</td><td align='left'>&mdash;&mdash;</td><td align='left'>delirium</td></tr>
+<tr><td align='left'>p. 306. l. 2.</td><td align='left'>&mdash;&mdash;</td><td align='left'>recet.</td><td align='left'>&mdash;&mdash;</td><td align='left'>recent.</td></tr>
+<tr><td align='left'>p. 308. l. 7.</td><td align='left'>&mdash;&mdash;</td><td align='left'>per</td><td align='left'>&mdash;&mdash;</td><td align='left'>Peruv.</td></tr>
+<tr><td align='left'>p. 313. l. 27.</td><td align='left'>&mdash;&mdash;</td><td align='left'>usual</td><td align='left'>&mdash;&mdash;</td><td align='left'>useful</td></tr>
+<tr><td align='left'>p. 300. to 314. passim</td><td align='left'>&mdash;&mdash;</td><td align='left'>Diarrh&aelig;a</td><td align='left'>&mdash;&mdash;</td><td align='left'>Diarrh&oelig;a</td></tr>
+<tr><td align='left'>p. 316. l. 11.</td><td align='left'>&mdash;&mdash;</td><td align='left'>remains</td><td align='left'>&mdash;&mdash;</td><td align='left'>remainder</td></tr>
+<tr><td align='left'>p. 524. l. 15.</td><td align='left'>&mdash;&mdash;</td><td align='left'>it</td><td align='left'>&mdash;&mdash;</td><td align='left'>iron.</td></tr>
+</table></div>
+
+
+
+
+<hr style="width: 65%;" />
+<h4>A <span class="smcap">Catalogue</span> of BOOKS written by</h4>
+
+<h2>JOSEPH PRIESTLEY, LL.D. F.R.S.,</h2>
+
+<h4><i>And printed for</i></h4>
+
+<h3>J. JOHNSON, <span class="smcap">Bookseller</span>, at No. 72,</h3>
+
+<h4>St. Paul's Church-Yard, London.</h4>
+
+
+<p>1. The <span class="smcap">History</span> and <span class="smcap">Present State</span> of <span class="smcap">Electricity</span>, with original
+Experiments, illustrated with Copper Plates. 4th Edit, corrected and
+enlarged, 4to. 1l. 1s.</p>
+
+<p>2. A <span class="smcap">Familiar Introduction</span> to the <span class="smcap">Study</span> of <span class="smcap">Electricity</span>, 2d Edit. 8vo.
+2s. 6d.</p>
+
+<p>3. The <span class="smcap">History</span> and <span class="smcap">Present State</span> of <span class="smcap">Discoveries</span> relating to <span class="smcap">Vision</span>,
+<span class="smcap">Light</span>, and <span class="smcap">Colours</span>, 2 vols. 4to. illustrated with a great Number of
+Copper Plates, 1l. 11s. 6d. in Boards.</p>
+
+<p>4. A <span class="smcap">Familiar Introduction</span> to the <span class="smcap">Theory</span> and <span class="smcap">Practice</span> of <span class="smcap">Perspective</span>,
+with Copper Plates, 5s. in Boards.</p>
+
+<p>5. <span class="smcap">Directions</span> for impregnating Water with <span class="smcap">Fixed Air</span>, in order to
+communicate to it the peculiar Spirit and Virtues of <span class="smcap">Pyrmont Water</span>, and
+other Mineral Waters of a similar Nature, 1s.</p>
+
+<p>6. Experiments and Observations on different Kinds of Air, with Copper
+Plates, 2d Edit. 5s. in Boards.</p>
+
+<p>7. A <span class="smcap">New Chart</span> of <span class="smcap">History</span>, containing a View of the principal
+Revolutions of Empire that have taken Place in the World; with a Book
+describing it, containing an Epitome of Universal History, 10s. 6d.</p>
+
+<p>8. A <span class="smcap">Chart</span> of <span class="smcap">Biography</span>, with a Book, containing an Explanation of it,
+and a Catalogue of all the Names inserted in it, 4th Edit, very much
+improved, 10s. 6d.</p>
+
+<p>9. An Essay on a Course of liberal Education for Civil and Active Life;
+with Plans of Lectures on, 1. The Study of History and general Policy.
+2. The History of England. 3. The Constitution and Laws of England. To
+which are added Remarks on Dr. Browne's proposed Code of Education.</p>
+
+<p>10. The <span class="smcap">Rudiments</span> of <span class="smcap">English Grammar</span>, adapted to the Use of Schools, 1s.
+6d.</p>
+
+<p>11. The above <span class="smcap">Grammar</span>, with Notes and Observations, for the Use of those
+who have made some Proficiency in the Language, 4th Ed. 3s.</p>
+
+<p>12. An <span class="smcap">Essay</span> on the <span class="smcap">First Principles</span> of <span class="smcap">Government</span>, and on the Nature of
+<span class="smcap">Political</span>, <span class="smcap">Civil</span>, and <span class="smcap">Religious Liberty</span>, 2d Edit, much enlarged, 5s.</p>
+
+<p>13. <span class="smcap">Institutes</span> of <span class="smcap">Natural</span> and <span class="smcap">Revealed Religion</span>, Vol. I. containing the
+Elements of Natural Religion; to which is prefixed, An Essay on the best
+Method of communicating religious Knowledge to the Members of Christian
+Societies, 2s. 6d. sewed.&mdash;Vol. II. containing the Evidences of the
+Jewish and Christian Revelation, 3s. sewed.&mdash;Vol. III. containing the
+Doctrines of Revelation, 2s. 6d. sewed.&mdash;Preparing for the Press (March
+1775) the fourth and last Part of this Work, containing a View of the
+Corruptions of Christianity.</p>
+
+<p>14. An Examination of Dr. Reid's Enquiry into the Human Mind, on the
+Principles of Common Sense, Dr. Beattie's Essay on the Nature and
+Immutability of Truth, and Dr. Oswald's Appeal to Common Sense in behalf
+of Religion. To which is added the Correspondence of Dr. Beattie and Dr.
+Oswald with the Author, 2d Edit. 5s. unbound.</p>
+
+<p>15. A <span class="smcap">free address</span> to <span class="smcap">Protestant Dissenters</span>, on the Subject of the
+Lord's Supper, the third Edition with Additions, 2s.</p>
+
+<p>16. The Additions to the Above may be had alone, 1s.</p>
+
+<p>17. An <span class="smcap">Address</span> to <span class="smcap">Protestant Dissenters</span>, on the Subject of giving the
+Lord's Supper to Children, 1s.</p>
+
+<p>18. <span class="smcap">Considerations</span> on <span class="smcap">Differences</span> of <span class="smcap">Opinion</span> among Christians; with a
+Letter to the Rev. Mr. <span class="smcap">Venn</span>, in Answer to his Examination of the Address
+to Protestant Dissenters, 1s. 6d.</p>
+
+<p>19. A <span class="smcap">Catechism</span> for <span class="smcap">Children</span> and <span class="smcap">Young Persons</span>, 2d Edit. 3d.</p>
+
+<p>20. A <span class="smcap">Scripture Catechism</span>, consisting of a Series of Questions, with
+References to the Scriptures instead of Answers, 3d.</p>
+
+<p>21. A Serious <span class="smcap">Address</span> to <span class="smcap">Masters</span> of <span class="smcap">Families</span>, with Forms of Family
+Prayer, 2d Edit. 6d.</p>
+
+<p>22. A View of the <span class="smcap">Principles</span> and <span class="smcap">Conduct</span> of the <span class="smcap">Protestant Dissenters</span>,
+with respect to the Civil and Ecclesiastical Constitution of England, 2d
+Edit. 1s. 6d.</p>
+
+<p>23. A Free <span class="smcap">Address</span> to <span class="smcap">Protestant Dissenters</span>, on the Subject of <span class="smcap">Church
+Discipline</span>; with a Preliminary Discourse concerning the Spirit of
+Christianity, and the Corruption of it by false Notions of Religion, 2s.
+6d.</p>
+
+<p>24. A <span class="smcap">Sermon</span> preached before the Congregation of <span class="smcap">Protestant Dissenters</span>,
+at Mill Hill Chapel, in Leeds, May 16, 1773, on Occasion of his
+resigning the Pastoral Office among them, 1s.</p>
+
+<p>25. A <span class="smcap">Free Address</span> to <span class="smcap">Protestant Dissenters</span>, as such. By a Dissenter. A
+new Edition, enlarged and corrected, 1s. 6d.&mdash;An Allowance is made to
+those who buy this Pamphlet to give away.</p>
+
+<p>26. Letters to the Author of <i>Remarks on several late Publications
+relative to the Dissenters, in a Letter to Dr. Priestley</i>, 1s.</p>
+
+<p>27. An <span class="smcap">Appeal</span> to the serious and candid Professors of Christianity on
+the following Subjects, viz. 1. The Use of Reason in Matters of
+Religion. 2. The Power of Man to do the Will of God. 3. Original Sin. 4.
+Election and Reprobation. 5. The Divinity of Christ. And, 6. Atonement
+for Sin by the Death of Christ, 4th Edit. 1d.</p>
+
+<p>28. A <span class="smcap">Familiar Illustration</span> of certain Passages of Scripture relating to
+the same Subject. 4d. or 3s. 6d. per Dozen.</p>
+
+<p>29. The <span class="smcap">Triumph</span> of <span class="smcap">Truth</span>; being an Account of the Trial of Mr. E.
+Elwall, for Heresy and Blasphemy, at Stafford Assizes, before Judge
+Denton, &amp;c. 2d Edit. 1d.</p>
+
+<p>30. <span class="smcap">Considerations</span> for the <span class="smcap">Use</span> of <span class="smcap">Young Men</span>, and the Parents of <span class="smcap">Young
+Men</span>, 2d.</p>
+
+
+<h4><i>Also, published under the Direction of Dr. PRIESTLEY</i>,</h4>
+
+<h3>THE THEOLOGICAL REPOSITORY.</h3>
+
+<h4>Consisting of original Essays, Hints, Queries, &amp;c. calculated to promote
+religious Knowledge, in 3 Volumes, 8vo, Price 18s. in Boards.</h4>
+
+
+<p>Among other Articles, too many to be enumerated in an Advertisement,
+these three Volumes will be found to contain such original and truly
+valuable Observations on the Doctrine of the <i>Atonement</i>, the
+<i>Pre-existence of Christ</i>, and the <i>Inspiration of the Scriptures</i>, more
+especially respecting the <i>Harmony of the Evangelists</i>, and the
+Reasoning of the Apostle Paul, as cannot fail to recommend them to those
+Persons, who wish to make a truly free Enquiry into these important
+Subjects.</p>
+
+<p>In the First Volume, which is now reprinted, several Articles are added,
+particularly <span class="smcap">Two Letters</span> from Dr. <span class="smcap">Thomas Shaw</span> to Dr. <span class="smcap">Benson</span>, relating to
+the Passage of the Israelites through the Red Sea.</p>
+
+<div class="figcenter" style="width: 700px;">
+<img src="images/illus-360.jpg" width="700" height="607" alt="To face the last page." title="" />
+<span class="caption">To face the last page.</span>
+</div>
+
+
+
+
+
+
+
+
+
+<pre>
+
+
+
+
+
+End of the Project Gutenberg EBook of Experiments and Observations on
+Different Kinds of Air, by Joseph Priestley
+
+*** END OF THIS PROJECT GUTENBERG EBOOK EXPERIMENTS, OBSERVATIONS ON AIR ***
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+</pre>
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+</body>
+</html>
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+The Project Gutenberg EBook of Experiments and Observations on Different
+Kinds of Air, by Joseph Priestley
+
+This eBook is for the use of anyone anywhere at no cost and with
+almost no restrictions whatsoever.  You may copy it, give it away or
+re-use it under the terms of the Project Gutenberg License included
+with this eBook or online at www.gutenberg.org
+
+
+Title: Experiments and Observations on Different Kinds of Air
+
+Author: Joseph Priestley
+
+Release Date: August 19, 2009 [EBook #29734]
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK EXPERIMENTS, OBSERVATIONS ON AIR ***
+
+
+
+
+Produced by Mark C. Orton, Steven Gibbs, Josephine Paolucci
+and the Online Distributed Proofreading Team at
+https://www.pgdp.net.
+
+
+
+
+
+
+
+[Illustration: _To face the Title._]
+
+
+
+
+EXPERIMENTS AND OBSERVATIONS ON DIFFERENT KINDS OF AIR.
+
+[Price 5s. unbound.]
+
+     Quamobrem, si qua est erga Creatorem humilitas, si qua operum
+     ejus reverentia et magnificatio, si qua charitas in homines, si
+     erga necessitates et aerumnas humanas relevandas studium, si
+     quis amor veritatis in naturalibus, et odium tenebrarum, et
+     intellectus purificandi desiderium; orandi sunt homines iterum
+     atque iterum, ut, missis philosophiis istis volaticis et
+     preposteris, quae theses hypothesibus anterposuerunt, et
+     experientiam captivam duxerunt, atque de operibus dei
+     triumpharunt, summisse, et cum veneratione quadam, ad volumen
+     creaturarum evolvendum accedant; atque in eo moram faciant,
+     meditentur, et ab opinionibus abluti et mundi, caste et integre
+     versentur.----In interpretatione ejus eruenda nulli operae
+     parcant, sed strenue procedant, persistant, immoriantur.
+
+     LORD BACON IN INSTAURATIONE MAGNA.
+
+
+
+
+
+
+EXPERIMENTS
+
+AND
+
+OBSERVATIONS
+
+ON DIFFERENT KINDS OF
+
+AIR.
+
+
+By JOSEPH PRIESTLEY, LL.D. F.R.S.
+
+The SECOND EDITION Corrected.
+
+     Fert animus Causas tantarum expromere rerum;
+     Immensumque aperitur opus.
+
+                            LUCAN
+
+LONDON:
+
+Printed for J. JOHNSON, No. 72, in St. Paul's Church-Yard.
+
+MDCCLXXV.
+
+
+    TO THE RIGHT HONOURABLE
+    THE EARL OF SHELBURNE,
+    THIS TREATISE IS
+    WITH THE GREATEST GRATITUDE
+    AND RESPECT,
+    INSCRIBED,
+    BY HIS LORDSHIP's
+    MOST OBLIGED,
+    AND OBEDIENT
+    HUMBLE SERVANT,
+    J. PRIESTLEY.
+
+Transcriber's Note: Footnotes have been moved to the end of the chapter.
+The errata listed at the end of the book have been corrected in the
+text. In the text, there are places where the apothecary symbols for
+ounce and dram are used. These are changed to oz. and dr. in the text
+file.
+
+
+
+
+THE PREFACE.
+
+
+One reason for the present publication has been the favourable reception
+of those of my _Observations on different kinds of air_, which were
+published in the Philosophical Transactions for the year 1772, and the
+demand for them by persons who did not chuse, for the sake of those
+papers only, to purchase the whole volume in which they were contained.
+Another motive was the _additions_ to my observations on this subject,
+in consequence of which my papers grew too large for such a publication
+as the _Philosophical Transactions_.
+
+Contrary, therefore, to my intention, expressed Philosophical
+Transactions, vol. 64. p. 90, but with the approbation of the President,
+and of my friends in the society, I have determined to send them no
+more papers for the present on this subject, but to make a separate and
+immediate publication of all that I have done with respect to it.
+
+Besides, considering the attention which, I am informed, is now given to
+this subject by philosophers in all parts of Europe, and the rapid
+progress that has already been made, and may be expected to be made in
+this branch of knowledge, all unnecessary delays in the publication of
+experiments relating to it are peculiarly unjustifiable.
+
+When, for the sake of a little more reputation, men can keep brooding
+over a new fact, in the discovery of which they might, possibly, have
+very little real merit, till they think they can astonish the world with
+a system as complete as it is new, and give mankind a prodigious idea of
+their judgment and penetration; they are justly punished for their
+ingratitude to the fountain of all knowledge, and for their want of a
+genuine love of science and of mankind, in finding their boasted
+discoveries anticipated, and the field of honest fame pre-occupied, by
+men, who, from a natural ardour of mind, engage in philosophical
+pursuits, and with an ingenuous simplicity immediately communicate to
+others whatever occurs to them in their inquiries.
+
+As to myself, I find it absolutely impossible to produce a work on this
+subject that shall be any thing like _complete_. My first publication I
+acknowledged to be very imperfect, and the present, I am as ready to
+acknowledge, is still more so. But, paradoxical as it may seem, this
+will ever be the case in the progress of natural science, so long as the
+works of God are, like himself, infinite and inexhaustible. In
+completing one discovery we never fail to get an imperfect knowledge of
+others, of which we could have no idea before; so that we cannot solve
+one doubt without creating several new ones.
+
+Travelling on this ground resembles Pope's description of travelling
+among the Alps, with this difference, that here there is not only
+_succession_, but an _increase_ of new objects and new difficulties.
+
+     So pleas'd at first the tow'ring Alps we try,
+     Mount o'er the vales, and seem to tread the sky.
+     Th' eternal snows appear already past,
+     And the first clouds and mountains seem the last,
+     But those attain'd, we tremble to survey
+     The growing labours of the lengthen'd way.
+     Th' increasing prospect tires our wand'ring eyes,
+     Hills peep o'er hills, and Alps on Alps arise.
+
+                            ESSAY ON CRITICISM.
+
+Newton, as he had very little knowledge of _air_, so he had few doubts
+concerning it. Had Dr. Hales, after his various and valuable
+investigations, given a list of all his _desiderata_, I am confident
+that he would not have thought of one in ten that had occurred to me at
+the time of my last publication; and my doubts, queries, and hints for
+new experiments are very considerably increased, after a series of
+investigations, which have thrown great light upon many things of which
+I was not able to give any explanation before.
+
+I would observe farther, that a person who means to serve the cause of
+science effectually, must hazard his own reputation so far as to risk
+even _mistakes_ in things of less moment. Among a multiplicity of new
+objects, and new relations, some will necessarily pass without
+sufficient attention; but if a man be not mistaken in the principal
+objects of his pursuits, he has no occasion to distress himself about
+lesser things.
+
+In the progress of his inquiries he will generally be able to rectify
+his own mistakes; or if little and envious souls should take a malignant
+pleasure in detecting them for him, and endeavouring to expose him, he
+is not worthy of the name of a philosopher, if he has not strength of
+mind sufficient to enable him not to be disturbed at it. He who does not
+foolishly affect to be above the failings of humanity, will not be
+mortified when it is proved that he is but a man.
+
+In this work, as well as in all my other philosophical writings, I have
+made it a rule not to conceal the _real views_ with which I have made
+experiments; because though, by following a contrary maxim, I might have
+acquired a character of greater sagacity, I think that two very good
+ends are answered by the method that I have adopted. For it both tends
+to make a narrative of a course of experiments more interesting, and
+likewise encourages other adventurers in experimental philosophy;
+shewing them that, by pursuing even false lights, real and important
+truths may be discovered, and that in seeking one thing we often find
+another.
+
+In some respects, indeed, this method makes the narrative _longer_, but
+it is by making it less tedious; and in other respects I have written
+much more concisely than is usual with those who publish accounts of
+their experiments. In this treatise the reader will often find the
+result of long processes expressed in a few lines, and of many such in a
+single paragraph; each of which, if I had, with the usual parade,
+described it at large (explaining first the _preparation_, then reciting
+the _experiment_ itself, with the _result_ of it, and lastly making
+suitable _reflections_) would have made as many sections or chapters,
+and have swelled my book to a pompous and respectable size. But I have
+the pleasure to think that those philosophers who have but little time
+to spare for _reading_, which is always the case with those who _do_
+much themselves, will thank me for not keeping them too long from their
+own pursuits; and that they will find rather more in the volume, than
+the appearance of it promises.
+
+I do not think it at all degrading to the business of experimental
+philosophy, to compare it, as I often do, to the diversion of _hunting_,
+where it sometimes happens that those who have beat the ground the most,
+and are consequently the best acquainted with it, weary themselves
+without starting any game; when it may fall in the way of a mere
+passenger; so that there is but little room for boasting in the most
+successful termination of the chace.
+
+The best founded praise is that which is due to the man, who, from a
+supreme veneration for the God of nature, takes pleasure in
+contemplating his _works_, and from a love of his fellow-creatures, as
+the offspring of the same all-wise and benevolent parent, with a
+grateful sense and perfect enjoyment of the means of happiness of which
+he is already possessed, seeks, with earnestness, but without murmuring
+or impatience, that greater _command of the powers of nature_, which can
+only be obtained by a more extensive and more accurate _knowledge_ of
+them; and which alone can enable us to avail ourselves of the numerous
+advantages with which we are surrounded, and contribute to make our
+common situation more secure and happy.
+
+Besides, the man who believes that there is a _governor_ as well as a
+_maker_ of the world (and there is certainly equal reason to believe
+both) will acknowledge his providence and favour at least as much in a
+successful pursuit of _knowledge_, as of _wealth_; which is a sentiment
+that entirely cuts off all boasting with respect to ourselves, and all
+envy and jealousy with respect to others; and disposes us mutually to
+rejoice in every new light that we receive, through whose hands soever
+it be conveyed to us.
+
+I shall pass for an enthusiast with some, but I am perfectly easy under
+the imputation, because I am happy in those views which subject me to
+it; but considering the amazing improvements in natural knowledge which
+have been made within the last century, and the many ages, abounding
+with men who had no other object but study, in which, however, nothing
+of this kind was done, there appears to me to be a very particular
+providence in the concurrence of those circumstances which have produced
+so great a change; and I cannot help flattering myself that this will be
+instrumental in bringing about other changes in the state of the world,
+of much more consequence to the improvement and happiness of it.
+
+This rapid progress of knowledge, which, like the progress of a _wave_
+of the sea, of _sound_, or of _light_ from the sun, extends itself not
+this way or that way only, but _in all directions_, will, I doubt not,
+be the means, under God, of extirpating _all_ error and prejudice, and
+of putting an end to all undue and usurped authority in the business of
+_religion_, as well as of _science_; and all the efforts of the
+interested friends of corrupt establishments of all kinds will be
+ineffectual for their support in this enlightened age: though, by
+retarding their downfal, they may make the final ruin of them more
+complete and glorious. It was ill policy in Leo the Xth to patronize
+polite literature. He was cherishing an enemy in disguise. And the
+English hierarchy (if there be any thing unsound in its constitution)
+has equal reason to tremble even at an air-pump, or an electrical
+machine.
+
+There certainly never was any period in which _natural knowledge_ made
+such a progress as it has done of late years, and especially in this
+country; and they who affect to speak with supercilious contempt of the
+publications of the present age in general, or of the Royal Society in
+particular, are only those who are themselves engaged in the most
+trifling of all literary pursuits, who are unacquainted with all real
+science, and are ignorant of the progress and present state of it.[1]
+
+It is true that the rich and the great in this country give less
+attention to these subjects than, I believe, they were ever known to do,
+since the time of Lord Bacon, and much less than men of rank and fortune
+in other countries give to them. But with us this loss is made up by
+men of leisure, spirit, and ingenuity, in the middle ranks of life,
+which is a circumstance that promises better for the continuance of this
+progress in useful knowledge than any noble or royal patronage. With us,
+politics chiefly engage the attention of those who stand foremost in the
+community, which, indeed, arises from the _freedom_ and peculiar
+_excellence_ of our constitution, without which even the spirit of men
+of letters in general, and of philosophers in particular, who never
+directly interfere in matters of government, would languish.
+
+It is rather to be regretted, however, that, in such a number of
+nobility and gentry, so very few should have any taste for scientifical
+pursuits, because, for many valuable purposes of science, _wealth_ gives
+a decisive advantage. If extensive and lasting _fame_ be at all an
+object, literary, and especially scientifical pursuits, are preferable
+to political ones in a variety of respects. The former are as much more
+favourable for the display of the human faculties than the latter, as
+the _system of nature_ is superior to any _political system_ upon earth.
+
+If extensive _usefulness_ be the object, science has the same advantage
+over politics. The greatest success in the latter seldom extends farther
+than one particular country, and one particular age; whereas a
+successful pursuit of science makes a man the benefactor of all mankind,
+and of every age. How trifling is the fame of any statesman that this
+country has ever produced to that of Lord Bacon, of Newton, or of Boyle;
+and how much greater are our obligations to such men as these, than to
+any other in the whole _Biographia Britannica_; and every country, in
+which science has flourished, can furnish instances for similar
+observations.
+
+Here my reader will thank me, and the writer will, I hope, forgive me,
+if I quote a passage from the postscript of a letter which I happen to
+have just received from that excellent, and in my opinion, not too
+enthusiastical philosopher, father Beccaria of Turin.
+
+     _Mi spiace che il mondo politico ch'e pur tanto passeggero,
+     rubbi il grande Franklin al mondo della natura, che non sa ne
+     cambiare, ne mancare._ In English. "I am sorry that the
+     _political world_, which is so very transitory, should take the
+     great Franklin from the _world of nature_, which can never
+     change, or fail."
+
+I own it is with peculiar pleasure that I quote this passage, respecting
+this truly great man, at a time when some of the infatuated politicians
+of this country are vainly thinking to build their wretched and
+destructive projects, on the ruins of his established reputation; a
+reputation as extensive as the spread of science itself, and of which it
+is saying very little indeed, to pronounce that it will last and
+flourish when the names of all his enemies shall be forgotten.
+
+I think it proper, upon this occasion, to inform my friends, and the
+public, that I have, for the present, suspended my design of writing
+_the history and present state of all the branches of experimental
+philosophy_. This has arisen not from any dislike of the undertaking,
+but, in truth, because I see no prospect of being reasonably indemnified
+for so much labour and expence, notwithstanding the specimens I have
+already given of that work (in the _history of electricity_, and of the
+_discoveries relating to vision, light, and colours_) have met with a
+much more favourable reception from the best judges both at home and
+abroad, than I expected. Immortality, if I should have any view to it,
+is not the proper price of such works as these.
+
+I propose, however, having given so much attention to the subject of
+_air_, to write, at my leisure, the history and present state of
+discoveries relating to it; in which case I shall, as a part of it,
+reprint this work, with such improvements as shall have occurred to me
+at that time; and I give this notice of it, that no person who intends
+to purchase it may have reason (being thus apprised of my intention) to
+complain of buying the same thing twice. If any person chuse it, he may
+save his five or six shillings for the present, and wait five or six
+years longer (if I should live so long) for the opportunity of buying
+the same thing, probably much enlarged, and at the same time a complete
+account of all that has been done by others relating to this subject.
+
+Though for the plain, and I hope satisfactory reason above mentioned, I
+shall probably write no other _histories_ of this kind, I shall, as
+opportunity serves, endeavour to provide _materials_ for such histories,
+by continuing my experiments, keeping my eyes open to such new
+appearances as may present themselves, investigating them as far as I
+shall be able, and never failing to communicate to the public, by some
+channel or other, the result of my observations.
+
+In the publication of this work I have thought that it would be
+agreeable to my readers to preserve, in some measure, the order of
+history, and therefore I have not thrown together all that I have
+observed with respect to each kind of air, but have divided the work
+into _two parts_; the former containing what was published before, in
+the Philosophical Transactions, with such observations and corrections
+as subsequent experience has suggested to me; and I have reserved for
+the latter part of the work an account of the experiments which I have
+made since that publication, and after a pretty long interruption in my
+philosophical pursuits, in the course of the last summer. Besides I am
+sensible that in the latter part of this work a different arrangement of
+the subjects will be more convenient, for their mutual illustration.
+
+Some persons object to the term _air_, as applied to _acid_, _alkaline_,
+and even _nitrous air_; but it is certainly very convenient to have a
+common term by which to denote things which have so many common
+properties, and those so very striking; all of them agreeing with the
+air in which we breathe, and with _fixed air_, in _elasticity_, and
+_transparency_, and in being alike affected by heat or cold; so that to
+the eye they appear to have no difference at all. With much more reason,
+as it appears to me, might a person object to the common term _metal_,
+as applied to things so very different from one another as gold,
+quicksilver, and lead.
+
+Besides, _acid_ and _alkaline_ air do not differ from _common air_ (in
+any respect that can countenance an objection to their having a common
+appellation) except in such properties as are common to it with _fixed
+air_, though in a different degree; viz. that of being imbibed by water.
+But, indeed, all kinds of air, common air itself not excepted, are
+capable of being imbibed by water in some degree.
+
+Some may think the terms acid and alkaline _vapour_ more proper than
+acid and alkaline _air_. But the term _vapour_ having always been
+applied to elastic matters capable of being condensed in the temperature
+of the atmosphere, especially the vapour of water, it seems harsh to
+apply it to any elastic substance, which at the same time that it is as
+transparent as the air we breathe, is no more affected by cold than it
+is.
+
+As my former papers were immediately translated into several foreign
+languages, I may presume that this treatise, having a better title to
+it, will be translated also; and, upon this presumption, I cannot help
+expressing a wish, that it may be done by persons who have a competent
+knowledge of _subject_, as well as of the _English language_. The
+mistakes made by some foreigners, have induced me to give this caution.
+
+     _London, Feb._
+     _1774._
+
+
+ADVERTISEMENT.
+
+The _weights_ mentioned in the course of this treatise are _Troy_, and
+what is called _an ounce measure of air_, is the space occupied by an
+ounce weight of water, which is equal to 480 grains, and is, therefore,
+almost two _cubic inches_ of water; for one cubic inch weighs 254
+grains.
+
+FOOTNOTES:
+
+[1] See Sir John Pringle's _Discourse on the different kinds of air_, p.
+29, which, if it became me to do it, I would recommend to the reader, as
+containing a just and elegant account of the several discoveries that
+have been successively made, relating to the subject of this treatise.
+
+
+
+
+THE CONTENTS.
+
+
+THE INTRODUCTION.
+
+Section I. _A general view of PRECEDING DISCOVERIES relating to
+           AIR_                                                    Page 1
+
+Sect. II. _An Account of the APPARATUS with which the following
+           Experiments were made_                                       6
+
+
+PART I.
+
+_Experiments and Observations made in, and before the Year 1772._      23
+
+Sect. I. _Of FIXED AIR_                                                25
+
+Sect. II. _Of AIR in which a CANDLE, or BRIMSTONE, has burned out_     43
+
+Sect. III. _Of INFLAMMABLE AIR_                                        55
+
+Sect. IV. _Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION_   70
+
+Sect. V. _Of AIR in which a mixture of BRIMSTONE and FILINGS of
+         IRON has stood_                                              105
+
+Sect. VI. _Of NITROUS AIR_                                            108
+
+Sect. VII. _Of AIR infected with the FUMES of BURNING CHARCOAL_       129
+
+Sect. VIII. _Of the effect of the CALCINATION of METALS, and of the
+             EFFLUVIA of PAINT made with WHITE-LEAD and OIL, on AIR_  133
+
+Sect. IX. _Of MARINE ACID AIR_                                        143
+
+Sect. X. _Miscellaneous Observations_                                 154
+
+
+PART II.
+
+_Experiments and Observations made in the Year 1773, and the Beginning of
+1774._
+
+Sect. I. _Observations on ALKALINE AIR_                               163
+
+Sect. II. _Of COMMON AIR diminished, and made noxious by various
+          processes_                                                  177
+
+Sect. III. _Of NITROUS AIR_                                           203
+
+Sect. IV. _Of MARINE ACID AIR_                                        229
+
+Sect. V. _Of INFLAMMABLE AIR_                                         242
+
+Sect. VI. _Of FIXED AIR_                                              248
+
+Sect. VII. MISCELLANEOUS EXPERIMENTS                                  252
+
+Sect. VIII. _QUERIES, SPECULATIONS, and HINTS_                        258
+
+
+THE APPENDIX.
+
+Number I. _EXPERIMENTS made by Mr. Hey to prove that there is no
+          OIL of VITRIOL in water impregnated with FIXED AIR_         288
+
+Number II. _A Letter from Mr. HEY to Dr. PRIESTLEY, concerning the
+            effects of fixed Air applied by way of Clyster_           292
+
+Number III. _Observations on the MEDICINAL USES of FIXED AIR. By
+            THOMAS PERCIVAL, M. D. Fellow of the ROYAL SOCIETY,
+            and of the SOCIETY of ANTIQUARIES in LONDON_              300
+
+Number IV. _Extract of a Letter from WILLIAM FALCONER, M. D. of BATH_ 314
+
+Number V. _Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT
+           MASSINGHAM, NORFOLK_                                       317
+
+Num. VI. _A Letter from Dr. FRANKLIN_                                 321
+
+Number VII. _Extract of Letter from Mr. HENRY of MANCHESTER_          323
+
+
+
+
+
+THE INTRODUCTION.
+
+
+
+
+SECTION I.
+
+_A general view of PRECEDING DISCOVERIES relating to air._
+
+
+For the better understanding of the experiments and observations on
+different kinds of air contained in this treatise, it will be useful to
+those who are not acquainted with the history of this branch of natural
+philosophy, to be informed of those facts which had been discovered by
+others, before I turned my thoughts to the subject; which suggested, and
+by the help of which I was enabled to pursue, my inquiries. Let it be
+observed, however, that I do not profess to recite in this place _all_
+that had been discovered concerning air, but only those discoveries the
+knowledge of which is necessary, in order to understand what I have done
+myself; so that any person who is only acquainted with the general
+principles of natural philosophy, may be able to read this treatise,
+and, with proper attention, to understand every part of it.
+
+That the air which constitutes the atmosphere in which we live has
+_weight_, and that it is _elastic_, or consists of a compressible and
+dilatable fluid, were some of the earliest discoveries that were made
+after the dawning of philosophy in this western part of the world.
+
+That elastic fluids, differing essentially from the air of the
+atmosphere, but agreeing with it in the properties of weight,
+elasticity, and transparency, might be generated from solid substances,
+was discovered by Mr. Boyle, though two remarkable kinds of factitious
+air, at least the effects of them, had been known long before to all
+miners. One of these is heavier than common air. It lies at the bottom
+of pits, extinguishes candles, and kills animals that breathe it, on
+which account it had obtained the name of the _choke damp_. The other is
+lighter than common air, taking its place near the roofs of
+subterraneous places, and because it is liable to take fire, and
+explode, like gunpowder, it had been called the _fire damp_. The word
+_damp_ signifies _vapour_ or _exhalation_ in the German and Saxon
+language.
+
+Though the former of these kinds of air had been known to be noxious,
+the latter I believe had not been discovered to be so, having always
+been found in its natural state, so much diluted with common air, as to
+be breathed with safety. Air of the former kind, besides having been
+discovered in various caverns, particularly the _grotta del Cane_ in
+Italy, had also been observed on the surface of fermenting liquors, and
+had been called _gas_ (which is the same with _geist_, or _spirit_) by
+Van Helmont, and other German chymists; but afterwards it obtained the
+name of _fixed air_, especially after it had been discovered by Dr.
+Black of Edinburgh to exist, in a fixed state, in alkaline salts, chalk,
+and other calcareous substances.
+
+This excellent philosopher discovered that it is the presence of the
+fixed air in these substances that renders them _mild_, and that when
+they are deprived of it, by the force of fire, or any other process,
+they are in that state which had been called _caustic_, from their
+corroding or burning animal and vegetable substances.
+
+Fixed air had been discovered by Dr. Macbride of Dublin, after an
+observation of Sir John Pringle's, which led to it, to be in a
+considerable degree antiseptic; and since it is extracted in great
+plenty from fermenting vegetables, he had recommended the use of _wort_
+(that is an infusion of malt in water) as what would probably give
+relief in the sea-scurvy, which is said to be a putrid disease.
+
+Dr. Brownrigg had also discovered that the same species of air is
+contained in great quantities in the water of the Pyrmont spring at Spa
+in Germany, and in other mineral waters, which have what is called an
+_acidulous_ taste, and that their peculiar flavour, briskness, and
+medicinal virtues, are derived from this ingredient.
+
+Dr. Hales, without seeming to imagine that there was any material
+difference between these kinds of air and common air, observed that
+certain substances and operations _generate_ air, and others _absorb_
+it; imagining that the diminution of air was simply a taking away from
+the common mass, without any alteration in the properties of what
+remained. His experiments, however, are so numerous, and various, that
+they are justly esteemed to be the solid foundation of all our knowledge
+of this subject.
+
+Mr. Cavendish had exactly ascertained the specific gravities of fixed
+and inflammable air, shewing the former of them to be 1-1/2 heavier
+than common air, and the latter ten times lighter. He also shewed that
+water would imbibe more than its own bulk of fixed air.
+
+Lastly, Mr. Lane discovered that water thus impregnated with fixed air
+will dissolve a considerable quantity of iron, and thereby become a
+strong chalybeate.
+
+These, I would observe, are by no means all the discoveries concerning
+air that have been made by the gentlemen whose names I have mentioned,
+and still less are they all that have been made by others; but they
+comprise all the previous knowledge of this subject that is necessary to
+the understanding of this treatise; except a few particulars, which will
+be mentioned in the course of the work, and which it is, therefore,
+unnecessary to recite in this place.
+
+
+
+
+SECTION II.
+
+_An account of the APPARATUS with which the following experiments were
+made._
+
+
+Rather than describe at large the manner in which every particular
+experiment that I shall have occasion to recite was made, which would
+both be very tedious, and require an unnecessary multiplicity of
+drawings, I think it more adviseable to give, at one view, an account of
+all my apparatus and instruments, or at least of every thing that can
+require a description, and of all the different operations and processes
+in which I employ them.
+
+It will be seen that my apparatus for experiments on air is, in fact,
+nothing more than the apparatus of Dr. Hales, Dr. Brownrigg, and Mr.
+Cavendish, diversified, and made a little more simple. Yet
+notwithstanding the simplicity of this apparatus, and the ease with
+which all the operations are conducted, I would not have any person, who
+is altogether without experience, to imagine that he shall be able to
+select any of the following experiments, and immediately perform it,
+without difficulty or blundering. It is known to all persons who are
+conversant in experimental philosophy, that there are many little
+attentions and precautions necessary to be observed in the conducting of
+experiments, which cannot well be described in words, but which it is
+needless to describe, since practice will necessarily suggest them;
+though, like all other arts in which the hands and fingers are made use
+of, it is only _much practice_ that can enable a person to go through
+complex experiments, of this or any other kind, with ease and readiness.
+
+For experiments in which air will bear to be confined by water, I first
+used an oblong trough made of earthen ware, as _a_ fig. 1. about eight
+inches deep, at one end of which I put thin flat stones, _b. b._ about
+an inch, or half an inch, under the water, using more or fewer of them
+according to the quantity of water in the trough. But I have since found
+it more convenient to use a larger wooden trough, of the same general
+shape, eleven inches deep, two feet long, and 1-1/2 wide, with a shelf
+about an inch lower than the top, instead of the flat stones
+above-mentioned. This trough being larger than the former, I have no
+occasion to make provision for the water being higher or lower, the bulk
+of a jar or two not making so great a difference as did before.
+
+The several kinds of air I usually keep in _cylindrical jars_, as _c_,
+_c_, fig. 1, about ten inches long, and 2-1/2 wide, being such as I have
+generally used for electrical batteries, but I have likewise vessels of
+very different forms and sizes, adapted to particular experiments.
+
+When I want to remove vessels of air from the large trough, I place them
+in _pots_ or _dishes_, of various sizes, to hold more or less water,
+according to the time that I have occasion to keep the air, as fig. 2.
+These I plunge in water, and slide the jars into them; after which they
+may be taken out together, and be set wherever it shall be most
+convenient. For the purpose of merely removing a jar of air from one
+place to another, where it is not to stand longer than a few days, I
+make use of common _tea-dishes_, which will hold water enough for that
+time, unless the air be in a state of diminution, by means of any
+process that is going on in it.
+
+If I want to try whether an animal will live in any kind of air, I first
+put the air into a small vessel, just large enough to give it room to
+stretch itself; and as I generally make use of _mice_ for this purpose,
+I have found it very convenient to use the hollow part of a tall
+beer-glass, _d_ fig. 1, which contains between two and three ounce
+measures of air. In this vessel a mouse will live twenty minutes, or
+half an hour.
+
+For the purpose of these experiments it is most convenient to catch the
+mice in small wire traps, out of which it is easy to take them, and
+holding them by the back of the neck, to pass them through the water
+into the vessel which contains the air. If I expect that the mouse will
+live a considerable time, I take care to put into the vessel something
+on which it may conveniently sit, out of the reach of the water. If the
+air be good, the mouse will soon be perfectly at its ease, having
+suffered nothing by its passing through the water. If the air be
+supposed to be noxious, it will be proper (if the operator be desirous
+of preserving the mice for farther use) to keep hold of their tails,
+that they may be withdrawn as soon as they begin to shew signs of
+uneasiness; but if the air be thoroughly noxious, and the mouse happens
+to get a full inspiration, it will be impossible to do this before it be
+absolutely irrecoverable.
+
+In order to _keep_ the mice, I put them into receivers open at the top
+and bottom, standing upon plates of tin perforated with many holes, and
+covered with other plates of the same kind, held down by sufficient
+weights, as fig. 3. These receivers stand upon _a frame of wood_, that
+the fresh air may have an opportunity of getting to the bottoms of them,
+and circulating through them. In the inside I put a quantity of paper or
+tow, which must be changed, and the vessel washed and dried, every two
+or three days. This is most conveniently done by having another
+receiver, ready cleaned and prepared, into which the mice may be
+transferred till the other shall be cleaned.
+
+Mice must be kept in a pretty exact temperature, for either much heat or
+much cold kills them presently. The place in which I have generally kept
+them is a shelf over the kitchen fire-place where, as it is usual in
+Yorkshire, the fire never goes out; so that the heat varies very little,
+and I find it to be, at a medium, about 70 degrees of Fahrenheit's
+thermometer. When they had been made to pass through the water, as they
+necessarily must be in order to a change of air, they require, and will
+bear a very considerable degree of heat, to warm and dry them.
+
+I found, to my great surprize, in the course of these experiments, that
+mice will live intirely without water; for though I have kept them for
+three or four months, and have offered them water several times, they
+would never taste it; and yet they continued in perfect health and
+vigour. Two or three of them will live very peaceably together in the
+same vessel; though I had one instance of a mouse tearing another almost
+in pieces, and when there was plenty of provisions for both of them.
+
+In the same manner in which a mouse is put into a vessel of any kind of
+air, a _plant_, or any thing else, may be put into it, viz. by passing
+it through the water; and if the plant be of a kind that will grow in
+water only, there will be no occasion to set it in a pot of earth, which
+will otherwise be necessary.
+
+There may appear, at first sight, some difficulty in opening the mouth
+of a phial, containing any substance, solid or liquid, to which water
+must not be admitted, in a jar of any kind of air, which is an operation
+that I have sometimes had recourse to; but this I easily effect by means
+of _a cork cut tapering_, and a strong, wire thrust through it, as in
+fig. 4, for in this form it will sufficiently fit the mouth of any
+phial, and by holding the phial in one hand, and the wire in the other,
+and plunging both my hands into the trough of water, I can easily convey
+the phial through the water into the jar; which must either be held by
+an assistant, or be fastened by strings, with its mouth projecting over
+the shelf. When the phial is thus conveyed into the jar, the cork may
+easily be removed, and may also be put into it again at pleasure, and
+conveyed the same way out again.
+
+When any thing, as a gallipot, &c. is to be supported at a considerable
+height within a jar, it is convenient to have such _wire stands_ as are
+represented fig. 5. They answer better than any other, because they take
+up but little room, and may be easily bended to any shape or height.
+
+If I have occasion to pour air from a vessel with a wide mouth into
+another with a very narrow one, I am obliged to make use of a funnel,
+fig. 6, but by this means the operation is exceedingly easy; first
+filling the vessel into which the air is to be conveyed with water, and
+holding the mouth of it, together with the funnel, both under water with
+one hand, while the other is employed in pouring the air; which,
+ascending through the funnel up into the vessel, makes the water
+descend, and takes its place. These funnels are best made of glass,
+because the air being visible through them, the quantity of it may be
+more easily estimated by the eye. It will be convenient to have several
+of these funnels of different sizes.
+
+In order to expel air from solid substances by means of heat, I
+sometimes put them into a _gun-barrel_, fig. 7, and filling it up with
+dry sand, that has been well burned, so that no air can come from it, I
+lute to the open end the stem of a tobacco pipe, or a small glass tube.
+Then having put the closed end of the barrel, which contains the
+materials, into the fire, the generated air, issuing through the tube,
+may be received in a vessel of quicksilver, with its mouth immersed in a
+bason of the same, suspended all together in wires, in the manner
+described in the figure: or any other fluid substance may be used
+instead of quicksilver.
+
+But the most accurate method of procuring air from several substances,
+by means of heat, is to put them, if they will bear it, into phials full
+of quicksilver, with the mouths immersed in the same, and then throw the
+focus of a burning mirror upon them. For this purpose the phials should
+be made with their bottoms round, and very thin, that they may not be
+liable to break with a pretty sudden application of heat.
+
+If I want to expel air from any liquid, I nearly fill a phial with it,
+and having a cork perforated, I put through it, and secure with cement,
+a glass tube, bended in the manner represented at _e_ fig. 1. I then put
+the phial into a kettle of water, which I set upon the fire and make to
+boil. The air expelled by the heat, from the liquor contained in the
+phial, issues through the tube, and is received in the bason of
+quicksilver, fig. 7. Instead of this suspended bason, I sometimes
+content myself with tying a flaccid bladder to the end of the tube, in
+both these processes, that it may receive the newly generated air.
+
+In experiments on those kinds of air which are readily imbibed by water,
+I always make use of quicksilver, in the manner represented fig. 8, in
+which _a_ is the bason of quicksilver, _b_ a glass vessel containing
+quicksilver, with its mouth immersed in it, _c_ a phial containing the
+ingredients from which the air is to be produced; and _d_ is a small
+recipient, or glass vessel designed to receive and intercept any liquor
+that may be discharged along with the air, which is to be transmitted
+free from any moisture into the vessel _b_. If there be no apprehension
+of moisture, I make use of the glass tube only, without any recipient,
+in the manner represented _e_ fig. 1. In order to invert the vessel _b_,
+I first fill it with quicksilver, and then carefully cover the mouth of
+it with a piece of soft leather; after which it may be turned upside
+down without any danger of admitting the air, and the leather may be
+withdrawn when it is plunged in the quicksilver.
+
+In order to generate air by the solution of metals, or any process of a
+similar nature, I put the materials into a phial, prepared in the manner
+represented at _e_ fig. 1, and put the end of the glass tube under the
+mouth of any vessel into which I want to convey the air. If heat be
+necessary I can easily apply to it a candle, or a red hot poker while it
+hangs in this position.
+
+When I have occasion to transfer air from a jar standing in the trough
+of water to a vessel standing in quicksilver, or in any other situation
+whatever, I make use of the contrivance represented fig. 9, which
+consists of a bladder, furnished at one end with a small glass tube
+bended, and at the other with a cork, perforated so as just to admit the
+small end of a funnel. When the common air is carefully pressed out of
+this bladder, and the funnel is thrust tightly into the cork, it may be
+filled with any kind of air as easily as a glass jar; and then a string
+being tied above the cork in which the funnel is inserted, and the
+orifice in the other cork closed, by pressing the bladder against it, it
+may be carried to any place, and if the tube be carefully wiped, the air
+may be conveyed quite free from moisture through a body of quicksilver,
+or any thing else. A little practice will make this very useful
+manoeuvre perfectly easy and accurate.
+
+In order to impregnate fluids with any kind of air, as water with fixed
+air, I fill a phial with the fluid larger or less as I have occasion (as
+_a_ fig. 10;) and then inverting it, place it with its mouth downwards,
+in a bowl _b_, containing a quantity of the same fluid; and having
+filled the bladder, fig. 9, with the air, I throw as much of it as I
+think proper into the phial, in the manner described above. To
+accelerate the impregnation, I lay my hand on the top of the phial, and
+shake it as much as I think proper.
+
+If, without having any air previously generated, I would convey it into
+the fluid immediately as it arises from the proper materials, I keep the
+same bladder in connection with a phial _c_ fig. 10, containing the same
+materials (as chalk, salt of tartar, or pearl ashes in diluted oil of
+vitriol, for the generation of fixed air) and taking care, lest, in the
+act of effervescence, any of the materials in the phial _c_ should get
+into the vessel _a_, to place this phial on a stand lower than that on
+which the bason was placed, I press out the newly generated air, and
+make it ascend directly into the fluid. For this purpose, and that I may
+more conveniently shake the phial _c_, which is necessary in some
+processes, especially with chalk and oil of vitriol, I sometimes make
+use of a flexible leathern tube _d_, and sometimes only a glass tube.
+For if the bladder be of a sufficient length, it will give room for the
+agitation of the phial; or if not, it is easy to connect two bladders
+together by means of a perforated cork, to which they may both be
+fastened.
+
+When I want to try whether any kind of air will admit a candle to burn
+in it, I make use of a cylindrical glass vessel, fig. 11. and a bit of
+wax candle _a_ fig. 12, fastened to the end of a wire _b_, and turned
+up, in such a manner as to be let down into the vessel with the flame
+upwards. The vessel should be kept carefully covered till the moment
+that the candle is admitted. In this manner I have frequently
+extinguished a candle more than twenty times successively, in a vessel
+of this kind, though it is impossible to dip the candle into it without
+giving the external air an opportunity of mixing with the air in the
+inside more or less. The candle _c_, at the other end of the wire is
+very convenient for holding under a jar standing in water, in order to
+burn as long as the inclosed air can supply it; for the moment that it
+is extinguished, it may be drawn through the water before any smoke can
+have mixed with the air.
+
+In order to draw air out of a vessel which has its mouth immersed in
+water, and thereby to raise the water to whatever height may be
+necessary, it is very convenient to make use of a glass _syphon_, fig.
+13, putting one of the legs up into the vessel, and drawing the air out
+at the other end by the mouth. If the air be of a noxious quality, it
+may be necessary to have a syringe fastened to the syphon, the manner of
+which needs no explanation. I have not thought it safe to depend upon a
+valve at the top of the vessel, which Dr. Hales sometimes made use of.
+
+If, however, a very small hole be made at the top of a glass vessel, it
+may be filled to any height by holding it under water, while the air is
+issuing out at the hole, which may then be closed with wax or cement.
+
+If the generated air will neither be absorbed by water, nor diminish
+common air, it may be convenient to put part of the materials into a
+cup, supported by a stand, and the other part into a small glass
+vessel, placed on the edge of it, as at _f_, fig. 1. Then having, by
+means of a syphon, drawn the air to at convenient height, the small
+glass vessel may be easily pushed into the cup, by a wire introduced
+through the water; or it may be contrived, in a variety of ways, only to
+discharge the contents of the small vessel into the larger. The distance
+between the boundary of air and water, before and after the operation,
+will shew the quantity of the generated air. The effect of processes
+that _diminish_ air may also be tried by the same apparatus.
+
+When I want to admit a particular kind of air to any thing that will not
+bear wetting, and yet cannot be conveniently put into a phial, and
+especially if it be in the form of a powder, and must be placed upon a
+stand (as in those experiments in which the focus of a burning mirror is
+to be thrown upon it) I first exhaust a receiver, in which it is
+previously placed; and having a glass tube, bended for the purpose, as
+in fig. 14, I screw it to the stem of a transfer of the air pump on
+which the receiver had been exhausted, and introducing it through the
+water into a jar of that kind of air with which I would fill the
+receiver, I only turn the cock, and I gain my purpose. In this method,
+however, unless the pump be very good, and several contrivances, too
+minute to be particularly described, be made use of a good deal of
+common air will get into the receiver.
+
+When I want to measure the goodness of any kind of air, I put two
+measures of it into a jar standing in water; and when I have marked upon
+the glass the exact place of the boundary of air and water, I put to it
+one measure of nitrous air; and after waiting a proper time, note the
+quantity of its diminution. If I be comparing two kinds of air that are
+nearly alike, after mixing them in a large jar, I transfer the mixture
+into a long glass tube, by which I can lengthen my scale to what degree
+I please.
+
+If the quantity of the air, the goodness of which I want to ascertain,
+be exceedingly small, so as to be contained in a part of a glass tube,
+out of which water will not run spontaneously, as _a_ fig. 15; I first
+measure with a pair of compasses the length of the column of air in the
+tube, the remaining part being filled with water, and lay it down upon a
+scale; and then, thrusting a wire of a proper thickness, _b_, into the
+tube, I contrive, by means of a thin plate of iron, bent to a sharp
+angle _c_, to draw it out again, when the whole of this little
+apparatus has been introduced through the water into a jar of nitrous
+air; and the wire being drawn out, the air from the jar must supply its
+place. I then measure the length of this column of nitrous air which I
+have got into the tube, and lay it also down upon the scale, so as to
+know the exact length of both the columns. After this, holding the tube
+under water, with a small wire I force the two separate columns of air
+into contact, and when they have been a sufficient time together, I
+measure the length of the whole, and compare it with the length of both
+the columns taken before. A little experience will teach the operator
+how far to thrust the wire into the tube, in order to admit as much air
+as he wants and no more.
+
+In order to take the electric spark in a quantity of any kind of air,
+which must be very small, to produce a sensible effect upon it, in a
+short time, by means of a common machine, I put a piece of wire into the
+end of a small tube, and fasten it with hot cement, as in fig. 16; and
+having got the air I want into the tube by means of the apparatus fig.
+15, I place it inverted in a bason containing either quicksilver, or any
+other fluid substance by which I chuse to have the air confined. I then,
+by the help of the air pump, drive out as much of the air as I think
+convenient, admitting the quicksilver, &c. to it, as at _a_, and
+putting a brass ball on the end of the wire, I take the sparks or shocks
+upon it, and thereby transmit them through the air to the liquor in the
+tube.
+
+To take the electric sparks in any kind of fluid, as oil, &c. I use the
+same apparatus described above, and having poured into the tube as much
+of the fluid as I conjecture I can make the electric spark pass through,
+I fill the rest with quicksilver; and placing it inverted in a bason of
+quicksilver, I take the sparks as before.
+
+If air be generated very fast by this process, I use a tube that is
+narrow at the top, and grows wider below, as fig. 17, that the
+quicksilver may not recede too soon beyond the striking distance.
+
+Sometimes I have used a different apparatus for this purpose,
+represented fig. 18. Taking a pretty wide glass tube, hermetically
+sealed at the upper-end, and open below, at about an inch, or at what
+distance I think convenient from the top, I get two holes made in it,
+opposite to each other. Through these I put two wires, and fastening
+them with warm cement, I fix them at what distance I please from each
+other. Between these wires I take the sparks, and the bubbles of air
+rise, as they are formed, to the top of the tube.
+
+
+
+
+PART I.
+
+_Experiments and Observations made in, and before the year 1772._
+
+
+In writing upon the subject of _different kinds of air_, I find myself
+at a loss for proper _terms_, by which to distinguish them, those which
+have hitherto obtained being by no means sufficiently characteristic, or
+distinct. The only terms in common use are, _fixed air_, _mephitic_, and
+_inflammable_. The last, indeed, sufficiently characterizes and
+distinguishes that kind of air which takes fire, and explodes on the
+approach of flame; but it might have been termed _fixed_ with as much
+propriety as that to which Dr. Black and others have given that
+denomination, since it is originally part of some solid substance, and
+exists in an unelastic state.
+
+All these newly discovered kinds of air may also be called _factitious_;
+and if, with others, we use the term _fixable_, it is still obvious to
+remark, that it is applicable to them all; since they are all capable of
+being imbibed by some substance or other, and consequently of being
+_fixed_ in them, after they have been in an elastic state.
+
+The term _mephitic_ is equally applicable to what is called _fixed air_,
+to that which is _inflammable_, and to many other kinds; since they are
+equally noxious, when breathed by animals. Rather, however, than either
+introduce new terms, or change the signification of old ones, I shall
+use the term _fixed air_, in the sense in which it is now commonly used,
+and distinguish the other kinds by their properties, or some other
+periphrasis. I shall be under a necessity, however, of giving names to
+those kinds of air, to which no names had been given by others, as
+_nitrous_, _acid_, and _alkaline_.
+
+
+
+
+SECTION I.
+
+_Of FIXED AIR._
+
+
+It was in consequence of living for some time in the neighbourhood of a
+public brewery, that I was induced to make experiments on fixed air, of
+which there is always a large body, ready formed, upon the surface of
+the fermenting liquor, generally about nine inches, or a foot in depth,
+within which any kind of substance may be very conveniently placed; and
+though, in these circumstances, the fixed air must be continually mixing
+with the common air, and is therefore far from being perfectly pure, yet
+there is a constant fresh supply from the fermenting liquor, and it is
+pure enough for many purposes.
+
+A person, who is quite a stranger to the properties of this kind of air,
+would be agreeably amused with extinguishing lighted candles, or chips
+of wood in it, as it lies upon the surface of the fermenting liquor; for
+the smoke readily unites with this kind of air, probably by means of the
+water which it contains; so that very little or none of the smoke will
+escape into the open air, which is incumbent upon it. It is remarkable,
+that the upper surface of this smoke, floating in the fixed air, is
+smooth, and well defined; whereas the lower surface is exceedingly
+ragged, several parts hanging down to a considerable distance within the
+body of the fixed air, and sometimes in the form of balls, connected to
+the upper stratum by slender threads, as if they were suspended. The
+smoke is also apt to form itself into broad flakes, parallel to the
+surface of the liquor, and at different distances from it, exactly like
+clouds. These appearances will sometimes continue above an hour, with
+very little variation. When this fixed air is very strong, the smoke of
+a small quantity of gunpowder fired in it will be wholly retained by it,
+no part escaping into the common air.
+
+Making an agitation in this air, the surface of it, (which still
+continues to be exactly defined) is thrown into the form of waves, which
+it is very amusing to look upon; and if, by this agitation, any of the
+fixed air be thrown over the side of the vessel, the smoke, which is
+mixed with it, will fall to the ground, as if it was so much water, the
+fixed air being heavier than common air.
+
+The red part of burning wood was extinguished in this air, but I could
+not perceive that a red-hot poker was sooner cooled in it.
+
+Fixed air does not instantly mix with common air. Indeed if it did, it
+could not be caught upon the surface of the fermenting liquor. A candle
+put under a large receiver, and immediately plunged very deep below the
+surface of the fixed air, will burn some time. But vessels with the
+smallest orifices, hanging with their mouths downwards in the fixed air,
+will _in time_ have the common air, which they contain, perfectly mixed
+with it. When the fermenting liquor is contained in vessels close
+covered up, the fixed air, on removing the cover, readily affects the
+common air which is contiguous to it; so that, candles held at a
+considerable distance above the surface will instantly go out. I have
+been told by the workmen, that this will sometimes be the case, when the
+candles are held two feet above the mouth of the vessel.
+
+Fixed air unites with the smoke of rosin, sulphur, and other electrical
+substances, as well as with the vapour of water; and yet, by holding the
+wire of a charged phial among these fumes, I could not make any
+electrical atmosphere, which surprized me a good deal, as there was a
+large body of this smoke, and it was so confined, that it could not
+escape me.
+
+I also held some oil of vitriol in a glass vessel within the fixed air,
+and by plunging a piece of red-hot glass into it, raised a copious and
+thick fume. This floated upon the surface of the fixed air like other
+fumes, and continued as long.
+
+Considering the near affinity between water and fixed air, I concluded
+that if a quantity of water was placed near the yeast of the fermenting
+liquor, it could not fail to imbibe that air, and thereby acquire the
+principal properties of Pyrmont, and some other medicinal mineral
+waters. Accordingly, I found, that when the surface of the water was
+considerable, it always acquired the pleasant acidulous taste that
+Pyrmont water has. The readiest way of impregnating water with this
+virtue, in these circumstances, is to take two vessels, and to keep
+pouring the water from one into the other, when they are both of them
+held as near the yeast as possible; for by this means a great quantity
+of surface is exposed to the air, and the surface is also continually
+changing. In this manner, I have sometimes, in the space of two or three
+minutes, made a glass of exceedingly pleasant sparkling water, which
+could hardly be distinguished from very good Pyrmont, or rather Seltzer
+water.
+
+But the _most effectual_ way of impregnating water with fixed air is to
+put the vessels which contain the water into glass jars, filled with
+the purest fixed air made by the solution of chalk in diluted oil of
+vitriol, standing in quicksilver. In this manner I have, in about two
+days, made a quantity of water to imbibe more than an equal bulk of
+fixed air, so that, according to Dr. Brownrigg's experiments, it must
+have been much stronger than the best imported Pyrmont; for though he
+made his experiments at the spring-head, he never found that it
+contained quite so much as half its bulk of this air. If a sufficient
+quantity of quicksilver cannot be procured, _oil_ may be used with
+sufficient advantage, for this purpose, as it imbibes the fixed air very
+slowly. Fixed air may be kept in vessels standing in water for a long
+time, if they be separated by a partition of oil, about half an inch
+thick. Pyrmont water made in these circumstances, is little or nothing
+inferior to that which has stood in quicksilver.
+
+The _readiest_ method of preparing this water for use is to agitate it
+strongly with a large surface exposed to the fixed air. By this means
+more than an equal bulk of air may be communicated to a large quantity
+of water in the space of a few minutes. But since agitation promotes the
+dissipation of fixed air from water, it cannot be made to imbibe so
+great a quantity in this method as in the former, where more time is
+taken.
+
+Easy directions for impregnating water with fixed air I have published
+in a small pamphlet, designed originally for the use of seamen in long
+voyages, on the presumption that it might be of use for preventing or
+curing the sea scurvy, equally with wort, which was recommended by Dr.
+Macbride for this purpose, on no other account than its property of
+generating fixed air, by its fermentation in the stomach.
+
+Water thus impregnated with fixed air readily dissolves iron, as Mr.
+Lane has discovered; so that if a quantity of iron filings be put to it,
+it presently becomes a strong chalybeate, and of the mildest and most
+agreeable kind.
+
+I have recommended the use of _chalk_ and oil of vitriol as the
+cheapest, and, upon the whole, the best materials for this purpose. But
+some persons prefer _pearl ashes_, _pounded marble_, or other calcareous
+or _alkaline substances_; and perhaps with reason. My own experience has
+not been sufficient to enable me to decide in this case.
+
+Whereas some persons had suspected that a quantity of the oil of vitriol
+was rendered volatile by this process, I examined it, by all the
+chemical methods that are in use; but could not find that water thus
+impregnated contained the least perceivable quantity of that acid.
+
+Mr. Hey, indeed, who assisted me in this examination, found that
+distilled water, impregnated with fixed air, did not mix so readily with
+soap as the distilled water itself; but this was also the case when the
+fixed air had passed through a long glass tube filled with alkaline
+salts, which, it may be supposed, would have imbibed any of the oil of
+vitriol that might have been contained in that air[2].
+
+Fixed air itself may be said to be of the nature of an acid, though of a
+weak and peculiar sort.----Mr. Bergman of Upsal, who honoured me with a
+letter upon the subject, calls it the _aerial acid_, and, among other
+experiments to prove it to be an acid, he says that it changes the blue
+juice of tournesole into red. This Mr. Hey found to be true, and he
+moreover discovered that when water tinged blue with the juice of
+tournesole, and then red with fixed air, has been exposed to the open
+air, it recovers its blue colour again.
+
+The heat of boiling water will expel all the fixed air, if a phial
+containing the impregnated water be held in it; but it will often
+require above half an hour to do it completely.
+
+Dr. Percival, who is particularly attentive to every improvement in the
+medical art, and who has thought so well of this impregnation as to
+prescribe it in several cases, informs me that it seems to be much
+stronger, and sparkles more, like the true Pyrmont water, after it has
+been kept some time. This circumstance, however, shews that, in time,
+the fixed air is more easily disengaged from the water; and though, in
+this state, it may affect the taste more sensibly, it cannot be of so
+much use in the stomach and bowels, as when the air is more firmly
+retained by the water.
+
+By the process described in my pamphlet, fixed air may be readily
+incorporated with wine, beer, and almost any other liquor whatever; and
+when beer, wine, or cyder, is become flat or dead (which is the
+consequence of the escape of the fixed air they contained) they may be
+revived by this means; but the delicate and agreeable flavour, or
+acidulous taste, communicated by fixed air, and which is very manifest
+in water, can hardly be perceived in wine, or any liquors which have
+much taste of their own.
+
+I should think that there can be no doubt, but that water thus
+impregnated with fixed air must have all the medicinal virtues of
+genuine Pyrmont or Seltzer water; since these depend upon the fixed air
+they contain. If the genuine Pyrmont water derives any advantage from
+its being a natural chalybeate, this may also be obtained by providing a
+common chalybeate water, and using it in these processes, instead of
+common water.
+
+Having succeeded so well with this artificial Pyrmont water, I imagined
+that it might be possible to give _ice_ the same virtue, especially as
+cold is known to promote the absorption of fixed air by water; but in
+this I found myself quite mistaken. I put several pieces of ice into a
+quantity of fixed air, confined by quicksilver, but no part of the air
+was absorbed in two days and two nights; but upon bringing it into a
+place where the ice melted, the air was absorbed as usual.
+
+I then took a quantity of strong artificial Pyrmont water, and putting
+it into a thin glass phial, I set it in a pot that was filled with snow
+and salt. This mixture instantly freezing the water that was contiguous
+to the sides of the glass, the air was discharged plentifully, so that
+I catched a considerable quantity, in a bladder tied to the mouth of the
+phial.
+
+I also took two quantities of the same Pyrmont water, and placed one of
+them where it might freeze, keeping the other in a cold place, but where
+it would not freeze. This retained its acidulous taste, though the phial
+which contained it was not corked; whereas the other being brought into
+the same place, where the ice melted very slowly, had at the same time
+the taste of common water only. That quantity of water which had been
+frozen by the mixture of snow and salt, was almost as much like snow as
+ice, such a quantity of air-bubbles were contained in it, by which it
+was prodigiously increased in bulk.
+
+The pressure of the atmosphere assists very considerably in keeping
+fixed air confined in water; for in an exhausted receiver, Pyrmont water
+will absolutely boil, by the copious discharge of its air. This is also
+the reason why beer and ale froth so much _in vacuo_. I do not doubt,
+therefore, but that, by the help of a condensing engine, water might be
+much more highly impregnated with the virtues of the Pyrmont spring; and
+it would not be difficult to contrive a method of doing it.
+
+The manner in which I made several experiments to ascertain the
+absorption of fixed air by different fluid substances, was to put the
+liquid into a dish, and holding it within the body of the fixed air at
+the brewery, to set a glass vessel into it, with its mouth inverted.
+This glass being necessarily filled with the fixed air, the liquor would
+rise into it when they were both taken into the common air, if the fixed
+air was absorbed at all.
+
+Making use of _ether_ in this manner, there was a constant bubbling from
+under the glass, occasioned by this fluid easily rising in vapour, so
+that I could not, in this method, determine whether it imbibed the air
+or not. I concluded however, that they did incorporate, from a very
+disagreeable circumstance, which made me desist from making any more
+experiments of the kind. For all the beer, over which this experiment
+was made, contracted a peculiar taste; the fixed air impregnated with
+the ether being, I suppose, again absorbed by the beer. I have also
+observed, that water which remained a long time within this air has
+sometimes acquired a very disagreeable taste. At one time it was like
+tar-water. How this was acquired, I was very desirous of making some
+experiments to ascertain, but I was discouraged by the fear of injuring
+the fermenting liquor. It could not come from the fixed air only.
+
+Insects and animals which breathe very little are stifled in fixed air,
+but are not soon quite killed in it. Butterflies and flies of other
+kinds will generally become torpid, and seemingly dead, after being held
+a few minutes over the fermenting liquor; but they revive again after
+being brought into the fresh air. But there are very great varieties
+with respect to the time in which different kinds of flies will either
+become torpid in the fixed air, or die in it. A large strong frog was
+much swelled, and seemed to be nearly dead, after being held about six
+minutes over the fermenting liquor; but it recovered upon being brought
+into the common air. A snail treated in the same manner died presently.
+
+Fixed air is presently fatal to vegetable life. At least sprigs of mint
+growing in water, and placed over the fermenting liquor, will often
+become quite dead in one day, or even in a less space of time; nor do
+they recover when they are afterwards brought into the common air. I am
+told, however, that some other plants are much more hardy in this
+respect.
+
+A red rose, fresh gathered, lost its redness, and became of a purple
+colour, after being held over the fermenting liquor about twenty-four
+hours; but the tips of each leaf were much more affected than the rest
+of it. Another red rose turned perfectly white in this situation; but
+various other flowers of different colours were very little affected.
+These experiments were not repeated, as I wish they might be done, in
+pure fixed air, extracted from chalk by means of oil of vitriol.
+
+For every purpose, in which it was necessary that the fixed air should
+be as unmixed as possible, I generally made it by pouring oil of vitriol
+upon chalk and water, catching it in a bladder fastened to the neck of
+the phial in which they were contained, taking care to press out all the
+common air, and also the first, and sometimes the second, produce of
+fixed air; and also, by agitation, making it as quickly as I possibly
+could. At other times, I made it pass from the phial in which it was
+generated through a glass tube, without the intervention of any bladder,
+which, as I found by experience, will not long make a sufficient
+separation between several kinds of air and common air.
+
+I had once thought that the readiest method of procuring fixed air, and
+in sufficient purity, would be by the simple process of burning chalk,
+or pounded lime-stone in a gun-barrel, making it pass through the stem
+of a tobacco-pipe, or a glass tube carefully luted to the orifice of it.
+In this manner I found that air is produced in great plenty; but, upon
+examining it, I found, to my very great surprise, that little more than
+one half of it was fixed air, capable of being absorbed by water; and
+that the rest was inflammable, sometimes very weakly, but sometimes
+pretty highly so.
+
+Whence this inflammability proceeds, I am not able to determine, the
+lime or chalk not being supposed to contain any other than fixed air. I
+conjecture, however, that it must proceed from the iron, and the
+separation of it from the calx may be promoted by that small quantity of
+oil of vitriol, which I am informed is contained in chalk, if not in
+lime-stone also.
+
+But it is an objection to this hypothesis, that the inflammable air
+produced in this manner burns blue, and not at all like that which is
+produced from iron, or any other metal, by means of an acid. It also has
+not the smell of that kind of inflammable air which is produced from
+mineral substances. Besides, oil of vitriol without water, will not
+dissolve iron; nor can inflammable air be got from it, unless the acid
+be considerably diluted; and when I mixed brimstone with the chalk,
+neither the quality nor the quantity of the air was changed by it.
+Indeed no air, or permanently elastic vapour, can be got from brimstone,
+or any oil.
+
+Perhaps this inflammable principle may come from some remains of the
+animals, from which it is thought that all calcareous matter proceeds.
+
+In the method in which I generally made the fixed air (and indeed
+always, unless the contrary be particularly mentioned, viz. by diluted
+oil of vitriol and chalk) I found by experiment that it was as pure as
+Mr. Cavendish made it. For after it had patted through a large body of
+water in small bubbles, still 1/50 or 1/60 part only was not absorbed by
+water. In order to try this as expeditiously as possible, I kept pouring
+the air from one glass vessel into another, immersed in a quantity of
+cold water, in which manner I found by experience, that almost any
+quantity may be reduced as far as possible in a very short time. But the
+most expeditious method of making water imbibe any kind of air, is to
+confine it in a jar; and agitate it strongly, in the manner described in
+my pamphlet on the impregnation of water with fixed air, and represented
+fig. 10.
+
+At the same time that I was trying the purity of my fixed air, I had the
+curiosity to endeavour to ascertain whether that part of it which is not
+miscible in water, be equally diffused through the whole mass; and, for
+this purpose, I divided a quantity of about a gallon into three parts,
+the first consisting of that which was uppermost, and the last of that
+which was the lowest, contiguous to the water; but all these parts were
+reduced in about an equal proportion, by passing through the water, so
+that the whole mass had been of an uniform composition. This I have also
+found to be the case with several kinds of air, which will, not properly
+incorporate.
+
+A mouse will live very well, though a candle will not burn in the
+residuum of the purest fixed air that I can make; and I once made a very
+large quantity for the sole purpose of this experiment. This, therefore,
+seems to be one instance of the generation of genuine common air, though
+vitiated in some degree. It is also another proof of the residuum of
+fixed air being, in part at least, common air, that it becomes turbid,
+and is diminished by the mixture of nitrous air, as will be explained
+hereafter.
+
+That fixed air only wants some addition to make it permanent, and
+immiscible with water if not in all respects, common air, I have been
+led to conclude, from several attempts which I once made to mix it with
+air in which a quantity of iron filings and brimstone, made into a paste
+with water, had stood; for, in several mixtures of this kind, I imagined
+that not much more than half of the fixed air could be imbibed by water;
+but, not being able to repeat the experiment, I conclude that I either
+deceived myself in it, or that I overlooked some circumstance on which
+the success of it depended.
+
+These experiments, however, whether they were fallacious or otherwise,
+induced me to try whether any alteration would be made in the
+constitution of fixed air, by this mixture of iron filings and
+brimstone. I therefore put a mixture of this kind into a quantity of as
+pure fixed air as I could make, and confined the whole in quicksilver,
+lest the water should absorb it before the effects of the mixture could
+take place. The consequence was, that the fixed air was diminished, and
+the quicksilver rose in the vessel, till about the fifth part was
+occupied by it; and, as near as I could judge, the process went on, in
+all respects, as if the air in the inside had been common air.
+
+What is most remarkable, in the result of this experiment, is, that the
+fixed air, into which this mixture had been put, and which had been in
+part diminished by it, was in part also rendered insoluble in water by
+this means. I made this experiment four times, with the greatest care,
+and observed, that in two of them about one sixth, and in the other two
+about one fourteenth, of the original quantity, was such as could not be
+absorbed by water, but continued permanently elastic. Lest I should have
+made any mistake with respect to the purity of the fixed air, the last
+time that I made the experiment, I set part of the fixed air, which I
+made use of, in a separate vessel, and found it to be exceedingly pure,
+so as to be almost wholly absorbed by water; whereas the other part, to
+which I had put the mixture, was far from being so.
+
+In one of these cases, in which fixed air was made immiscible with
+water, it appeared to be not very noxious to animals; but in another
+case, a mouse died in it pretty soon. This difference probably arose
+from my having inadvertently agitated the air in water rather more in
+one case than in the other.
+
+As the iron is reduced to a calx by this process, I once concluded, that
+it is phlogiston that fixed air wants, to make it common air; and, for
+any thing I yet know this may be the case, though I am ignorant of the
+method of combining them; and when I calcined a quantity of lead in
+fixed air, in the manner which will be described hereafter, it did not
+seem to have been less soluble in water than it was before.
+
+FOOTNOTES:
+
+[2] An account of Mr. Hey's experiments will be found in the Appendix to
+these papers.
+
+
+
+
+SECTION II.
+
+_Of AIR in which a CANDLE, or BRIMSTONE, has burned out._
+
+
+It is well known that flame cannot subsist long without change of air,
+so that the common air is necessary to it, except in the case of
+substances, into the composition of which nitre enters, for these will
+burn _in vacuo_, in fixed air, and even under water, as is evident in
+some rockets, which are made for this purpose. The quantity of air which
+even a small flame requires to keep it burning is prodigious. It is
+generally said, that an ordinary candle _consumes_, as it is called,
+about a gallon in a minute. Considering this amazing consumption of air,
+by fires of all kinds, volcanos, &c. it becomes a great object of
+philosophical inquiry, to ascertain what change is made in the
+constitution of the air by flame, and to discover what provision there
+is in nature for remedying the injury which the atmosphere receives by
+this means. Some of the following experiments will, perhaps, be thought
+to throw light upon the subject.
+
+The diminution of the quantity of air in which a candle, or brimstone,
+has burned out, is various; But I imagine that, at a medium, it may be
+about one fifteenth, or one sixteenth of the whole; which is one third
+as much as by animal or vegetable substances putrefying in it, by the
+calcination of metals, or by any of the other causes of the complete
+diminution of air, which will be mentioned hereafter.
+
+I have sometimes thought, that flame disposes the common air to deposit
+the fixed air it contains; for if any lime-water be exposed to it, it
+immediately becomes turbid. This is the case, when wax candles, tallow
+candles, chips of wood, spirit of wine, ether, and every other substance
+which I have yet tried, except brimstone, is burned in a close glass
+vessel, standing in lime-water. This precipitation of fixed air (if this
+be the case) may be owing to something emitted from the burning bodies,
+which has a stronger affinity with the other constituent parts of the
+atmosphere[3].
+
+If brimstone be burned in the same circumstances, the lime-water
+continues transparent, but still there may have been the same
+precipitation of the fixed part of the air; but that, uniting with the
+lime and the vitriolic acid, it forms a selenetic salt, which is soluble
+in water. Having evaporated a quantity of water thus impregnated, by
+burning brimstone a great number of times over it, a whitish powder
+remained, which had an acid taste; but repeating the experiment with a
+quicker evaporation, the powder had no acidity, but was very much like
+chalk. The burning of brimstone but once over a quantity of lime-water,
+will affect it in such a manner, that breathing into it will not make it
+turbid, which otherwise it always presently does.
+
+Dr. Hales supposed, that by burning brimstone repeatedly in the same
+quantity of air, the diminution would continue without end. But this I
+have frequently tried, and not found to be the case. Indeed, when the
+ignition has been imperfect in the first instance, a second firing of
+the same substance will increase the effect of the first, &c. but this
+progress soon ceases.
+
+In many cases of the diminution of air, the effect is not immediately
+apparent, even when it stands in water; for sometimes the bulk of air
+will not be much reduced, till it has passed several times through a
+quantity of water, which has thereby a better opportunity of absorbing
+that part of the air, which had not been perfectly detatched from the
+rest. I have sometimes found a very great reduction of a mass of air, in
+consequence of passing but once through cold water. If the air has stood
+in quicksilver, the diminution is generally inconsiderable, till it has
+undergone this operation, there not being any substance exposed to the
+air that could absorb any part of it.
+
+I could not find any considerable alteration in the specific gravity of
+the air, in which candles, or brimstone, had burned out. I am satisfied,
+however, that it is not heavier than common air, which must have been
+manifest, if so great a diminution of the quantity had been owing, as
+Dr. Hales and others supposed, to the elasticity of the whole mass being
+impaired. After making several trials for this purpose, I concluded that
+air, thus diminished in bulk, is rather lighter than common air, which
+favours the supposition of the fixed, or heavier part of the common air,
+having been precipitated.
+
+An animal will live nearly, if not quite as long, in air in which
+candles have burned out, as in common air. This fact surprized me very
+greatly, having imagined that what is called the _consumption_ of air by
+flame, or respiration, to have been of the same nature, and in the same
+degree; but I have since found, that this fact has been observed by many
+persons, and even so early as by Mr. Boyle. I have also observed, that
+air, in which brimstone has burned, is not in the least injurious to
+animals, after the fumes, which at first make it very cloudy, have
+intirely subsided.
+
+I must, in this place, admonish my reader not to confound the simple
+_burning of brimstone_, or of matches (_i. e._ bits of wood dipped in
+it) and the burning of brimstone with a burning mirror, or any _foreign
+heat_. The effect of the former is nothing more than that of any other
+_flame_, or _ignited vapour_, which will not burn, unless the air with
+which it is surrounded be in a very pure state, and which is therefore
+extinguished when the air begins to be much vitiated. Lighted brimstone,
+therefore reduces the air to the same state as lighted wood. But the
+focus of a burning mirror thrown for a sufficient time either upon
+brimstone, or wood, after it has ceased to burn of its own accord, and
+has become _charcoal_, will have a much greater effect: of the same
+kind, diminishing the air to its utmost extent, and making it thoroughly
+noxious. In fact, as will be seen hereafter, more phlogiston is expelled
+from these substances in the latter case than in the former. I never,
+indeed, actually carried this experiment so far with brimstone; but from
+the diminution of air that I did produce by this means, I concluded
+that, by continuing the process some time longer, it would have been
+effected.
+
+Having read, in the Memoirs of the Philosophical Society at Turin, vol.
+I. p. 41. that air in which candles had burned out was perfectly
+restored, so that other candles would burn in it again as well as ever,
+after having been exposed to a considerable degree of _cold_, and
+likewise after having been compressed in bladders, (for the cold had
+been supposed to have produced this effect by nothing but
+_condensation_) I repeated those experiments, and did, indeed, find,
+that when I compressed the air in _bladders_, as the Count de Saluce,
+who made the observation, had done, the experiment succeeded: but having
+had sufficient reason to distrust bladders, I compressed the air in a
+glass vessel standing in water; and then I found, that this process is
+altogether ineffectual for the purpose. I kept the air compressed much
+more, and much longer, than the Count had done, but without producing
+any alteration in it. I also find, that a greater degree of cold than
+that which he applied, and of longer continuance, did by no means
+restore this kind of air: for when I had exposed the phials which
+contained it a whole night, in which the frost was very intense; and
+also when I kept it surrounded with a mixture of snow and salt, I found
+it, in all respects, the same as before.
+
+It is also advanced, in the same Memoir, p. 41. that _heat_ only, as the
+reverse of _cold_, renders air unfit for candles burning in it. But I
+repeated the experiment of the Count for that purpose, without finding
+any such effect from it. I also remember that, many years ago, I filled
+an exhausted receiver with air, which had passed through a glass tube
+made red-hot, and found that a candle would burn in it perfectly well.
+Also, rarefaction by the air-pump does not injure air in the least
+degree.
+
+Though this experiment failed, I have been so happy, as by accident to
+have hit upon a method of restoring air, which has been injured by the
+burning of candles, and to have discovered at least one of the
+restoratives which nature employs for this purpose. It is _vegetation_.
+This restoration of vitiated air, I conjecture, is effected by plants
+imbibing the phlogistic matter with which it is overloaded by the
+burning of inflammable bodies. But whether there be any foundation for
+this conjecture or not, the fact is, I think, indisputable. I shall
+introduce the account of my experiments on this subject, by reciting
+some of the observations which I made on the growing of plants in
+confined air, which led to this discovery.
+
+One might have imagined that, since common air is necessary to
+vegetable, as well as to animal life, both plants and animals had
+affected it in the same manner; and I own I had that expectation, when I
+first put a sprig of mint into a glass jar, standing inverted in a
+vessel of water: but when it had continued growing there for some
+months, I found that the air would neither extinguish a candle, nor was
+it at all inconvenient to a mouse, which I put into it.
+
+The plant was not affected any otherwise than was the necessary
+consequence of its confined situation; for plants growing in several
+other kinds of air, were all affected in the very same manner. Every
+succession of leaves was more diminished in size than the preceding,
+till, at length, they came to be no bigger than the heads of pretty
+small pins. The root decayed, and the stalk also, beginning from the
+root; and yet the plant continued to grow upwards, drawing its
+nourishment through a black and rotten stem. In the third or fourth set
+of leaves, long and white hairy filaments grew from the insertion of
+each leaf and sometimes from the body of the stem, shooting out as far
+as the vessel in which it grew would permit, which, in my experiments,
+was about two inches. In this manner a sprig of mint lived, the old
+plant decaying, and new ones shooting up in its place, but less and less
+continually, all the summer season.
+
+In repeating this experiment, care must be taken to draw away all the
+dead leaves from about the plant, lest they should putrefy, and affect
+the air. I have found that a fresh cabbage leaf, put under a glass
+vessel filled with common air, for the space of one night only, has so
+affected the air, that a candle would not burn in it the next morning,
+and yet the leaf had not acquired any smell of putrefaction.
+
+Finding that candles would burn very well in air in which plants had
+grown a long time, and having had some reason to think, that there was
+something attending vegetation, which restored air that had been injured
+by respiration, I thought it was possible that the same process might
+also restore the air that had been injured by the burning of candles.
+
+Accordingly, on the 17th of August 1771, I put a sprig of mint into a
+quantity of air, in which a wax candle had burned out, and found that,
+on the 27th of the same month, another candle burned perfectly well in
+it. This experiment I repeated, without the least variation in the
+event, not less than eight or ten times in the remainder of the summer.
+
+Several times I divided the quantity of air in which the candle had
+burned out, into two parts, and putting the plant into one of them, left
+the other in the same exposure, contained, also, in a glass vessel
+immersed in water, but without any plant; and never failed to find, that
+a candle would burn in the former, but not in the latter.
+
+I generally found that five or six days were sufficient to restore this
+air, when the plant was in its vigour; whereas I have kept this kind of
+air in glass vessels, immersed in water many months, without being able
+to perceive that the least alteration had been made in it. I have also
+tried a great variety of experiments upon it, as by condensing,
+rarefying, exposing to the light and heat, &c. and throwing into it the
+effluvia of many different substances, but without any effect.
+
+Experiments made in the year 1772, abundantly confirmed my conclusion
+concerning the restoration of air, in which candles had burned out by
+plants growing in it. The first of these experiments was made in the
+month of May; and they were frequently repeated in that and the two
+following months, without a single failure.
+
+For this purpose I used the flames of different substances, though I
+generally used wax or tallow candles. On the 24th of June the experiment
+succeeded perfectly well with air in which spirit of wine had burned
+out, and on the 27th of the same month it succeeded equally well with
+air in which brimstone matches had burned out, an effect of which I had
+despaired the preceding year.
+
+This restoration of air, I found, depended upon the _vegetating state_
+of the plant; for though I kept a great number of the fresh leaves of
+mint in a small quantity of air in which candles had burned out, and
+changed them frequently, for a long space of time, I could perceive no
+melioration in the state of the air.
+
+This remarkable effect does not depend upon any thing peculiar to
+_mint_, which was the plant that I always made use of till July 1772;
+for on the 16th of that month, I found a quantity of this kind of air to
+be perfectly restored by sprigs of _balm_, which had grown in it from
+the 7th of the same month.
+
+That this restoration of air was not owing to any _aromatic effluvia_ of
+these two plants, not only appeared by the _essential oil of mint_
+having no sensible effect of this kind; but from the equally complete
+restoration of this vitiated air by the plant called _groundsel_, which
+is usually ranked among the weeds, and has an offensive smell. This was
+the result of an experiment made the 16th of July, when the plant had
+been growing in the burned air from the 8th of the same month. Besides,
+the plant which I have found to be the most effectual of any that I have
+tried for this purpose is _spinach_, which is of quick growth, but will
+seldom thrive long in water. One jar of burned air was perfectly
+restored by this plant in four days, and another in two days. This last
+was observed on the 22d of July.
+
+In general, this effect may be presumed to have taken place in much less
+time than I have mentioned; because I never chose to make a trial of
+the air, till I was pretty sure, from preceding observations, that the
+event which I had expected must have taken place, if it would succeed at
+all; lest, returning back that part of the air on which I made the
+trial, and which would thereby necessarily receive a small mixture of
+common air, the experiment might not be judged to be quite fair; though
+I myself might be sufficiently satisfied with respect to the allowance
+that was to be made for that small imperfection.
+
+FOOTNOTES:
+
+[3] The supposition, mentioned in this and other passages of the first
+part of this publication, viz. that the diminution of common air, by
+this and other processes is, in part at least, owing to the
+precipitation of the fixed air from it, the reader will find confirmed
+by the experiments and observations in the second part.
+
+
+
+
+SECTION III.
+
+_Of INFLAMMABLE AIR._
+
+
+I have generally made inflammable air in the manner described by Mr.
+Cavendish, in the Philosophical Transactions, from iron, zinc, or tin;
+but chiefly from the two former metals, on account of the process being
+the least troublesome: but when I extracted it from vegetable or animal
+substances, or from coals, I put them into a gun-barrel, to the orifice
+of which I luted a glass tube, or the stem of a tobacco-pipe, and to the
+end of this I tied a flaccid bladder in order to catch the generated
+air; or I received the air in a vessel of quicksilver, in the manner
+represented Fig. 7.
+
+There is not, I believe, any vegetable or animal substance whatever, nor
+any mineral substance, that is inflammable, but what will yield great
+plenty of inflammable air, when they are treated in this manner, and
+urged with a strong heat; but, in order to get the most air, the heat
+must be applied as suddenly, and as vehemently, as possible. For,
+notwithstanding the same care be taken in luting, and in every other
+respect, six or even ten times more air may be got by a sudden heat than
+by a slow one, though the heat that is last applied be as intense as
+that which was applied suddenly. A bit of dry oak, weighing about twelve
+grains, will generally yield about a sheep's bladder full of inflammable
+air with a brisk heat, when it will only give about two or three ounce
+measures, if the same heat be applied to it very gradually. To what this
+difference is owing, I cannot tell. Perhaps the phlogiston being
+extricated more slowly may not be intirely expelled, but form another
+kind of union with its base; so that charcoal made with a heat slowly
+applied shall contain more phlogiston than that which is made with a
+sudden heat. It may be worth while to examine the properties of the
+charcoal with this view.
+
+Inflammable air, when it is made by a quick process, has a very strong
+and offensive smell, from whatever substance it be generated; but this
+smell is of three different kinds, according as the air is extracted
+from mineral, vegetable, or animal substances. The last is exceedingly
+fetid; and it makes no difference, whether it be extracted from a bone,
+or even an old and dry tooth, from soft muscular flesh; or any other
+part of the animal. The burning of any substance occasions the same
+smell: for the gross fume which arises from them, before they flame, is
+the inflammable air they contain, which is expelled by heat, and then
+readily ignited. The smell of inflammable air is the very same, as far
+as I am able to perceive, from whatever substance of the same kingdom it
+be extracted. Thus it makes no difference whether it be got from iron,
+zinc, or tin, from any kind of wood, or, as was observed before, from
+any part of an animal.
+
+If a quantity of inflammable air be contained in a glass vessel standing
+in water, and have been generated very fast, it will smell even through
+the water, and this water will also soon become covered with a thin
+film, assuming all the different colours. If the inflammable air have
+been generated from iron, this matter will appear to be a red okre, or
+the earth of iron, as I have found by collecting a considerable quantity
+of it; and if it have been generated from zinc, it is a whitish
+substance, which I suppose to be the calx of the metal. It likewise
+settles to the bottom of the vessel, and when the water is stirred, it
+has very much the appearance of wool. When water is once impregnated in
+this manner, it will continue to yield this scum for a considerable time
+after the air is removed from it. This I have often observed with
+respect to iron.
+
+Inflammable air, made by a violent effervescence, I have observed to be
+much more inflammable than that which is made by a weak effervescence,
+whether the water or the oil of vitriol prevailed in the mixture. Also
+the offensive smell was much stronger in the former case than in the
+latter. The greater degree of inflammability appeared by the greater
+number of successive explosions, when a candle was presented to the neck
+of a phial filled with it.[4] It is possible, however, that this
+diminution of inflammability may, in some measure, arise from the air
+continuing so much longer in the bladder when it is made very slowly;
+though I think the difference is too great for this cause to have
+produced the whole of it. It may, perhaps, deserve to be tried by a
+different process, without a bladder.
+
+Inflammable air is not thought to be miscible with water, and when kept
+many months, seems, in general, to be as inflammable as ever. Indeed,
+when it is extracted from vegetable or animal substances, a part of it
+will be imbibed by the water in which it stands; but it may be presumed,
+that in this case, there was a mixture of fixed air extracted from the
+substance along with it. I have indisputable evidence, however, that
+inflammable air, standing long in water, has actually lost all its
+inflammability, and even come to extinguish flame much more than that
+air in which candles have burned out. After this change it appears to be
+greatly diminished in quantity, and it still continues to kill animals
+the moment they are put into it.
+
+This very remarkable fact first occurred to my observation on the
+twenty-fifth of May 1771, when I was examining a quantity of inflammable
+air, which had been made from zinc, near three years before. Upon this,
+I immediately set by a common quart-bottle filled with inflammable air
+from iron, and another equal quantity from zinc; and examining them in
+the beginning of December following, that from the iron was reduced near
+one half in quantity, if I be not greatly mistaken; for I found the
+bottle half full of water, and I am pretty clear that it was full of air
+when it was set by. That which had been produced from zinc was not
+altered, and filled the bottle as at first.
+
+Another instance of this kind occurred to my observation on the 19th of
+June 1772, when a quantity of air, half of which had been inflammable
+air from zinc, and half air in which mice had died, and which had been
+put together the 30th of July 1771, appeared not to be in the least
+inflammable, but extinguished flame, as much as any kind of air that I
+had ever tried. I think that, in all, I have had four instances of
+inflammable air losing its inflammability, while it stood in water.
+
+Though air tainted with putrefaction extinguishes flame, I have not
+found that animals or vegetables putrefying in inflammable air render it
+less inflammable. But one quantity of inflammable air, which I had set
+by in May 1771, along with the others above mentioned, had had some
+putrid flesh in it; and this air had lost its inflammability, when it
+was examined at the same time with the other in the December following.
+The bottle in which this air had been kept, smelled exactly like very
+strong Harrogate water. I do not think that any person could have
+distinguished them.
+
+I have made plants grow for several months in inflammable air made from
+zinc, and also from oak; but, though the plants grew pretty well, the
+air still continued inflammable. The former, indeed, was not so highly
+inflammable as when it was fresh made, but the latter was quite as much
+so; and the diminution of inflammability in the former case, I attribute
+to some other cause than the growth of the plant.
+
+No kind of air, on which I have yet made the experiment, will conduct
+electricity; but the colour of an electric spark is remarkably different
+in some different kinds of air, which seems to shew that they are not
+equally good non-conductors. In fixed air, the electric spark is
+exceedingly white; but in inflammable air it is of a purple, or red
+colour. Now, since the most vigorous sparks are always the whitest, and,
+in other cases, when the spark is red, there is reason to think that the
+electric matter passes with difficulty, and with less rapidity: it is
+possible that the inflammable air may contain particles which conduct
+electricity, though very imperfectly; and that the whiteness of the
+spark in the fixed air, may be owing to its meeting with no conducting
+particles at all. When an explosion was made in a quantity of
+inflammable air, it was a little white in the center, but the edges of
+it were still tinged with a beautiful purple. The degree of whiteness in
+this case was probably owing to the electric matter rushing with more
+violence in an explosion than in a common spark.
+
+Inflammable air kills animals as suddenly as fixed air, and, as far as
+can be perceived, in the same manner, throwing them into convulsions,
+and thereby occasioning present death. I had imagined that, by animals
+dying in a quantity of inflammable air, it would in time become less
+noxious; but this did not appear to be the case; for I killed great
+number of mice in a small quantity of this air; which I kept several
+months for this purpose, without its being at all sensibly mended; the
+last, as well as the first mouse, dying the moment it was put into it.
+
+I once imagined that, since fixed and inflammable air are the reverse of
+one another, in several remarkable properties, a mixture of them would
+make common air; and while I made the mixtures in bladders, I imagined
+that I had succeeded in my attempt; but I have since found that thin
+bladders do not sufficiently prevent the air that is contained in them
+from mixing with the external air. Also corks will not sufficiently
+confine different kinds of air, unless the phials in which they are
+confined be set with their mouths downwards, and a little water lie in
+the necks of them, which, indeed, is equivalent to the air standing in
+vessels immersed in water. In this manner, however, I have kept
+different kinds of air for several years.
+
+Whatever methods I took to promote the mixture of fixed and inflammable
+air, they were all ineffectual. I think it my duty, however, to recite
+the issue of an experiment or two of this kind, in which equal mixtures
+of these two kinds of air had stood near three years, as they seem to
+shew that they had in part affected one another, in that long space of
+time. These mixtures I examined April 27, 1771. One of them had stood in
+quicksilver, and the other in a corked phial, with a little water in it.
+On opening the latter in water, the water instantly rushed in, and
+filled almost half of the phial, and very little more was absorbed
+afterwards. In this case the water in the phial had probably absorbed a
+considerable part of the fixed air, so that the inflammable air was
+exceedingly rarefied; and yet the whole quantity that must have been
+rendered non-elastic was ten times more than the bulk of the water, and
+it has not been found that water can contain much more than its own
+bulk of fixed air. But in other cases I have found the diminution of a
+quantity of air, and especially of fixed air, to be much greater than I
+could well account for by any kind of absorption.
+
+The phial which had stood immersed in quicksilver had lost very little
+of its original quantity of air; and being now opened in water, and left
+there, along with another phial, which was just then filled, as this had
+been three years before, viz. with air half inflammable and half fixed,
+I observed that the quantity of both was diminished, by the absorption
+of the water, in the same proportion.
+
+Upon applying a candle to the mouths of the phials which had been kept
+three years, that which had stood in quicksilver went off at one
+explosion, exactly as it would have done if there had been a mixture of
+common air with the inflammable. As a good deal depends upon the
+apertures of the vessels in which the inflammable air is mixed, I mixed
+the two kinds of air in equal proportions in the same phial, and after
+letting the phial stand some days in water, that the fixed air might be
+absorbed, I applied a candle to it, but it made ten or twelve explosions
+(stopping the phial after each of them) before the inflammable matter
+was exhausted.
+
+The air which had been confined in the corked phial exploded in the very
+same manner as an equal and fresh mixture of the two kinds of air in the
+same phial, the experiment being made as soon as the fixed air was
+absorbed, as before; so that in this case, the two kinds of air did not
+seem to have affected one another at all.
+
+Considering inflammable air as air united to, or loaded with phlogiston,
+I exposed to it several substances, which are said to have a near
+affinity with phlogiston, as oil of vitriol, and spirit of nitre (the
+former for above a month), but without making any sensible alteration in
+it.
+
+I observed, however, that inflammable air, mixed with the fumes of
+smoking spirit of nitre, goes off at one explosion, exactly like a
+mixture of half common and half inflammable air. This I tried several
+times, by throwing the inflammable air into a phial full of spirit of
+nitre, with its mouth immersed in a bason containing some of the same
+spirit, and then applying the flame of a candle to the mouth of the
+phial, the moment that it was uncovered, after it had been taken out of
+the bason.
+
+This remarkable effect I hastily concluded to have arisen from the
+inflammable air having been in part deprived of its inflammability, by
+means of the stronger affinity, which the spirit of nitre had with
+phlogiston, and therefore I imagined that by letting them stand longer
+in contact, and especially by agitating them strongly together, I should
+deprive the air of all its inflammability; but neither of these
+operations succeeded, for still the air was only exploded at once, as
+before.
+
+And lastly, when I passed a quantity of inflammable air, which had been
+mixed with the fumes of spirit of nitre, through a body of water, and
+received it in another vessel, it appeared not to have undergone any
+change at all, for it went off in several successive explosions, like
+the purest inflammable air. The effect above-mentioned must, therefore,
+have been owing to the fumes of the spirit of nitre supplying the place
+of common air for the purpose of ignition, which is analogous to other
+experiments with nitre.
+
+Having had the curiosity, on the 25th of July 1772, to expose a great
+variety of different kinds of air to water out of which the air it
+contained had been boiled, without any particular view; the result was,
+in several respects, altogether unexpected, and led to a variety of new
+observations on the properties and affinities of several kinds of air
+with respect to water. Among the rest three fourths of that which was
+inflammable was absorbed by the water in about two days, and the
+remainder was inflammable, but weakly so.
+
+Upon this, I began to agitate a quantity of strong inflammable air in a
+glass jar, standing in a pretty large trough of water, the surface of
+which was exposed to the common air, and I found that when I had
+continued the operation about ten minutes, near one fourth of the
+quantity of air had disappeared; and finding that the remainder made an
+effervescence with nitrous air, I concluded that it must have become fit
+for respiration, whereas this kind of air is, at the first, as noxious
+as any other kind whatever. To ascertain this, I put a mouse into a
+vessel containing 2-1/2 ounce measures of it, and observed that it lived
+in it twenty minutes, which is as long as a mouse will generally live in
+the same quantity of common air. This mouse was even taken out alive,
+and recovered very well. Still also the air in which it had breathed so
+long was inflammable, though very weakly so. I have even found it to be
+so when a mouse has actually died in it. Inflammable air thus diminished
+by agitation in water, makes but one explosion on the approach of a
+candle, exactly like a mixture of inflammable air with common air.
+
+From this experiment I concluded that, by continuing the same process, I
+should deprive inflammable air of all its inflammability, and this I
+found to be the case; for, after a longer agitation, it admitted a
+candle to burn in it, like common air, only more faintly; and indeed by
+the test of nitrous air it did not appear to be near so good as common
+air. Continuing the same process still farther, the air which had been
+most strongly inflammable a little before, came to extinguish a candle,
+exactly like air in which a candle had burned out, nor could they be
+distinguished by the test of nitrous air.
+
+I found, by repeated trials, that it was difficult to catch the time in
+which inflammable air obtained from metals, in coming to extinguish
+flame, was in the state of common air, so that the transition from the
+one to the other must be very short. Indeed I think that in many,
+perhaps in most cases, there may be no proper medium at all, the
+phlogiston passing at once from that mode of union with its base which
+constitutes inflammable air, to that which constitutes an air that
+extinguishes flame, being so much overloaded as to admit of no more. I
+readily, however, found this middle state in a quantity of inflammable
+air extracted from oak, which air I had kept a year, and in which a
+plant had grown, though very poorly, for some part of the time. A
+quantity of this air, after being agitated in water till it was
+diminished about one half, admitted a candle to burn in it exceedingly
+well, and was even hardly to be distinguished from common air by the
+test of nitrous air.
+
+I took some pains to ascertain the quantity of diminution, in fresh made
+and very highly-inflammable air from iron, at which it ceased to be
+inflammable, and, upon the whole, I concluded that it was so when it was
+diminished a little more than one half; for a quantity which was
+diminished exactly one half had something inflammable in it, but in the
+slightest degree imaginable. It is not improbable, however, but there
+may be great differences in the result of this experiment.
+
+Finding that water would imbibe inflammable air, I endeavoured to
+impregnate water with it, by the same process by which I had made water
+imbibe fixed air; but though I found that distilled water would imbibe
+about one fourteenth of its bulk of inflammable air, I could not
+perceive that the taste of it was sensibly altered.
+
+FOOTNOTES:
+
+[4] To try this, after every explosion, which immediately follows the
+presenting of the flame, the mouth of the phial should be closed (I
+generally do it with a finger of the hand in which I hold the phial) for
+otherwise the inflammable air will continue burning, though invisibly in
+the day time, till the whole be consumed.
+
+
+
+
+SECTION IV.
+
+_Of AIR infected with ANIMAL RESPIRATION, or PUTREFACTION._
+
+
+That candles will burn only a certain time, in a given quantity of air
+is a fact not better known, than it is that animals can live only a
+certain time in it; but the cause of the death of the animal is not
+better known than that of the extinction of flame in the same
+circumstances; and when once any quantity of air has been rendered
+noxious by animals breathing in it as long as they could, I do not know
+that any methods have been discovered of rendering it fit for breathing
+again. It is evident, however, that there must be some provision in
+nature for this purpose, as well as for that of rendering the air fit
+for sustaining flame; for without it the whole mass of the atmosphere
+would, in time, become unfit for the purpose of animal life; and yet
+there is no reason to think that it is, at present, at all less fit for
+respiration than it has ever been. I flatter myself, however, that I
+have hit upon two of the methods employed by nature for this great
+purpose. How many others there may be, I cannot tell.
+
+When animals die upon being put into air in which other animals have
+died, after breathing in it as long as they could, it is plain that the
+cause of their death is not the want of any _pabulum vitae,_ which has
+been supposed to be contained in the air, but on account of the air
+being impregnated with something stimulating to their lungs; for they
+almost always die in convulsions, and are sometimes affected so
+suddenly, that they are irrecoverable after a single inspiration, though
+they be withdrawn immediately, and every method has been taken to bring
+them to life again. They are affected in the same manner, when they are
+killed in any other kind of noxious air that I have tried, viz. fixed
+air, inflammable air, air filled with the fumes of brimstone, infected
+with putrid matter, in which a mixture of iron filings and brimstone has
+stood, or in which charcoal has been burned, or metals calcined, or in
+nitrous air, &c.
+
+As it is known that _convulsions_ weaken, and exhaust the vital powers,
+much more than the most vigorous _voluntary_ action of the muscles,
+perhaps these universal convulsions may exhaust the whole of what we may
+call the _vis vitae_ at once, at least that the lungs may be rendered
+absolutely incapable of action, till the animal be suffocated, or be
+irrecoverable for want of respiration.
+
+If a mouse (which is an animal that I have commonly made use of for the
+purpose of these experiments) can stand the first shock of this
+stimulus, or has been habituated to it by degrees, it will live a
+considerable time in air in which other mice will die instantaneously. I
+have frequently found that when a number of mice have been confined in a
+given quantity of air, less than half the time that they have actually
+lived in it, a fresh mouse being introduced to them has been instantly
+thrown into convulsions, and died. It is evident, therefore, that if the
+experiment of the Black Hole were to be repeated, a man would stand the
+better chance of surviving it, who should enter at the first, than at
+the last hour.
+
+I have also observed, that young mice will always live much longer than
+old ones, or than those which are full grown, when they are confined in
+the same quantity of air. I have sometimes known a young mouse to live
+six hours in the same circumstances in which an old mouse has not lived
+one. On these accounts, experiments with mice, and, for the same reason,
+no doubt, with other animals also, have a considerable degree of
+uncertainty attending them; and therefore, it is necessary to repeat
+them frequently, before the result can be absolutely depended upon. But
+every person of feeling will rejoice with me in the discovery of
+_nitrous air_, to be mentioned hereafter, which supersedes many
+experiments with the respiration of animals, being a much more accurate
+test of the purity of air.
+
+The discovery of the provision in nature for restoring air, which has
+been injured by the respiration of animals, having long appeared to me
+to be one of the most important problems in natural philosophy, I have
+tried a great variety of schemes in order to effect it. In these my
+guide has generally been to consider the influences to which the
+atmosphere is, in fact, exposed; and, as some of my unsuccessful trials
+may be of use to those who are disposed to take pains in the farther
+investigation of this subject, I shall mention the principal of them.
+
+The noxious effluvium with which air is loaded by animal respiration, is
+not absorbed by standing, without agitation; in fresh or salt water. I
+have kept it many months in fresh water, when, instead of being
+meliorated, it has seemed to become even more deadly, so as to require
+more time to restore it, by the methods which will be explained
+hereafter, than air which has been lately made noxious. I have even
+spent several hours in pouring this air from one glass vessel into
+another, in water, sometimes as cold, and sometimes as warm, as my hands
+could bear it, and have sometimes also wiped the vessels many times,
+during the course of the experiment, in order to take off that part of
+the noxious matter, which might adhere to the glass vessels, and which
+evidently gave them an offensive smell; but all these methods were
+generally without any sensible effect. The _motion_, also, which the air
+received in these circumstances, it is very evident, was of no use for
+this purpose. I had not then thought of the simple, but most effectual
+method of agitating air in water, by putting it into a tall jar and
+shaking it with my hand.
+
+This kind of air is not restored by being exposed to the _light_, or by
+any other influence to which it is exposed, when confined in a thin
+phial, in the open air, for some months.
+
+Among other experiments, I tried a great variety of different
+_effluvia_, which are continually exhaling into the air, especially of
+those substances which are known to resist putrefaction; but I could not
+by these means effect any melioration of the noxious quality of this
+kind of air.
+
+Having read, in the memoirs of the Imperial Society, of a plague not
+affecting a particular village, in which there was a large sulphur-work,
+I immediately fumigated a quantity of this kind of air; or (which will
+hereafter appear to be the very same thing) air tainted with
+putrefaction, with the fumes of burning brimstone, but without any
+effect.
+
+I once imagined, that the _nitrous acid_ in the air might be the general
+restorative which I was in quest of; and the conjecture was favoured, by
+finding that candles would burn in air extracted from saltpetre. I
+therefore spent a good deal of time in attempting, by a burning glass,
+and other means, to impregnate this noxious air, with some effluvium of
+saltpetre, and, with the same view, introduced into it the fumes of the
+smoaking spirit of nitre; but both these methods were altogether
+ineffectual.
+
+In order to try the effect of _heat_, I put a quantity of air, in which
+mice had died, into a bladder, tied to the end of the stem of a
+tobacco-pipe, at the other end of which was another bladder, out of
+which the air was carefully pressed. I then put the middle part of the
+stem into a chafing-dish of hot coals, strongly urged with a pair of
+bellows; and, pressing the bladders alternately, I made the air pass
+several times through the heated part of the pipe. I have also made
+this kind of air very hot, standing in water before the fire. But
+neither of these methods were of any use.
+
+_Rarefaction_ and _condensation_ by instruments were also tried, but in
+vain.
+
+Thinking it possible that the _earth_ might imbibe the noxious quality
+of the air, and thence supply the roots of plants with such putrescent
+matter as is known to be nutritive to them, I kept a quantity of air, in
+which mice had died, in a phial, one half of which was filled with fine
+garden-mould; but, though it stood two months in these circumstances, it
+was not the better for it.
+
+I once imagined that, since several kinds of air cannot be long
+separated from common air, by being confined in bladders, in bottles
+well corked; or even closed with ground stopples, the affinity between
+this noxious air and the common air might be so great, that they would
+mix through a body of water interposed between them; the water
+continually receiving from the one, and giving to the other, especially
+as water receives some kind of impregnation from, I believe, every kind
+of air to which it is contiguous; but I have seen no reason to
+conclude, that a mixture of any kind of air with the common air can be
+produced in this manner.
+
+I have kept air in which mice have died, air in which candles have
+burned out, and inflammable air, separated from the common air, by the
+slightest partition of water that I could well make, so that it might
+not evaporate in a day or two, if I should happen not to attend to them;
+but I found no change in them after a month or six weeks. The
+inflammable air was still inflammable, mice died instantly in the air in
+which other mice had died before, and candles would not burn where they
+had burned out before.
+
+Since air tainted with animal or vegetable putrefaction is the same
+thing with air rendered noxious by animal respiration, I shall now
+recite the observations which I have made upon this kind of air, before
+I treat of the method of restoring them.
+
+That these two kinds of air are, in fact, the same thing, I conclude
+from their having several remarkable common properties, and from their
+differing in nothing that I have been able to observe. They equally
+extinguish flame, they are equally noxious to animals, they are
+equally, and in the same way, offensive to the smell, and they are
+restored by the same means.
+
+Since air which has passed through the lungs is the same thing with air
+tainted with animal putrefaction, it is probable that one use of the
+lungs is to carry off a _putrid effluvium_, without which, perhaps, a
+living body might putrefy as soon as a dead one.
+
+When a mouse putrefies in any given quantity of air, the bulk of it is
+generally increased for a few days; but in a few days more it begins to
+shrink up, and in about eight or ten days, if the weather be pretty
+warm, it will be found to be diminished 1/6, or 1/5 of its bulk. If it
+do not appear to be diminished after this time, it only requires to be
+passed through water, and the diminution will not fail to be sensible. I
+have sometimes known almost the whole diminution to take place, upon
+once or twice passing through the water. The same is the case with air,
+in which animals have breathed as long as they could. Also, air in which
+candles have burned out may almost always be farther reduced by this
+means.
+
+All these processes, as I observed before, seem to dispose the compound
+mass of air to part with some constituent part belonging to it (which
+appears to be the _fixed air_ that enters into its constitution) and
+this being miscible with water, must be brought into contact with it, in
+order to mix with it to the most advantage, especially when its union
+with the other constituent principles of the air is but partially
+broken.
+
+I have put mice into vessels which had their mouths immersed in
+quicksilver, and observed that the air was not much contracted after
+they were dead or cold; but upon withdrawing the mice, and admitting
+lime water to the air, it immediately became turbid, and was contracted
+in its dimensions as usual.
+
+I tried the same thing with air tainted with putrefaction, putting a
+dead mouse to a quantity of common air, in a vessel which had its mouth
+immersed in quicksilver, and after a week I took the mouse out, drawing
+it through the quicksilver, and observed that, for some time, there was
+an apparent increase of the air perhaps about 1/20. After this, it stood
+two days in the quicksilver, without any sensible alteration; and then
+admitting water to it, it began to be absorbed, and continued so, till
+the original quantity was diminished about 1/6. If, instead of common
+water, I had made use of lime-water in this experiment, I make no doubt
+but it would have become turbid.
+
+If a quantity of lime-water in a phial be put under a glass vessel
+standing in water, it will not become turbid, and provided the access of
+the common air be prevented, it will continue lime-water, I do not know
+how long; but if a mouse be left to putrefy in the vessel, the water
+will deposit all its lime in a few days. This is owing to the fixed air
+deposited by the common air, and perhaps also from more fixed air
+discharged from the putrefying substances in some part of the process of
+putrefaction.
+
+The air that is discharged from putrefying substances seems, in some
+cases, to be chiefly fixed air, with the addition of some other
+effluvium, which has the power of diminishing common air. The
+resemblance between the true putrid effluvium and fixed air in the
+following experiment, which is as decisive as I can possibly contrive
+it, appeared to be very great; indeed much greater than I had expected.
+I put a dead mouse into a tall glass vessel, and having filled the
+remainder with quicksilver, and set it, inverted, in a pot of
+quicksilver, I let it stand about two months, in which time the putrid
+effluvium issuing from the mouse had filled the whole vessel, and part
+of the dissolved blood, which lodged upon the surface of the
+quicksilver, began to be thrown out. I then filled another glass vessel,
+of the same size and shape, with as pure fixed air as I could make, and
+exposed them both, at the same time, to a quantity of lime-water. In
+both cases the water grew turbid alike, it rose equally fast in both the
+vessels, and likewise equally high; so that about the same quantity
+remained unabsorbed by the water. One of these kinds of air, however,
+was exceedingly sweet and pleasant, and the other insufferably
+offensive; one of them also would have made an addition to any quantity
+of common air, with which it had been mixed, and the other would have
+diminished it. This, at least, would have been the consequence, if the
+mouse itself had putrefied in any quantity of common air.
+
+It seems to depend, in some measure, upon the _time_, and other
+circumstances, in the dissolution of animal or vegetable substances,
+whether they yield the proper putrid effluvium, or fixed, or inflammable
+air; but the experiments which I have made upon this subject, have not
+been numerous enough to enable me to decide with certainty concerning
+those circumstances.
+
+Putrid cabbage, green or boiled, infects the air in the very same manner
+as putrid animal substances. Air thus tainted is equally contracted in
+its dimensions, it equally extinguishes flame, and is equally noxious to
+animals; but they affect the air very differently, if the heat that is
+applied to them be considerable.
+
+If beef or mutton, raw or boiled, be placed so near to the fire, that
+the heat to which it is exposed shall equal, or rather exceed, that of
+the blood, a considerable quantity of air will be generated in a day or
+two, about 1/7th of which I have generally found to be absorbed by
+water, while all the rest was inflammable; but air generated from
+vegetables, in the same circumstances, will be almost all fixed air, and
+no part of it inflammable. This I have repeated again and again, the
+whole process being in quicksilver; so that neither common air nor
+water, had any access to the substance on which the experiment was made;
+and the generation of air, or effluvium of any kind, except what might
+be absorbed by quicksilver, or resorbed by the substance itself, might
+be distinctly noted.
+
+A vegetable substance, after standing a day or two in these
+circumstances, will yield nearly all the air that can be extracted from
+it, in that degree of heat; whereas an animal substance will continue
+to give more air, or effluvium, of some kind or other, with very little
+alteration, for many weeks. It is remarkable, however, that though a
+piece of beef or mutton, plunged in quicksilver, and kept in this degree
+of heat, yield air, the bulk of which is inflammable, and contracts no
+putrid smell (at least, in a day or two) a mouse treated in the same
+manner, yields the proper putrid effluvium, as indeed the smell
+sufficiently indicates.
+
+That the putrid effluvium will mix with water seems to be evident from
+the following experiment. If a mouse be put into a jar full of water,
+standing with its mouth inverted in another vessel of water, a
+considerable quantity of elastic matter (and which may, therefore, be
+called _air_) will soon be generated, unless the weather be so cold as
+to check all putrefaction. After a short time, the water contracts an
+extremely fetid and offensive smell, which seems to indicate that the
+putrid effluvium pervades the water, and affects the neighbouring air;
+and since, after this, there is often no increase of the air, that seems
+to be the very substance which is carried off through the water, as fast
+as it is generated; and the offensive smell is a sufficient proof that
+it is not fixed air. For this has a very agreeable flavour, whether it
+be produced by fermentation, or extracted from chalk by oil of vitriol;
+affecting not only the mouth, but even the nostrils; with a pungency
+which is peculiarly pleasing to a certain degree, as any person may
+easily satisfy himself, who will chuse to make the experiment.
+
+If the water in which the mouse was immersed, and which is saturated
+with the putrid air, be changed, the greater part of the putrid air,
+will, in a day or two, be absorbed, though the mouse continues to yield
+the putrid effluvium as before; for as soon as this fresh water becomes
+saturated with it, it begins to be offensive to the smell, and the
+quantity of the putrid air upon its surface increases as before. I kept
+a mouse producing putrid air in this manner for the space of several
+months.
+
+Six ounce measures of air not readily absorbed by water, appeared to
+have been generated from one mouse, which had been putrefying eleven
+days in confined air, before it was put into a jar which was quite
+filled with water, for the purpose of this observation.
+
+Air thus generated from putrid mice standing in water, without any
+mixture of common air, extinguishes flame, and is noxious to animals,
+but not more so than common air only tainted with putrefaction. It is
+exceedingly difficult and tedious to collect a quantity of this putrid
+air, not miscible in water, so very great a proportion of what is
+collected being absorbed by the water in which it is kept; but what that
+proportion is, I have not endeavoured to ascertain. It is probably the
+same proportion that that part of fixed air, which is not readily
+absorbed by water, bears to the rest; and therefore this air, which I at
+first distinguished by the name of _the putrid effluvium_, is probably
+the same with fixed air, mixed with the phlogistic matter, which, in
+this and other processes, diminishes common air.
+
+Though a quantity of common air be diminished by any substance
+putrefying in it, I have not yet found the same effect to be produced by
+a mixture of putrid air with common air; but, in the manner in which I
+have hitherto made the experiment, I was obliged to let the putrid air
+pass through a body of water, which might instantly absorb the
+phlogistic matter that diminished the common air.
+
+Insects of various kinds live perfectly well in air tainted with animal
+or vegetable putrefaction, when a single inspiration of it would have
+instantly killed any other animal. I have frequently tried the
+experiment with flies and butterflies. The _aphides_ also will thrive as
+well upon plants growing in this kind of air, as in the open air. I
+have even been frequently obliged to take plants out of the putrid air
+in which they were growing, on purpose to brush away the swarms of these
+insects which infected them; and yet so effectually did some of them
+conceal themselves, and so fast did they multiply, in these
+circumstances, that I could seldom keep the plants quite clear of them.
+
+When air has been freshly and strongly tainted with putrefaction, so as
+to smell through the water, sprigs of mint have presently died, upon
+being put into it, their leaves turning black; but if they do not die
+presently, they thrive in a most surprizing manner. In no other
+circumstances have I ever seen vegetation so vigorous as in this kind of
+air, which is immediately fatal to animal life. Though these plants have
+been crouded in jars filled with this air, every leaf has been full of
+life; fresh shoots have branched out in various directions, and have
+grown much faster than other similar plants, growing in the same
+exposure in common air.
+
+This observation led me to conclude, that plants, instead of affecting
+the air in the same manner with animal respiration, reverse the effects
+of breathing, and tend to keep the atmosphere sweet and wholesome, when
+it is become noxious, in consequence of animals either living and
+breathing, or dying and putrefying in it.
+
+In order to ascertain this, I took a quantity of air, made thoroughly
+noxious, by mice breathing and dying in it, and divided it into two
+parts; one of which I put into a phial immersed in water; and to the
+other (which was contained in a glass jar, standing in water) I put a
+sprig of mint. This was about the beginning of August 1771, and after
+eight or nine days, I found that a mouse lived perfectly well in that
+part of the air, in which the sprig of mint had grown, but died the
+moment it was put into the other part of the same original quantity of
+air; and which I had kept in the very same exposure, but without any
+plant growing in it.
+
+This experiment I have several times repeated; sometimes using air in
+which animals had breathed and died, and at other times using air,
+tainted with vegetable or animal putrefaction; and generally with the
+same success.
+
+Once, I let a mouse live and die in a quantity of air which had been
+noxious, but which had been restored by this process, and it lived
+nearly as long as I conjectured it might have done in an equal quantity
+of fresh air; but this is so exceedingly various, that it is not easy to
+form any judgment from it; and in this case the symptom of _difficult
+respiration_ seemed to begin earlier than it would have done in common
+air.
+
+Since the plants that I made use of manifestly grow and thrive in putrid
+air; since putrid matter is well known to afford proper nourishment for
+the roots of plants; and since it is likewise certain that they receive
+nourishment by their leaves as well as by their roots, it seems to be
+exceedingly probable, that the putrid effluvium is in some measure
+extracted from the air, by means of the leaves of plants, and therefore
+that they render the remainder more fit for respiration.
+
+Towards the end of the year some experiments of this kind did not answer
+so well as they had done before, and I had instances of the relapsing of
+this restored air to its former noxious state. I therefore suspended my
+judgment concerning the efficacy of plants to restore this kind of
+noxious air, till I should have an opportunity of repeating my
+experiments, and giving more attention to them. Accordingly I resumed
+the experiments in the summer of the year 1772, when I presently had the
+most indisputable proof of the restoration of putrid air by vegetation;
+and as the fact is of some importance, and the subsequent variation in
+the state of this kind of air is a little remarkable, I think it
+necessary to relate some of the facts pretty circumstantially.
+
+The air, on which I made the first experiments, was rendered exceedingly
+noxious by mice dying in it on the 20th of June. Into a jar nearly
+filled with one part of this air, I put a sprig of mint, while I kept
+another part of it in a phial, in the same exposure; and on the 27th of
+the same month, and not before, I made a trial of them, by introducing a
+mouse into a glass vessel, containing 2-1/2 ounce measures filled with
+each kind of air; and I noted the following facts.
+
+When the vessel was filled with the air in which the mint had grown, a
+very large mouse lived five minutes in it, before it began to shew any
+sign of uneasiness. I then took it out, and found it to be as strong and
+vigorous as when it was first put in; whereas in that air which had been
+kept in the phial only, without a plant growing in it, a younger mouse
+continued not longer than two or three seconds, and was taken out quite
+dead. It never breathed after, and was immediately motionless. After
+half an hour, in which time the larger mouse (which I had kept alive,
+that the experiment might be made on both the kinds of air with the very
+same animal) would have been sufficiently recruited, supposing it to
+have received any injury by the former experiment, was put into the same
+vessel of air; but though it was withdrawn again, after being in it
+hardly one second, it was recovered with difficulty, not being able to
+stir from the place for near a minute. After two days, I put the same
+mouse into an equal quantity of common air, and observed that it
+continued seven minutes without any sign of uneasiness; and being very
+uneasy after three minutes longer, I took it out. Upon the whole, I
+concluded that the restored air wanted about one fourth of being as
+wholesome as common air. The same thing also appeared when I applied the
+test of nitrous air.
+
+In the seven days, in which the mint was growing in this jar of noxious
+air, three old shoots had extended themselves about three inches, and
+several new ones had made their appearance in the same time. Dr.
+Franklin and Sir John Pringle happened to be with me, when the plant had
+been three or four days in this state, and took notice of its vigorous
+vegetation, and remarkably healthy appearance in that confinement.
+
+On the 30th of the same month, a mouse lived fourteen minutes, breathing
+naturally all the time, and without appearing to be much uneasy, till
+the last two minutes, in the vessel containing two ounce measures and a
+half of air which had been rendered noxious, by mice breathing in it
+almost a year before, and which, I had found to be most highly noxious
+on the 19th of this month, a plant having grown in it, but not
+exceedingly well, these eleven days; on which account I had deferred
+making the trial so long. The restored air was affected by a mixture of
+nitrous air, almost as much as common air.
+
+As this putrid air was thus easily restored to a considerable degree of
+fitness for respiration, by plants growing in it, I was in hopes that by
+the same means it might in time be so much more perfectly restored, that
+a candle would burn in it; and for this purpose I kept plants growing in
+the jars which contained this air till the middle of August following,
+but did not take sufficient care to pull out all the old and rotten
+leaves. The plants, however, had grown, and looked so well upon the
+whole, that I had no doubt but that the air must constantly have been in
+a mending state; when I was exceedingly surprized to find, on the 24th
+of that month, that though the air in one of the jars had not grown
+worse, it was no better; and that the air in the other jar was so much
+worse than it had been, that a mouse would have died in it in a few
+seconds. It also made no effervescence with nitrous air, as it had done
+before.
+
+Suspecting that the same plant might be capable of restoring putrid air
+to a certain degree only, or that plants might have a contrary tendency
+in some stages of their growth, I withdrew the old plant, and put a
+fresh one in its place; and found that, after seven days, the air was
+restored to its former wholesome state. This fact I consider as a very
+remarkable one, and well deserving of a farther investigation, as it may
+throw more light upon the principles of vegetation. It is not, however,
+a single fact; for I had several instances of the same kind in the
+preceding year; but it seemed so very extraordinary, that air should
+grow worse by the continuance of the same treatment by which it had
+grown better, that, whenever I observed it, I concluded that I had not
+taken sufficient care to satisfy myself of its previous restoration.
+
+That plants are capable of perfectly restoring air injured by
+respiration, may, I think, be inferred with certainty from the perfect
+restoration, by this means, of air which had passed through my lungs, so
+that a candle would burn in it again, though it had extinguished flame
+before, and apart of the same original quantity of air still continued
+to do so. Of this one instance occurred in the year 1771, a sprig of
+mint having grown in a jar of this kind of air, from the 25th of July to
+the 17th of August following; and another trial I made, with the same
+success, the 7th of July 1772, the plant having grown in it from the
+29th of June preceding. In this case also I found that the effect was
+not owing to any virtue in the leaves of mint; for I kept them
+constantly changed in a quantity of this kind of air, for a considerable
+time, without making any sensible alteration in it.
+
+These proofs of a partial restoration of air by plants in a state of
+vegetation, though in a confined and unnatural situation, cannot but
+render it highly probable, that the injury which is continually done to
+the atmosphere by the respiration of such a number of animals, and the
+putrefaction of such masses of both vegetable and animal matter, is, in
+part at least, repaired by the vegetable creation. And, notwithstanding
+the prodigious mass of air that is corrupted daily by the
+above-mentioned causes; yet, if we consider the immense profusion of
+vegetables upon the face of the earth, growing in places, suited to
+their nature, and consequently at full liberty to exert all their
+powers, both inhaling and exhaling, it can hardly be thought, but that
+it may be a sufficient counterbalance to it, and that the remedy is
+adequate to the evil.
+
+Dr. Franklin, who, as I have already observed, saw some of my plants in
+a very flourishing state, in highly noxious air, was pleased to express
+very great satisfaction with the result of the experiments. In his
+answer to the letter in which I informed him of it, he says,
+
+"That the vegetable creation should restore the air which is spoiled by
+the animal part of it, looks like a rational system, and seems to be of
+a piece with the rest. Thus fire purifies water all the world over. It
+purifies it by distillation, when it raises it in vapours, and lets it
+fall in rain; and farther still by filtration, when, keeping it fluid,
+it suffers that rain to percolate the earth. We knew before that putrid
+animal substances were converted into sweet vegetables, when mixed with
+the earth, and applied as manure; and now, it seems, that the same
+putrid substances, mixed with the air, have a similar effect. The strong
+thriving state of your mint in putrid air seems to shew that the air is
+mended by taking something from it, and not by adding to it." He adds,
+"I hope this will give some check to the rage of destroying trees that
+grow near houses, which has accompanied our late improvements in
+gardening, from an opinion of their being unwholesome. I am certain,
+from long observation, that there is nothing unhealthy in the air of
+woods; for we Americans have every where our country habitations in the
+midst of woods, and no people on earth enjoy better health, or are more
+prolific."
+
+Having rendered inflammable air perfectly innoxious by continued
+_agitation in a trough of water_, deprived of its air, I concluded that
+other kinds of noxious air might be restored by the same means; and I
+presently found that this was the case with putrid air, even of more
+than a year's standing. I shall observe once for all, that this process
+has never failed to restore any kind of noxious air on which I have
+tried it, viz. air injured by respiration or putrefaction, air infected
+with the fumes of burning charcoal, and of calcined metals, air in which
+a mixture of iron filings and brimstone, that in which paint made of
+white lead and oil has stood, or air which has been diminished by a
+mixture of nitrous air. Of the remarkable effect which this process has
+on nitrous air itself, an account will be given in its proper place.
+
+If this process be made in water deprived of air, either by the
+air-pump, by boiling, or by distillation, or if fresh rain-water be
+used, the air will always be diminished by the agitation; and this is
+certainly the fairest method of making the experiment. If the water be
+fresh pump-water, there will always be an increase of the air by
+agitation, the air contained in the water being set loose, and joining
+that which is in the jar. In this case, also, the air has never failed
+to be restored; but then it might be suspected that the melioration was
+produced by the addition of some more wholesome ingredient. As these
+agitations were made in jars with wide mouths, and in a trough which had
+a large surface exposed to the common air, I take it for granted that
+the noxious effluvia, whatever they be, were first imbibed by the water,
+and thereby transmitted to the common atmosphere. In some cases this was
+sufficiently indicated by the disagreeable smell which attended the
+operation.
+
+After I had made these experiments, I was informed that an ingenious
+physician and philosopher had kept a fowl alive twenty-four hours, in a
+quantity of air in which another fowl of the same size had not been able
+to live longer than an hour, by contriving to make the air, which it
+breathed, pass through no very large quantity of acidulated water, the
+surface of which was not exposed to the common air; and that even when
+the water was not acidulated, the fowl lived much longer than it could
+have done, if the air which it breathed had not been drawn through the
+water.
+
+As I should not have concluded that this experiment would have succeeded
+so well, from any observations that I had made upon the subject, I took
+a quantity of air in which mice had died, and agitated it very strongly,
+first in about five times its own quantity of distilled water, in the
+manner in which I had impregnated water with fixed air; but though the
+operation was continued a long time, it made no sensible change in the
+properties of the air. I also repeated the operation with pump-water,
+but with as little effect. In this case, however, though the air was
+agitated in a phial, which had a narrow neck, the surface of the water
+in the bason was considerably large, and exposed to the common
+atmosphere, which must have tended a little to favour the experiment.
+
+In order to judge more precisely of the effect of these different
+methods of agitating air, I transferred the very noxious air, which I
+had hot been able to amend in the least degree by the former method,
+into an open jar, standing in a trough of water; and when I had agitated
+it till it was diminished about one third, I found it to be better than
+air in which candles had burned out, as appeared by the test of the
+nitrous air; and a mouse lived in 2-1/2 ounce measures of it a quarter
+of an hour, and was not sensibly affected the first ten or twelve
+minutes.
+
+In order to determine whether the addition of any _acid_ to the water,
+would make it more capable of restoring putrid air, I agitated a
+quantity of it in a phial containing very strong vinegar; and after that
+in _aqua fortis_, only half diluted with water; but by neither of these
+processes was the air at all mended, though the agitation was repeated,
+at intervals, during a whole day, and it was moreover allowed to stand
+in that situation all night.
+
+Since, however, water in these experiments must have imbibed and
+retained a certain portion of the noxious effluvia, before they could be
+transmitted to the external air, I do not think it improbable but that
+the agitation of the sea and large lakes may be of some use for the
+purification of the atmosphere, and the putrid matter contained in water
+may be imbibed by aquatic plants, or be deposited in some other manner.
+
+Having found, by several experiments above-mentioned that the proper
+putrid effluvium is something quite distinct from fixed air, and
+finding, by the experiments of Dr. Macbride, that fixed air corrects
+putrefaction; it occured to me, that fixed air, and air tainted with
+putrefaction, though equally, noxious when separate, might make a
+wholesome mixture, the one, correcting the other; and I was confirmed in
+this opinion by, I believe, not less than fifty or sixty instances, in
+which air, that had been made in the highest degree noxious, by
+respiration or putrefaction, was so far sweetened, by a mixture of about
+four times as much fixed air, that afterwards mice lived in it
+exceedingly well, and in some cases almost as long as in common air. I
+found it, indeed, to be more difficult to restore _old_ putrid air by
+this means; but I hardly ever failed to do it, when the two kinds of air
+had stood a long time together; by which I mean about a fortnight or
+three weeks.
+
+The reason why I do not absolutely conclude that the restoration of air
+in these cases was the effect of fixed air, is that, when I made a trial
+of the mixture, I sometimes agitated the two kinds of air pretty
+strongly together, in a trough of water, or at least passed it several
+times through water, from one jar to another, that the superfluous fixed
+air might be absorbed, not suspecting at that time that the agitation
+could have any other effect. But having since found that very violent,
+and especially long-continued agitation in water, without any mixture of
+fixed air, never failed to render any kind of noxious air in some
+measure fit for respiration (and in one particular instance the mere
+transferring of the air from one vessel to another through the water,
+though for a much longer time than I ever used for the mixtures of air,
+was of considerable use for the same purpose) I began to entertain some
+doubt of the efficacy of fixed air in this case. In some cases also the
+mixture of fixed air had by no means so much effect on the putrid air
+as, from the generality of my observations, I should have expected.
+
+I was always aware, indeed, that it might be said, that, the residuum of
+fixed air not being very noxious, such an addition must contribute to
+mend the putrid air; but, in order to obviate this objection, I once
+mixed the residuum of as much fixed air as I had found, by a variety of
+trials, to be sufficient to restore a given quantity of putrid air, with
+an equal quantity of that air, without making any sensible melioration
+of it.
+
+Upon the whole, I am inclined to think that this process could hardly
+have succeeded so well as it did with me, and in so great a number of
+trials, unless fixed air have some tendency to correct air tainted with
+respiration or putrefaction; and it is perfectly agreeable to the
+analogy of Dr. Macbride's discoveries, and may naturally be expected
+from them, that it should have such an effect.
+
+By a mixture of fixed air I have made wholesome the residuum of air
+generated by putrefaction only, from mice plunged in water. This, one
+would imagine, _a priori_, to be the most noxious of all kinds of air.
+For if common air only tainted with putrefaction be so deadly, much more
+might one expect that air to be so, which was generated from
+putrefaction only; but it seems to be nothing more than common air (or
+at least that kind of fixed air which is not absorbed by water) tainted
+with putrefaction, and therefore requires no other process to sweeten
+it. In this case, however, we seem to have an instance of the generation
+of genuine common air, though mixed with something that is foreign to
+it. Perhaps the residuum of fixed air may be another instance of the
+same nature, and also the residuum of inflammable air, and of nitrous
+air, especially nitrous air loaded with phlogiston, after long agitation
+in water.
+
+Fixed air is equally diffused through the whole mass of any quantity of
+putrid air with which it is mixed: for dividing the mixture into two
+equal parts, they were reduced in the same proportion by passing through
+water. But this is also the case with some of the kinds of air which
+will not incorporate, as inflammable air, and air in which brimstone has
+burned.
+
+If fixed air tend to correct air which has been injured by animal
+respiration or putrefaction, _lime kilns_, which discharge great
+quantities of fixed air, may be wholesome in the neighbourhood of
+populous cities, the atmosphere of which must abound with putrid
+effluvia. I should think also that physicians might avail themselves of
+the application of fixed air in many putrid disorders, especially as it
+may be so easily administered by way of _clyster_, where it would often
+find its way to much of the putrid matter. Nothing is to be apprehended
+from the distention of the bowels by this kind of air, since it is so
+readily absorbed by any fluid or moist substance.
+
+Since fixed air is not noxious _per se_, but, like fire, only in excess,
+I do not think it at all hazardous to attempt to _breathe_ it. It is
+however easily conveyed into the _stomach_, in natural or artificial
+Pyrmont water, in briskly-fermenting liquors, or a vegetable diet. It
+is even possible, that a considerable quantity of fixed air might be
+imbibed by the absorbing vessels of the skin, if the whole body, except
+the head, should be suspended over a vessel of strongly-fermenting
+liquor; and in some putrid disorders this treatment might be very
+salutary. If the body was exposed quite naked, there would be very
+little danger from the cold in this situation, and the air having freer
+access to the skin might produce a greater effect. Being no physician, I
+run no risk by throwing out these random, and perhaps whimsical
+proposals.[5]
+
+Having communicated my observations on fixed air, and especially my
+scheme of applying it by way of _clyster_ in putrid disorders, to Mr.
+Hey, an ingenious surgeon in Leeds a case presently occurred, in which
+he had an opportunity of giving it a trial; and mentioning it to Dr.
+Hird and Dr. Crowther, two physicians who attended the patient, they
+approved the scheme, and it was put in execution; both by applying the
+fixed air by way of clyster, and at the same time making the patient
+drink plentifully of liquors strongly impregnated with it. The event
+was such, that I requested Mr. Hey to draw up a particular account of
+the case, describing the whole of the treatment, that the public might
+be satisfied that this new application of fixed air is perfectly safe,
+and also, have an opportunity of judging how far it had the effect which
+I expected from it; and as the application is new, and not unpromising,
+I shall subjoin his letter to me on the subject, by way of _Appendix_ to
+these papers.
+
+When I began my inquires into the properties of different kinds of air,
+I engaged my friend Dr. Percival to attend to the _medicinal uses_ of
+them, being sensible that his knowledge of philosophy as well as of
+medicine would give him a singular advantage for this purpose. The
+result of his observations I shall also insert in the Appendix.
+
+FOOTNOTES:
+
+[5] Some time after these papers were first printed, I was pleased to
+find the same proposal in _Dr. Alexander's Experimental Essays_.
+
+
+
+
+SECTION V.
+
+_Of AIR in which a mixture of BRIMSTONE and FILINGS of IRON has stood._
+
+
+Reading in Dr. Hales's account of his experiments, that there was a
+great diminution of the quantity of air in which _a mixture of powdered
+brimstone and filings of iron, made into a paste with water_, had stood,
+I repeated the experiment, and found the diminution greater than I had
+expected. This diminution of air is made as effectually, and as
+expeditiously, in quicksilver as in water; and it may be measured with
+the greatest accuracy, because there is neither any previous expansion
+or increase of the quantity of air, and because it is some time before
+this process begins to have any sensible effect. This diminution of air
+is various; but I have generally found it to be between one fifth and
+one fourth of the whole.
+
+Air thus diminished is not heavier, but rather lighter than common air;
+and though lime-water does not become turbid when it is exposed to this
+air, it is probably owing to the formation of a selenitic salt, as was
+the case with the simple burning of brimstone above-mentioned. That
+something proceeding from the brimstone strongly affects the water which
+is confined in the same place with this mixture, is manifest from the
+very strong smell that it has of the volatile spirit of vitriol.
+
+I conclude that the diminution of air by this, process is of the same
+kind with the diminution of it in the other cases, because when this
+mixture is put into air which has been previously diminished, either by
+the burning of candles, by respiration, or putrefaction, though it never
+fails to diminish it something more, it is, however, no farther than
+this process alone would have done it. If a fresh mixture be introduced
+into a quantity of air which had been reduced by a former mixture, it
+has little or no farther effect.
+
+I once observed, that when a mixture of this kind was taken out of a
+quantity of air in which a candle had before burned out, and in which it
+had stood for several days, it was quite cold and black, as it always
+becomes in a confined place; but it presently grew very hot, smoaked
+copously, and smelled very offensively; and when it was cold, it was
+brown, like the rust of iron.
+
+I once put a mixture of this kind to a quantity of inflammable air, made
+from iron, by which means it was diminished 1/9 or 1/10 in its bulk;
+but, as far as I could judge, it was still as inflammable as ever.
+Another quantity of inflammable air was also reduced in the same
+proportion, by a mouse putrefying in it; but its inflammability was not
+seemingly lessened.
+
+Air diminished by this mixture of iron filings and brimstone, is
+exceedingly noxious to animals, and I have not perceived that it grows
+any better by keeping in water. The smell of it is very pungent and
+offensive.
+
+The quantity of this mixture which I made use of in the preceding
+experiments, was from two to four ounce measures; but I did not
+perceive, but that the diminution of the quantity of air (which was
+generally about twenty ounce measures) was as great with the smallest,
+as with the largest quantity. How small a quantity is necessary to
+diminish a given quantity of air to a _maximum_, I have made no
+experiments to ascertain.
+
+As soon as this mixture of iron filings with, brimstone and water,
+begins to ferment, it also turns black, and begins to swell, and it
+continues to do so, till it occupies twice as much space as it did at
+first. The force with which it expands is great; but how great it is I
+have not endeavoured to determine.
+
+When this mixture is immersed in water, it generates no air, though it
+becomes black, and swells.
+
+
+
+
+SECTION VI.
+
+_Of NITROUS AIR._
+
+
+Ever since I first read Dr. Hales's most excellent _Statical Essays_, I
+was particularly struck with that experiment of his, of which an account
+is given, VOL. I, p. 224. and VOL. II, p. 280. in which common air, and
+air generated from the Walton pyrites, by spirit of nitre, made a turbid
+red mixture, and in which part of the common air was absorbed; but I
+never expected to have the satisfaction of seeing this remarkable
+appearance, supposing it to be peculiar to that particular mineral.
+Happening to mention this subject to the Hon. Mr. Cavendish, when I was
+in London, in the spring of the year 1772, he said that he did not
+imagine but that other kinds of pyrites, or the metals might answer as
+well, and that probably the red appearance of the mixture depended upon
+the spirit of nitre only. This encouraged me to attend to the subject;
+and having no pyrites, I began with the solution of the different metals
+in spirit of nitre, and catching the air which was generated in the
+solution, I presently found what I wanted, and a good deal more.
+
+Beginning with the solution of brass, on the 4th of June 1772, I first
+found this remarkable species of air, only one effect of which, was
+casually observed by Dr. Hales; and he gave so little attention to it,
+and it has been so much unnoticed since his time, that, as far as I
+know, no name has been given to it. I therefore found myself, contrary
+to my first resolution, under an absolute necessity of giving a name to
+this kind of air myself. When I first began to speak and write of it to
+my friends, I happened to distinguish it by the name of _nitrous air_,
+because I had procured it by means of spirit of nitre only; and though I
+cannot say that I altogether like the term, neither myself nor any of my
+friends, to whom I have applied for the purpose, have been able to hit
+upon a better; so that I am obliged, after all, to content myself with
+it.
+
+I have found that this kind of air is readily procured from iron,
+copper, brass, tin, silver, quicksilver, bismuth, and nickel, by the
+nitrous acid only, and from gold and the regulus of antimony by _aqua
+regia_. The circumstances attending the solution of each of these metals
+are various, but hardly worth mentioning, in treating of the properties
+of the _air_ which they yield; which, from what metal soever it is
+extracted, has, as far as I have been able to observe, the very same
+properties.
+
+One of the most conspicuous properties of this kind of air is the great
+diminution of any quantity of common air with which it is mixed,
+attended with a turbid red, or deep orange colour, and a considerable
+heat. The _smell_ of it, also, is very strong, and remarkable, but very
+much resembling that of smoking spirit of nitre.
+
+The diminution of a mixture of this and common air is not an equal
+diminution of both the kinds, which is all that Dr. Hales could observe,
+but of about one fifth of the common air, and as much of the nitrous air
+as is necessary to produce that effect; which, as I have found by many
+trials, is about one half as much as the original quantity of common
+air. For if one measure of nitrous air be put to two measures of common
+air, in a few minutes (by which time the effervescence will be over, and
+the mixture will have recovered its transparency) there will want about
+one ninth of the original two measures; and if both the kinds of air be
+very pure, the diminution will still go on slowly, till in a day or two,
+the whole will be reduced to one fifth less than the original quantity
+of common air. This farther diminution, by long standing, I had not
+observed at the time of the first publication of these papers.
+
+I hardly know any experiment that is more adapted to amaze and surprize
+than this is, which exhibits a quantity of air, which, as it were,
+devours a quantity of another kind of air half as large as itself, and
+yet is so far from gaining any addition to its bulk, that it is
+considerably diminished by it. If, after this full saturation of common
+air with nitrous air, more nitrous air be put to it, it makes an
+addition equal to its own bulk, without producing the least redness, or
+any other visible effect.
+
+If the smallest quantity of common air be put to any larger quantity of
+nitrous air, though the two together will not occupy so much space as
+they did separately, yet the quantity will still be larger than that of
+the nitrous air only. One ounce measure of common air being put to near
+twenty ounce measures of nitrous air, made an addition to it of about
+half an ounce measure. This being a much greater proportion than the
+diminution of common air, in the former experiment, proves that part of
+the diminution in the former case is in the nitrous air. Besides, it
+will presently appear, that nitrous air is subject to a most remarkable
+diminution; and as common air, in a variety of other cases, suffers a
+diminution from one fifth to one fourth, I conclude, that in this case
+also it does not exceed that proportion, and therefore that the
+remainder of the diminution respects the nitrous air.
+
+In order to judge whether the _water_ contributed to the diminution of
+this mixture of nitrous and common air, I made the whole process several
+times in quicksilver, using one third of nitrous, and two thirds of
+common air, as before. In this case the redness continued a very long
+time, and the diminution was not so great as when the mixtures had been
+made in water, there remaining one seventh more than the original
+quantity of common air.
+
+This mixture stood all night upon the quicksilver; and the next morning
+I observed that it was no farther diminished upon the admission of
+water to it, nor by pouring it several times through the water, and
+letting it stand in water two days.
+
+Another mixture, which had stood about six hours on the quicksilver, was
+diminished a little more upon the admission of water, but was never less
+than the original quantity of common air. In another case however, in
+which the mixture had stood but a very short time in quicksilver, the
+farther diminution, which took place upon the admission of water, was
+much more considerable; so that the diminution, upon the whole, was very
+nearly as great as if the process had been intirely in water.
+
+It is evident from these experiments, that the diminution is in part
+owing to the absorption by the water; but that when the mixture is kept
+a long time, in a situation in which there is no water to absorb any
+part of it, it acquires a constitution, by which it is afterwards
+incapable of being absorbed by water, or rather, there is an addition to
+the quantity of air by nitrous air produced by the solution of the
+quicksilver.
+
+It will be seen, in the second part of this work, that, in the
+decomposition of nitrous air by its mixture with common air, there is
+nothing at hand when the process is made in quicksilver, with which the
+acid that entered into its composition can readily unite.
+
+In order to determine whether the fixed part of common air was deposited
+in the diminution of it by nitrous air, I inclosed a vessel full of
+lime-water in the jar in which the process was made, but it occasioned
+no precipitation of the lime; and when the vessel was taken out, after
+it had been in that situation a whole day, the lime was easily
+precipitated by breathing into it as usual.
+
+But though the precipitation of the lime was not sensible in this method
+of making the experiment, it is sufficiently so when the whole process
+is made in lime-water, as will be seen in the second part of this work;
+so that we have here another evidence of the deposition of fixed air
+from common air. I have made no alteration, however, in the preceding
+paragraph, because it may not be unuseful, as a caution to future
+experimenters.
+
+It is exceedingly remarkable that this effervescence and diminution,
+occasioned by the mixture of nitrous air, is peculiar to common air, or
+_air fit for respiration_; and, as far as I can judge, from a great
+number of observations, is at least very nearly, if not exactly, in
+proportion to its fitness for this purpose; so that by this means the
+goodness of air may be distinguished much more accurately than it can be
+done by putting mice, or any other animals, to breathe in it.
+
+This was a most agreeable discovery to me, as I hope it may be an useful
+one to the public; especially as, from this time, I had no occasion for
+so large a stock of mice as I had been used to keep for the purpose of
+these experiments, using them only in those which required to be very
+decisive; and in these cases I have seldom failed to know beforehand in
+what manner they would be affected.
+
+It is also remarkable that, on whatever account air is unfit for
+respiration, this same test is equally applicable. Thus there is not the
+least effervescence between nitrous and fixed air, or inflammable air,
+or any species of diminished air. Also the degree of diminution being
+from nothing at all to more than one third of the whole of any quantity
+of air, we are, by this means, in possession of a prodigiously large
+_scale_, by which we may distinguish very small degrees of difference in
+the goodness of air.
+
+I have not attended much to this circumstance, having used this test
+chiefly for greater differences; but, if I did not deceive myself, I
+have perceived a real difference in the air of my study, after a few
+persons have been with me in it, and the air on the outside of the
+house. Also a phial of air having been sent me, from the neighbourhood
+of York, it appeared not to be so good as the air near Leeds; that is,
+it was not diminished so much by an equal mixture of nitrous air, every
+other circumstance being as nearly the same as I could contrive. It may
+perhaps be possible, but I have not yet attempted it, to distinguish
+some of the different winds, or the air of different times of the year,
+&c. &c. by this test.
+
+By means of this test I was able to determine what I was before in doubt
+about, viz. the _kind_ as well as the _degree_ of injury done to air by
+candles burning in it. I could not tell with certainty, by means of
+mice, whether it was at all injured with respect to respiration; and yet
+if nitrous air may be depended upon for furnishing an accurate test, it
+must be rather more than one third worse than common air, and have been
+diminished by the same general cause of the other diminutions of air.
+For when, after many trials, I put one measure of thoroughly putrid and
+highly noxious air, into the same vessel with two measures of good
+wholesome air, and into another vessel an equal quantity, viz. three
+measures of air in which a candle had burned out; and then put equal
+quantities of nitrous air to each of them, the latter was diminished
+rather more than the former.
+
+It agrees with this observation, that _burned air_ is farther diminished
+both by putrefaction, and a mixture of iron filings and brimstone; and I
+therefore take it for granted by every other cause of the diminution of
+air. It is probable, therefore, that burned air is air so far loaded
+with phlogiston, as to be able to extinguish a candle, which it may do
+long before it is fully saturated.
+
+Inflammable air with a mixture of nitrous air burns with a green flame.
+This makes a very pleasing experiment when it is properly conducted. As,
+for some time, I chiefly made use of _copper_ for the generation of
+nitrous air, I first ascribed this circumstance to that property of this
+metal, by which it burns with a green flame; but I was presently
+satisfied that it must arise from the spirit of nitre, for the effect is
+the very same from which ever of the metals the nitrous air is
+extracted, all of which I tried for this purpose, even silver and gold.
+
+A mixture of oil of vitriol and spirit of nitre in equal proportions
+dissolved iron, and the produce was nitrous air; but a less degree of
+spirit of nitre in the mixture produced air that was inflammable, and
+which burned with a green flame. It also tinged common air a little red,
+and diminished it, though not much.
+
+The diminution of common air by a mixture of nitrous air, is not so
+extraordinary as the diminution which nitrous air itself is subject to
+from a mixture of iron filings and brimstone, made into a paste with
+water. This mixture, as I have already observed, diminishes common air
+between one fifth and one fourth, but has no such effect upon any kind
+of air that has been diminished, and rendered noxious by any other
+process; but when it is put to a quantity of nitrous air, it diminishes
+it so much, that no more than one fourth of the original quantity will
+be left.
+
+The effect of this process is generally perceived in five or six hours,
+about which time the visible effervesence of the mixture begins; and in
+a very short time it advances so rapidly, that in about an hour almost
+the whole effect will have taken place. If it be suffered to stand a day
+or two longer, the air will still be diminished farther, but only a very
+little farther, in proportion to the first diminution. The glass jar,
+in which the air and this mixture have been confined, has generally been
+so much heated in this process, that I have not been able to touch it.
+
+Nitrous air thus diminished has not so strong a smell as nitrous air
+itself, but smells just like common air in which the same mixture has
+stood; and it is not capable of being diminished any farther, by a fresh
+mixture of iron and brimstone.
+
+Common air saturated with nitrous air is also no farther diminished by
+this mixture of iron filings and brimstone, though the mixture ferments
+with great heat, and swells very much in it.
+
+Plants die very soon, both in nitrous air, and also in common air
+saturated with nitrous air, but especially in the former.
+
+Neither nitrous air, nor common air saturated with nitrous air, differ
+in specific gravity from common air. At least, the difference is so
+small, that I could not be sure there was any; sometimes about three
+pints of it seeming to be about half a grain heavier, and at other times
+as much lighter than common air.
+
+Having, among other kinds of air, exposed a quantity of nitrous air to
+water out of which the air had been well boiled, in the experiment to
+which I have more than once referred (as having been the occasion of
+several new and important observations) I found that 19/20 of the whole
+was absorbed. Perceiving, to my great surprize, that so very great a
+proportion of this kind of air was miscible with water, I immediately
+began to agitate a considerable quantity of it, in a jar standing in a
+trough of the same kind of water; and, with about four times as much
+agitation as fixed air requires, it was so far absorbed by the water,
+that only about one fifth remained. This remainder extinguished flame,
+and was noxious to animals.
+
+Afterwards I diminished a pretty large quantity of nitrous air to one
+eighth of its original bulk, and the remainder still retained much of
+its peculiar smell, and diminished common air a little. A mouse also
+died in it, but not so suddenly as it would have done in pure nitrous
+air. In this operation the peculiar smell of nitrous air is very
+manifest, the water being first impregnated with the air, and then
+transmitting it to the common atmosphere.
+
+This experiment gave me the hint of impregnating water with nitrous air,
+in the manner in which I had before done it with fixed air; and I
+presently found that distilled water would imbibe about one tenth of its
+bulk of this kind of air, and that it acquired a remarkably acid and
+astringent taste from it. The smell of water thus impregnated is at
+first peculiarly pungent. I did not chuse to swallow any of it, though,
+for any thing that I know, it may be perfectly innocent, and perhaps, in
+some cases, salutary.
+
+This kind of air is retained very obstinately by water. In an exhausted
+receiver a quantity of water thus saturated emitted a whitish fume, such
+as sometimes issues from bubbles of this air when it is first generated,
+and also some air-bubbles; but though it was suffered to stand a long
+time in this situation, it still retained its peculiar taste; but when
+it had stood all night pretty near the fire, the water was become quite
+vapid, and had deposited a filmy kind of matter, of which I had often
+collected a considerable quantity from the trough in which jars
+containing this air had stood. This I suppose to be a precipitate of the
+metal, by the solution of which the nitrous air was generated. I have
+not given so much attention to it as to know, with certainty, in what
+circumstances this _deposit_ is made, any more than I do the matter
+deposited from inflammable air above-mentioned; for I cannot get it, at
+least in any considerable quantity, when I please; whereas I have often
+found abundance of it, when I did not expect it at all.
+
+The nitrous air with which I made the first impregnation of water was
+extracted from copper; but when I made the impregnation with air from
+quicksilver, the water had the very same taste, though the matter
+deposited from it seemed to be of a different kind; for it was whitish,
+whereas the other had a yellowish tinge. Except the first quantity of
+this impregnated water, I could never deprive any more that I made of
+its peculiar taste. I have even let some of it stand more than a week,
+in phials with their mouths open, and sometimes very near the fire,
+without producing any alteration in it[6].
+
+Whether any of the spirit of nitre contained in the nitrous air be mixed
+with the water in this operation, I have not yet endeavoured to
+determine. This, however, may probably be the case, as the spirit of
+nitre is, in a considerable degree, volatile[7].
+
+It will perhaps be thought, that the most _useful_, if not the most
+remarkable, of all the properties of this extraordinary kind of air, is
+its power of preserving animal substances from putrefaction, and of
+restoring those that are already putrid, which it possesses in a far
+greater degree than fixed air. My first observation of this was
+altogether casual. Having found nitrous air to suffer so great a
+diminution as I have already mentioned by a mixture of iron filings and
+brimstone, I was willing to try whether it would be equally diminished
+by other causes of the diminution of common air, especially by
+putrefaction; and for this purpose I put a dead mouse into a quantity of
+it, and placed it near the fire, where the tendency to putrefaction was
+very great. In this case there was a considerable diminution, viz. from
+5-1/4 to 3-1/4; but not so great as I had expected, the antiseptic power
+of the nitrous air having checked the tendency to putrefaction; for
+when, after a week, I took the mouse out, I perceived, to my very great
+surprize, that it had no offensive smell.
+
+Upon this I took two other mice, one of them just killed, and the other
+soft and putrid, and put them both into the same jar of nitrous air,
+standing in the usual temperature of the weather, in the months of July
+and August of 1772; and after twenty-five days, having observed that
+there was little or no change in the quantity of the air, I took the
+mice out; and, examining them, found them both perfectly sweet, even
+when cut through in several places. That which had been put into the air
+when just dead was quite firm; and the flesh of the other, which had
+been putrid and soft, was still soft, but perfectly sweet.
+
+In order to compare the antiseptic power of this kind of air with that
+of fixed air, I examined a mouse which I had inclosed in a phial full of
+fixed air, as pure as I could make it, and which I had corked very
+close; but upon opening this phial in water about a month after, I
+perceived that a large quantity of putrid effluvium had been generated;
+for it rushed with violence out of the phial; and the smell that came
+from it, the moment the cork was taken out, was insufferably offensive.
+Indeed Dr. Macbride says, that he could only restore very thin pieces
+of putrid flesh by means of fixed air. Perhaps the antiseptic power of
+these kinds of air may be in proportion to their acidity.
+
+If a little pains were taken with this subject, this remarkable
+antiseptic power of nitrous air might possibly be applied to various
+uses, perhaps to the preservation of the more delicate birds, fishes,
+fruits, &c. mixing it in different proportions with common or fixed air.
+Of this property of nitrous air anatomists may perhaps avail themselves,
+as animal substances may by this means be preserved in their natural
+soft state; but how long it will answer for this purpose, experience
+only can shew.
+
+I calcined lead and tin in the manner hereafter described in a quantity
+of nitrous air, but with very little sensible effect; which rather
+surprized me; as, from the result of the experiment with the iron
+filings and brimstone, I had expected a very great diminution of the
+nitrous air by this process; the mixture of iron filings and brimstone,
+and the calcination of metals, having the same effect upon common air,
+both of them diminishing it in nearly the same proportion. But though I
+made the metals _fume_ copiously in nitrous air, there might be no real
+_calcination_, the phlogiston not being separated, and the proper
+calcination prevented by there being no _fixed_ _air_, which is
+necessary to the formation of the calx, to unite with it.
+
+Nitrous air is procured from all the proper metals by spirit of nitre,
+except lead, and from all the semi-metals that I have tried, except
+zinc. For this purpose I have used bismuth and nickel, with spirit of
+nitre only, and regulus of antimony and platina, with _aqua regia_.
+
+I got little or no air from lead by spirit of nitre, and have not yet
+made any experiments to ascertain the nature of this solution. With zinc
+I have taken a little pains.
+
+Four penny-weights and seventeen grains of zinc dissolved in spirit of
+nitre, to which as much water was added, yielded about twelve ounce
+measures of air, which had, in some degree, the properties of nitrous
+air, making a slight effervescence with common air, and diminishing it
+about as much as nitrous air, which had been itself diminished one half
+by washing in water. The smell of them both was also the same; so that I
+concluded it to be the same thing, that part of the nitrous air, which
+is imbibed by water, being retained in this solution.
+
+In order to discover whether this was the case, I made the solution boil
+in a sand-heat. Some air came from it in this state, which seemed to be
+the same thing, with nitrous air diminished about one sixth, or one
+eighth, by washing in water. When the fluid part was evaporated, there
+remained a brown fixed substance, which was observed by Mr. Hellot, who
+describes it, Ac. Par. 1735, M. p. 35. A part of this I threw into a
+small red-hot crucible; and covering it immediately with a receiver,
+standing in water, I observed that very dense red fumes rose from it,
+and filled the receiver. This redness continued about as long as that
+which is occasioned by a mixture of nitrous and common air; the air was
+also considerably diminished within the receiver. This substance,
+therefore, must certainly have contained within it the very same thing,
+or principle, on which the peculiar properties of nitrous air depend.
+
+It is remarkable, however, that though the air within the receiver was
+diminished about one fifth by this process, it was itself as much
+affected with a mixture of nitrous air, as common air is, and a candle
+burned in it very well. This may perhaps be attributed to some effect of
+the spirit of nitre, in the composition of that brown substance.
+
+Nitrous air, I find, will be considerably diminished in its bulk by
+standing a long time in water, about as much as inflammable air is
+diminished in the same circumstances. For this purpose I kept for some
+months a quart-bottle full of each of these kinds of air; but as
+different quantities of inflammable air vary very much in this respect,
+it is not improbable but that nitrous air may vary also.
+
+From one trial that I made, I conclude that nitrous air may be kept in a
+bladder much better than most other kinds of air. The air to which I
+refer was kept about a fortnight in a bladder, through which the
+peculiar smell of the nitrous air was very sensible for several days. In
+a day or two the bladder became red, and was much contracted in its
+dimensions. The air within it had lost very little of its peculiar
+property of diminishing common air.
+
+I did not endeavour to ascertain the exact quantity of nitrous air
+produced from given quantities, of all the metals which yield it; but
+the few observations which I did make for this purpose I shall recite in
+this place:
+
+     dwt. gr.
+
+     6     0      of silver yielded 17-1/2 ounce measures.
+     5    19      of quicksilver     4-1/2
+     1     2-1/2  of copper         14-1/2
+     2     0      of brass          21
+     0    20      of iron           16
+     1     5      of bismuth         6
+     0    12      of nickel          4
+
+FOOTNOTES:
+
+[6] I have since found, that nitrous air has never failed to escape from
+the water, which has been impregnated with it, by long exposure to the
+open air.
+
+[7] This suspicion has been confirmed by the ingenious Mr. Bewley, of
+Great Massingham in Norfolk, who has discovered that the acid taste of
+this water is not the necessary consequence of its impregnation with
+nitrous air, but is the effect of the _acid vapour_, into which part of
+this air is resolved, when it is decomposed by a mixture with common
+air. This, it will be seen, exactly agrees with my own observation on
+the constitution of nitrous air, in the second part of this work. A more
+particular account of Mr. Bewley's observation will be given in the
+_Appendix_.
+
+
+
+
+SECTION VII.
+
+_Of AIR infected with the FUMES of BURNING CHARCOAL._
+
+
+Air infected with the fumes of burning charcoal is well known to be
+noxious; and the Honourable Mr. Cavendish favoured me with an account of
+some experiments of his, in which a quantity of common air was reduced
+from 180 to 162 ounce measures, by passing through a red-hot iron tube
+filled with the dust of charcoal. This diminution he ascribed to such a
+_destruction_ of common air as Dr. Hales imagined to be the consequence
+of burning. Mr. Cavendish also observed, that there had been a
+generation of fixed air in this process, but that it was absorbed by
+sope leys. This experiment I also repeated, with a small variation of
+circumstances, and with nearly the same result.
+
+Afterwards, I endeavoured to ascertain, by what appears to me to be an
+easier and more certain method, in what manner air is affected with the
+fumes of charcoal, viz. by suspending bits of charcoal within glass
+vessels, filled to a certain height with water, and standing inverted
+in another vessel of water, while I threw the focus of a burning mirror,
+or lens, upon them. In this manner I diminished a given quantity of air
+one fifth, which is nearly in the same proportion with other diminutions
+of air.
+
+If, instead of pure water, I used _lime-water_ in this process, it never
+failed to become turbid by the precipitation of the lime, which could
+only be occasioned by fixed air, either discharged from the charcoal, or
+deposited by the common air. At first I concluded that it came from the
+charcoal; but considering that it is not probable that fixed air,
+confined in any substance, can bear so great a degree of heat as is
+necessary to make charcoal, without being wholly expelled; and that in
+other diminutions of common air, by phlogiston only, there appears to be
+a deposition of fixed air, I have now no doubt but that, in this case
+also, it is supplied from the same source.
+
+This opinion is the more probable, from there being the same
+precipitation of lime, in this process, with whatever degree of heat the
+charcoal had been made. If, however, the charcoal had not been made with
+a very considerable degree of heat, there never failed to be a permanent
+addition of inflammable air produced; which agrees with what I observed
+before, that, in converting dry wood into charcoal, the greatest part
+is changed into inflammable air.
+
+I have sometimes found, that charcoal which was made with the most
+intense heat of a smith's fire, which vitrified part of a common
+crucible in which the charcoal was confined, and which had been
+continued above half an hour, did not diminish the air in which the
+focus of a burning mirror was thrown upon it; a quantity of inflammable
+air equal to the diminution of the common air being generated in the
+process: whereas, at other times, I have not perceived that there was
+any generation of inflammable air, but a simple diminution of common
+air, when the charcoal had been made with a much less degree of heat.
+This subject deserves to be farther investigated.
+
+To make the preceding experiment with still more accuracy, I repeated it
+in quicksilver; when I perceived that there was a small increase of the
+quantity of air, probably from a generation of inflammable air. Thus it
+stood without any alteration a whole night, and part of the following
+day; when lime-water, being admitted to it, it presently became turbid,
+and, after some time, the whole quantity of air, which was about four
+ounce measures, was diminished one fifth, as before. In this case, I
+carefully weighed the piece of charcoal, which was exactly two grains,
+and could not find that it was sensibly diminished in weight by the
+operation.
+
+Air thus diminished by the fumes of burning charcoal not only
+extinguishes flame, but is in the highest degree noxious to animals; it
+makes no effervescence with nitrous air, and is incapable of being
+diminished any farther by the fumes of more charcoal, by a mixture of
+iron filings and brimstone, or by any other cause of the diminution of
+air that I am acquainted with.
+
+This observation, which respects all other kinds of diminished air,
+proves that Dr. Hales was mistaken in his notion of the _absorption_ of
+air in those circumstances in which he observed it. For he supposed that
+the remainder was, in all cases, of the same nature with that which had
+been absorbed, and that the operation of the same cause would not have
+failed to produce a farther diminution; whereas all my observations shew
+that air, which has once been fully diminished by any cause whatever, is
+not only incapable of any farther diminution, either from the same or
+from any other cause, but that it has likewise acquired _new
+properties_, most remarkably different from those which it had before,
+and that they are, in a great measure, the same in all the cases. These
+circumstances give reason to suspect, that the cause of diminution is,
+in reality, the same in all the cases. What this cause is, may, perhaps,
+appear in the next course of observations.
+
+
+
+
+SECTION VIII.
+
+_Of the effect of the CALCINATION of METALS, and of the EFFLUVIA of
+PAINT made with WHITE-LEAD and OIL, on AIR._
+
+
+Having been led to suspect, from the experiments which I had made with
+charcoal, that the diminution of air in that case, and perhaps in other
+cases also, was, in some way or other the consequence of its having more
+than its usual quantity of phlogiston, it occurred to me, that the
+calcination of metals, which are generally supposed to consist of
+nothing but a metallic earth united to phlogiston, would tend to
+ascertain the fact, and be a kind of _experimentum crucis_ in the case.
+
+Accordingly, I suspended pieces of lead and tin in given quantities of
+air, in the same manner as I had before treated the charcoal; and
+throwing the focus of a burning mirror or lens upon them, so as to make
+them fume copiously. I presently perceived a diminution of the air. In
+the first trial that I made, I reduced four ounce measures of air to
+three, which is the greatest diminution of common air that I had ever
+observed before, and which I account for, by supposing that, in other
+cases, there was not only a cause of diminution, but causes of addition
+also, either of fixed or inflammable air, or some other permanently
+elastic matter, but that the effect of the calcination of metals being
+simply the escape of phlogiston, the cause of diminution was alone and
+uncontrouled.
+
+The air, which I had thus diminished by calcination of lead, I
+transferred into another clean phial, but found that the calcination of
+more lead in it (or at least the attempt to make a farther calcination)
+had no farther effect upon it. This air also, like that which had been
+infected with the fumes of charcoal, was in the highest degree noxious,
+made no effervescence with nitrous air, was no farther diminished by the
+mixture of iron filings and brimstone, and was not only rendered
+innoxious, but also recovered, in a great measure, the other properties
+of common air, by washing in water.
+
+It might be suspected that the noxious quality of air in which _lead_
+was calcined, might be owing to some fumes peculiar to that metal; but
+I found no sensible difference between the properties of this air, and
+that in which _tin_ was calcined.
+
+The _water_ over which metals are calcined acquires a yellowish tinge,
+and an exceedingly pungent smell and taste, pretty much (as near as I
+can recollect, for I did not compare them together) like that over which
+brimstone has been frequently burned. Also a thin and whitish pellicle
+covered both the surface of the water, and likewise the sides of the
+phial in which the calcination was made; insomuch that, without
+frequently agitating the water, it grew so opaque by this constantly
+accumulating incrustation, that the sun-beams could not be transmitted
+through it in a quantity sufficient to produce the calcination.
+
+I imagined, however, that, even when this air was transferred into a
+clean phial, the metals were not so easily melted or calcined as they
+were in fresh air; for the air being once fully saturated with
+phlogiston, may not so readily admit any more, though it be only to
+transmit it to the water. I also suspected that metals were not easily
+melted or calcined in inflammable, fixed, or nitrous air, or any kind
+of diminished air.[8] None of these kinds of air suffered any change by
+this operation; nor was there any precipitation of lime, when charcoal
+was heated in any of these kinds of air standing in lime-water. This
+furnishes another, and I think a pretty decisive proof, that, in the
+precipitation of lime by charcoal, the fixed air does not come from the
+charcoal, but from the common air. Otherwise it is hard to assign a
+reason, why the same degree of heat (or at least a much greater) should
+not expel the fixed air from this substance, though surrounded by these
+different kinds of air, and why the fixed air might not be transmitted
+through them to the lime-water.
+
+Query. May not water impregnated with phlogiston from calcined metals,
+or by any other method, be of some use in medicine? The effect of this
+impregnation is exceedingly remarkable; but the principle with which it
+is impregnated is volatile, and intirely escapes in a day or two, if the
+surface of the water be exposed to the common atmosphere.
+
+It should seem that phlogiston is retained more obstinately by charcoal
+than it is by lead or tin; for when any given quantity of air is fully
+saturated with phlogiston from charcoal, no heat that I have yet applied
+has been able to produce any more effect upon it; whereas, in the same
+circumstances, lead and tin may still be calcined, at least be made to
+emit a copious fume, in which some part of the phlogiston may be set
+loose. The air indeed, can take no more; but the water receives it, and
+the sides of the phial also receive an addition of incrustation. This is
+a white powdery substance, and well deserves to be examined. I shall
+endeavour to do it at my leisure.
+
+Lime-water never became turbid by the calcination of metals over it, the
+calx immediately seizing the precipitated fixed air, in preference to
+the lime in the water; but the colour, smell, and taste of the water was
+always changed and the surface of it became covered with a yellow
+pellicle, as before.
+
+When this process was made in quicksilver, the air was diminished only
+one fifth; and upon water being admitted to it, no more was absorbed;
+which is an effect similar to that of a mixture of nitrous and common
+air, which was mentioned before.
+
+The preceding experiments on the calcination of metals suggested to me a
+method of explaining the cause of the mischief which is known to arise
+from fresh _paint_, made with white-lead (which I suppose is an
+imperfect calx of lead) and oil.
+
+To verify my hypothesis, I first put a small pot full of this kind of
+paint, and afterwards (which answered much better, by exposing a greater
+surface of the paint) I daubed several pieces of paper with it, and put
+them under a receiver, and observed, that in about twenty-four hours,
+the air was diminished between one fifth and one fourth, for I did not
+measure it very exactly. This air also was, as I expected to find, in
+the highest degree noxious; it did not effervesce with nitrous air, it
+was no farther diminished by a mixture of iron filings and brimstone,
+and was made wholesome by agitation in water deprived of all air.
+
+I think it appears pretty evident, from the preceding experiments on the
+calcination of metals that air is, some way or other, diminished in
+consequence of being highly charged with phlogiston; and that agitation
+in water restores it, by imbibing a great part of the phlogistic
+matter.
+
+That water has a considerable affinity with phlogiston, is evident from
+the strong impregnation which it receives from it. May not plants also
+restore air diminished by putrefaction by absorbing part of the
+phlogiston with which it is loaded? The greater part of a dry plant, as
+well as of a dry animal substance, consists of inflammable air, or
+something that is capable of being converted into inflammable air; and
+it seems to be as probable that this phlogistic matter may have been
+imbibed by the roots and leaves of plants, and afterwards incorporated
+into their substance, as that it is altogether produced by the power of
+vegetation. May not this phlogistic matter be even the most essential
+part of the food and support of both vegetable and animal bodies?
+
+In the experiments with metals, the diminution of air seems to be the
+consequence of nothing but a saturation with phlogiston; and in all the
+other cases of the diminution of air, I do not see but that it may be
+effected by the same means. When a vegetable or animal substance is
+dissolved by putrefaction, the escape of the phlogistic matter (which,
+together with all its other constituent parts, is then let loose from
+it) may be the circumstance that produces the diminution of the air in
+which it putrefies. It is highly improbable that what remains after an
+animal body has been thoroughly dissolved by putrefaction, should yield
+so great a quantity of inflammable air, as the dried animal substance
+would have done. Of this I have not made an actual trial, though I have
+often thought of doing it, and still intend to do it; but I think there
+can be no doubt of the result.
+
+Again, iron, by its fermentation with brimstone and water, is evidently
+reduced to a calx, so that phlogiston must have escaped from it.
+Phlogiston also must evidently be set loose by the ignition of charcoal,
+and is not improbably the matter which flies off from paint, composed of
+white-lead and oil. Lastly, since spirit of nitre is known to have a
+very remarkable affinity with phlogiston, it is far from being
+improbable that nitrous air may also produce the same effect by the same
+means.
+
+To this hypothesis it may be objected, that, if diminished air be air
+saturated with phlogiston, it ought to be inflammable. But this by no
+means follows; since its inflammability may depend upon some particular
+_mode of combination_, or degree of affinity, with which we are not
+acquainted. Besides, inflammable air seems to consist of some other
+principle, or to have some other constituent part, besides phlogiston
+and common air, as is probable from that remarkable deposit, which, as I
+have observed, is made by inflammable air, both from iron and zinc.
+
+It is not improbable, however, but that a greater degree of heat may
+inflame that air which extinguishes a common candle, if it could be
+conveniently applied. Air that is inflammable, I observe, extinguishes
+red-hot wood; and indeed inflammable substances can only be those which,
+in a certain degree of heat, have a less affinity with the phlogiston
+they contain, than the air, or some other contiguous substance, has with
+it; so that the phlogiston only quits one substance, with which it was
+before combined, and enters another, with which it may be combined in a
+very different manner. This substance, however, whether it be air or any
+thing else, being now fully saturated with phlogiston, and not being
+able to take any more, in the same circumstances, must necessarily
+extinguish fire, and put a stop to the ignition of all other bodies,
+that is, to the farther escape of phlogiston from them.
+
+That plants restore noxious air, by imbibing the phlogiston with which
+it is loaded, is very agreeable to the conjectures of Dr. Franklin,
+made many years ago, and expressed in the following extract from the
+last edition of his Letters, p. 346.
+
+"I have been inclined to think that the fluid _fire_, as well as the
+fluid _air_, is attracted by plants in their growth, and becomes
+consolidated with the other materials of which they are formed, and
+makes a great part of their substance; that, when they come to be
+digested, and to suffer in the vessels a kind of fermentation, part of
+the fire, as well as part of the air, recovers its fluid active state
+again, and diffuses itself in the body, digesting and separating it;
+that the fire so re-produced, by digestion and separation, continually
+leaving the body, its place is supplied by fresh quantities, arising
+from the continual separation; that whatever quickens the motion of the
+fluids in an animal, quickens the separation, and re-produces more of
+the fire, as exercise; that all the fire emitted by wood, and other
+combustibles, when burning, existed in them before in a solid state,
+being only discovered when separating; that some fossils, as sulphur,
+sea-coal, &c. contain a great deal of solid fire; and that, in short,
+what escapes and is dissipated in the burning of bodies, besides water
+and earth, is generally the air and fire, that before made parts of the
+solid."
+
+FOOTNOTES:
+
+[8] I conclude from the experiments of M. Lavoisier, which were made
+with a much better burning lens than I had an opportunity of making use
+of, that there was no _real calcination_ of the metals, though they were
+made to _fume_ in inflammable or nitrous air; because he was not able to
+produce more than a slight degree of calcination in any given quantity
+of common air.
+
+
+
+
+SECTION IX.
+
+_Of MARINE ACID AIR._
+
+
+Being very much struck with the result of an experiment of the Hon. Mr.
+Cavendish, related Phil. Trans. Vol. LVI. p. 157, by which, though, he
+says, he was not able to get any inflammable air from copper, by means
+of spirit of salt, he got a much more remarkable kind of air, viz. one
+that lost its elasticity by coming into contact with water, I was
+exceedingly desirous of making myself acquainted with it. On this
+account, I began with making the experiment in quicksilver, which I
+never failed to do in any case in which I suspected that air might
+either be absorbed by water, or be in any other manner affected by it;
+and by this means I presently got a much more distinct idea of the
+nature and effects of this curious solution.
+
+Having put some copper filings into a small phial, with a quantity of
+spirit of salt; and making the air (which was generated in great plenty,
+on the application of heat) ascend into a tall glass vessel full of
+quicksilver, and standing in quicksilver, the whole produce continued a
+considerable time without any change of dimensions. I then introduced a
+small quantity of water to it; when about three fourths of it (the whole
+being about four ounce measures) presently, but gradually, disappeared,
+the quicksilver rising in the vessel. I then introduced a considerable
+quantity of water; but there was no farther diminution of the air, and
+the remainder I found to be inflammable.
+
+Having frequently continued this process a long time after the admission
+of the water, I was much amused with observing the large bubbles of the
+newly generated air, which came through the quicksilver, the sudden
+diminution of them when they came to the water, and the very small
+bubbles which went through the water. They made, however, a continual,
+though slow, increase of inflammable air.
+
+Fixed air, being admitted to the whole produce of this air from copper,
+had no sensible effect upon it. Upon the admission of water, a great
+part of the mixture presently disappeared; another part, which I suppose
+to have been the fixed air, was absorbed slowly; and in this particular
+case the very small permanent residuum did not take fire; but it is
+very possible that it might have done so, if the quantity had been
+greater.
+
+The solution of _lead_ in the marine acid is attended with the very same
+phaenomena as the solution of copper in the same acid; about three
+fourths of the generated air disappearing on the admission of water; and
+the remainder being inflammable.
+
+The solutions of iron, tin, and zinc, in the marine acid, were all
+attended with the same phaenomena as the solutions of copper and lead,
+but in a less degree; for in iron one eighth, in tin one sixth, and in
+zinc one tenth of the generated air disappeared on the admission of
+water. The remainder of the air from iron, in this case, burned with a
+green, or very light blue flame.
+
+I had always thought it something extraordinary that a species of air
+should _lose its elasticity_ by the mere _contact_ of any thing, and
+from the first suspected that it must have been _imbibed_ by the water
+that was admitted to it; but so very great a quantity of this air
+disappeared upon the admission of a very small quantity of water, that
+at first I could not help concluding that appearances favoured the
+former hypothesis. I found, however, that when I admitted a much
+smaller quantity of water, confined in a narrow glass tube, a part only
+of the air disappeared, and that very slowly, and that more of it
+vanished upon the admission of more water. This observation put it
+beyond a doubt, that this air was properly _imbibed_ by the water,
+which, being once fully saturated with it, was not capable of receiving
+any more.
+
+The water thus impregnated tasted very acid, even when it was much
+diluted with other water, through which the tube containing it was
+drawn. It even dissolved iron very fast, and generated inflammable air.
+This last observation, together with another which immediately follows,
+led me to the discovery of the true nature of this remarkable kind of
+air.
+
+Happening, at one time, to use a good deal of copper and a small
+quantity of spirit of salt, in the generation of this kind of air, I was
+surprized to find that air was produced long after, I could not but
+think that the acid must have been saturated with the metal; and I also
+found that the proportion of inflammable air to that which was absorbed
+by the water continually diminished, till, instead of being one fourth
+of the whole, as I had first observed, it was not so much as one
+twentieth. Upon this, I concluded that this subtle air did not arise
+from the copper, but from the spirit of salt; and presently making the
+experiment with the acid only, without any copper, or metal of any kind,
+this air was immediately produced in as great plenty as before; so that
+this remarkable kind of air is, in fact, nothing more than the vapour,
+or fumes of spirit of salt, which appear to be of such a nature, that
+they are not liable to be condensed by cold, like the vapour of water,
+and other fluids, and therefore may be very properly called an _acid
+air_, or more restrictively, the _marine acid air_.
+
+This elastic acid vapour, or acid air, extinguishes flame, and is much
+heavier than common air; but how much heavier, will not be easy to
+ascertain. A cylindrical glass vessel, about three fourths of an inch in
+diameter, and four inches deep, being filled with it, and turned upside
+down, a lighted candle may be let down into it more than twenty times
+before it will burn at the bottom. It is pleasing to observe the colour
+of the flame in this experiment; for both before the candle goes out,
+and also when it is first lighted again, it burns with a beautiful
+green, or rather light-blue flame, such as is seen when common salt is
+thrown into the fire.
+
+When this air is all expelled from any quantity of spirit of salt, which
+is easily perceived by the subsequent vapour being condensed by cold,
+the remainder is a very weak acid, barely capable of dissolving iron.
+
+Being now in the possession of a new subject of experiments, viz. an
+elastic acid vapour, in the form of a permanent air, easily procured,
+and effectually confined by glass and quicksilver, with which it did not
+seem to have any affinity; I immediately began to introduce a variety of
+substances to it; in order to ascertain its peculiar properties and
+affinities, and also the properties of those other bodies with respect
+to it.
+
+Beginning with _water_, which, from preceding observations, I knew would
+imbibe it, and become impregnated with it; I found that 2-1/2 grains of
+rain-water absorbed three ounce measures of this air, after which it was
+increased one third in its bulk, and weighed twice as much as before; so
+that this concentrated vapour seems to be twice as heavy as rain-water:
+Water impregnated with it makes the strongest spirit of salt that I have
+seen, dissolving iron with the most rapidity. Consequently, two thirds
+of the best spirit of salt is nothing more than mere phlegm or water.
+
+Iron filings, being admitted to this air, were dissolved by it pretty
+fast, half of the air disappearing, and the other half becoming
+inflammable air, not absorbed by water. Putting chalk to it, fixed air
+was produced.
+
+I had not introduced many substances to this air, before I discovered
+that it had an affinity with _phlogiston_, so that it would deprive
+other substances of it, and form with it such an union as constitutes
+inflammable air; which seems to shew, that inflammable air universally
+consists of the union of some acid vapour with phlogiston.
+
+Inflammable air was produced, when to this acid air I put spirit of
+wine, oil of olives, oil of turpentine, charcoal, phosphorus, bees-wax,
+and even sulphur. This last observation, I own, surprized me; for, the
+marine acid being reckoned the weakest of the three mineral acids, I did
+not think that it had been capable of dislodging the oil of vitriol from
+this substance; but I found that it had the very same effect both upon
+alum and nitre; the vitriolic acid in the former case, and the nitrous
+in the latter, giving place to the stronger vapour of spirit of salt.
+
+The rust of iron, and the precipitate of nitrous air made from copper,
+also imbibed this air very fast, and the little that remained of it was
+inflammable air; which proves, that these calces contain phlogiston. It
+seems also to be pretty evident, from this experiment, that the
+precipitate above mentioned is a real calx of the metal, by the solution
+of which the nitrous air is generated.
+
+As some remarkable circumstances attend the absorption of this acid air,
+by the substances above-mentioned, I shall briefly mention them.
+
+Spirit of wine absorbs this air as readily as water itself, and is
+increased in bulk by that means. Also, when it is saturated, it
+dissolves iron with as much rapidity, and still continues inflammable.
+
+Oil of olives absorbs this air very slowly, and at the same time, it
+turns almost black, and becomes glutinous. It is also less miscible with
+water, and acquires a very disagreeable smell. By continuing upon the
+surface of the water, it became white, and its offensive smell went off
+in a few days.
+
+Oil of turpentine absorbed this air very fast, turning brown, and almost
+black. No inflammable air was formed, till I raised more of the acid
+air than the oil was able to absorb, and let it stand a considerable
+time; and still the air was but weakly inflammable. The same was the
+case with the oil of olives, in the last mentioned experiment; and it
+seems to be probable, that, the longer this acid air had continued in
+contact with the oil, the more phlogiston it would have extracted from
+it. It is not wholly improbable, but that, in the intermediate state,
+before it becomes inflammable air, it may be nearly of the nature of
+common air.
+
+Bees-wax absorbed this air very slowly. About the bigness of a hazel-nut
+of the wax being put to three ounce measures of the acid air, the air
+was diminished one half in two days, and, upon the admission of water,
+half of the remainder also disappeared. This air was strongly
+inflammable.
+
+Charcoal absorbed this air very fast. About one fourth of it was
+rendered immiscible in water, and was but weakly inflammable.
+
+A small bit of _phosphorus_, perhaps about half a grain, smoked, and
+gave light in the acid air, just as it would have done in common air
+confined. It was not sensibly wasted after continuing about twelve
+hours in that state, and the bulk of the air was very little diminished.
+Water being admitted to it absorbed it as before, except about one fifth
+of the whole. It was but weakly inflammable.
+
+Putting several pieces of _sulphur_ to this air, it was absorbed but
+slowly. In about twenty-four hours about one fifth of the quantity had
+disappeared; and water being admitted to the remainder, very little more
+was absorbed. The remainder was inflammable, and burned with a blue
+flame.
+
+Notwithstanding the affinity which this acid air appears to have with
+phlogiston, it is not capable of depriving all bodies of it. I found
+that dry wood, crusts of bread, and raw flesh, very readily imbibed this
+air, but did not part with any of their phlogiston to it. All these
+substances turned very brown, after they had been some time exposed to
+this air, and tasted very strongly of the acid when they were taken out;
+but the flesh, when washed in water, became very white, and the fibres
+easily separated from one another, even more than they would have done
+if it had been boiled or roasted[9].
+
+When I put a piece of _saltpetre_ to this air it was presently
+surrounded with a white fume, which soon filled the whole vessel,
+exactly like the fume which bursts from the bubbles of nitrous air, when
+it is generated by a vigorous fermentation, and such as is seen when
+nitrous air is mixed with this acid air. In about a minute, the whole
+quantity of air was absorbed, except a very little, which might be the
+common air that had lodged upon the surface of the spirit of salt within
+the phial.
+
+A piece of _alum_ exposed to this air turned yellow, absorbed it as fast
+as the saltpetre had done, and was reduced by it to the form of a
+powder. Common salt, as might be expected, had no effect whatever on
+this marine acid air.
+
+I had also imagined, that if air diminished by the processes
+above-mentioned was affected in this manner, in consequence of its being
+saturated with phlogiston, a mixture of this acid air might imbibe that
+phlogiston, and render it wholesome again; but I put about one fourth of
+this air to a quantity of air in which metals had been calcined, without
+making any sensible alteration in it. I do not, however, infer from
+this, that air is not diminished by means of phlogiston, since the
+common air, like some other substances, may hold the phlogiston too
+fast, to be deprived of it by this acid air.
+
+I shall conclude my account of these experiments with observing, that
+the electric spark is visible in acid air, exactly as it is in common
+air; and though I kept making this spark a considerable time in a
+quantity of it, I did not perceive that any sensible alteration was made
+in it. A little inflammable air was produced, but not more than might
+have come from the two iron nails which I made use of in taking the
+sparks.
+
+FOOTNOTES:
+
+[9] It will be seen, in the second part of this work, that, in some of
+these processes, I had afterwards more success.
+
+
+
+
+SECTION X.
+
+MISCELLANEOUS OBSERVATIONS.
+
+
+1. As many of the preceding observations relate to the _vinous_ and
+_putrefactive_ fermentations, I had the curiosity to endeavour to
+ascertain in what manner the air would be affected by the _acetous_
+fermentation. For this purpose I inclosed a phial full of small beer in
+a jar standing in water; and observed that, during the first two or
+three days, there was an increase of the air in the jar, but from that
+time it gradually decreased, till at length there appeared to be a
+diminution of about one tenth of the whole quantity.
+
+During this time the whole surface of it was gradually covered with a
+scum, beautifully corrugated. After this there was an increase of the
+air till there was more than the original quantity; but this must have
+been fixed air, not incorporated with the rest of the mass; for,
+withdrawing the beer, which I found to be sour, after it had stood 18 or
+20 days under the jar, and passing the air several times through cold
+water, the original quantity was diminished about one ninth. In the
+remainder a candle would not burn, and a mouse would have died
+presently.
+
+The smell of this air was exceedingly pungent, but different from that
+of the putrid effluvium. A mouse lived perfectly well in this air, thus
+affected with the acetous fermentation; after it had stood several days
+mixed with four times the quantity of fixed air.
+
+2. All the kinds of factitious air on which I have yet made the
+experiment are highly noxious, except that which is extracted from
+saltpetre, or alum; but in this even a candle burned just as in common
+air[10]. In one quantity which I got from saltpetre a candle not only
+burned, but the flame was increased, and something was heard like a
+hissing, similar to the decrepitation of nitre in an open fire. This
+experiment was made when the air was fresh made, and while it probably
+contained some particles of nitre, which would have been deposited
+afterwards. The air was extracted from these substances by heating them
+in a gun-barrel, which was much corroded and soon spoiled by the
+experiment. What effect this circumstance may have had upon the air I
+have not considered.
+
+November 6, 1772, I had the curiosity to examine the state of a quantity
+of this air which had been extracted from saltpetre above a year, and
+which at first was perfectly wholesome; when, to my very great surprize,
+I found that it was become, in the highest degree, noxious. It made no
+effervescence with nitrous air, and a mouse died the moment it was put
+into it. I had not, however, washed it in rain-water quite ten minutes
+(and perhaps less time would have been sufficient) when I found, upon
+trial, that it was restored to its former perfectly wholesome state. It
+effervesced with nitrous air as much as the best common air ever does;
+and even a candle burned in it very well, which I had never before
+observed of any kind of noxious air meliorated by agitation in water.
+This series of facts, relating to air extracted from nitre, appear to me
+to be very extraordinary and important, and, in able hands, may lead to
+considerable discoveries.
+
+3. There are many substances which impregnate common air in a very
+remarkable manner, but without making it noxious to animals. Among other
+things I tried volatile alkaline salts, and camphor; the latter of which
+I melted with a burning-glass, in air inclosed in a phial. The mouse,
+which was put into this air, sneezed and coughed very much, especially
+after it was taken out; but it presently recovered, and did not appear
+to have been sensibly injured.
+
+4. Having made several experiments with a mixture of iron filings and
+brimstone, kneaded to a paste with water, I had the curiosity to try
+what would be the effect of substituting _brass dust_ in the place of
+the iron filings. The result was, that when this mixture had stood about
+three weeks, in a given quantity of air, it had turned black, but was
+not increased in bulk. The air also was neither sensibly increased nor
+decreased, but the nature of it was changed; for it extinguished flame,
+it would have killed a mouse presently, and was not restored by fixed
+air, which had been mixed with it several days.
+
+5. I have frequently mentioned my having, at one time, exposed equal
+quantities of different kinds of air in jars standing in boiled water.
+_Common air_ in this experiment was diminished four sevenths, and the
+remainder extinguished flame. This experiment demonstrates that water
+does not absorb air equally, but that it decomposes it, taking one part,
+and leaving the rest. To be quite sure of this fact, I agitated a
+quantity of common air in boiled water, and when I had reduced it from
+eleven ounce measures to seven, I found that it extinguished a candle,
+but a mouse lived in it very well. At another time a candle barely went
+out when the air was diminished one third, and at other times I have
+found this effect lake place at other very different degrees of
+diminution.
+
+This difference I attribute to the differences in the state of the water
+with respect to the air contained in it; for sometimes it had stood
+longer than at other times before I made use of it. I also used
+distilled-water, rain-water, and water out of which the air had been
+pumped, promiscuously with rain water. I even doubt, not but that, in a
+certain state of the water, there might be no sensible difference in
+the bulk of the agitated air, and yet at the end of the process it would
+extinguish a candle, air being supplied from the water in the place of
+that part of the common air which had been absorbed.
+
+It is certainly a little extraordinary that the very same process should
+so far mend putrid air, as to reduce it to the standard of air in which
+candles have burned out; and yet that it should so far injure common and
+wholesome air as to reduce it to about the same standard: but so the
+fact certainly is. If air extinguish flame in consequence of its being
+previously saturated with phlogiston, it must, in this case, have been
+transferred from the water to the air, and it is by no means
+inconsistent with this hypothesis to suppose, that, if the air be over
+saturated with phlogiston, the water will imbibe it, till it be reduced
+to the same proportion that agitation in water would have communicated
+to it.
+
+To a quantity of common air, thus diminished by agitation in water, till
+it extinguished a candle, I put a plant, but it did not so far restore
+it as that a candle would burn in it again; which to me appeared not a
+little extraordinary, as it did not seem to be in a worse state than air
+in which candles had burned out, and which had never failed to be
+restored by the same means.
+
+I had no better success with a quantity of permanent air which I had
+collected from my pump-water. Indeed these experiments were begun before
+I was acquainted with that property of nitrous air, which makes it so
+accurate a measure of the goodness of other kinds of air; and it might
+perhaps be rather too late in the year when I made the experiments.
+Having neglected these two jars of air, the plants died and putrefied in
+both of them; and then I found the air in them both to be highly
+noxious, and to make no effervescence with nitrous air.
+
+I found that a pint of my pump-water contained about one fourth of an
+ounce measure of air, one half of which was afterwards absorbed by
+standing in fresh pump-water. A candle would not burn in this air, but a
+mouse lived in it very well. Upon the whole, it seemed to be in about
+the same state as air in which a candle had burned out.
+
+6. I once imagined that, by mere _stagnation_, air might become unfit
+for respiration, or at least the burning of candles; but if this be the
+case, and the change be produced gradually, it must require a long time
+for the purpose. For on the 22d of September 1772, I examined a quantity
+of common air, which had been kept in a phial, without agitation, from
+May 1771, and found it to be in no respect worse than fresh air, even by
+the test of the nitrous air.
+
+7. The crystallization of nitre makes no sensible alteration in the air
+in which the process is made. For this purpose I dissolved as much nitre
+as a quantity of hot water would contain, and let it cool under a
+receiver, standing in water.
+
+8. November 6, 1772, a quantity of inflammable air, which, by long
+keeping, had come to extinguish flame, I observed to smell very much
+like common air in which a mixture of iron filings and brimstone had
+stood. It was not, however, quite so strong, but it was equally noxious.
+
+9. Bismuth and nickel are dissolved in the marine acid with the
+application of a considerable degree of heat; but little or no air is
+got from either of them; but, what I thought a little remarkable, both
+of them smelled very much like Harrowgate water, or liver of sulphur.
+This smell I have met with several times in the course of my
+experiments, and in processes very different from one another.
+
+FOOTNOTES:
+
+[10] Experiments, of which an account will be given in the second part
+of this work, make it probable, that though a candle burned even _more
+than well_ in this air, an animal would not have lived in it. At the
+time of this first publication, however, I had no idea of this being
+possible in nature.
+
+
+
+
+PART II.
+
+_Experiments and Observations made in the Year 1773, and the Beginning
+of 1774._
+
+
+
+
+SECTION I.
+
+_Observations on ALKALINE AIR._
+
+
+After I had made the discovery of the _marine acid air_, which the
+vapour of spirit of salt may properly enough be called, and had made
+those experiments upon it, of which I have given an account in the
+former part of this work, and others which I propose to recite in this
+part; it occurred to me, that, by a process similar to that by which
+this _acid_ air is expelled from the spirit of salt, an _alkaline_ air
+might be expelled from substances containing volatile alkali.
+
+Accordingly I procured some volatile spirit of sal ammoniac, and having
+put it into a thin phial, and heated it with the flame of a candle, I
+presently found that a great quantity of vapour was discharged from it;
+and being received in a vessel of quicksilver, standing in a bason of
+quicksilver, it continued in the form of a transparent and permanent
+air, not at all condensed by cold; so that I had the same opportunity of
+making experiments upon it, as I had before on the acid air, being in
+the same favourable circumstances.
+
+With the same ease I also procured this air from _spirit of hartshorn_,
+and _sal volatile_ either in a fluid or solid form, i. e. from those
+volatile alkaline salts which are produced by the distillation of sal
+ammoniac with fixed alkalis. But in this case I soon found that the
+alkaline air I procured was not pure; for the fixed air, which entered
+into the composition of my materials, was expelled along with it. Also,
+uniting again with the alkaline air, in the glass tube through which
+they were conveyed, they stopped it up, and were often the means of
+bursting my vessels.
+
+While these experiments were new to me, I imagined that I was able to
+procure this air with peculiar advantage and in the greatest abundance,
+either from the salts in a dry state, when they were just covered with
+water, or in a perfectly fluid state; for, upon applying a candle to the
+phials in which they were contained, there was a most astonishing
+production of air; but having examined it, I found it to be chiefly
+fixed air, especially after the first or second produce from the same
+materials; and removing my apparatus to a trough of water and using the
+water instead of quicksilver, I found that it was not presently absorbed
+by it.
+
+This, however, appears to be an easy and elegant method of procuring
+fixed air, from a small quantity of materials, though there must be a
+mixture of alkaline air along with it; as it is by means of its
+combination with this principle only, that it is possible, that so much
+fixed air should be retained in any liquid. Water, at least, we know,
+cannot be made to contain much more than its own bulk of fixed air.
+
+After this disappointment, I confined myself to the use of that volatile
+spirit of sal ammoniac which is procured by a distillation with slaked
+lime, which contains no fixed air; and which seems, in a general state,
+to contain about as much alkaline air, as an equal quantity of spirit of
+salt contains of the acid air.
+
+Wanting, however, to procure this air in greater quantities, and this
+method being rather expensive, it occurred to me, that alkaline air
+might, probably, be procured, with the most ease and convenience, from
+the original materials, mixed in the same proportions that chemists had
+found by experience to answer the best for the production of the
+volatile spirit of sal ammoniac. Accordingly I mixed one fourth of
+pounded sal ammoniac, with three fourths of slaked lime; and filling a
+phial with the mixture, I presently found it completely answered my
+purpose. The heat of a candle expelled from this mixture a prodigious
+quantity of alkaline air; and the same materials (as much as filled an
+ounce phial) would serve me a considerable time, without changing;
+especially when, instead of a glass phial, I made use of a small iron
+tube, which I find much more convenient for the purpose.
+
+As water soon begins to rise in this process, it is necessary, if the
+air is intended to be conveyed perfectly _dry_ into the vessel of
+quicksilver, to have a small vessel in which this water (which is the
+common volatile spirit of sal ammoniac) may be received. This small
+vessel must be interposed between the vessel which contains the
+materials for the generation of the air, and that in which it is to be
+received, as _d_ fig. 8.
+
+This _alkaline_ air being perfectly analogous to the _acid_ air, I was
+naturally led to investigate the properties of it in the same manner,
+and nearly in the same order. From this analogy I concluded, as I
+presently found to be the fact, that this alkaline air would be readily
+imbibed by water, and, by its union with it, would form a volatile
+spirit of sal ammoniac. And as the water, when admitted to the air in
+this manner, confined by quicksilver, has an opportunity of fully
+saturating itself with the alkaline vapour, it is made prodigiously
+stronger than any volatile spirit of sal ammoniac that I have ever seen;
+and I believe stronger than it can be made in the common way.
+
+In order to ascertain what addition, with respect to quantity and
+weight, water would acquire by being saturated with alkaline air, I put
+1-1/4 grains of rain-water into a small glass tube, closed at one end
+with cement, and open at the other, the column of water measuring 7/10
+of an inch; and having introduced it through the quicksilver into a
+vessel containing alkaline air, observed that it absorbed 7/8 of an
+ounce measure of the _air_, and had then gained about half a grain in
+weight, and was increased to 8-1/2 tenths of an inch in length. I did
+not make a second experiment of this kind, and therefore will not answer
+for the exactness of these proportions in future trials. What I did
+sufficiently answered my purpose, in a general view of the subject.
+
+When I had, at one time, saturated a quantity of distilled water with
+alkaline air, so that a good deal of the air remained unabsorbed on the
+surface of the water, I observed that, as I continued to throw up more
+air, a considerable proportion of it was imbibed, but not the whole; and
+when I had let the apparatus stand a day, much more of the air that lay
+on the surface was imbibed. And after the water would imbibe no more of
+the _old_ air, it imbibed _new_. This shews that water requires a
+considerable time to saturate itself with this kind of air, and that
+part of it more readily unites with water than the rest.
+
+The same is also, probably, the case with all the kinds of air with
+which water can be impregnated. Mr. Cavendish made this observation with
+respect to fixed air, and I repeated the whole process above-mentioned
+with acid air, and had precisely the same result. The alkaline water
+which I procured in this experiment was, beyond comparison, stronger to
+the smell, than any spirit of sal ammoniac that I had seen.
+
+This experiment led me to attempt the making of spirit of sal ammoniac
+in a larger quantity, by impregnating distilled water with this alkaline
+air. For this purpose I filled a piece of a gun-barrel with the
+materials above-mentioned, and luted to the open end of it a small glass
+tube, one end of which was bent, and put within the mouth of a glass
+vessel, containing a quantity of distilled water upon quicksilver,
+standing in a bason of quicksilver, as in fig. 7. In these circumstances
+the heat of the fire, applied gradually, expelled the alkaline air,
+which, passing through the tube, and the quicksilver, came at last to
+the water, which, in time, became fully saturated with it.
+
+By this means I got a very strong alkaline liquor, from which I could
+again expel the alkaline air which I had put into it, whenever it
+happened to be more convenient to me to get it in that manner. This
+process may easily be performed in a still larger way; and by this means
+a liquor of the same nature with the volatile spirit of sal ammoniac,
+might be made much stronger, and much cheaper, than it is now made.
+
+Having satisfied myself with respect to the relation that alkaline air
+bears to water, I was impatient to find what would be the consequence
+of mixing this new air with the other kinds with which I was acquainted
+before, and especially with _acid_ air; having a notion that these two
+airs, being of opposite natures, might compose a _neutral air_, and
+perhaps the very same thing with common air. But the moment that these
+two kinds of air came into contact, a beautiful white cloud was formed,
+and presently filled the whole vessel in which they were contained. At
+the same time the quantity of air began to diminish, and, at length,
+when the cloud was subsided, there appeared to be formed a solid _while
+salt_, which was found to be the common _sal ammoniac_, or the marine
+acid united to the volatile alkali.
+
+The first quantity that I produced immediately deliquesced, upon being
+exposed to the common air; but if it was exposed in a very dry and warm
+place, it almost all evaporated, in a white cloud. I have, however,
+since, from the same materials, produced the salt above-mentioned in a
+state not subject to deliquesce or evaporate. This difference, I find,
+is owing to the proportion of the two kinds of air in the compound. It
+is only volatile when there is more than a due proportion of either of
+the constituent parts. In these cases the smell of the salts is
+extremely pungent, but very different from one another; being manifestly
+acid, or alkaline, according to the prevalence of each of these airs
+respectively.
+
+_Nitrous air_ admitted to alkaline air likewise occasioned a whitish
+cloud, and part of the air was absorbed; but it presently grew clear
+again; leaving only a little dimness on the sides of the vessel. This,
+however, might be a kind of salt, formed by the union of the two kinds
+of air. There was no other salt formed that I could perceive. Water
+being admitted to this mixture of nitrous and alkaline air presently
+absorbed the latter, and left the former possessed of its peculiar
+properties.
+
+_Fixed air_ admitted to alkaline air formed oblong and slender crystals,
+which crossed one another, and covered the sides of the vessel in the
+form of net-work. These crystals must be the same thing with the
+volatile alkalis which chemists get in a solid form, by the distillation
+of sal ammoniac with fixed alkaline salts.
+
+_Inflammable air_ admitted to alkaline air exhibited no particular
+appearance. Water, as in the former experiment, absorbed the alkaline
+air, and left the inflammable air as it was before. It was remarkable,
+however, that the water which was admitted to them became whitish, and
+that this white cloud settled, in the form of a white powder, to the
+bottom of the vessel.
+
+Alkaline air mixed with _common air_, and standing together several
+days, first in quicksilver, and then in water (which absorbed the
+alkaline air) it did not appear that there was any change produced in
+the common air: at least it was as much diminished by nitrous air as
+before. The same was the case with a mixture of acid air and common air.
+
+Having mixed air that had been diminished by the fermentation of a
+mixture of iron filings and brimstone with alkaline air, the water
+absorbed the latter, but left the former, with respect to the test of
+nitrous air (and therefore, as I conclude, with respect to all its
+properties) the same that it was before.
+
+_Spirit of wine_ imbibes alkaline air as readily as water, and seems to
+be as inflammable afterwards as before.
+
+Alkaline air contracts no union with _olive oil_. They were in contact
+almost two days, without any diminution of the air. Oil of turpentine,
+and essential oil of mint, absorbed a very small quantity of alkaline
+air, but were not sensibly changed by it.
+
+_Ether_, however, imbibed alkaline air pretty freely; but it was
+afterwards as inflammable as before, and the colour was not changed. It
+also evaporated as before, but I did not attend to this last
+circumstance very accurately.
+
+_Sulphur_, _nitre_, _common salt_, and _flints_, were put to alkaline
+air without imbibing any part of it; but _charcoal_, _spunge_, bits of
+_linen cloth_, and other substances of that nature, seemed to condense
+this air upon their surfaces; for it began to diminish immediately upon
+their being put to it; and when they were taken out the alkaline smell
+they had contracted was so pungent as to be almost intolerable,
+especially that of the spunge. Perhaps it might be of use to recover
+persons from swooning. A bit of spunge, about as big as a hazel nut,
+presently imbibed an ounce measure of alkaline air.
+
+A piece of the inspissated juice of _turnsole_ was made very dry and
+warm, and yet it imbibed a great quantity of the air; by which it
+contracted a most pungent smell, but the colour of it was not changed.
+
+_Alum_ undergoes a very remarkable change by the action of alkaline air.
+The outward shape and size remain the same, but the internal structure
+is quite changed, becoming opaque, beautifully white, and, to
+appearance, in all respects, like alum which had been roasted; and so as
+not to be at all affected by a degree of heat that would have reduced it
+to that state by roasting. This effect is produced slowly; and if a
+piece of alum be taken out of alkaline air before the operation is over,
+the inside will be transparent, and the outside, to an equal thickness,
+will be a white crust.
+
+I imagine that the alkaline vapour seizes upon the water that enters
+into the constitution of crude alum, and which would have been expelled
+by heat. Roasted alum also imbibes alkaline air, and, like the raw alum
+that has been exposed to it, acquires a taste that is peculiarly
+disagreeable.
+
+_Phosphorus_ gave no light in alkaline air, and made no lasting change
+in its dimensions. It varied, indeed, a little, being sometimes
+increased and sometimes diminished, but after a day and a night, it was
+in the same state as at the first. Water absorbed this air just as if
+nothing had been put to it.
+
+Having put some _spirit of salt_ to alkaline air, the air was presently
+absorbed, and a little of the white salt above-mentioned was formed. A
+little remained unabsorbed, and transparent, but upon the admission of
+common air to it, it instantly became white.
+
+_Oil of vitriol_, also formed a white salt with alkaline air, and this
+did not rise in white fumes.
+
+Acid air, as I have observed in my former papers, extinguishes a candle.
+Alkaline air, on the contrary, I was surprized to find, is slightly
+inflammable; which, however, seems to confirm the opinion of chemists,
+that the volatile alkali contains phlogiston.
+
+I dipped a lighted candle into a tall cylindrical vessel, filled with
+alkaline air, when it went out three or four times successively; but at
+each time the flame was considerably enlarged, by the addition of
+another flame, of a pale yellow colour; and at the last time this light
+flame descended from the top of the vessel to the bottom. At another
+time, upon presenting a lighted candle to the mouth of the same vessel,
+filled with the same kind of air, the yellowish flame ascended two
+inches higher than the flame of the candle. The electric spark taken in
+alkaline air is red, as it is in common inflammable air.
+
+Though alkaline air be inflammable, it appeared, by the following
+experiment, to be heavier than the common inflammable air, as well as to
+contract no union with it. Into a vessel containing a quantity of
+inflammable air, I put half as much alkaline air, and then about the
+same quantity of acid air. These immediately formed a white cloud, but
+it did not rise within the space that was occupied by the inflammable
+air; so that this latter had kept its place above the alkaline air, and
+had not mixed with it.
+
+That alkaline air is lighter than acid air is evident from the
+appearances that attend the mixture, which are indeed very beautiful.
+When acid air is introduced into a vessel containing alkaline air, the
+white cloud which they form appears at the bottom only, and ascends
+gradually. But when the alkaline air is put to the acid, the whole
+becomes immediately cloudy, quite to the top of the vessel.
+
+In the last place, I shall observe that alkaline air, as well as acid,
+dissolves _ice_ as fast as a hot fire can do it. This was tried when
+both the kinds of air, and every instrument made use of in the
+experiment, had been exposed to a pretty intense frost several hours. In
+both cases, also, the water into which the ice was melted dissolved more
+ice, to a considerable quantity.
+
+
+
+
+SECTION II.
+
+_Of COMMON AIR diminished and made noxious by various processes._
+
+
+It will have been observed that, in the first publication of my papers,
+I confined myself chiefly to the narration of the new _facts_ which I
+had discovered, barely mentioning any _hypotheses_ that occurred to me,
+and never seeming to lay much stress upon them. The reason why I was so
+much upon my guard in this respect was, left, in consequence of
+attaching myself to any hypothesis too soon, the success of my future
+inquiries might be obstructed. But subsequent experiments having thrown
+great light upon the preceding ones and having confirmed the few
+conjectures I then advanced, I may now venture to speak of my hypotheses
+with a little less diffidence. Still, however, I shall be ready to
+relinquish any notions I may now entertain, if new facts should
+hereafter appear not to favour them.
+
+In a great variety of cases I have observed that there is a remarkable
+_diminution_ of common, or respirable air, in proportion to which it is
+always rendered unfit for respiration, indisposed to effervesce with
+nitrous air, and incapable of farther diminution from any other cause.
+The circumstances which produce this effect I had then observed to be
+the burning of candles, the respiration of animals, the putrefaction of
+vegetables or animal substances, the effervescence of iron filings and
+brimstone, the calcination of metals, the fumes of charcoal, the
+effluvia of paint made of white-lead and oil, and a mixture of nitrous
+air.
+
+All these processes, I observed, agree in this one circumstance, and I
+believe in no other, that the principle which the chemists call
+_phlogiston_ is set loose; and therefore I concluded that the diminution
+of the air was, in some way or other, the consequence of the air
+becoming overcharged with phlogiston,[11] and that water, and growing
+vegetables, tend to restore this air to a state fit for respiration, by
+imbibing the superfluous phlogiston. Several experiments which I have
+since made tend to confirm this supposition.
+
+Common air, I find, is diminished, and rendered noxious, by _liver of
+sulphur_, which the chemists say exhales phlogiston, and nothing else.
+The diminution in this case was one fifth of the whole, and afterwards,
+as in other similar cases, it made no effervescence with nitrous air.
+
+I found also, after Dr. Hales, that air is diminished by _Homberg's
+pyrophorus_.
+
+The same effect is produced by firing _gunpowder_ in air. This I tried
+by firing the gunpowder in a receiver half exhausted, by which the air
+was rather more injured than it would have been by candles burning in
+it.
+
+Air is diminished by a cement made with one half common coarse
+turpentine and half bees-wax. This was the result of a very casual
+observation. Having, in an air-pump of Mr. Smeaton's construction,
+closed that end of the syphon-gage, which is exposed to the outward air,
+with this cement (which I knew would make it perfectly air-light)
+instead of sealing it hermetically; I observed that, in a course of
+time, the quicksilver in that leg kept continually rising, so that the
+measures I marked upon it were of no use to me; and when I opened that
+end of the tube, and closed it again, the same consequence always took
+place. At length, suspecting that this effect must have arisen from the
+bit of _cement_ diminishing the air to which it was exposed, I covered
+all the inside of a glass tube with it, and one end of it being quite
+closed with the cement, I set it perpendicular, with its open end
+immersed in a bason of quicksilver; and was presently satisfied that my
+conjecture was well founded: for, in a few days, the quicksilver rose so
+much within the tube, that the air in the inside appeared to be
+diminished about one sixth.
+
+To change this air I filled the tube with quicksilver, and pouring it
+out again, I replaced the tube in its former situation; when the air was
+diminished again, but not so fast as before. The same lining of cement
+diminished the air a third time. How long it will retain this power I
+cannot tell. This cement had been made several months before I made
+this experiment with it. I must observe, however, that another quantity
+of this kind of cement, made with a finer and more liquid turpentine,
+had not the power of diminishing air, except in a very small proportion.
+Also the common red cement has this property in the same small degree.
+Common air, however, which had been confined in a glass vessel lined
+with this cement about a month, was so far injured that a candle would
+not burn in it. In a longer time it would, I doubt not, have become
+thoroughly noxious.
+
+Iron that has been suffered to rust in nitrous air diminishes common air
+very fast, as I shall have occasion to mention when I give a
+continuation of my experiments on nitrous air.
+
+Lastly, the same effect, I find, is produced by the _electric spark_,
+though I had no expectation of this event when I made the experiment.
+
+This experiment, however, and those which I have made in pursuance of
+it, has fully confirmed another of my conjectures, which relates to the
+_manner_ in which air is diminished by being overcharged with
+phlogiston, viz. the phlogiston having a nearer affinity with some of
+the constituent parts of the air than the fixed air which enters into
+the composition of it, in consequence of which the fixed air is
+precipitated.
+
+This I first imagined from perceiving that lime-water became turbid by
+burning candles over it, p. 44. This was also the case with lime-water
+confined in air in which an animal substance was putrefying, or in which
+an animal died, p. 79. and that in which charcoal was burned, p. 81.
+But, in all these cases, there was a possibility of the fixed air being
+discharged from the candle, the putrefying substance, the lungs of the
+animal, or the charcoal. That there is a precipitation of lime when
+nitrous air is mixed with common air, I had not then observed, but I
+have since found it to be the case.
+
+That there was no precipitation of lime when brimstone was burned, I
+observed, p. 45. might be owing to the fixed air and the lime uniting
+with the vitriolic acid, and making a salt, which was soluble in water;
+which salt I, indeed, discovered by the evaporation of the water.
+
+I also observed, p. 46, 105. that diminished air being rather lighter
+than common air is a circumstance in favour of the fixed, or the
+heavier part of the common air, having been precipitated.
+
+It was upon this idea, together with others similar to it, that I took
+so much pains to mix fixed air with air diminished by respiration or
+putrefaction, in order to make it fit for respiration again; and I
+thought that I had, in general, succeeded to a considerable degree, p.
+99, &c. I will add, also, what I did not mention before, that I once
+endeavoured, but without effect, to preserve mice alive in the same
+unchanged air, by supplying them with fixed air, when the air in which
+they were confined began to be injured by their respiration. Without
+effect, also, I confined for some months, a quantity of quick lime in a
+given quantity of common air, thinking it might extract the fixed air
+from it.
+
+The experiments which I made with electricity were solely intended to
+ascertain what has often been attempted, but, as far as I know, had
+never been fully accomplished, viz. to change the blue colour of
+liquors, tinged with vegetable juices, red.
+
+For this purpose I made use of a glass tube, about one tenth of an inch
+diameter in the inside, as in fig. 16. In one end of this I cemented a
+piece of wire _b_, on which I put a brass ball. The lower part from _a_
+was filled with water tinged blue, or rather purple, with the juice of
+turnsole, or archil. This is easily done by an air-pump, the tube being
+set in a vessel of the tinged water.
+
+Things being thus prepared, I perceived that, after I had taken the
+electric spark, between the wire _b_, and the liquor at _a_, about a
+minute, the upper part of it began to look red, and in about two minutes
+it was very manifestly so; and the red part, which was about a quarter
+of an inch in length, did not readily mix with the rest of the liquor. I
+observed also, that if the tube lay inclined while I took the sparks,
+the redness extended twice as far on the lower side as on the upper.
+
+The most important, though the least expected observation, however, was
+that, in proportion as the liquor became red, it advanced nearer to the
+wire, so that the space of air in which the sparks were taken was
+diminished; and at length I found that the diminution was about one
+fifth of the whole space; after which more electrifying produced no
+sensible effect.
+
+To determine whether the cause of the change of colour was in the _air_,
+or in the _electric matter_, I expanded the air which had been
+diminished in the tube by means of an air-pump, till it expelled all the
+liquor, and admitted fresh blue liquor into its place; but after that,
+electricity produced no sensible effect, either on the air, or on the
+liquor; so that it was evident that the electric matter had decomposed
+the air, and had made it deposite something that was of an acid nature.
+
+In order to determine whether the _wire_ had contributed any thing to
+this effect, I used wires of different metals, iron, copper, brass, and
+silver; but the result was the very same with them all.
+
+It was also the same when, by means of a bent glass tube, I made the
+electric spark without any wire at all, in the following manner. Each
+leg of the tube, fig. 19. stood in a bason of quicksilver; which, by
+means of an air-pump, was made to ascend as high as _a, a_, in each leg,
+while the space between _a_ and _b_ in each contained the blue liquor,
+and the space between _b_ and _b_ contained common air. Things being
+thus disposed, I made the electric spark perform the circuit from one
+leg to the other, passing from the liquor in one leg of the tube to the
+liquor in the other leg, through the space of air. The effect was, that
+the liquor, in both the legs, became red, and the space of air between
+them was contracted, as before.
+
+Air thus diminished by electricity makes no effervescence with, and is
+no farther diminished by a mixture of nitrous air; so that it must have
+been in the highest degree noxious, exactly like air diminished by any
+other process.
+
+In order to determine what the _acid_ was, which was deposited by the
+air, and which changed the colour of the blue liquor, I exposed a small
+quantity of the liquor so changed to the common air, and found that it
+recovered its blue colour, exactly as water, tinged with the same blue,
+and impregnated with fixed air, will do. But the following experiment
+was still more decisive to this purpose. Taking the electric spark upon
+_lime-water_, instead of the blue liquor, the lime was precipitated as
+the air diminished.
+
+From these experiments it pretty clearly follows, that the electric
+matter either is, or contains phlogiston; since it does the very same
+thing that phlogiston does. It is also probable, from these experiments,
+that the sulphureous smell, which is occasioned by electricity, being
+very different from that of fixed air, the phlogiston in the electric
+matter itself may contribute to it.
+
+It was now evident that common air diminished by any one of the
+processes above-mentioned being the same thing, as I have observed, with
+air diminished by any other of them (since it is not liable to be
+farther diminished by any other) the loss which it sustains, in all the
+cases, is, in part, that of the _fixed air_ which entered into its
+constitution. The fixed air thus precipitated from common air by means
+of phlogiston unites with lime, if any lime water be ready to receive
+it, unless there be some other substance at hand, with which it has a
+greater affinity, as the _calces of metals_.
+
+If the whole of the diminution of common air was produced by the
+deposition of fixed air, it would be easy to ascertain the quantity of
+fixed air that is contained in any given quantity of common air. But it
+is evident that the whole of the diminution of common air by phlogiston
+is not owing to the precipitation of fixed air, because a mixture of
+nitrous air will make a great diminution in all kinds of air that are
+fit for respiration, even though they never were common air, and though
+nothing was used in the process for generating them that can be supposed
+to yield fixed air.
+
+Indeed, it appears, from some of the experiments, that the diminution of
+some of these kinds of air by nitrous air is so great, and approaches so
+nearly to the quantity of the diminution of common air by the same
+process, as to shew that, unless they be very differently affected by
+phlogiston, very little is to be allowed to the loss of fixed air in the
+diminution of common air by nitrous air.
+
+The kinds of air on which this experiment was made were inflammable air,
+nitrous air diminished by iron filings and brimstone, and nitrous air
+itself; all of which are produced by the solution of metals in acids;
+and also on common air diminished and made noxious, and therefore
+deprived of its fixed air by phlogistic processes; and they were
+restored to a great degree of purity by agitation in water, out of which
+its own air had been carefully boiled.
+
+To five parts of inflammable air, which had been agitated in water till
+it was diminished about one half (at which time part of it fired with a
+weak explosion) I put one part of nitrous air, which diminished it one
+eighth of the whole. This was done in lime-water, without any
+precipitation of lime. To compare this with common air, I mixed the same
+quantity, viz. five parts of this, and one part of nitrous air: when
+considerable crust of lime was formed upon the surface of the lime
+water, though the diminution was very little more than in the former
+process. It is possible, however, that the common air might have taken
+more nitrous air before it was fully saturated, so as to begin to
+receive an addition to its bulk.
+
+I agitated in water a quantity of nitrous air phlogisticated with iron
+filings and brimstone, and found it to be so far restored, that three
+fourths of an ounce measure of nitrous air being put to two ounce
+measures of it, made no addition to it.
+
+But the most remarkable of these experiments is that which I made with
+_nitrous air_ itself which I had no idea of the possibility of reducing
+to a state fit for respiration by any process whatever, at the time of
+my former publication on this subject. This air, however, itself,
+without any previous phlogistication, is purified by agitation in water
+till it is diminished by fresh nitrous air, and to a very considerable
+degree.
+
+In a pretty long time I agitated nitrous air in water, supplying it from
+time to time with more, as the former quantity diminished, till only one
+eighteenth of the whole quantity remained; in which state it was so
+wholesome, that a mouse lived in two ounce measures of it more than ten
+minutes, without shewing any sign of uneasiness; so that I concluded it
+must have been about as good as air in which candles had burned out.
+After agitating it again in water, I put one part of fresh nitrous air
+to five parts of this air, and it was diminished one ninth part. I then
+agitated it a third time, and putting more nitrous air to it, it was
+diminished again in the same proportion, and so a fourth time; so that,
+by continually repeating the process, it would, I doubt not, have been
+all absorbed. These processes were made in lime-water, without forming
+any incrustation on the surface of it.
+
+Lastly, I took a quantity of common air, which had been diminished and
+made noxious by phlogistic processes; and when it had been agitated in
+water, I found that it was diminished by nitrous air, though not so much
+as it would have been at the first. After cleansing it a second time, it
+was diminished again by the same means; and, after that, a third time;
+and thus there can be no doubt but that, in time, the whole quantity
+would have disappeared. For I have never found that agitation in water,
+deprived of its own air, made any addition to a quantity of noxious air;
+though, _a priori_, it might have been imagined that, as a saturation
+with phlogiston diminishes air, the extraction of phlogiston would
+increase the bulk of it. On the contrary, agitation in water always
+diminished noxious air a little; indeed, if water be deprived of all its
+own air, it is impossible to agitate any kind of air in it without some
+loss. Also, when noxious air has been restored by plants, I never
+perceived that it gained any addition to its bulk by that means. There
+was no incrustation of the lime-water in the above-mentioned experiment.
+
+It is not a little remarkable, that those kinds of air which never had
+been common air, as inflammable air, phlogisticated nitrous air, and
+nitrous air itself, when rendered wholesome by agitation in water,
+should be more diminished by fresh nitrous air, than common air which
+had been made noxious, and restored by the same process; and yet, from
+the few trials that I have made, I could not help concluding that this
+is the case.
+
+In this course of experiments I was very near deceiving myself, in
+consequence of transferring the nitrous air which I made use of in a
+bladder, in the manner described, p. 15. fig. 9. so as to conclude that
+there was a precipitation of lime in all the above-mentioned cases, and
+that even nitrous air itself produced that effect. But after repeated
+trials, I found that there was no precipitation of lime, except, in the
+first diminution of common air, when the nitrous air was transferred in
+a glass vessel.
+
+That the calces of metals contain air, of some kind or other, and that
+this air contributes to the additional weight of the calces, above that
+of the metals from which they are made, had been observed by Dr. Hales;
+and Mr. Hartley had informed me, that when red-lead is boiled in linseed
+oil, there is a prodigious discharge of air before they incorporate. I
+had likewise found, that no weight is either gained or lost by the
+calcination of tin in a close glass vessel; but I purposely deferred
+making any more experiments on the subject, till we should have some
+weather in which I could make use of a large burning lens, which I had
+provided for that and other purposes; but, in the mean time, I was led
+to the discovery in a different manner.
+
+Having, by the last-recited experiments, been led to consider the
+electric matter as phlogiston, or something containing phlogiston, I was
+endeavouring to revivify the calx of lead with it; when I was surprized
+to perceive a considerable generation of air. It occurred to me, that
+possibly this effect might arise from the _heat_ communicated to the
+red-lead by the electric sparks, and therefore I immediately filled a
+small phial with the red-lead, and heating it with a candle, I presently
+expelled from it a quantity of air about four or five times the bulk of
+the lead, the air being received in a vessel of quicksilver. How much
+more air it would have yielded, I did not try.
+
+Along with the air, a small quantity of _water_ was likewise thrown out;
+and it immediately occurred to me, that this water and air together must
+certainly be the cause of the addition of weight in the calx. It still
+remained to examine what kind of air this was; but admitting water to
+it, I found that it was imbibed by it, exactly like _fixed air_, which I
+therefore immediately concluded it must be[12].
+
+After this, I found that Mr. Lavoisier had completely discovered the
+same thing, though his apparatus being more complex, and less accurate
+than mine, he concluded that more of the air discharged from the calces
+of metals was immiscible with water than I found it to be. It appeared
+to me that I had never obtained fixed air more pure.
+
+It being now pretty clearly determined, that common air is made to
+deposit the fixed air which entered into the constitution of it, by
+means of phlogiston, in all the cases of diminished air, it will follow,
+that in the precipitation of lime, by breathing into lime-water the
+fixed air, which incorporates with lime, comes not from the lungs, but
+from the common air, decomposed by the phlogiston exhaled from them, and
+discharged, after having been taken in with the aliment, and having
+performed its function in the animal system.
+
+Thus my conjecture is more confirmed, that the cause of the death of
+animals in confined air is not owing to the want of any _pabulum vitae_,
+which the air had been supposed to contain, but to the want of a
+discharge of the phlogistic matter, with which the system was loaded;
+the air, when once saturated with it, being no sufficient _menstruum_ to
+take it up.
+
+The instantaneous death of animals put into air so vitiated, I still
+think is owing to some _stimulus_, which, by causing immediate,
+universal and violent convulsions, exhausts the whole of the _vis vitae_
+at once; because, as I have observed, the manner of their death is the
+very same in all the different kinds of noxious air.
+
+To this section on the subject of diminished, and noxious air, or as it
+might have been called _phlogisticated air_, I shall subjoin a letter
+which I addressed to Sir John Pringle, on the noxious quality of the
+effluvia of putrid marshes, and which was read at a meeting of the Royal
+Society, December 16, 1773.
+
+This letter which is printed in the Philosophical Transactions, Vol. 74,
+p. 90. is immediately followed by another paper, to which I would refer
+my reader. It was written by Dr. Price, who has so greatly distinguished
+himself, and done such eminent service to his country, and to mankind,
+by his calculations relating to the probabilities of human life, and was
+suggested by his hearing this letter read at the Royal Society. It
+contains a confirmation of my observations on the noxious effects of
+stagnant waters by deductions from Mr. Muret's account of the Bills of
+Mortality for a parish situated among marshes, in the district of Vaud,
+belonging to the Canton of Bern in Switzerland.
+
+     To Sir JOHN PRINGLE, Baronet.
+
+     DEAR SIR,
+
+Having pursued my experiments on different kinds of air considerably
+farther, in several respects, than I had done when I presented the last
+account of them to the Royal Society; and being encouraged by the
+favourable notice which the Society has been pleased to take of them, I
+shall continue my communications on this subject; but, without waiting
+for the result of a variety of processes, which I have now going on, or
+of other experiments, which I propose to make, I shall, from time to
+time, communicate such detached articles, as I shall have given the most
+attention to, and with respect to which, I shall have been the most
+successful in my inquiries.
+
+Since the publication of my papers, I have read two treatises, written
+by Dr. Alexander, of Edinburgh, and am exceedingly pleased with the
+spirit of philosophical inquiry, which they discover. They appear to me
+to contain many new, curious, and valuable observations; but one of the
+_conclusions_, which he draws from his experiments, I am satisfied, from
+my own observations, is ill founded, and from the nature of it, must be
+dangerous. I mean his maintaining, that there is nothing to be
+apprehended from the neighbourhood of putrid marshes.
+
+I was particularly surprised, to meet with such an opinion as this, in a
+book inscribed to yourself, who have so clearly explained the great
+mischief of such a situation, in your excellent treatise _on the
+diseases of the army_. On this account, I have thought it not improper,
+to address to you the following observations and experiments, which I
+think clearly demonstrate the fallacy of Dr. Alexander's reasoning,
+indisputably establish your doctrine, and indeed justify the
+apprehensions of all mankind in this case.
+
+I think it probable enough, that putrid matter, as Dr. Alexander has
+endeavoured to prove, will preserve other substances from putrefaction;
+because, being already saturated with the putrid effluvium, it cannot
+readily take any more; but Dr. Alexander was not aware, that air thus
+loaded with putrid effluvium is exceedingly noxious when taken into the
+lungs. I have lately, however, had an opportunity of fully ascertaining
+how very noxious such air is.
+
+Happening to use at Calne, a much larger trough of water, for the
+purpose of my experiments, than I had done at Leeds, and not having
+fresh water so near at hand as I had there, I neglected to change it,
+till it turned black, and became offensive, but by no means to such a
+degree, as to deter me from making use of it. In this state of the
+water, I observed bubbles of air to rise from it, and especially in one
+place, to which some shelves, that I had in it, directed them; and
+having set an inverted glass vessel to catch them, in a few days I
+collected, a considerable quantity of this air, which issued
+spontaneously from the putrid water; and putting nitrous air to it, I
+found that no change of colour or diminution ensued, so that it must
+have been, in the highest degree, noxious. I repeated the same
+experiment several times afterwards, and always with the same result.
+
+After this, I had the curiosity to try how wholesome air would be
+affected by this water; when, to my real surprise, I found, that after
+only one minute's agitation in it, a candle would not burn in it; and,
+after three or four minutes, it was in the same state with the air,
+which had issued spontaneously from the same water.
+
+I also found, that common air, confined in a glass vessel, in _contact_
+only with this water, and without any agitation, would not admit a
+candle to burn in it after two days.
+
+These facts certainly demonstrate, that air which either arises from
+stagnant and putrid water, or which has been for some time in contact
+with it, must be very unfit for respiration; and yet Dr. Alexander's
+opinion is rendered so plausible by his experiments, that it is very
+possible that many persons may be rendered secure, and thoughtless of
+danger, in a situation in which they must necessarily breathe it. On
+this account, I have thought it right to make this communication as
+early as I conveniently could; and as Dr. Alexander appears to be an
+ingenuous and benevolent man, I doubt not but he will thank me for it.
+
+That air issuing from water, or rather from the soft earth, or mud, at
+the bottom of pits containing water, is not always unwholesome, I have
+also had an opportunity of ascertaining. Taking a walk, about two years
+ago, in the neighbourhood of Wakefield, in Yorkshire, I observed bubbles
+of air to arise, in remarkably great plenty, from a small pool of water,
+which, upon inquiry, I was informed had been the place, where some
+persons had been boring the ground, in order to find coal. These
+bubbles of air having excited my curiosity, I presently returned, with a
+bason, and other vessels proper for my purpose, and having stirred the
+mud with a long stick, I soon got about a pint of this air; and,
+examining it, found it to be good, common air; at least a candle burned
+in it very well. I had not then discovered the method of ascertaining
+the goodness of common air, by a mixture of nitrous air. Previous to the
+trial, I had suspected that this air would have been found to be
+inflammable.
+
+I shall conclude this letter with observing, that I have found a
+remarkable difference in different kinds of water, with respect to their
+effect on common air agitated in them, and which I am not yet able to
+account for. If I agitate common air in the water of a deep well, near
+my house in Calne, which is hard, but clear and sweet, a candle will not
+burn in it after three minutes. The same is the case with the
+rain-water, which I get from the roof of my house. But in distilled
+water, or the water of a spring-well near the house, I must agitate the
+air about twenty minutes, before it will be so much injured. It may be
+worth while, to make farther experiments with respect to this property
+of water.
+
+In consequence of using the rain-water, and the well-water above
+mentioned, I was very near concluding, contrary to what I have asserted
+in this treatise, that common air suffers a decomposition by great
+rarefaction. For when I had collected a considerable quantity of air,
+which had been rarefied about four hundred times, by an excellent pump
+made for me by Mr. Smeaton, I always found, that if I filled my
+receivers with the water above mentioned, though I did it so gradually
+as to occasion as little agitation as possible, a candle would not burn
+in the air that remained in them. But when I used distilled water, or
+fresh spring-water, I undeceived myself.
+
+I think myself honoured by the attention, which, from the first, you
+have given to my experiments, and am, with the greatest respect,
+
+     Dear Sir,
+
+       Your most obliged
+
+         Humble Servant,
+
+     London, 7 Dec. 1773.
+
+           J. PRIESTLEY.
+
+
+POSTSCRIPT.
+
+I cannot help expressing my surprize, that so clear and intelligible an
+account, of Mr. SMEATON'S air-pump, should have been before the public
+so long, as ever since the publication of the forty-seventh volume of
+the Philosophical Transactions, printed in 1752, and yet that none of
+our philosophical instrument-makers should use the construction. The
+superiority of this pump, to any that are made upon the common plan, is,
+indeed, prodigious. Few of them will rarefy more than 100 times, and, in
+a general way, not more than 60 or 70 times; whereas this instrument
+must be in a poor state indeed, if it does not rarefy 200 or 300 times;
+and when it is in good order, it will go as far as 1000 times, and
+sometimes even much farther than that; besides, this instrument is
+worked with much more ease, than a common air-pump, and either exhausts
+or condenses at pleasure. In short, to a person engaged in philosophical
+pursuits, this instrument is an invaluable acquisition. I shall have
+occasion to recite some experiments, which I could not have made, and
+which, indeed, I should hardly have dared to attempt, if I had not been
+possessed of such an air-pump as this. It is much to be wished, that
+some person of spirit in the trade would attempt the construction of an
+instrument, which would do great credit to himself, as well as be of
+eminent service to philosophy.
+
+FOOTNOTES:
+
+[11] On this account, if it was thought convenient to introduce a new
+term (or rather make a new application of a term already in use among
+chemists) it might not be amiss to call air that has been diminished,
+and made noxious by any of the processes above mentioned, or others
+similar to them, by the common appellation of _phlogisticated air_; and,
+if it was necessary, the particular process by which it was
+phlogisticated might be added; as common air phlogisticated by charcoal,
+air phlogisticated by the calcination of metals, nitrous air
+phlogisticated with the liver of sulphur, &c.
+
+[12] Here it becomes me to ask pardon of that excellent philosopher
+Father Beccaria of Turin, for conjecturing that the phlogiston, with
+which he revivified metals, did not come from the electric matter
+itself, but from what was discharged from other pieces of metal with
+which he made the experiment. See History of Electricity, p. 277, &c.
+This _revivification of metals_ by electricity completes the proof of
+the electric matter being, or containing phlogiston.
+
+
+
+
+SECTION III.
+
+_Of NITROUS AIR._
+
+
+Since the publication of my former papers I have given more attention to
+the subject of nitrous air than to any other species of air; and having
+been pretty fortunate in my inquiries, I shall be able to lay before my
+reader a more satisfactory account of the curious phenomena occasioned
+by it, and also of its nature and constitution, than I could do before,
+though much still remains to be investigated concerning it, and many new
+objects of inquiry are started.
+
+With a view to discover where the power of nitrous air to diminish
+common air lay, I evaporated to dryness a quantity of the solution of
+copper in diluted spirit of nitre; and having procured from it a
+quantity of a _green precipitate_, I threw the focus of a burning-glass
+upon it, when it was put into a vessel of quicksilver, standing inverted
+in a bason of quicksilver. In this manner I procured air from it, which
+appeared to be, in all respects, nitrous air; so that part of the same
+principle which had escaped during the solution, in the form of _air_,
+had likewise been retained in it, and had not left it in the evaporation
+of the water.
+
+With great difficulty I also procured a small quantity of the same kind
+of air from a solution of _iron_ in spirit of nitre, by the same
+process.
+
+Having, for a different purpose, fired some paper, which had been dipped
+in a solution of copper in diluted spirit of nitre, in nitrous air, I
+found there was a considerable addition to the quantity of it; upon
+which I fired some of the same kind of paper in quicksilver and
+presently observed that air was produced from it in great plenty. This
+air, at the first, seemed to have some singular properties, but
+afterwards I found that it was nothing more than a mixture of nitrous
+air, from the precipitate of the solution, and of inflammable air, from
+the paper; but that the former was predominant.
+
+In the mixture of this kind of air with common air, in a trough of water
+which had been putrid, but which at that time seemed to have recovered
+its former sweetness (for it was not in the least degree offensive to
+the smell) a phenomenon sometimes occurred, which for a long time
+exceedingly delighted and puzzled me; but which was afterwards the means
+of letting me see much farther into the constitution of nitrous air than
+I had been able to see before.
+
+When the diminution of the air was nearly completed, the vessel in which
+the mixture was made began to be filled with the most beautiful _white
+fumes_, exactly resembling the precipitation of some white substance in
+a transparent menstruum, or the falling of very fine snow; except that
+it was much thicker below than above, as indeed is the case in all
+chemical precipitations. This appearance continued two or three minutes.
+
+At other times I went over the same process, as nearly as possible in
+the same manner, but without getting this remarkable appearance, and was
+several times greatly disappointed and chagrined, when I baulked the
+expectations of my friends, to whom I had described, and meant to have
+shewn it. This made me give all the attention I possibly could to this
+experiment, endeavouring to recollect every circumstance, which, though
+unsuspected at the time, might have contributed to produce this new
+appearance; and I took a great deal of pains to procure a quantity of
+this air from the paper above mentioned for the purpose, which, with a
+small burning lens, and an uncertain sun, is not a little troublesome.
+But all that I observed for some time was, that I stood the best chance
+of succeeding when I _warmed_ the vessel in which the mixture was made,
+and _agitated_ the air during the effervescence.
+
+Finding, at length, that, with the same preparation and attentions, I
+got the same appearance from a mixture of nitrous and common air in the
+same trough of water, I concluded that it could not depend upon any
+thing peculiar to the precipitate of the _copper_ contained in the
+_paper_ from which the air was procured, as I had at first imagined, but
+upon what was common to it, and pure nitrous air.
+
+Afterwards, having, (with a view to observe whether any crystals would
+be formed by the union of volatile alkali, and nitrous air, similar to
+those formed by it and fixed air, as described by Mr. Smeth in his
+_Dissertation on fixed Air_) opened the mouth of a phial which was half
+filled with a volatile alkaline liquor, in a jar of nitrous air (in the
+manner described p. 11. fig. 4.) I had an appearance which perfectly
+explained the preceding. All that part of the phial which was above the
+liquor, and which contained common air, was filled with beautiful
+_white clouds_, as if some fine white powder had been instantly thrown
+into it, and some of these clouds rose within the jar of nitrous air.
+This appearance continued about a minute, and then intirely disappeared,
+the air becoming transparent.
+
+Withdrawing the phial, and exposing it to the common air, it there also
+became turbid, and soon after the transparency returned. Introducing it
+again into the nitrous air, the clouds appeared as before. In this
+manner the white fumes, and transparency, succeeded each other
+alternately, as often as I chose to repeat the experiment, and would no
+doubt have continued till the air in the jar had been thoroughly diluted
+with common air. These appearances were the same with any substance that
+contained _volatile alkali_, fluid or solid.
+
+When, instead of the small phial, I used a large and tall glass jar,
+this appearance was truly fine and striking, especially when the water
+in the trough was very transparent. For I had only to put the smallest
+drop of a volatile alkaline liquor, or the smallest bit of the solid
+salt, into the jar, and the moment that the mouth of it was opened in a
+jar of nitrous air, the white clouds above mentioned began to be formed
+at the mouth, and presently descended to the bottom, so as to fill the
+whole, were it ever so large, as with fine snow.
+
+In considering this experiment, I soon perceived that this curious
+appearance must have been occasioned by the mixture of the nitrous and
+common air, and therefore that the white clouds must be _nitrous
+ammoniac_, formed by the acid of the nitrous air, set loose in the
+decomposition of it by common air, while the phlogiston, which must be
+another constituent part of nitrous air, entering the common air, is the
+cause of the diminution it suffers in this process; as it is the cause
+of a similar diminution, in a variety of other processes.
+
+I would observe, that it is not peculiar to nitrous air to be a test of
+the fitness of air for respiration. Any other process by which air is
+diminished and made noxious answers the same purpose. Liver of sulphur
+for instance, the calcination of metals, or a mixture of iron filings
+and brimstone will do just the same thing; but the application of them
+is not so easy, or elegant, and the effect is not so soon perceived. In
+fact, it is _phlogiston_ that is the test. If the air be so loaded with
+this principle that it can take no more, which is seen by its not being
+diminished in any of the processes above mentioned, it is noxious; and
+it is wholesome in proportion to the quantity of phlogiston that it is
+able to take.
+
+This, I have no doubt, is the true theory of the diminution of common
+air by nitrous air, the redness of the appearance being nothing more
+than the usual colour of the fumes, of spirit of nitre, which is now
+disengaged from the superabundant phlogiston with which it was combined
+in the nitrous air, and ready to form another union with any thing that
+is at hand, and capable of it.
+
+With the volatile alkali it forms nitrous ammoniac, water imbibes it
+like any other acid, even quicksilver is corroded by it; but this action
+being slow, the redness in this mixture of nitrous and common air
+continues much longer when the process is made in quicksilver, than when
+it is made in water, and the diminution, as I have also observed; is by
+no means so great.
+
+I was confirmed in this opinion when I put a bit of volatile alkaline
+salt into the jar of quicksilver in which I made the mixture of nitrous
+and common air. In these circumstances, the vessel being previously
+filled with the alkaline fumes, the acid immediately joined them, formed
+the white clouds above mentioned, and the diminution proceeded almost
+as far as when the process was made in water. That it did not proceed
+quite so far, I attribute chiefly to the small quantity of calx formed
+by the slight solution of mercury with the acid fumes not being able to
+absorb all the fixed air that is precipitated from the common air by the
+phlogiston.
+
+In part, also, it may be owing to the small quantify of surface in the
+quicksilver in the vessels that I made use of; in consequence of which
+the acid fumes could act upon it only in a slow succession, so that part
+of them, as well as of the fixed air, had an opportunity of forming
+another union with the diminished air.
+
+This, as I have observed before, was so much the case when the process
+was made in quicksilver, without any volatile alkali, that when water
+was admitted to it, after some time, it was not capable of dissolving
+that union, tho' it would not have taken place if the process had been
+in water from the first.
+
+In diversifying this experiment, I found that it appeared to very great
+advantage when I suspended a piece of volatile salt in the common air,
+previous to the admission of nitrous air to it, inclosing it in a bit
+of gauze, muslin, or a small net of wire. For, presently after the
+redness of the mixture begins to go off, the white cloud, like snow,
+begins to descend from the salt, as if a white powder was shaken out of
+the bag that contains it. This white cloud presently fills the whole
+vessel, and the appearance will last about five minutes.
+
+If the salt be not put to the mixture of these two kinds of air till it
+has perfectly recovered its transparency, the effervescence being
+completely over, no white cloud will be formed; and, what is rather more
+remarkable, there is nothing of this appearance when the salt is put
+into the nitrous air itself. The reason of this must be, that the acid
+of the nitrous air has a nearer affinity with its phlogiston than with
+the volatile alkali; though the phlogiston having a nearer affinity with
+something in the common air, the acid being thereby set loose, will
+unite with the alkaline vapour, if it be at hand to unite with it.
+
+There is also very little, if any white cloud formed upon holding a
+piece of the volatile salt within the mouth of a phial containing
+smoking spirit of nitre. Also when I threw the focus of a burning mirror
+upon some sal ammoniac in nitrous air, and filled the whole vessel with
+white fumes which arose from it, they were soon dispersed, and the air
+was neither diminished nor altered.
+
+I was now fully convinced, that the white cloud which I casually
+observed, in the first of these experiments, was occasioned by the
+volatile alkali emitted from the water, which was in a slight degree
+putrid; and that the warming, and agitation of the vessels, had promoted
+the emission of the putrid, or alkaline effluvium.
+
+I could not perceive that the diminution of common air by the mixture of
+nitrous air was sensibly increased by the presence of the volatile
+alkali. It is possible, however, that, by assisting the water to take up
+the acid, something less of it may be incorporated with the remaining
+diminished air than would otherwise have been; but I did not give much
+attention to this circumstance.
+
+When the phial in which I put the alkaline salts contained any kind of
+noxious air, the opening of it in nitrous air was not followed by any
+thing of the appearance above mentioned. This was the case with
+inflammable air. But when, after agitating the inflammable air in water,
+I had brought it to a state in which it was diminished a little by the
+mixture of nitrous air, the cloudy appearance was in the same
+proportion; so that this appearance seems to be equally a test of the
+fitness of air for respiration, with the redness which attends the
+mixture of it with nitrous air only.
+
+Having generally fastened the small bag which contained the volatile
+salt to a piece of brass wire in the preceding experiment, I commonly
+found the end of it corroded, and covered with a blue substance. Also
+the salt itself, and sometimes the bag was died blue. But finding that
+this was not the case when I used an iron wire in the same
+circumstances, but that it became _red_, I was satisfied that both the
+metals had been dissolved by the volatile alkali. At first I had a
+suspicion that the blue might have come from the copper, out of which
+the nitrous air had been made. But when the nitrous air was made from
+iron, the appearances were, in all respects, the same.
+
+I have observed, in the preceding section, that if nitrous air be mixed
+with common air in _lime-water_, the surface of the water, where it is
+contiguous to that mixture, will be covered with an incrustation of
+lime, shewing that some fixed air had been deposited in the process. It
+is remarkable, however, as I there also just mentioned, that this is
+the case when nitrous air alone is put to a vessel of lime-water, after
+it has been kept in a _bladder_, or only transferred from one vessel to
+another by a bladder, in the manner described, p. 15. fig. 9.
+
+As I had used the same bladder for transferring various kinds of air,
+and among the rest _fixed air_, I first imagined that this effect might
+have been occasioned by a mixture of this fixed air with the nitrous
+air, and therefore took a fresh bladder; but still the effect was the
+same. To satisfy myself farther, that the bladder had produced this
+effect, I put one into a jar of nitrous air, and after it had continued
+there a day and a night, I found that the nitrous air in this jar,
+though it was transferred in a glass vessel, made lime-water turbid.
+
+Whether there was any thing in the preparation of these bladders that
+occasioned their producing this effect, I cannot tell. They were such as
+I procure from the apothecaries. The thing seems to deserve farther
+examination, as there seems, in this case, to be the peculiar effect of
+fixed air from other causes, or else a production of fixed air from
+materials that have not been supposed to yield it, at least not in
+circumstances similar to these.
+
+As fixed air united to water dissolves iron, I had the curiosity to try
+whether fixed air alone would do it; and as nitrous air is of an _acid_
+nature, as well as fixed air, I, at the same time, exposed a large
+surface of iron to both the kinds; first filling two eight ounce phials
+with nails, and then with quicksilver, and after that displacing the
+quicksilver in one of the phials by fixed air, and in the other by
+nitrous air; then inverting them, and leaving them with their mouths
+immersed in basons of quicksilver.
+
+In these circumstances the two phials stood about two months, when no
+sensible change at all was produced in the fixed air, or in the iron
+which had been exposed to it, but a most remarkable, and most unexpected
+change was made in the nitrous air; and in pursuing the experiment, it
+was transformed into a species of air, with properties which, at the
+time of my first publication on this subject, I should not have
+hesitated to pronounce impossible, viz. air in which a candle burns
+quite naturally and freely, and which is yet in the highest degree
+noxious to animals, insomuch that they die the moment they are put into
+it; whereas, in general, animals live with little sensible inconvenience
+in air in which candles have burned out. Such, however, is nitrous air,
+after it has been long exposed to a large surface of iron.
+
+It is not less extraordinary, that a still longer continuance of nitrous
+air in these circumstances (but _how long_ depends upon too many, and
+too minute circumstances to be ascertained with exactness) makes it not
+only to admit a candle to burn in it, but enables it to burn with an
+_enlarged flame_, by another flame (extending every where to an equal
+distance from that of the candle, and often plainly distinguishable from
+it) adhering to it. Sometimes I have perceived the flame of the candle,
+in these circumstances, to be twice as large as it is naturally, and
+sometimes not less than five or six times larger; and yet without any
+thing like an _explosion_, as in the firing of the weakest inflammable
+air.
+
+Nor is the farther progress in the transmutation of nitrous air, in
+these circumstances, less remarkable. For when it has been brought to
+the state last mentioned, the agitation of it in fresh water almost
+instantly takes off that peculiar kind of inflammability, so that it
+extinguishes a candle, retaining its noxious quality. It also retains
+its power of diminishing common air in a very great degree.
+
+But this noxious quality, like the noxious quality of all other kinds of
+air that will bear agitation in water, is taken out of it by this
+operation, continued about five minutes; in which process it suffers a
+farther and very considerable diminution. It is then itself diminished
+by fresh nitrous air, and animals live in it very well, about as well as
+in air in which candles have burned out.
+
+Lastly, One quantity of nitrous air, which had been exposed to iron in
+quicksilver, from December 18 to January 20, and which happened to stand
+in water till January 31 (the iron still continuing in the phial) was
+fired with an explosion, exactly like a weak inflammable air. At the
+same time another quantity of nitrous air, which had likewise been
+exposed to iron, standing in quicksilver, till about the same time, and
+had then stood in water only, without iron, only admitted a candle to
+burn in it with an enlarged flame, as in the cases above mentioned. But
+whether the difference I have mentioned in the circumstances of these
+experiments contributed to this difference in the result, I cannot tell.
+
+Nitrous air treated in the manner above mentioned is diminished about
+one fourth by standing in quicksilver; and water admitted to it will
+absorb about half the remainder; but if water only, and no quicksilver,
+be used from the beginning, the nitrous air will be diminished much
+faster and farther; so that not more than one fourth, one sixth, or one
+tenth of the original quantity will remain. But I do not know that there
+is any difference in the constitution of the air which remains in these
+two cases.
+
+The water which has imbibed this nitrous air exposed to iron is
+remarkably green, also the phial containing it becomes deeply, and, I
+believe, indelibly tinged with green; and if the water be put into
+another vessel, it presently deposits a considerable quantity of matter,
+which when dry appears to be the earth or ochre of iron; from which it
+is evident, that the acid of the nitrous air dissolves the iron; while
+the phlogiston, being set loose, diminishes nitrous air, as in the
+process of the iron filings and brimstone.
+
+Upon this hint, instead of using _iron_, I introduced a pot of _liver of
+sulphur_ into a jar of nitrous air, and presently found, that what I had
+before done by means of iron in six weeks, or two months, I could do by
+liver of sulphur (in consequence, no doubt, of its giving its phlogiston
+more freely) in less than twenty-four hours, especially when the process
+was kept warm.
+
+It is remarkable, however, that if the process with liver of sulphur be
+suffered to proceed, the nitrous air will be diminished much farther.
+At one time not more than one twentieth of the original quantity
+remained, and how much farther it right have been diminished, I cannot
+tell. In this great diminution, it does not admit a candle to burn in it
+at all; and I generally found this to be the case whenever the
+diminution had proceeded beyond three fourths of the original
+quantity[13].
+
+It is something remarkable, that though the diminution of nitrous air by
+iron filings and brimstone very much resembles the diminution of it by
+iron only, or by liver of sulphur, yet the iron filings and brimstone
+never bring it to such a state as that a candle will burn in it; and
+also that, after this process, it is never capable of diminishing common
+air. But when it is considered that these properties are destroyed by
+agitation in water, this difference in the result of processes, in other
+respects similar, will appear less extraordinary; and they agree in
+this, that long agitation in water makes both these kinds of nitrous air
+equally fit for respiration, being equally diminished by fresh nitrous
+air. It is possible that there would have been a more exact agreement
+in the result of these processes, if they had been made in equal degrees
+of _heat_; but the process with iron was made in the usual temperature
+of the atmosphere, and that with liver of sulphur generally near a fire.
+
+It may clearly, I think, be inferred from these experiments, that all
+the difference between fresh nitrous air, that state of it in which it
+is partially inflammable, or wholly so, that in which it again
+extinguishes candles, and that in which it finally becomes fit for
+respiration, depends upon some difference in the _mode of the
+combination_ of its acid with phlogiston, or on the _proportion_ between
+these two ingredients in its composition; and it is not improbable but
+that, by a little more attention to these experiments, the whole mystery
+of this proportion and combination may be explained.
+
+I must not omit to observe that there was something peculiar in the
+result of the first experiment which I made with nitrous air exposed to
+iron; which was that, without any agitation in water, it was diminished
+by fresh nitrous air, and that a candle burned in it quite naturally. To
+what this difference was owing I cannot tell. This air, indeed, had been
+exposed to the iron a week or two longer than in any of the other
+cases, but I do not imagine that this circumstance could have produced
+that difference.
+
+When the process is in water with iron, the time in which the diminution
+is accomplished is exceedingly various; being sometimes completed in a
+few days, whereas at other times it has required a week or a fortnight.
+Some kinds of iron also produced this effect much sooner than others,
+but on what circumstances this difference depends I do not know. What
+are the varieties in the result of this experiment when it is made in
+quicksilver I cannot tell, because, on account of its requiring more
+time, I have not repeated it so often; but I once found that nitrous air
+was not sensibly changed by having been exposed to iron in quicksilver
+nine days; whereas in water a very considerable alteration was always
+made in much less than half that time.
+
+It may just deserve to be mentioned, that nitrous air extremely rarified
+in an air-pump dissolves iron, and is diminished by it as much as when
+it is in its native state of condensation.
+
+It is something remarkable, though I never attended to it particularly
+before I made these last experiments, and it may tend to throw some
+light upon them, that when a candle is extinguished, as it never fails
+to be, in nitrous air, the flame seems to be a little enlarged at its
+edges, by another bluish flame added to it, just before its extinction.
+
+It is proper to observe in this place, that the electric spark taken in
+nitrous air diminishes it to one fourth of its original quantity, which
+is about the quantity of its diminution by iron filings and brimstone,
+and also by liver of sulphur without heat. The air is also brought by
+electricity to the same state as it is by iron filings and brimstone,
+not diminishing common air. If the electric spark be taken in it when it
+is confined by water tinged with archil, it is presently changed from
+blue to red, and that to a very great degree.
+
+When the iron nails or wires, which I have used to diminish nitrous air,
+had done their office, I laid them aside, not suspecting that they could
+be of any other philosophical use; but after having lain exposed to the
+open air almost a fortnight; having, for some other purpose, put some of
+them into a vessel containing common air, standing inverted, and
+immersed in water, I was surprized to observe that the air in which they
+were confined was diminished. The diminution proceeded so fast, that
+the process was completed in about twenty-four hours; for in that time
+the air was diminished about one fifth, so that it made no effervescence
+with nitrous air, and was, therefore, no doubt, highly noxious, like air
+diminished by any other process.
+
+This experiment I have repeated a great number of times, with the same
+phials, filled with nails or wires that have been suffered to rust in
+nitrous air, but their power of diminishing common air grows less and
+less continually. How long it will be before it is quite exhausted I
+cannot tell. This diminution of air I conclude must arise from the
+phlogiston, either of the nitrous air or the iron, being some way
+entangled in the rust, in which the wires were encrusted, and afterwards
+getting loose from it.
+
+To the experiments upon iron filings and brimstone in nitrous air, I
+must add, that when a pot full of this mixture had absorbed as much as
+it could of a jar of nitrous air (which is about three fourths of the
+whole) I put fresh nitrous air to it, and it continued to absorb, till
+three or four jars full of it disappeared; but the absorption was
+exceedingly slow at the last. Also when I drew this pot through the
+water, and admitted fresh nitrous air to it, it absorbed another jar
+full, and then ceased. But when I scraped off the outer surface of this
+mixture, which had been so long exposed to the nitrous air, the
+remainder absorbed more of the air.
+
+When I took the top of the mixture which I had scraped off and threw
+upon it the focus of a burning-glass, the air in which it was confined
+was diminished, and became quite noxious; yet when I endeavoured to get
+air from this matter in a jar full of quicksilver, I was able to procure
+little or nothing.
+
+It is not a little remarkable that nitrous air diminished by iron
+filings and brimstone, which is about one fourth, cannot, by agitation
+in water, be diminished much farther; whereas pure nitrous air may, by
+the same process, be diminished to one twentieth of its whole bulk, and
+perhaps much more. This is similar to the effect of the same mixture,
+and of phlogiston in other cases, on fixed air; for it so far changes
+its constitution, that it is afterwards incapable of mixing with water.
+It is similar also to the effect of phlogiston in acid air, which of
+itself is almost instantly absorbed by water; but by this addition it is
+first converted into inflammable air, which does not readily mix with
+water, and which, by long agitation in water, becomes of another
+constitution, still less miscible with water.
+
+I shall close this section with a few other observations of a
+miscellaneous nature.
+
+Nitrous air is as much diminished both by iron filings, and also by
+liver of sulphur, when confined in quicksilver, as when it is exposed to
+water.
+
+Distilled water tinged blue with the juice of turnsole becomes red on
+being impregnated with nitrous air; but by being exposed a week or a
+fortnight to the common atmosphere, in open and shallow vessels, it
+recovers its blue colour; though, in that time, the greater part of the
+water will be evaporated. This shews that in time nitrous air escapes
+from the water with which it is combined, just as fixed air does, though
+by no means so readily[14].
+
+Having dissolved silver, copper, and iron in equal quantities of spirit
+of nitre diluted with water, the quantities of nitrous air produced from
+them were in the following proportion; from iron 8, from copper 6-1/4,
+from silver 6. In about the same proportion also it was necessary to
+mix water with the spirit of nitre in each case, in order to make it
+dissolve these metals with equal rapidity, silver requiring the least
+water, and iron the most.
+
+Phosphorus gave no light in nitrous air, and did not take away from its
+power of diminishing common air; only when the redness of the mixture
+went off, the vessel in which it was made was filled with white fumes,
+as if there had been some volatile alkali in it. The phosphorus itself
+was unchanged.
+
+There is something remarkable in the effect of nitrous air on _insects_
+that are put into it. I observed before that this kind of air is as
+noxious as any whatever, a mouse dying the moment it is put into it; but
+frogs and snails (and therefore, probably, other animals whose
+respiration is not frequent) will bear being exposed to it a
+considerable time, though they die at length. A frog put into nitrous
+air struggled much for two or three minutes, and moved now and then for
+a quarter of an hour, after which it was taken out, but did not recover.
+_Wasps_ always died the moment they were put into the nitrous air. I
+could never observe that they made the least motion in it, nor could
+they be recovered to life afterwards. This was also the case in general
+with _spiders_, _flies_, and _butterflies_. Sometimes, however, spiders
+would recover after being exposed about a minute to this kind of air.
+
+Considering how fatal nitrous air is to insects, and likewise its great
+antiseptic power, I conceived that considerable use might be made of it
+in medicine, especially in the form of _clysters_, in which fixed air
+had been applied with some success; and in order to try whether the
+bowels of an animal would bear the injection of it, I contrived, with
+the help of Mr. Hey, to convey a quantity of it up the anus of a dog.
+But he gave manifest signs of uneasiness, as long as he retained it,
+which was a considerable time, though in a few hours afterwards he was
+as lively as ever, and seemed to have suffered nothing from the
+operation.
+
+Perhaps if nitrous air was diluted either with common air, or fixed air,
+the bowels might bear it better, and still it might be destructive to
+_worms_ of all kinds, and be of use to check or correct putrefaction in
+the intestinal canal, or other parts of the system. I repeat it once
+more that, being no physician, I run no risk by such proposals as these;
+and I cannot help flattering myself that, in time, very great medicinal
+use will be made of the application of these different kinds of air to
+the animal system. Let ingenious physicians attend to this subject, and
+endeavour to lay hold of the new _handle_ which is now presented them,
+before it be seized by rash empiricks; who, by an indiscriminate and
+injudicious application, often ruin the credit of things and processes
+which might otherwise make an useful addition to the _materia_ and _ars
+medica_.
+
+In the first publication of my papers, having experienced the remarkable
+antiseptic power of nitrous air, I proposed an attempt to preserve
+anatomical preparations, &c. by means of it; but Mr. Hey, who made the
+trial, found that, after some months, various animal substances were
+shriveled, and did not preserve their natural forms in this kind of
+air.
+
+FOOTNOTES:
+
+[13] The result of several of these experiments I had the pleasure of
+trying in the presence of the celebrated Mr. De Luc of Geneva, when he
+was upon a visit to Lord Shelburne in Wiltshire.
+
+[14] I have not repeated this experiment with that variation of
+circumstances which an attention to Mr. Bewley's observation will
+suggest.
+
+
+
+
+SECTION IV.
+
+_Of MARINE ACID AIR._
+
+
+In my former experiments on this species of air I procured it from
+spirit of salt, but I have since hit upon a much less expensive method
+of getting it, by having recourse to the process by which the spirit of
+salt is itself originally made. For this purpose I fill a small phial
+with common salt, pour upon it a small quantity of concentrated oil of
+vitriol, and receive the fumes emitted by it in a vessel previously
+filled with quicksilver, and standing in a bason of quicksilver, in
+which it appears in the form of a perfectly _transparent air_, being
+precisely the same thing with that which I had before expelled from the
+spirit of salt.
+
+This method of procuring acid air is the more convenient, as a phial,
+once prepared in this manner, will suffice, for common experiments, many
+weeks; especially if a little more oil of vitriol be occasionally put to
+it. It only requires a little more heat at the last than at the first.
+Indeed, at the first, the heat of a person's hand will often be
+sufficient to make it throw out the vapour. In warm weather it will
+even keep smoking many days without the application of any other heat.
+
+On this account, it should be placed where there are no instruments, or
+any thing of metal, that can be corroded by this acid vapour. It is from
+dear-bought experience that I give this advice. It may easily be
+perceived when this phial is throwing out this acid vapour, as it always
+appears, in the open air, in the form of a light cloud; owing, I
+suppose, to the acid attracting to itself, and uniting with, the
+moisture that is in the common atmosphere.
+
+By this process I even made a stronger spirit of salt than can be
+procured in any other way. For having a little water in the vessel which
+contains the quicksilver, it imbibes the acid vapour, and at length
+becomes truly saturated with it. Having, in this manner, impregnated
+pure water with acid air, I could afterwards expel the same air from it,
+as from common spirit of salt.
+
+I observed before that this acid vapour, or air, has a strong affinity
+with _phlogiston_, so that it decomposes many substances which contain
+it, and with them forms a permanently inflammable air, no more liable to
+be imbibed by water than inflammable air procured by any other process,
+being in fact the very same thing; and that, in some cases, it even
+dislodges spirit of nitre and oil of vitriol, which in general appear to
+be stronger acids than itself. I have since observed that, by giving it
+more time, it will extract phlogiston from substances from which I at
+first concluded that it was not able to do it, as from dry wood, crusts
+of bread not burnt, dry flesh, and what is more extraordinary from
+flints. As there was something peculiar to itself in the process or
+result of each of these experiments, it may not be improper to mention
+them distinctly.
+
+Pieces of dry _cork wood_ being put to the acid air, a small quantity
+remained not imbibed by water, and was inflammable.
+
+Very dry pieces of _oak_, being exposed to this air a day and a night,
+after imbibing a considerable quantity of it, produced air which was
+inflammable indeed, but in the slightest degree imaginable. It seemed to
+be very nearly in the state of common air.
+
+A piece of _ivory_ imbibed the acid vapour very slowly. In a day and a
+night, however, about half an ounce measure of permanent air was
+produced, and it was pretty strongly inflammable. The ivory was not
+discoloured, but was rendered superficially soft, and clammy, tasting
+very acid.
+
+Pieces of _beef_, roasted, and made quite dry, but not burnt, absorbed
+the acid vapour slowly; and when it had continued in this situation all
+night, from five ounce measures of the air, half a measure was
+permanent, and pretty strongly inflammable. This experiment succeeded a
+second time exactly in the same manner; but when I used pieces of white
+dry _chicken-flesh_ though I allowed the same time, and in other
+respects the process seemed to go on in the same manner, I could not
+perceive that any part of the remaining air was inflammable.
+
+Some pieces of a whitish kind of _flint_, being put into a quantity of
+acid air, imbibed but a very little of it in a day and a night; but of
+2-1/2 ounce measures of it, about half a measure remained unabsorbed by
+water, and this was strongly inflammable, taking fire just like an equal
+mixture of inflammable and common air. At another time, however, I could
+not procure any inflammable air by this means, but to what circumstance
+these different results were owing I cannot tell.
+
+That inflammable air is produced from _charcoal_ in acid air I observed
+before. I have since found that it may likewise be procured from _pit
+coal_, without being charred.
+
+Inflammable air I had also observed to arise from the exposure of spirit
+of wine, and various _oily_ substances, to the vapour of spirit of salt.
+I have since made others of a similar nature, and as peculiar
+circumstances attended some of these experiments, I shall recite them
+more at large.
+
+_Essential oil of mint_ absorbed this air pretty fast, and presently
+became of a deep brown colour. When it was taken out of this air it was
+of the consistence of treacle, and sunk in water, smelling differently
+from what it did before; but still the smell of the mint was
+predominant. Very little or none of the air was fixed, so as to become
+inflammable; but more time would probably have produced this effect.
+
+_Oil of turpentine_ was also much thickened, and became of a deep brown
+colour, by being saturated with acid air.
+
+_Ether_ absorbed acid air very fast, and became first of a turbid white,
+and then of a yellow and brown colour. In one night a considerable
+quantity of permanent air was produced, and it was strongly inflammable.
+
+Having, at one time, fully saturated a quantity of ether with acid air,
+I admitted bubbles of common air to it, through the quicksilver, by
+which it was confined, and observed that white fumes were made in it, at
+the entrance of every bubble, for a considerable time.
+
+At another time, having fully saturated a small quantity of ether with
+acid air, and having left the phial in which it was contained nearly
+full of the air, and inverted, it was by some accident overturned; when,
+instantly, the whole room was filled with a visible fume, like a white
+cloud, which had very much the smell of ether, but peculiarly offensive.
+Opening the door and window of the room, this light cloud filled a long
+passage, and another room. In the mean time the ether was seemingly all
+vanished, but some time after the surface of the quicksilver in which
+the experiment had been made was covered with a liquor that tasted very
+acid; arising, probably, from the moisture in the atmosphere attracted
+by the acid vapour with which the ether had been impregnated.
+
+This visible cloud I attribute to the union of the moisture in the
+atmosphere with the compound of the acid air and ether. I have since
+saturated other quantities of ether with acid air, and found it to be
+exceedingly volatile, and inflammable. Its exhalation was also visible,
+but not in so great a degree as in the case above mentioned.
+
+_Camphor_ was presently reduced into a fluid state by imbibing acid air,
+but there seemed to be something of a whitish sediment in it. After
+continuing two days in this situation I admitted water to it;
+immediately upon which the camphor resumed its former solid state, and,
+to appearance, was the very same substance that it had been before; but
+the taste of it was acid, and a very small part of the air was
+permanent, and slightly inflammable.
+
+The acid air seemed to make no impression upon a piece of Derbyshire
+_spar_, of a very dark colour, and which, therefore, seemed to contain a
+good deal of phlogiston.
+
+As the acid air has so near an affinity with phlogiston, I expected that
+the fumes of _liver of sulphur_, which chemists agree to be phlogistic,
+would have united with it, so as to form inflammable air; but I was
+disappointed in that expectation. This substance imbibed half of the
+acid air to which it was introduced: one fourth of the remainder, after
+standing one day in quicksilver, was imbibed by water, and what was left
+extinguished a candle. This experiment, however, seems to prove that
+acid air and phlogiston may form a permanent kind of air that is not
+inflammable. Perhaps it may be air in such a state as common air loaded
+with phlogiston, and from which the fixed air has been precipitated. Or
+rather, it may be the same thing with inflammable air, that has lost its
+inflammability by long standing in water. It well deserves a farther
+examination.
+
+The following experiments are those in which the _stronger acids_ were
+made use of, and therefore they may assist us farther to ascertain their
+affinities with certain substances, with respect to this marine acid in
+the form of air.
+
+I put a quantity of strong concentrated _oil of vitriol_ to acid air,
+but it was not at all affected by it in a day and a night. In order to
+try whether it would not have more power in a more condensed state, I
+compressed it with an additional atmosphere; but upon taking off this
+pressure, the air expanded again, and appeared to be not at all
+diminished. I also put a quantity of strong _spirit of nitre_ to it
+without any sensible effect. We may conclude, therefore, that the
+marine acid, in this form of air, is not able to dislodge the other
+acids from their union with water.
+
+_Blue vitriol_, which is formed by the union of the vitriolic acid with
+copper, turned to a dark green the moment that it was put to the acid
+air, which it absorbed, though slowly. Two pieces, as big as small nuts,
+absorbed three ounce measures of the air in about half an hour. The
+green colour was very superficial; for it was easily wiped or washed
+off.
+
+_Green copperas_ turned to a deeper green upon being put into acid air,
+which it absorbed slowly. _White copperas_ absorbed this air very fast,
+and was dissolved in it.
+
+_Sal ammoniac_, being the union of spirit of salt with volatile alkali,
+was no more affected with the acid air than, as I have observed before,
+common salt was.
+
+I also introduced to the acid air various other substances, without any
+particular expectation; and it may be worth while to give an account of
+the results, that the reader may draw from them such conclusions as he
+shall think reasonable.
+
+_Borax_ absorbed acid air about as fast as blue vitriol, but without any
+thing else that was observable.
+
+Fine white _sugar_ absorbed this air slowly, was thoroughly penetrated
+with it, became of a deep brown colour, and acquired a smell that was
+peculiarly pungent.
+
+A piece of _quick lime_ being put to about twelve or fourteen ounce
+measures of acid air, and continuing in that situation about two days,
+there remained one ounce measure of air that was not absorbed by water,
+and it was very strongly inflammable, as much so as a mixture of half
+inflammable and half common air. Very particular care was taken that no
+common air mixed with the acid air in this process. At another time,
+from about half the quantity of acid air above mentioned, with much less
+quick-lime, and in the space of one day, I got half an ounce measure of
+air that was inflammable in a slight degree only. This experiment proves
+that some part of the phlogiston which escapes from the fuel, in contact
+with which the lime is burned, adheres to it. But I am very far from
+thinking that the causticity of quick-lime is at all owing to this
+circumstance.
+
+I have made a few more experiments on the mixture of acid air with
+_other kinds of air_, and think that it may be worth while to mention
+them, though nothing of consequence, at least nothing but negative
+conclusions, can be drawn from them.
+
+A quantity of common air saturated with nitrous air was put to a
+quantity of acid air, and they continued together all night, without any
+sensible effect. The quantity of both remained the same, and water being
+admitted to them, it absorbed all the acid air, and left the other just
+as before.
+
+A mixture of two thirds of air diminished by iron filings and brimstone,
+and one third acid air, were mixed together, and left to stand four
+weeks in quicksilver. But when the mixture was examined, water presently
+imbibed all the acid air, and the diminished air was found to be just
+the same that it was before. I had imagined that the acid air might have
+united with the phlogiston with which the diminished air was
+overcharged, so as to render it wholsome; and I had read an account of
+the stench arising from putrid bodies being corrected by acid fumes.
+
+The remaining experiments, in which the acid air was principally
+concerned, are of a miscellaneous nature.
+
+I put a piece of dry _ice_ to a quantity of acid air (as was observed in
+the section concerning _alkaline_ air) taking it with a forceps, which,
+as well as the air itself, and the quicksilver by which it had been
+confined; had been exposed to the open air for an hour, in a pretty
+strong frost. The moment it touched the air it was dissolved as fast as
+it would have been by being thrown into a hot fire, and the air was
+presently imbibed. Putting fresh pieces of ice to that which was
+dissolved before, they were also dissolved immediately, and the water
+thus procured did not freeze again, though it was exposed a whole night,
+in a very intense frost.
+
+Flies and spiders die in acid air, but not so quickly as in nitrous air.
+This surprized me very much; as I had imagined that nothing could be
+more speedily fatal to all animal life than this pure acid vapour.
+
+As inflammable air, I have observed, fires at one explosion in the
+vapour of smoking spirit of nitre, just like an equal mixture of
+inflammable and common air, I thought it was possible that the fume
+which naturally rises from common spirit of salt might have the same
+effect, but it had not. For this purpose I treated the spirit of salt,
+as I had before done the smoking spirit of nitre; first filling a phial
+with it, then inverting it in a vessel containing a quantity of the same
+acid; and having thrown the inflammable air into it, and thereby driven
+out all the acid, turning it with its mouth upwards, and immediately
+applying a candle to it.
+
+Acid air not being so manageable as most of the other kinds of air, I
+had recourse to the following peculiar method, in order to ascertain its
+_specific gravity_. Having filled an eight ounce phial with this air,
+and corked it up, I weighed it very accurately; and then, taking out the
+cork, I blew very strongly into it with a pair of bellows, that the
+common air might take place of the acid; and after this I weighed it
+again, together with the cork, but I could not perceive the least
+difference in the weight. I conclude, however, from this experiment,
+that the acid air is heavier than the common air, because the mouth of
+the phial and the inside of it were evidently moistened by the water
+which the acid vapour had attracted from the air, which moisture must
+have added to the weight of the phial.
+
+
+
+
+SECTION V.
+
+_Of INFLAMMABLE AIR._
+
+
+It will have appeared from my former experiments, that inflammable air
+consists chiefly, if not wholly, of the union of an acid vapour with
+phlogiston; that as much of the phlogiston as contributes to make air
+inflammable is imbibed by the water in which it is agitated; that in
+this process it soon becomes fit for respiration, and by the continuance
+of it comes at length to extinguish flame. These observations, and
+others which I have made upon this kind of air, have been confirmed by
+my later experiments, especially those in which I have connected
+_electrical experiments_ with those on air.
+
+The electric spark taken in any kind of _oil_ produces inflammable air,
+as I was led to observe in the following manner. Having found, as will
+be mentioned hereafter, that ether doubles the quantity of any kind of
+air to which it is admitted; and being at that time engaged in a course
+of experiments to ascertain the effect of the electric matter on all the
+different kinds of air, I had the curiosity to try what it would do with
+_common air_, thus increased by means of ether. The very first spark, I
+observed, increased the quantity of this air very considerably, so that
+I had very soon six or eight times as much as I began with; and whereas
+water imbibes all the ether that is put to any kind of air, and leaves
+it without any visible change, with respect to quantity or quality, this
+air, on the contrary, was not imbibed by water. It was also very little
+diminished by the mixture of nitrous air. From whence it was evident,
+that it had received an addition of some other kind of air, of which it
+now principally consisted.
+
+In order to determine whether this effect was produced by the _wire_, or
+the _cement_ by which the air was confined (as I thought it possible
+that phlogiston might be discharged from them) I made the experiment in
+a glass syphon, fig. 19, and by that means I contrived to make the
+electric spark pass from quicksilver through the air on which I made the
+experiment, and the effect was the same as before. At one time there
+happened to be a bubble of common air, without any ether, in one part of
+the syphon, and another bubble with ether in another part of it; and it
+was very amusing to observe how the same electric sparks diminished the
+former of these bubbles, and increased the latter.
+
+It being evident that the _ether_ occasioned the difference that was
+observable in these two cases, I next proceeded to take the electric
+spark in a quantity of ether only, without any air whatever; and
+observed that every spark produced a small bubble; and though, while the
+sparks were taken in the ether itself, the generation of air was slow,
+yet when so much air was collected, that the sparks were obliged to pass
+through it, in order, to come to the ether and the quicksilver on which
+it rested, the increase was exceedingly rapid; so that, making the
+experiment in small tubes, as fig. 16, the quicksilver soon receded
+beyond the striking distance. This air, by passing through water, was
+diminished to about one third, and was inflammable.
+
+One quantity of air produced in this manner from ether I suffered to
+stand two days in water, and after that I transferred it several times
+through the water, from one vessel to another, and still found that it
+was very strongly inflammable; so that I have no doubt of its being
+genuine inflammable air, like that which is produced from metals by
+acids, or by any other chemical process.
+
+Air produced from ether, mixed both with common and nitrous air, was
+likewise inflammable; but in the case of the nitrous air, the original
+quantity bore a very small proportion to the quantity generated.
+
+Concluding that the inflammable matter in this air came from the ether,
+as being of the class of _oils_, I tried other kinds of oil, as _oil of
+olives_, _oil of turpentine_, and _essential oil of mint_, taking the
+electric spark in them, without any air to begin with, and found that
+inflammable air was produced in this manner from them all. The
+generation of air from oil of turpentine was the quickest, and from the
+oil of olives the slowest in these three cases.
+
+By the same process I got inflammable air from _spirit of wine_, and
+about as copiously as from the essential oil of mint. This air continued
+in water a whole night, and when it was transferred into another vessel
+was strongly inflammable.
+
+In all these cases the inflammable matter might be supposed to arise
+from the inflammable substances on which the experiments were made. But
+finding that, by the same process I could get inflammable air from the
+_volatile spirit of sal ammoniac_, I conclude that the phlogiston was in
+part supplied by the electric matter itself. For though, as I have
+observed before, the alkaline air which is expelled from the spirit of
+sal ammoniac be inflammable, it is so in a very slight degree, and can
+only be perceived to be so when there is a considerable quantity of it.
+
+Endeavouring to procure air from a caustic alkaline liquor, accurately
+made for me by Mr. Lane, and also from spirit of salt, I found that the
+electric spark could not be made visible in either of them; so that they
+must be much more perfect conductors of electricity than water, or other
+fluid substances. This experiment well deserves to be prosecuted.
+
+I observed before that inflammable air, by standing long in water, and
+especially by agitation in water, loses its inflammability; and that in
+the latter case, after passing through a state in which it makes some
+approach to common air (just admitting a candle to burn in it) it comes
+to extinguish a candle. I have since made another observation of this
+kind, which well deserves to be recited. It relates to the inflammable
+air generated from oak the 27th of July 1771, of which I have made
+mention before.
+
+This air I have observed to have been but weakly inflammable some months
+after it was generated, and to have been converted into pretty good or
+wholesome air by no great degree of agitation in water; but on the 27th
+of March 1773, I found the remainder of it to be exceedingly good air. A
+candle burned in it perfectly well, and it was diminished by nitrous air
+almost as much as common air.
+
+I shall conclude this section with a few miscellaneous observations of
+no great importance.
+
+Inflammable air is not changed by being made to pass many times through
+a red-hot iron tube. It is also no more diminished or changed by the
+fumes of liver of sulphur, or by the electric spark, than I have before
+observed it to have been by a mixture of iron filings and brimstone.
+When the electric spark was taken in it, it was confined by a quantity
+of water tinged blue with the juice of archil, but the colour remained
+unchanged.
+
+I put two _wasps_ into inflammable air, and let them remain there a
+considerable time, one of them near an hour. They presently ceased to
+move, and seemed to be quite dead for about half an hour after they were
+taken into the open air; but then they came to life again, and presently
+after seemed to be as well as ever they had been.
+
+
+
+
+SECTION VI.
+
+_Of FIXED AIR._
+
+
+The additions I have made to my observations on _fixed air_ are neither
+numerous nor considerable.
+
+The most important of them is a confirmation of my conjecture, that
+fixed air is capable of forming an union with phlogiston, and thereby
+becoming a kind of air that is not miscible with water. I had produced
+this effect before by means of iron filings and brimstone, fermenting in
+this kind of air; but I have since had a much more decisive and elegant
+proof of it by _electricity_. For after taking a small electric
+explosion, for about an hour, in the space of an inch of fixed air,
+confined in a glass tube one tenth of an inch in diameter, fig. 16, I
+found that when water was admitted to it, only one fourth of the air was
+imbibed. Probably the whole of it would have been rendered immiscible in
+water, if the electrical operation had been continued a sufficient time.
+This air continued several days in water, and was even agitated in water
+without any farther diminution. It was not, however, common air, for it
+was not diminished by nitrous air.
+
+By means of iron filings and brimstone I have, since my former
+experiments, procured a considerable quantity of this kind of air in a
+method something different from that which I used before. For having
+placed a pot of this mixture under a receiver, and exhausted it with a
+pump of Mr. Smeaton's construction, I filled it with fixed air, and then
+left it plunged under water; so that no common air could have access to
+it. In this manner, and in about a week, there was, as near as I can
+recollect, one sixth, or at least one eighth of the whole converted into
+a permanent air, not imbibed by water.
+
+From this experiment I expected that the same effect would have been
+produced on fixed air by the fumes of _liver of sulphur_; but I was
+disappointed in that expectation, which surprised me not a little;
+though this corresponds in some measure, to the effect of phlogiston
+exhaled from this substance on acid air. Perhaps more time may be
+requisite for this purpose, for this process was not continued more than
+a day and a night.
+
+Iron filings and brimstone, I have observed, ferment with great heat in
+nitrous air, and I have since observed that this process is attended
+with greater heat in fixed air than in common air.
+
+Though fixed air incorporated with water dissolves iron, fixed air
+without water has no such power, as I observed before. I imagined that,
+if it could have dissolved iron, the phlogiston would have united with
+the air, and have made it immiscible with water, as in the former
+instances; but after being confined in a phial full of nails from the
+15th of December to the 4th of October following, neither the iron nor
+the air appeared to have been affected by their mutual contact.
+
+Having exposed equal quantities of common and fixed air, in equal and
+similar cylindrical glass vessels, to equal degrees of heat, by placing
+them before a fire, and frequently changing their situations, I observed
+that they were expanded exactly alike, and when removed from the fire
+they both recovered their former dimensions.
+
+Having had some small suspicion that liver of sulphur, besides emitting
+phlogiston, might also yield some fixed air (which is known to be
+contained in the salt of tartar from which it is made) I mixed the two
+ingredients, viz. salt of tartar and brimstone, and putting them into a
+thin phial, and applying the flame of a candle to it, so as to form the
+liver of sulphur, I received the air that came from it in this process
+in a vessel of quicksilver. In this manner I procured a very
+considerable quantity of fixed air, so that I judged it was all
+discharged from the tartar. But though it is possible that a small
+quantity of it may remain in liver of sulphur, when it is made in the
+most perfect manner, it is not probable that it can be expelled without
+heat.
+
+
+
+
+SECTION VII.
+
+MISCELLANEOUS EXPERIMENTS.
+
+
+1. It is something extraordinary that, though ether, as I found, cannot
+be made to assume the form of air (the vapour arising from it by heat,
+being soon condensed by cold, even in quicksilver) yet that a very small
+quantity of ether put to any kind of air, except the acid, and alkaline,
+which it imbibes, almost instantly doubles the apparent quantity of it;
+but upon passing this air through water, it is presently reduced to its
+original quantity again, with little or no change of quality.
+
+I put about the quantity of half a nut-shell full of ether, inclosed in
+a glass tube, through a body of quicksilver, into an ounce measure of
+common air, confined by quicksilver; upon which it presently began to
+expand, till it occupied the space of two ounce measures. It then
+gradually contracted about one sixth of an ounce measure. Putting more
+ether to it, it again expanded to two ounce measures; but no more
+addition of ether would make it expand any farther. Withdrawing the
+quicksilver, and admitting water to this air, without any agitation, it
+began to be absorbed; but only about half an ounce measure had
+disappeared after it had stood an hour in the water. But by once passing
+it through water the air was reduced to its original dimensions. Being
+tried by a mixture of nitrous air, it appeared not to be so good as
+fresh air, though the injury it had received was not considerable.
+
+All the phenomena of dilatation and contraction were nearly the same,
+when, instead of common air, I used nitrous air, fixed air, inflammable
+air, or any species of phlogisticated common air. The quantity of each
+of these kinds of air was nearly doubled while they were kept in
+quicksilver, but fixed air was not so much increased as the rest, and
+phlogisticated air less; but after passing through the water, they
+appeared not to have been sensibly changed by the process.
+
+2. Spirit of wine yields no air by means of heat, the vapours being soon
+condensed by cold, like the vapour of water; yet when, in endeavouring
+to procure air from it, I made it boil, and catched the air which had
+rested on the surface of the spirit, and which had been expelled by the
+heat together with the vapour, in a vessel of quicksilver, and
+afterwards admitted acid air to it, the vessel was filled with white
+fumes, as if there had been a mixture of alkaline air along with it. To
+what this appearance was owing I cannot tell, and indeed I did not
+examine into it.
+
+3. Having been informed by Dr. Small and Mr. Bolton of Birmingham, that
+paper dipped in a solution of copper in spirit of nitre would take fire
+with a moderate heat (a fact which I afterwards found mentioned in the
+Philosophical Transactions) it occurred to me that this would be very
+convenient for experiments relating to _ignition_ in different kinds of
+air; and indeed I found that it was easily fired, either by a burning
+lens, or the approach of red-hot iron on the outside of the phial in
+which it was contained, and that any part of it being once fired, the
+whole was presently reduced to ashes; provided it was previously made
+thoroughly dry, which, however, it is not very easy to do.
+
+With this preparation, I found that this paper burned freely in all
+kinds of air, but not in _vacuo_, which is also the case with gunpowder;
+and, as I have in effect observed before, all the kinds of air in which
+this paper was burned received an addition to their bulk, which
+consisted partly of nitrous air, from the nitrous precipitate, and
+partly of inflammable air, from the paper. As some of the circumstances
+attending the ignition of this paper in some of the kinds of air were a
+little remarkable, I shall just recite them.
+
+Firing this paper in _inflammable_ air, which it did without any
+ignition of the inflammable air itself, the quantity increased
+regularly, till the phial in which the process was made was nearly full;
+but then it began to decrease, till one third of the whole quantity
+disappeared.
+
+A piece of this paper being put to three ounce measures of _acid_ air, a
+great part of it presently turned yellow, and the air was reduced to one
+third of the original quantity, at the same time becoming reddish,
+exactly like common air in a phial containing smoking spirit of nitre.
+After this, by the approach of hot iron, I set fire to the paper;
+immediately upon which there was a production of air which more than
+filled the phial. This air appeared, upon examination, to be very little
+different from pure nitrous air. I repeated this experiment with the
+same event.
+
+Paper dipped in a solution of mercury, zinc, or iron, in nitrous acid,
+has, in a small degree, the same property with paper dipped in a
+solution of copper in the same acid.
+
+4. Gunpowder is also fired in all kinds of air, and, in the quantity in
+which I tried it, did not make any sensible change in them, except that
+the common air in which it was fired would not afterwards admit a candle
+to burn in it. In order to try this experiment I half exhausted a
+receiver, and then with a burning-glass fired the gunpowder which had
+been previously put into it. By this means I could fire a greater
+quantity of gunpowder in a small quantity of air, and avoid the hazard
+of blowing up, and breaking my receiver.
+
+I own that I was rather afraid of firing gunpowder in inflammable air,
+but there was no reason for my fear; for it exploded quite freely in
+this air, leaving it, in all respects, just as it was before.
+
+In order to make this experiment, and indeed almost all the experiments
+of firing gunpowder in different kinds of air, I placed the powder upon
+a convenient stand within my receiver, and having carefully exhausted it
+by a pump of Mr. Smeaton's construction, I filled the receiver with any
+kind of air by the apparatus described, p. 19, fig. 14, taking the
+greatest care that the tubes, &c. which conveyed the air should contain
+little or no common air. In the experiment with inflammable air a
+considerable mixture of common air would have been exceedingly
+hazardous: for, by that assistance, the inflammable air might have
+exploded in such a manner, as to have been dangerous to the operator.
+Indeed, I believe I should not have ventured to have made the experiment
+at all with any other pump besides Mr. Smeaton's.
+
+Sometimes, I filled a glass vessel with quicksilver, and introduced the
+air to it, when it was inverted in a bason of quicksilver. By this means
+I intirely avoided any mixture of common air; but then it was not easy
+to convey the gunpowder into it, in the exact quantity that was
+requisite for my purpose. This, however, was the only method by which I
+could contrive to fire gunpowder in acid or alkaline air, in which it
+exploded just as it did in nitrous or fixed air.
+
+I burned a considerable quantity of gunpowder in an exhausted receiver
+(for it is well known that it will not explode in it) but the air I got
+from it was very inconsiderable, and in these circumstances was
+necessarily mixed with common air. A candle would not burn in it.
+
+
+
+
+SECTION VIII.
+
+_QUERIES, SPECULATIONS, and HINTS._
+
+
+I begin to be apprehensive lest, after being considered as a _dry
+experimenter_, I should pass, with many of my readers, into the opposite
+character of a _visionary theorist_. A good deal of theory has been
+interspersed in the course of this work, but, not content with this, I
+am now entering upon a long section, which contains nothing else.
+
+The conjectures that I have ventured to advance in the body of the work
+will, I hope, be found to be pretty well supported by facts; but the
+present section will, I acknowledge, contain many _random thoughts_. I
+have, however, thrown them together by themselves, that readers of less
+imagination, and who care not to advance beyond the regions of plain
+fact, may, if they please, proceed no farther, that their delicacy be
+not offended.
+
+In extenuation of my offence, let it, however, be considered, that
+_theory_ and _experiment_ necessarily go hand in hand, every process
+being intended to ascertain some particular _hypothesis_, which, in
+fact, is only a conjecture concerning the circumstances or the cause of
+some natural operation; consequently that the boldest and most original
+experimenters are those, who, giving free scope to their imaginations,
+admit the combination of the most distant ideas; and that though many of
+these associations of ideas, will be wild and chimerical, yet that
+others will have the chance of giving rise to the greatest and most
+capital discoveries; such as very cautious, timid, sober, and
+slow-thinking people would never have come at.
+
+Sir Isaac Newton himself, notwithstanding the great advantage which he
+derived from a habit of _patient thinking_, indulged bold and excentric
+thoughts, of which his Queries at the end of his book of Optics are a
+sufficient evidence. And a quick conception of distant analogies, which
+is the great key to unlock the secret of nature, is by no means
+incompatible with the spirit of _perseverance_, in investigations
+calculated to ascertain and pursue those analogies.
+
+
+Sec. 1. _Speculations concerning the CONSTITUENT PRINCIPLES of the
+different kinds of AIR, and the CONSTITUTION and ORIGIN of the
+ATMOSPHERE, &c._
+
+All the kinds of air that appear to me to be essentially distinct from
+each other are _fixed air_, _acid_ and _alkaline_; for these, and
+another principle, called _phlogiston_, which I have not been able to
+exhibit in the form of _air_, and which has never yet been exhibited by
+itself in _any form_, seem to constitute all the kinds of air that I am
+acquainted with.
+
+Acid air and phlogiston constitute an air which either extinguishes
+flame, or is itself inflammable, according, probably, to the quantity of
+phlogiston combined in it, or the mode of combination. When it
+extinguishes flame, it is probably so much charged with the phlogistic
+matter, as to take no more from a burning candle, which must, therefore,
+necessarily go out in it. When it is inflammable, it is probably so much
+charged with phlogiston, that the heat communicated by a burning candle
+makes it immediately separate itself from the other principle with which
+it was united, in which separation _heat_ is produced, as in other cases
+of ignition; the action and reaction, which necessarily attends the
+separation of the constituent principles, exciting probably a vibratory
+motion in them.
+
+Since inflammable, air, by agitation in water, first comes to lose its
+inflammability, so as to be fit for respiration, and even to admit a
+candle to burn in it, and then comes to extinguish a candle; it seems
+probable that water imbibes a great part of this extraordinary charge of
+phlogiston. And that water _can_ be impregnated with phlogiston, is
+evident from many of my experiments, especially those in which metals
+were calcined over it.
+
+Water having this affinity with phlogiston, it is probable that it
+always contains a considerable portion of it; which phlogiston having a
+stronger affinity with the acid air, which is perhaps the basis of
+common air, may by long agitation be communicated to it, so as to leave
+it over saturated, in consequence of which it will extinguish a candle.
+
+It is possible, however, that inflammable air and air which extinguishes
+a candle may differ from one another in the _mode_ of the combination of
+these two constituent principles, as well as in the proportional
+quantity of each; and by agitation in water, or long standing, that mode
+of combination may change. This we know to be the case with other
+substances, as with _milk_, from which, by standing only, _cream_ is
+separated; which by agitation becomes _butter_. Also many substances,
+being at rest, putrefy, and thereby become quite different from what
+they were before. If this be the case with inflammable air, the water
+may imbibe either of the constituent parts, whenever any proportion of
+it is spontaneously separated from the rest; and should this ever be
+that phlogiston, with which air is but slightly overcharged, as by the
+burning of a candle, it will be recovered to a state in which a candle
+may burn in it again.
+
+It will be observed, however, that it was only in one instance that I
+found that strong inflammable air, in its transition to a state in which
+it extinguishes a candle, would admit a candle to burn in it, and that
+was very faintly; that then the air was far from being pure, as appeared
+by the test of nitrous air; and that it was only from a particular
+quantity of inflammable air which I got from oak, and which had stood a
+long time in water, that I ever got air which was as pure as common air.
+Indeed, it is much more easy to account for the passing of inflammable
+air into a state in which it extinguishes candles, without any
+intermediate state, in which it will admit a candle to burn in it, than
+otherwise. This subject requires and deserves farther investigation. It
+will also be well worth while to examine what difference the agitation
+of air in natural or artificial _sea-water_ will occasion.
+
+Since acid air and phlogiston make inflammable air, and since
+inflammable air is convertible into air fit for respiration, it seems
+not to be improbable, that these two ingredients are the only essential
+principles of common air. For this change is produced by agitation in
+water only, without the addition of any fixed air, though this kind of
+air, like various other things of a foreign nature, may be combined with
+it.
+
+Considering also what prodigious quantities of inflammable air are
+produced by the burning of small pieces of wood or pit-coal, it may not
+be improbable but that the _volcanos_, with which there are evident
+traces of almost the whole surface of the earth having been overspread,
+may have been the origin of our atmosphere, as well as (according to the
+opinion of some) of all the solid land.
+
+The superfluous phlogiston of the air, in the state in which it issues
+from volcanos, may have been imbibed by the waters of the sea, which it
+is probable originally covered the surface of the earth, though part of
+it might have united with the acid vapour exhaled from the sea, and by
+this union have made a considerable and valuable addition to the common
+mass of air; and the remainder of this over-charge of phlogiston may
+have been imbibed by plants as soon as the earth was furnished with
+them.
+
+That an acid vapour is really exhaled from the sea, by the heat of the
+sun, seems to be evident from the remarkably different states of the
+atmosphere, in this respect, in hot and cold climates. In Hudson's bay,
+and also in Russia, it is said, that metals hardly ever rust, whereas
+they are remarkably liable to rust in Barbadoes, and other islands
+between the tropics. See Ellis's Voyage, p. 288. This is also the case
+in places abounding with salt-springs, as Nantwich in Cheshire.
+
+That mild air should consist of parts of so very different a nature as
+an acid vapour and phlogiston, one of which is so exceedingly corrosive,
+will not appear surprising to a chemist, who considers the very strong
+affinity which these two principles are known to have with each other,
+and the exceedingly different properties which substances composed by
+them possess. This is exemplified in common _sulphur_, which is as mild
+as air, and may be taken into the stomach with the utmost safety, though
+nothing can be more destructive than one of its constituent parts,
+separately taken, viz. oil of vitriol. Common air, therefore,
+notwithstanding its mildness, may be composed of similar principles, and
+be a real _sulphur_.
+
+That the fixed air which makes part of the atmosphere is not presently
+imbibed by the waters of the sea, on which it rests, may be owing to the
+union which this kind of air also appears to be capable of forming with
+phlogiston. For fixed air is evidently of the nature of an acid; and it
+appears, in fact, to be capable of being combined with phlogiston, and
+thereby of constituting a species of air not liable to be imbibed by
+water. Phlogiston, however, having a stronger affinity with acid air,
+which I suppose to be the basis of common air, it is not surprising
+that, uniting with this, in preference to the fixed air, the latter
+should be precipitated, whenever a quantity of common air is made
+noxious by an over-charge of phlogiston.
+
+The fixed air with which our atmosphere abounds may also be supplied by
+volcanos, from the vast masses of calcareous matter lodged in the earth,
+together with inflammable air. Also a part of it may be supplied from
+the fermentation of vegetables upon the surface of it. At present, as
+fast as it is precipitated and imbibed by one process, it may be set
+loose by others.
+
+Whether there be, upon, the whole, an increase or a decrease of the
+general mass of the atmosphere is not easy to conjecture, but I should
+imagine that it rather increases. It is true that many processes
+contribute to a great visible diminution of common air, and that when by
+other processes it is restored to its former wholesomeness, it is not
+increased in its dimensions; but volcanos and fires still supply vast
+quantities of air, though in a state not yet fit for respiration; and it
+will have been seen in my experiments, that vegetable and animal
+substances, dissolved by putrefaction, not only emit phlogiston, but
+likewise yield a considerable quantity of permanent elastic air,
+overloaded indeed with phlogiston, as might be expected, but capable of
+being purified by those processes in nature by which other noxious air
+is purified.
+
+That particles are continually detaching themselves from the surfaces of
+all solid bodies, even the metallic ones, and that these particles
+constitute the most permanent part of the atmosphere, as Sir Isaac
+Newton supposed, does not appear to me to be at all probable.
+
+My readers will have observed, that not only is common air liable to be
+diminished by a mixture of nitrous air, but likewise air originally
+produced from inflammable air, and even from nitrous air itself, which
+never contained any fixed air. From this it may be inferred, that the
+whole of the diminution of common air by phlogiston is not owing to the
+precipitation of fixed air, but from a real contraction of its
+dimensions, in consequence of its union with phlogiston. Perhaps an
+accurate attention to the specific gravity of air procured from these
+different materials, and in these different states, may determine this
+matter, and assist us in investigating the nature of phlogiston.
+
+In what _manner_ air is diminished by phlogiston, independent of the
+precipitation of any of its constituent parts, is not easy to conceive;
+unless air thus diminished be heavier than air not diminished, which I
+did not find to be the case. It deserves, however, to be tried with more
+attention. That phlogiston should communicate absolute _levity_ to the
+bodies with which it is combined, is a supposition that I am not willing
+to have recourse to, though it would afford an easy solution of this
+difficulty.
+
+I have likewise observed, that a mouse will live almost as long in
+inflammable air, when it has been agitated in water, and even before it
+has been deprived of all its inflammability, as in common air; and yet
+that in this state it is not, perhaps, so much diminished by nitrous air
+as common air is. In this case, therefore, the diminution seems to have
+been occasioned by a contraction of dimensions, and not by a loss of any
+constituent part; so that the air is really better, that is, more fit
+for respiration, than, by the test of nitrous air, it would seem to be.
+
+If this be the case (for it is not easy to judge with accuracy by
+experiments with small animals) nitrous air will be an accurate test of
+the goodness of _common air_ only, that is, air containing a
+considerable proportion of fixed air. But this is the most valuable
+purpose for which a test of the goodness of air can be wanted. It will
+still, indeed, serve for a measure of the goodness of air that does not
+contain fixed air; but, a smaller degree of diminution in this case,
+must be admitted to be equivalent to a greater diminution in the other.
+
+As I could never, by means of growing vegetables, bring air which had
+been thoroughly noxious to so pure a state as that a candle would burn
+in it, it may be suspected that something else besides _vegetation_ is
+necessary to produce this effect. But it should be considered, that no
+part of the common atmosphere can ever be in this highly noxious state,
+or indeed in a state in which a candle will not burn in it; but that
+even air reduced to this state, either by candles actually burning out
+in it, or by breathing it, has never failed to be perfectly restored by
+vegetation, at least so far that candles would burn in it again, and, to
+all appearance, as well, and as long as ever; so that the growing
+vegetables, with which the surface of the earth is overspread, may, for
+any thing that appears to the contrary, be a cause of the purification
+of the atmosphere sufficiently adequate to the effect.
+
+It may likewise be suspected, that since _agitation in water_ injures
+pure common air, the agitation of the sea may do more harm than good in
+this respect. But it requires a much more violent and longer continued
+agitation of air in water than is ever occasioned by the waves of the
+sea to do the least sensible injury to it. Indeed a light agitation of
+air in _putrid water_ injures it very materially; but if the water be
+sweet, this effect is not produced, except by a long and tedious
+operation, whereas it requires but a very short time, in comparison, to
+restore a quantity of any of the most noxious kinds of air to a very
+great degree of wholesomeness by the same process.
+
+Dr. Hales found that he could breathe the same air much longer when, in
+the course of his respiration, it was made to pass through several folds
+of cloth dipped in vinegar, in a solution of sea-salt, or in salt of
+tartar, especially the last. Statical Essays, vol. 1. p. 266. The
+experiment is valuable, and well deserves to be repeated with a greater
+variety of circumstances. I imagine that the effect was produced by
+those substances, or by the _water_ which they attracted from the air,
+imbibing the phlogistic matter discharged from the lungs. Perhaps the
+phlogiston may unite with the watery part of the atmosphere, in
+preference to any other part of it, and may by that means be more easily
+transferred to such salts as imbibe moisture.
+
+Sir Isaac Newton defines _flame_ to be _fumus candens_, considering all
+_smoke_ as being of the same nature, and capable of ignition. But the
+smoke of common fuel consists of two very different things. That which
+rises first is mere _water_, loaded with some of the grosser parts of
+the fuel, and is hardly more capable of becoming red hot than water
+itself; but the other kind of smoke, which alone is capable of ignition,
+is properly _inflammable air_, which is also loaded with other
+heterogeneous matter, so as to appear like a very dense smoke. A lighted
+candle soon shews them to be essentially different from each other. For
+one of them instantly takes fire, whereas the other extinguishes a
+candle.
+
+It is remarkable that gunpowder will take fire, and explode in all kinds
+of air, without distinction, and that other substances which contain
+_nitre_ will burn freely in those circumstances. Now since nothing can
+burn, unless there be something at hand to receive the phlogiston, which
+is set loose in the act of ignition, I do not see how this fact can be
+accounted for, but by supposing that the acid of nitre, being peculiarly
+formed to unite with phlogiston, immediately receives it. And if the
+sulphur, which is thereby formed, be instantly decomposed again, as the
+chemists in general say, thence comes the explosion of gunpowder, which,
+however, requires the reaction of some incumbent atmosphere, and without
+which the materials will only _melt_, and be _dispersed_ without
+explosion.
+
+Nitrous air seems to consist of the nitrous acid vapour united to
+phlogiston, together, perhaps, with some small portion of the metallic
+calx; just as inflammable air consists of the vitriolic or marine acid,
+and the same phlogistic principle. It should seem, however, that
+phlogiston has a stronger affinity with the marine acid, if that be the
+basis of common air; for nitrous air being admitted to common air, it is
+immediately decomposed; probably by the phlogiston joining with the acid
+principle of the common air, while the fixed air which it contained is
+precipitated, and the acid of the nitrous air is absorbed by the water
+in which the mixture is made, or unites with any volatile alkali that
+happens to be at hand.
+
+This, indeed, is hardly agreeable to the hypothesis of most chemists,
+who suppose that the nitrous acid is stronger than the marine, so as to
+be capable of dislodging it from any base with which it may be combined;
+but it agrees with my own experiments on marine acid air, which shew
+that, in many cases, this _weaker acid_, as it is called, is capable of
+separating both the vitriolic and the nitrous acids from the phlogiston
+with which they are combined.
+
+On the other hand, the solution of metals in the different acids seems
+to shew, that the nitrous acid forms a closer union with phlogiston than
+the other two; because the air which is formed by the nitrous acid is
+not inflammable, like that which is produced by the oil of vitriol, or
+the spirit of salt. Also, the same weight of iron does not yield half
+the quantity of nitrous air that it does of inflammable.
+
+The great diminution of nitrous air by phlogiston is not easily
+accounted for, unless we suppose that its superabundant acid, uniting
+more intimately with the phlogiston, constitutes a species of _sulphur_
+that is not easily perceived or catched; though, in the process with
+iron, and also in that with liver of sulphur, part of the redundant
+phlogiston forms such an union with the acid as gives it a kind of
+inflammability.
+
+It appears to me to be very probable, that the spirit of nitre might be
+exhibited in the form of _air_, if it were possible to find any fluid by
+which it could be confined; but it unites with quicksilver as well as
+with water, so that when, by boiling the spirit of nitre, the fumes are
+driven through the glass tube, fig. 8, they instantly seize upon the
+quicksilver through which they are to be conveyed, and uniting with it,
+form a substance that stops up the tube: a circumstance which has more
+than once exposed me to very disagreeable accidents, in consequence of
+the bursting of the phials.
+
+I do not know any inquiry more promising than the investigation of the
+properties of _nitre_, the _nitrous acid_, and _nitrous air_. Some of
+the most wonderful phenomena in nature are connected with them, and the
+subject seems to be fully within our reach.
+
+
+Sec. 2. _Speculations arising from the consideration of the similarity of
+the ELECTRIC MATTER and PHLOGISTON._
+
+There is nothing in the history of philosophy more striking than the
+rapid progress of _electricity_. Nothing ever appeared more trifling
+than the first effects which were observed of this agent in nature, as
+the attraction and repulsion of straws, and other light substances. It
+excited more attention by the flashes of _light_ which it exhibited. We
+were more seriously alarmed at the electrical _shock_, and the effects
+of the electrical _battery_; and we were astonished to the highest
+degree by the discovery of the similarity of electricity with
+_lightning_, and the _aurora borealis_, with the connexion it seems to
+have with _water-spouts_, _hurricanes_, and _earthquakes_, and also with
+the part that is probably assigned to it in the system of _vegetation_,
+and other the most important processes in nature.
+
+Yet, notwithstanding all this, we have been, within a few years, more
+puzzled than ever with the electricity of the _torpedo_, and of the
+_anguille temblante_ of Surinam, especially since that most curious
+discovery of Mr. Walsh's, that the former of these wonderful fishes has
+the power of giving a proper electrical shock; the electrical matter
+which proceeds from it performing a real circuit from one part of the
+animal to the other; while both the fish which performs this experiment
+and all its apparatus are plunged in water, which is known to be a
+conducting substance.
+
+Perhaps, however, by considering this fact in connexion with a few
+others, and especially with what I have lately observed concerning the
+identity of electricity and phlogiston, a little light may be thrown
+upon this subject, in consequence of which we may be led to consider
+electricity in a still more important light. Many of my readers, I am
+aware, will smile at what I am going to advance; but the apprehension of
+this shall not interrupt my speculations, how chimerical soever they may
+be thought to be.
+
+The facts, the consideration of which I would combine with that of the
+electricity of the torpedo, are the following.
+
+First, The remarkable electricity of the feathers of a paroquet,
+observed by Mr. Hartmann, an account of which may be seen in Mr.
+Rozier's Journal for Sept. 1771. p. 69. This bird never drinks, but
+often washes itself; but the person who attended it having neglected to
+supply it with water for this purpose, its feathers appeared to be
+endued with a proper electrical virtue, repelling one another, and
+retaining their electricity a long time after they were plucked from the
+body of the bird, just as they would have done if they had received
+electricity from an excited glass tube.
+
+Secondly, The electric matter directed through the body of any muscle
+forces it to contract. This is known to all persons who attend to what
+is called the electrical shock; which certainly occasions a proper
+_convulsion_, but has been more fully illustrated by Father Beccaria.
+See my _History of Electricity_, p. 402.
+
+Lastly, Let it be considered that the proper nourishment of an animal
+body, from which the source and materials of all muscular motion must be
+derived, is probably some modification of phlogiston. Nothing will
+nourish that does not contain phlogiston, and probably in such a state
+as to be easily separated from it by the animal functions.
+
+That the source of muscular motion is phlogiston is still more probable,
+from the consideration of the well known effects of vinous and
+spirituous liquors, which consist very much of phlogiston, and which
+instantly brace and strengthen the whole nervous and muscular system;
+the phlogiston in this case being, perhaps, more easily extricated, and
+by a less tedious animal process, than in the usual method of extracting
+it from mild aliments. Since, however, the mildest aliments do the same
+thing more slowly and permanently, that spirituous liquors do suddenly
+and transiently, it seems probable that their operation is ultimately
+the same.
+
+This conjecture is likewise favoured by my observation, that respiration
+and putrefaction affect common air in the same manner, and in the same
+manner in which all other processes diminish air and make it noxious,
+and which agree in nothing but the emission of phlogiston. If this be
+the case, it should seem that the phlogiston which we take in with our
+aliment, after having discharged its proper function in the animal
+system (by which it probably undergoes some unknown alteration) is
+discharged as _effete_ by the lungs into the great common _menstruum_,
+the atmosphere.
+
+My conjecture suggested (whether supported or not) by these facts, is,
+that animals have a power of converting phlogiston, from the state in
+which they receive it in their nutriment, into that state in which it is
+called the electrical fluid; that the brain, besides its other proper
+uses, is the great laboratory and repository for this purpose; that by
+means of the nerves this great principle, thus exalted, is directed into
+the muscles, and forces them to act, in the same manner as they are
+forced into action when the electric fluid is thrown into them _ab
+extra_.
+
+I farther suppose, that the generality of animals have no power of
+throwing this generated electricity any farther than the limits of their
+own system; but that the _torpedo_, and animals of a similar
+construction, have likewise the power, by means of an additional
+apparatus, of throwing it farther, so as to affect other animals, and
+other substances at a distance from them.
+
+In this case, it should seem that the electric matter discharged from
+the animal system (by which it is probably more exhausted and fatigued
+than by ordinary muscular motion) would never return to it, at least so
+as to be capable of being made use of a second time, and yet if the
+structure of these animals be such as that the electric matter shall
+dart from one part of them only, while another part is left suddenly
+deprived of it, it may make a circuit, as in the Leyden phial.
+
+As to the _manner_ in which the electric matter makes a muscle contract,
+I do not pretend to have any conjecture worth mentioning. I only imagine
+that whatever can make the muscular fibres recede from one another
+farther than the parts of which they consist, must have this effect.
+
+Possibly, the _light_ which is said to proceed from some animals, as
+from cats and wild beasts, when they are in pursuit of their prey in the
+night, may not only arise, as it has hitherto been supposed to do, from
+the friction of their hairs or bristles, &c. but that violent muscular
+exertion may contribute to it. This may assist them occasionally to
+catch their prey; as glow-worms, and other insects, are provided with a
+constant light for that purpose, to the supply of which light their
+nutriment may also contribute.
+
+I would not even say that the light which is said to have proceeded from
+some human bodies, of a particular temperament, and especially on some
+extraordinary occasions, may not have been of the electrical kind, that
+is, produced independently of friction, or with less friction than
+would have produced it in other persons; as in those cases related by
+Bartholin in his treatice _De luce animalium_. See particularly what he
+says concerning Theodore king of the Goths, p. 54, concerning Gonzaga
+duke of Mantua, p. 57, and Gothofred Antonius, p. 123: But I would not
+have my readers suppose that I lay much stress upon stories no better
+authenticated than these.
+
+The electric matter in passing through non-conducting substances always
+emits _light_. This light I have been sometimes inclined to suspect
+might have been supplied from the substance through which it passes. But
+I find that after the electric spark has diminished a quantity of air as
+much as it possibly can, so that it has no more visible effect upon it,
+the electric light in that air is not at all lessened. It is probable,
+therefore, that electric light comes from the electric matter itself;
+and this being a modification of phlogiston, it is probable that _all
+light_ is a modification of phlogiston also. Indeed, since no other
+substances besides such as contain phlogiston are capable of ignition,
+and consequently of becoming luminous, it was on this account pretty
+evident, prior to these deductions from electrical phenomena, that light
+and phlogiston are the same thing, in different forms or states.
+
+It appears to me that _heat_ has no more proper connexion with
+phlogiston than it has with water, or any other constituent part of
+bodies; but that it is a state into which the parts of bodies are thrown
+by their action and reaction with respect to one another; and probably
+(as the English philosophers in general have supposed) the heated state
+of bodies may consist of a subtle vibratory motion of their parts. Since
+the particles which constitute light are thrown from luminous bodies
+with such amazing velocity, it is evident that, whatever be the cause of
+such a projection, the reaction consequent upon it must be considerable.
+This may be sufficient not only to keep up, but also to increase the
+vibration of the parts of those bodies in which the phlogiston is not
+very firmly combined; and the difference between the substances which
+are called _inflammable_ and others which also contain phlogiston may be
+this, that in the former the heat, or the vibration occasioned by the
+emission of their own phlogiston, may be sufficient to occasion the
+emission of more, till the whole be exhausted; that is, till the body be
+reduced to ashes. Whereas in bodies which are not inflammable, the heat
+occasioned by the emission of their own phlogiston may not be sufficient
+for this purpose, but an additional heat _ab extra_ may be necessary.
+
+Some philosophers dislike the term _phlogiston_; but, for my part, I can
+see no objection to giving that, or any other name, to a _real
+something_, the presence or absence of which makes so remarkable
+difference in bodies, as that of _metallic calces_ and _metals_, _oil of
+vitriol_ and _brimstone_, &c. and which may be transferred from one
+substance to another, according to certain known laws, that is, in
+certain definite circumstances. It is certainly hard to conceive how any
+thing that answers this description can be only a mere _quality_, or
+mode of bodies, and not _substance_ itself, though incapable of being
+exhibited alone. At least, there can be no harm in giving this name to
+any _thing_, or any _circumstance_ that is capable of producing these
+effects. If it should hereafter appear not to be a substance, we may
+change our phraseology, if we think proper.
+
+On the other hand I dislike the use of the term _fire_, as a constituent
+principle of natural bodies, because, in consequence of the use that has
+generally been made of that term, it includes another thing or
+circumstance, viz. _heat_, and thereby becomes ambiguous, and is in
+danger of misleading us. When I use the term phlogiston, as a principle
+in the constitution of bodies, I cannot mislead myself or others,
+because I use one and the same term to denote only one and the same
+_unknown cause_ of certain well-known effects. But if I say that _fire_
+is a principle in the constitution of bodies, I must, at least,
+embarrass myself with the distinction of fire _in a state of action_,
+and fire _inactive_, or quiescent. Besides I think the term phlogiston
+preferable to that of fire, because it is not in common use, but
+confined to philosophy; so that the use of it may be more accurately
+ascertained.
+
+Besides, if phlogiston and the electric matter be the same thing, though
+it cannot be exhibited alone, in a _quiescent state_, it may be
+exhibited alone under one of its modifications, when it is in _motion_.
+And if light be also phlogiston, or some modification or subdivision of
+phlogiston, the same thing is capable of being exhibited alone in this
+other form also.
+
+In my paper on the _conducting power of charcoal_, (See Philosophical
+Transactions, vol. 60. p. 221) I observed that there is a remarkable
+resemblance between metals and charcoal; as in both these substances
+there is an intimate union of phlogiston with an earthy base; and I said
+that, had there been any phlogiston in _water_, I should have concluded,
+that there had been no conducting power in nature, but in consequence of
+an union of this principle with some base; for while metals have
+phlogiston they conduct electricity, but when they are deprived of it
+they conduct no longer. Now the affinity which I have observed between
+phlogiston and water leads me to conclude that water, in its natural
+state, does contain some portion of phlogiston; and according to the
+hypothesis just now mentioned they must be intimately united, because
+water is not inflammable.
+
+I think, therefore, that after this state of hesitation and suspence, I
+may venture to lay it down as a characteristic distinction between
+conducting and non-conducting substances, that the former contain
+phlogiston intimately united with some base, and that the latter, if
+they contain phlogiston at all, retain it more loosely. In what manner
+this circumstance facilitates the passing of the electric matter through
+one substance, and obstructs its passage through another, I do not
+pretend to say. But it is no inconsiderable thing to have advanced but
+_one step_ nearer to an explanation of so very capital a distinction of
+natural bodies, as that into conductors and non-conductors of
+electricity.
+
+I beg leave to mention in this place, as favourable to this hypothesis,
+a most curious discovery made very lately by Mr. Walsh, who being
+assisted by Mr. De Luc to make a more perfect vacuum in the double or
+arched barometer, by boiling the quicksilver in the tube, found that the
+electric spark or shock would no more pass through it, than through a
+stick of solid glass. He has also noted several circumstances that
+affect this vacuum in a very extraordinary manner. But supposing that
+vacuum to be perfect, I do not see how we can avoid inferring from the
+fact, that some _substance_ is necessary to conduct electricity; and
+that it is not capable, by its own expansive power, of extending itself
+into spaces void of all matter, as has generally been supposed, on the
+idea of there being nothing to obstruct its passage.
+
+Indeed if this was the case, I do not see how the electric matter could
+be retained within the body of the earth, or any of the planets, or
+solid orbs of any kind. In nature we see it make the most splendid
+appearance in the upper and thinner regions of the atmosphere, just as
+it does in a glass tube nearly exhausted; but if it could expand itself
+beyond that degree of rarity, it would necessarily be diffused into the
+surrounding vacuum, and continue and be condensed there, at least in a
+greater proportion than in or near any solid body, as Newton supposed
+concerning his _ether_.
+
+If that mode of vibration which constitutes heat be the means of
+converting phlogiston from that state in which it makes a part of solid
+bodies, and eminently contributes to the firmness of their texture into
+that state in which it diminishes common air; may not that peculiar kind
+of vibration by which Dr. Hartley supposes the brain to be affected, and
+by which he endeavours to explain all the phenomena of sensation, ideas,
+and muscular motion, be the means by which the phlogiston, which is
+conveyed into the system by nutriment, is converted into that form or
+modification of it of which the electric fluid consists.
+
+These two states of phlogiston may be conceived to resemble, in some
+measure, the two states of fixed air, viz. elastic, or non-elastic; a
+solid, or a fluid.
+
+
+
+
+THE APPENDIX.
+
+
+In this Appendix I shall present the reader with the communications of
+several of my friends on the subject of the preceding work. Among them I
+should with pleasure have inserted some curious experiments, made by Dr.
+Hulme of Halifax, on the air extracted from Buxton water, and on the
+impregnation of several fluids, with different kinds of air; but that he
+informs me he proposes to make a separate publication on the subject.
+
+
+NUMBER I.
+
+     _EXPERIMENTS made by Mr. Hey to prove that there is no OIL of
+     VITRIOL in water impregnated with FIXED AIR._
+
+It having been suggested, that air arising from a fermenting mixture of
+chalk and oil of vitriol might carry up with it a small portion of the
+vitriolic acid, rendered volatile by the act of fermentation; I made the
+following experiments, in order to discover whether the acidulous taste,
+which water impregnated with such air affords, was owing to the presence
+of any acid, or only to the fixed air it had absorbed.
+
+EXPERIMENT I.
+
+I mixed a tea-spoonful of syrup of violets with an ounce of distilled
+water, saturated with fixed air procured from chalk by means of the
+vitriolic acid; but neither upon the first mixture, nor after standing
+24 hours, was the colour of the syrup at all changed, except by its
+simple dilution.
+
+EXPERIMENT II.
+
+A portion of the same distilled water, unimpregnated with fixed air, was
+mixed with the syrup in the same proportion: not the least difference in
+colour could be perceived betwixt this and the above-mentioned mixture.
+
+EXPERIMENT III.
+
+One drop of oil of vitriol being mixed with a pint of the same distilled
+water, an ounce of this water was mixed with a tea-spoonful of the
+syrup. This mixture was very distinguishable in colour from the two
+former, having a purplish cast, which the others wanted.
+
+EXPERIMENT IV.
+
+The distilled water impregnated with so small a quantity of vitriolic
+acid, having a more agreeable taste than when alone, and yet manifesting
+the presence of an acid by means of the syrup of violets; I subjected it
+to some other tests of acidity. It formed curds when agitated with soap,
+lathered with difficulty, and very imperfectly; but not the least
+ebullition could be discovered upon dropping in spirit of sal ammoniac,
+or solution of salt of tartar, though I had taken care to render the
+latter free from causticity by impregnating it with fixed air.
+
+EXPERIMENT V.
+
+The distilled water saturated with fixed air neither effervesced, nor
+shewed any clouds, when mixed with the fixed or volatile alkali.
+
+EXPERIMENT VI.
+
+No curd was formed by pouring this water upon an equal quantity of milk,
+and boiling them together.
+
+EXPERIMENT VII.
+
+When agitated with soap, this water produced curds, and lathered with
+some difficulty; but not so much as the distilled water mixed with
+vitriolic acid in the very small proportion above-mentioned. The same
+distilled water without any impregnation of fixed air lathered with soap
+without the least previous curdling. River-water, and a pleasant
+pump-water not remarkably hard, were compared with these. The former
+produced curds before it lathered, but not quite in so great a quantity
+as the distilled water impregnated with fixed air: the latter caused a
+stronger curd than any of the others above-mentioned.
+
+EXPERIMENT VIII.
+
+Apprehending that the fixed air in the distilled water occasioned the
+coagulation, or separation of the oily part of the soap, only by
+destroying the causticity of the _lixivium_, and thereby rendering the
+union less perfect betwixt that and the tallow, and not by the presence
+of any acid; I impregnated a fresh quantity of the same distilled water
+with fixed air, which had passed through half a yard of a wide
+barometer-tube filled with salt of tartar; but this water caused the
+same curdling with soap as the former had done, and appeared in every
+respect to be exactly the same.
+
+EXPERIMENT IX.
+
+Distilled water saturated with fixed air formed a white cloud and
+precipitation, upon being mixed with a solution of _saccharum saturni_.
+I found likewise, that fixed air, after passing through the tube filled
+with alkaline salt, upon being let into a phial containing a solution of
+the metalic salt in distilled water, caused a perfect separation of the
+lead, in the form of a white powder; for the water, after this
+precipitation, shewed no cloudiness upon a fresh mixture of the
+substances which had before rendered it opaque.
+
+
+NUMBER II.
+
+     _A Letter from Mr. HEY to Dr. PRIESTLEY, concerning the Effects
+     of fixed Air applied by way of Clyster._
+
+                                      Leeds, Feb. 15th, 1772.
+
+     Reverend Sir,
+
+Having lately experienced the good effects of fixed air in a putrid
+fever, applied in a manner, I believe not heretofore made use of, I
+thought it proper to inform you of the agreeable event, as the method of
+applying this powerful corrector of putrefaction took its rise
+principally from your observations and experiments on factitious air;
+and now, at your request, I send the particulars of the case I mentioned
+to you, as far as concerns the administration of this remedy.
+
+January 8, 1772, Mr. Lightbowne, a young gentleman who lives with me,
+was seized with a fever, which, after continuing about ten days, began
+to be attended with those symptoms that indicate a putrescent state of
+the fluids.
+
+18th, His tongue was black in the morning when I first visited him, but
+the blackness went off in the day-time upon drinking: He had begun to
+doze much the preceding day, and now he took little notice of those that
+were about him: His belly was loose, and had been so for some days: his
+pulse beat 110 strokes in a minute, and was rather low: he was ordered
+to take twenty-five grains of Peruvian bark with five of tormentil-root
+in powder every four hours, and to use red wine and water cold as his
+common drink.
+
+19th, I was called to visit him early in the morning, on account of a
+bleeding at the nose which had come on: he lost about eight ounces of
+blood, which was of a loose texture: the haemorrhage was suppressed,
+though not without some difficulty, by means of tents made of soft lint,
+dipped in cold water strongly impregnated with tincture of iron, which
+were introduced within the nostrils quite through to their posterior
+apertures; a method which has never yet failed me in like cases. His
+tongue was now covered with a thick black pellicle, which was not
+diminished by drinking: his teeth were furred with the same kind of
+sordid matter, and even the roof of his mouth and sauces were not free
+from it: his looseness and stupor continued, and he was almost
+incessantly muttering to himself: he took this day a scruple of the
+Peruvian bark with ten grains of tormentil every two or three hours: a
+starch clyster, containing a drachm of the compound powder of bole,
+without opium, was given morning and evening: a window was set open in
+his room, though it was a severe frost, and the floor was frequently
+sprinkled with vinegar.
+
+20th, He continued nearly in the same state: when roused from his
+dozing, he generally gave a sensible answer to the questions asked him;
+but he immediately relapsed, and repeated his muttering. His skin was
+dry, and harsh, but without _petechiae_. He sometimes voided his urine
+and _faeces_ into the bed, but generally had sense enough to ask for the
+bed-pan: as he now nauseated the bark in substance, it was exchanged
+for Huxham's tincture, of which he took a table spoonful every two hours
+in a cup full of cold water: he drank sometimes a little of the tincture
+of roses, but his common liquors were red wine and water, or rice-water
+and brandy acidulated with elixir of vitriol: before drinking, he was
+commonly requested to rinse his mouth with water to which a little honey
+and vinegar had been added. His looseness rather increased, and the
+stools were watery, black, and foetid: It was judged necessary to
+moderate this discharge, which seemed to sink him, by mixing a drachm of
+the _theriaca Andromachi_ with each clyster.
+
+21st. The same putrid symptoms remained, and a _subsultus tendinum_ came
+on: his stools were more foetid; and so hot, that the nurse assured me
+she could not apply her hand to the bed-pan, immediately after they were
+discharged, without feeling pain on this account: The medicine and
+clysters were repeated.
+
+Reflecting upon the disagreeable necessity we seemed to lie under of
+confining this putrid matter in the intestines, lest the evacuation
+should destroy the _vis vitae_ before there was time to correct its bad
+quality, and overcome its bad effects, by the means we were using; I
+considered, that, if this putrid ferment could be more immediately
+corrected, a stop would probably be put to the flux, which seemed to
+arise from, or at least to be encreased by it; and the _fomes_ of the
+disease would likewise be in a great measure removed. I thought nothing
+was so likely to effect this, as the introduction of fixed air into the
+alimentary canal, which, from the experiments of Dr. Macbride, and
+those you have made since his publication, appears to be the most
+powerful corrector of putrefaction hitherto known. I recollected what
+you had recommended to me as deserving to be tried in putrid diseases, I
+mean, the injection of this kind of air by way of clyster, and judged
+that in the present case such a method was clearly indicated.
+
+The next morning I mentioned my reflections to Dr. Hird and Dr.
+Crowther, who kindly attended this young gentleman at my request, and
+proposed the following method of treatment, which, with their
+approbation, was immediately entered upon. We first gave him five grains
+of ipecacuanha, to evacuate in the most easy manner part of the putrid
+_colluvies_: he was then allowed to drink freely of brisk orange-wine,
+which contained a good deal of fixed air, yet had not lost its
+sweetness. The tincture of bark was continued as before; and the water
+which he drank along with it, was impregnated with fixed air from the
+atmosphere of a large vat of fermenting wort, in the manner I had
+learned from you. Instead of the astringent clyster, air alone was
+injected, collected from a fermenting mixture of chalk and oil of
+vitriol: he drank a bottle of orange-wine in the course of this day, but
+refused any other liquor except water and his medicine: two bladders
+full of air were thrown up in the afternoon.
+
+23d. His stools were less frequent; their heat likewise and peculiar
+_foetor_ were considerably diminished; his muttering was much abated,
+and the _subsultus tendinum_ had left him. Finding that part of the air
+was rejected when given with a bladder in the usual way, I contrived a
+method of injecting it which was not so liable to this inconvenience. I
+took the flexible tube of that instrument which is used for throwing up
+the fume of tobacco, and tied a small bladder to the end of it that is
+connected with the box made for receiving the tobacco, which I had
+previously taken off from the tube: I then put some bits of chalk into a
+six ounce phial until it was half filled; upon these I poured such a
+quantity of oil of vitriol as I thought capable of saturating the chalk,
+and immediately tied the bladder, which I had fixed to the tube, round
+the neck of the phial: the clyster-pipe, which was fastened to the other
+end of the tube, was introduced into the _anus_ before the oil of
+vitriol was poured upon the chalk. By this method the air passed
+gradually into the intestines as it was generated; the rejection of it
+was in a great measure prevented; and the inconvenience of keeping the
+patient uncovered during the operation was avoided.
+
+24th, He was so much better, that there seemed to be no necessity for
+repeating the clysters: the other means were continued. The window of
+his room was now kept shut.
+
+25th, All the symptoms of putrescency had left him; his tongue and teeth
+were clean; there remained no unnatural blackness or _foetor_ in his
+stool, which had now regained their proper consistence; his dozing and
+muttering were gone off; and the disagreeable odour of his breath and
+perspiration was no longer perceived. He took nourishment to-day, with
+pleasure; and, in the afternoon, sat up an hour in his chair.
+
+His fever, however, did not immediately leave him; but this we
+attributed to his having caught cold from being incautiously uncovered,
+when the window was open, and the weather extremely severe; for a cough,
+which had troubled him in some degree from the beginning, increased, and
+he became likewise very hoarse for several days, his pulse, at the same
+time, growing quicker: but these complaints also went off, and he
+recovered, without any return of the bad symptoms above-mentioned.
+
+     I am, Reverend Sir,
+
+       Your obliged humble Servant,
+
+         WM. HEY.
+
+
+POSTSCRIPT
+
+                                      October 29, 1772.
+
+Fevers of the putrid kind have been so rare in this town, and in its
+neighbourhood, since the commencement of the present year, that I have
+not had an opportunity of trying again the effects of fixed air, given
+by way of clyster, in any case exactly similar to Mr. Lightbowne's. I
+have twice given water saturated with fixed air in a fever of the
+putrescent kind, and it agreed very well with the patients. To one of
+them the aerial clysters were administred, on account of a looseness,
+which attended the fever, though the stools were not black, nor
+remarkably hot or foetid.
+
+These clysters did not remove the looseness, though there was often a
+greater interval than usual betwixt the evacuations, after the injection
+of them. The patient never complained of any uneasy distention of the
+belly from the air thrown up, which, indeed, is not to be wondered at,
+considering how readily this kind of air is absorbed by aqueous and
+other fluids, for which sufficient time was given, by the gradual manner
+of injecting it. Both those patients recovered though the use of fixed
+air did not produce a crisis before the period at which such fevers
+usually terminate. They had neither of them the opportunity of drinking
+such wine as Mr. Lightbowne took, after the use of fixed air was entered
+upon; and this, probably, was some disadvantage to them.
+
+I find the methods of procuring fixed air, and impregnating water with
+it, which you have published, are preferable to those I made use of in
+Mr. Lightbowne's case.
+
+The flexible tube used for conveying the fume of tobacco into the
+intestines, I find to be a very convenient instrument in this case, by
+the method before-mentioned (only adding water to the chalk, before the
+oil of vitriol is instilled, as you direct) the injection of air may be
+continued at pleasure, without any other inconvenience to the patient,
+than what may arise from his continuing in one position during the
+operation, which scarcely deserves to be mentioned, or from the
+continuance of the clyster-pipe within the anus, which is but trifling,
+if it be not shaken much, or pushed against the rectum.
+
+When I said in my letter, that fixed air appeared to be the greatest
+corrector of putrefaction hitherto known, your philosophical researches
+had not then made you acquainted with that most remarkably antiseptic
+property of nitrous air. Since you favoured me with a view of some
+astonishing proofs of this, I have conceived hopes, that this kind of
+air may likewise be applied medicinally to great advantage.
+
+     W. H.
+
+
+NUMBER III.
+
+     _Observations on the MEDICINAL USES of FIXED AIR. By THOMAS
+     PERCIVAL, M. D. Fellow of the ROYAL SOCIETY, and of the SOCIETY
+     of ANTIQUARIES in LONDON._
+
+These Observations on the MEDICINAL USES OF FIXED AIR have been before
+published in the Second Volume of my Essays; but are here reprinted with
+considerable additions. They form a part of an experimental inquiry into
+this interesting and curious branch of Physics; in which the friendship
+of Dr. Priestley first engaged me, in concert with himself.
+
+                                      Manchester, March 16, 1774.
+
+In a course of Experiments, which is yet unfinished, I have had frequent
+opportunities of observing that FIXED AIR may in no inconsiderable
+quantity be breathed without danger or uneasiness. And it is a
+confirmation of this conclusion, that at Bath, where the waters
+copiously exhale this mineral spirit,[15] the bathers inspire it with
+impunity. At Buxton also, where the Bath is in a close vault, the
+effects of such _effluvia_, if noxious, must certainly be perceived.
+
+Encouraged by these considerations, and still more by the testimony of a
+very judicious Physician at Stafford, in favour of this powerful
+antiseptic remedy, I have administered fixed air in a considerable
+number of cases of the PHTHISIS PULMONALIS, by directing my patients to
+inspire the steams of an effervescing mixture of chalk and vinegar; or
+what I have lately preferred, of vinegar and potash. The hectic fever
+has in several instances been considerably abated, and the matter
+expectorated has become less offensive, and better digested. I have not
+yet been so fortunate in any one case, as to effect a cure; although the
+use of mephitic air has been accompanied with proper internal medicines.
+But Dr. Withering, the gentleman referred to above, informs me, that he
+has been more successful. One Phthisical patient under his care has by a
+similar course intirely recovered; another was rendered much better; and
+a third, whose case was truly deplorable, seemed to be kept alive by it
+more than two months. It may be proper to observe that fixed air can
+only be employed with any prospect of success, in the latter stages of
+the _phthisis pulmonalis_, when a purulent expectoration takes place.
+After the rupture and discharge of a VOMICA also, such a remedy promises
+to be a powerful palliative. Antiseptic fumigations and vapours have
+been long employed, and much extolled in cases of this kind. I made the
+following experiment, to determine whether their efficacy, in any
+degree, depends on the separation of fixed air from their substance.
+
+One end of a bent tube was fixed in a phial full of lime-water; the
+other end in a bottle of the tincture of myrrh. The junctures were
+carefully luted, and the phial containing the tincture of myrrh was
+placed in water, heated almost to the boiling point, by the lamp of a
+tea-kettle. A number of air-bubbles were separated, but probably not of
+the mephitic kind, for no precipitation ensued in the lime water. This
+experiment was repeated with the _tinct. tolutanae, ph. ed._ and with
+_sp, vinos. camp._ and the result was entirely the same. The medicinal
+action therefore of the vapours raised from such tinctures, cannot be
+ascribed to the extrication of fixed air; of which it is probable bodies
+are deprived by _chemical solution_ as well as by _mixture_.
+
+If mephitic air be thus capable of correcting purulent matter in the
+lungs, we may reasonably infer it will be equally useful when applied
+externally to foul ULCERS. And experience confirms the conclusion. Even
+the sanies of a CANCER, when the carrot poultice failed, has been
+sweetened by it, the pain mitigated, and a better digestion produced.
+The cases I refer to are now in the Manchester infirmary, under the
+direction of my friend Mr. White, whose skill as a surgeon, and
+abilities as a writer are well known to the public.
+
+Two months have elapsed since these observations were written,[16] and
+the same remedy, during that period, has been assiduously applied, but
+without any further success. The progress of the cancers seems to be
+checked by the fixed air; but it is to be feared that a cure will not be
+effected. A palliative remedy, however, in a disease so desperate and
+loathsome, may be considered as a very valuable acquisition. Perhaps
+NITROUS AIR might be still more efficacious. This species of factitious
+air is obtained from all the metals except zinc, by means of the nitrous
+acid; and Dr. Priestley informs me, that as a sweetener and antiseptic
+it far surpasses fixed air. He put two mice into a quantity of it, one
+just killed, the other offensively putrid. After twenty-five days they
+were both perfectly sweet.
+
+In the ULCEROUS SORE THROAT much advantage has been experienced from the
+vapours of effervescing mixtures drawn into the _fauces_[17]. But this
+remedy should not supersede the use of other antiseptic
+applications.[18]
+
+A physician[19] who had a very painful APTHOUS ULCER at the point of his
+tongue, found great relief, when other remedies failed, from the
+application of fixed air to the part affected. He held his tongue over
+an effervescing mixture of potash and vinegar; and as the pain was
+always mitigated, and generally removed by this vaporisation, he
+repeated it, whenever the anguish arising from the ulcer was more than
+usually severe. He tried a combination of potash and oil of vitriol well
+diluted with water; but this proved stimulant and increased his pain;
+probably owing to some particles of the acid thrown upon the tongue, by
+the violence of the effervescence. For a paper stained with the purple
+juice of radishes, when held at an equal distance over two vessels, the
+one containing potash and vinegar, the other the same alkali and
+_Spiritus vitrioli tenuis_, was unchanged by the former, but was spotted
+with red, in various parts, by the latter.
+
+In MALIGNANT FEVERS wines abounding with fixed air may be administered,
+to check the septic ferment, and sweeten the putrid _colluvies_ in the
+_primae viae_. If the laxative quality of such liquors be thought an
+objection to the use of them, wines of a greater age may be given,
+impregnated with mephitic air, by a simple but ingenious contrivance of
+my friend Dr. Priestley.[20]
+
+The patient's common drink might also be medicated in the same way. A
+putrid DIARRH[OE]A frequently occurs in the latter stage of such
+disorder, and it is a most alarming and dangerous symptom. If the
+discharge be stopped by astringents, a putrid _fomes_ is retained in the
+body, which aggravates the delirium and increases the fever. On the
+contrary, if it be suffered to take its course, the strength of the
+patient must soon be exhausted, and death unavoidably ensue. The
+injection of mephitic air into the intestines, under these
+circumstances, bids fair to be highly serviceable. And a case of this
+deplorable kind, has lately been communicated to me, in which the vapour
+of chalk and oil of vitriol conveyed into the body by the machine
+employed for tobacco clysters, quickly restrained the _diarrhoea_,
+corrected the heat and foetor of the stools, and in two days removed
+every symptom of danger[21]. Two similar instances of the salutary
+effects of mephitic air, thus administered, have occurred also in my own
+practice, the history of which I shall briefly lay before the reader.
+May we not presume that the same remedy would be equally useful in the
+DYSENTERY? The experiment is at least worthy of trial.
+
+Mr. W----, aged forty-four years, corpulent, inactive, with a short
+neck, and addicted to habits of intemperance, was attacked on the 7th of
+July 1772, with symptoms which seemed to threaten an apoplexy. On the
+8th, a bilious looseness succeeded, with a profuse hoemorrhage from
+the nose. On the 9th, I was called to his assistance. His countenance
+was bloated, his eyes heavy, his skin hot, and his pulse hard, full, and
+oppressed. The diarrhoea continued; his stools were bilious and very
+offensive; and he complained of griping pains in his bowels. He had
+lost, before I saw him, by the direction of Mr. Hall, a surgeon of
+eminence in Manchester, eight ounces of blood from the arm, which was of
+a lax texture; and he had taken a saline mixture every sixth hour. The
+following draught was prescribed, and a dose of rhubarb directed to be
+administered at night.
+
+      Rx. _Aq. Cinnam. ten._        oz. j.
+     _Succ. Limon. recent._         oz. ss.
+     _Salis Nitri gr. xij. Syr. e Succo Limon. dr. j. M. f. Haust._
+     _4tis horis sumendus._
+
+July 11. The _Diarrhoea_ was more moderate; his griping pains were
+abated; and he had less stupor and dejection in his countenance. Pulse
+90, not so hard or oppressed. As his stools continued to be foetid,
+the dose of rhubarb was repeated; and instead of simple cinnamon-water,
+his draughts were prepared with an infusion of columbo root.
+
+12. The _Diarrhoea_ continued; his stools were involuntary; and he
+discharged in this way a quantity of black, grumous, and foetid blood.
+Pulse hard and quick; skin hot; tongue covered with a dark fur; abdomen
+swelled; great stupor. Ten grains of columbo root, and fifteen of the
+_Gummi rubrum astringens_ were added to each draught. Fixed air, under
+the form of clysters, was injected every second or third hour; and
+directions were given to supply the patient plentifully with water,
+artificially impregnated with mephitic air. A blister was also laid
+between his shoulders.
+
+13. The Diarrhoea continued, with frequent discharges of blood; but
+the stools had now lost their foetor. Pulse 120; great flatulence in
+the bowels, and fulness in the belly. The clysters of fixed air always
+diminished the tension of the _Abdomen_, abated flatulence, and made the
+patient more easy and composed for some time after their injection. They
+were directed to be continued, together with the medicated water. The
+nitre was omitted, and a scruple of the _Confect. Damocratis_ was given
+every fourth hour, in an infusion of columbo root.
+
+14. The Diarrhoea was how checked, His other symptoms continued as
+before. Blisters were applied to the arms; and a drachm and a half of
+the _Tinctura Serpentariae_ was added to each draught.
+
+15. His pulse was feeble, quicker and more irregular. He dosed much;
+talked incoherently; and laboured under a slight degree of _Dyspnaea_.
+His urine, which had hitherto assumed no remarkable appearance, now
+became pale. Though he discharged wind very freely, his belly was much
+swelled, except for a short time after the injection of the
+air-clysters. The following draughts were then prescribed.
+
+     Rx _Camphorae mucilag. G. Arab, solutae gr. viij. Infus. Rad.
+     Columbo oz. jfs Tinct. Serpent. dr. ij Confect. Card.
+     scruple j Syr. e Cort. Aurant dr. i m. f. Haust. 4tis horis
+     sumendus._
+
+Directions were given to foment his feet frequently with vinegar and
+warm water.
+
+16. He has had no stools since the 14th. His _Abdomen_ is tense. No
+change in the other symptoms. The _Tinct. Serpent._ was omitted in his
+draughts, and an equal quantity of _Tinct. Rhaei Sp._ substituted in its
+place.
+
+In the evening he had a motion to stool, of which he was for the first
+time so sensible, as to give notice to his attendants. But the
+discharge, which was considerable and slightly offensive, consisted
+almost entirely of blood, both in a coagulated and in a liquid state.
+His medicines were therefore varied as follows:
+
+     Rx. _Decoct. Cort. Peruv. oz. iss Tinct. Cort. ejusd. dr. ij. Confect.
+     Card. scruple j Gum. Rubr. Astring. gr.
+     xv. Pulv. Alnmin. gr. vij. m. f. Haustus 4tis horis
+     sumendus._
+
+Red Port wine was now given more freely in his medicated water; and his
+nourishment consisted of sago and salep.
+
+In this state, with very little variation, he continued for several
+days; at one time ostive, and at another discharging small quantities of
+faeces, mixed with grumous blood. The air-clysters were continued, and
+the astringents omitted.
+
+20. His urine was now of an amber colour, and deposited a slight
+sediment. His pulse was more regular, and although still very quick,
+abated in number ten strokes in a minute. His head was less confused,
+and his sleep seemed to be refreshing. No blood appeared in his stools,
+which were frequent, but small in quantity; and his _Abdomen_ was less
+tense than usual. He was extremely deaf; but gave rational answers to
+the few questions which were proposed to him; and said he felt no pain.
+
+21. He passed a very restless night; his delirium recurred; his pulse
+beat 125 strokes in a minute; his urine was of a deep amber colour when
+first voided; but when cold assumed the appearance of cow's whey. The
+_Abdomen_ was not very tense, nor had he any further discharge of blood.
+
+Directions were given to shave his head, and to wash it with a mixture
+of vinegar and brandy; the quantity of wine in his drink was diminished;
+and the frequent use of the pediluvium was enjoined. The air-clysters
+were discontinued, as his stools were not offensive, and his _Abdomen_
+less distended.
+
+22. His pulse was now small, irregular, and beat 130 strokes in a
+minute. The _Dyspnoea_ was greatly increased; his skin was hot, and
+bedewed with a clammy moisture; and every symptom seemed to indicate the
+approach of death. In this state he continued till evening, when he
+recruited a little. The next day he had several slight convulsions. His
+urine which was voided plentifully, still put on the appearance of whey
+when cold. Cordial and antispasmodic draughts, composed of camphor,
+tincture of castor, and _Sp. vol. aromat._ were now directed; and wine
+was liberally administered.
+
+24. He rose from his bed, and by the assistance of his attendants walked
+across the chamber. Soon after he was seized with a violent convulsion,
+in which he expired.
+
+To adduce a case which terminated fatally as a proof of the efficacy of
+any medicine, recommended to the attention of the public, may perhaps
+appear singular; but cannot be deemed absurd, when that remedy answered
+the purposes for which it was intended. For in the instance before us;
+fixed air was employed, not with an expectation that it would cure the
+fever, but to obviate the symptoms of putrefaction, and to allay the
+uneasy irritation in the bowels. The disease was too malignant, the
+nervous system too violently affected, and the strength of the patient
+too much exhausted by the discharges of blood which he suffered, to
+afford hopes of recovery from the use of the most powerful antiseptics.
+
+But in the succeeding case the event proved more fortunate.
+
+Elizabeth Grundy, aged seventeen, was attacked on the 10th of December
+1772, with the usual symptoms of a continued fever. The common method of
+cure was pursued; but the disease increased, and soon assumed a putrid
+type.
+
+On the 23d I found her in a constant delirium, with a _subsultus
+tendinum_. Her skin was hot and dry, her tongue black, her thirst
+immoderate, and her stools frequent, extremely offensive, and for the
+most part involuntary. Her pulse beat 130 strokes in a minute; she dosed
+much; and was very deaf. I directed wine to be administered freely; a
+blister to be applied to her back; the _pediluvium_ to be used several
+times in the day; and mephitic air to be injected under the form of a
+clyster every two hours. The next day her stools were less frequent, had
+lost their foetor, and were no longer discharged involuntarily; her
+pulse was reduced to 110 strokes in the minute; and her delirium was
+much abated. Directions were given to repeat the clysters, and to supply
+the patient liberally with wine. These means were assiduously pursued
+several days; and the young woman was so recruited by the 28th, that the
+injections were discontinued. She was now quite rational, and not averse
+to medicine. A decoction of Peruvian bark was therefore prescribed, by
+the use of which she speedily recovered her health.
+
+I might add a third history of a putrid disease, in which the mephitic
+air is now under trial, and which affords the strongest proof both of
+the _antiseptic_, and of the _tonic_ powers of this remedy; but as the
+issue of the case remains yet undetermined (though it is highly
+probable, alas! that it will be fatal) I shall relate only a few
+particulars of it. Master D. a boy of about twelve years of age, endowed
+with an uncommon capacity, and with the most amiable dispositions, has
+laboured many months under a hectic fever, the consequence of several
+tumours in different parts of his body. Two of these tumours were laid
+open by Mr. White, and a large quantity of purulent matter was
+discharged from them. The wounds were very properly treated by this
+skilful surgeon, and every suitable remedy, which my best judgment could
+suggest, was assiduously administered. But the matter became sanious, of
+a brown colour, and highly putrid. A _Diarrhoea_ succeeded; the
+patient's stools were intolerably offensive, and voided without his
+knowledge. A black fur collected about his teeth; his tongue was covered
+with _Aphthae_; and his breath was so foetid, as scarcely to be
+endured. His strength was almost exhausted; a _subsultus tendinum_ came
+on; and the final period of his sufferings seemed to be rapidly
+approaching. As a last, but almost hopeless, effort, I advised the
+injection of clysters of mephitic air. These soon corrected the foetor
+of the patient's stools; restrained his _Diarrhoea_; and seemed to
+recruit his strength and spirits. Within the space of twenty-four hours
+his wounds assumed a more favourable appearance; the matter discharged
+from them became of a better colour and consistence; and was no longer
+so offensive to the smell. The use of this remedy has been continued
+several days, but is now laid aside. A large tumour is suddenly formed
+under the right ear; swallowing is rendered difficult and painful; and
+the patient refuses all food and medicine. Nourishing clysters are
+directed; but it is to be feared that these will renew the looseness,
+and that this amiable youth will quickly sink under his disorder[22].
+
+The use of _wort_ from its saccharine quality, and disposition to
+ferment, has lately been proposed as a remedy for the SEA SCURVY. Water
+or other liquors, already abounding with fixed air in a separate state,
+should seem to be better adapted to this purpose; as they will more
+quickly correct the putrid disposition of the fluids, and at the same
+time, by their gentle stimulus[23] increase the powers of digestion, and
+give new strength to the whole system.
+
+Dr. Priestley, who suggested both the idea and the means of executing
+it, has under the sanction of the College of Physicians, proposed the
+scheme to the Lords of the Admiralty, who have ordered trial to be made
+of it, on board some of his Majesty's ships of war. Might it not however
+give additional efficacy to this remedy, if instead of simple water, the
+infusion of malt were to be employed?
+
+I am persuaded such a medicinal drink might be prescribed also with
+great advantage in SCROPHULOUS COMPLAINTS, when not attended with a
+hectic fever; and in other disorders in which a general acrimony
+prevails, and the crasis of the blood is destroyed. Under such
+circumstances, I have seen _vibices_ which spread over the body,
+disappear in a few days from the use of wort.
+
+A gentleman who is subject to a scorbutic eruption in his face, for
+which he has used a variety of remedies with no very beneficial effect,
+has lately applied the fumes of chalk and oil of vitriol to the parts
+affected. The operation occasions great itching and pricking in the
+skin, and some degree of drowsiness, but evidently abates the serous
+discharge, and diminishes the eruption. This patient has several
+symptoms which indicate a genuine scorbutic DIATHESIS; and it is
+probable that fixed air, taken internally, would be an useful medicine
+in this case.
+
+The saline draughts of Riverius are supposed to owe their antiemetic
+effects to the air, which is separated from the salt of wormwood during
+the act of effervescence. And the tonic powers of many mineral waters
+seem to depend on this principle. I was lately desired to visit a lady
+who had most severe convulsive REACHINGS. Various remedies had been
+administered without effect, before I saw her. She earnestly desired a
+draught of malt liquor, and was indulged with half a pint of Burton beer
+in brisk effervescence. The vomitings ceased immediately, and returned
+no more. Fermenting liquors, it is well known, abound with fixed air. To
+this, and to the cordial quality of the beer, the favourable effect
+which it produced, may justly be ascribed. But I shall exceed my design
+by enlarging further on this subject. What has been advanced it is
+hoped, will suffice to excite the attention of physicians to a remedy
+which is capable of being applied to so many important medicinal
+purposes.
+
+
+NUMBER IV.
+
+_Extract of a Letter from WILLIAM FALCONER, M.D. of BATH._
+
+                                      Jan 6, 1774,
+
+     Reverend Sir,
+
+I once observed the same taste you mention (Philosophical Transactions,
+p. 156. of this Volume, p. 35.) viz. like tar water, in some water that
+I impregnated with fixed air about three years ago. I did not then know
+to what to attribute it, but your experiment seems to clear it up. I
+happened to have spent all my acid for raising effervescence, and to
+supply its place I used a bottle of dulcified spirit of nitre, which I
+knew was greatly under-saturated with spirit of wine; from which, as
+analogous to your observation, I imagine the effect proceeded.
+
+As[24] to the coagulation of the blood of animals by fixed Air, I fear
+it will scarce stand the test of experiment, as I this day gave it, I
+think, a fair trial, in the following manner.
+
+A young healthy man, at 20 years old, received a contusion by a fall,
+was instantly carried to a neighbouring surgeon, and, at my request,
+bled in the following manner.
+
+I inserted a glass funnel into the neck of a large clear phial about oz.
+x. contents, and bled him into it to about oz. viii. By these means the
+blood was exposed to the air as little a time as possible, as it flowed
+into the bottle as it came from the orifice.
+
+As soon as the quantity proposed was drawn, the bottle was carefully
+corked, and brought to me. It was then quite fluid, nor was there the
+least separation of its parts.
+
+On the surface of this I conveyed several streams of fixed air (having
+first placed the bottle with the blood in a bowl of water, heated as
+nearly to the human heat as possible) from the mixture of the vitriolic
+acid and lixiv. tartar, which I use preferably to other alkalines, as
+being (as Dr. Cullen observes) in the mildest state, and therefore most
+likely to generate most air.
+
+I shook the phial often, and threw many streams of air on the blood, as
+I have often practised with success for impregnating water; but could
+not perceive the smallest signs of coagulation, although it stood in an
+atmosphere of fixed air 20 minutes or more. I then uncorked the bottles,
+and poured off about oz. ii to which I added about 6 or 7 gtts of spirit
+of vitriol, which coagulated it immediately. I set the remainder in a
+cold place and it coagulated, as near as I could judge, in the same time
+that blood would have done newly drawn from the vein.
+
+P. 82. Perhaps the circumilance of putrid vegetables yielding all fixed
+and no inflammable air may be the causes of their proving so antiseptic,
+even when putrid, as appears by Mr. Alexander's Experiments.
+
+P. 86. Perhaps the putrid air continually exhaled may be one cause of
+the luxuriancy of plants growing on dunghills or in very rich soils.
+
+P. 146. Your observation that inflammable air consists of the union of
+some acid vapour with phlogiston, puts me in mind of an old observation
+of Dr. Cullen, that the oil separated from soap by an acid was much more
+inflammable than before, resembling essential oil, and soluble in V. sp.
+
+I have tried fixed air as an antiseptic taken in by respiration, but
+with no great success. In one case it seemed to be of service, in two it
+seemed indifferent, and in one was injurious, by exciting a cough.
+
+
+NUMBER V.
+
+_Extract of a Letter from Mr. WILLIAM BEWLEY, of GREAT MASSINGHAM,
+NORFOLK._
+
+                                      March 23, 1774.
+
+     Dear Sir,
+
+When I first received your paper, I happened to have a process going on
+for the preparation of _nitrous ether_, without distillation.[25] I had
+heretofore always taken for granted that the elastic fluid generated in
+that preparation was _fixed_ air: but on examination I found this
+combination of the nitrous acid with inflammable spirits, produced an
+elastic fluid that had the same general properties with the air that you
+unwillingly, though very properly, in my opinion, term _nitrous_; as I
+believe it is not to be procured without employing the _nitrous_ acid,
+either in a simple state, or compounded, as in _aqua regia_. I shall
+suggest, however, by and by some doubts with respect to it's title to
+the appellation of _air_.
+
+Water impregnated with your nitrous air _certainly_, as you suspected
+from it's taste, contains the nitrous acid. On saturating a quantity of
+this water with a fixed alcali, and then evaporating, &c. I have
+procured two chrystals of nitre. But the principal observations that
+have occurred to me on the subject of nitrous air are the following. My
+experiments have been few and made by snatches, under every disadvantage
+as to apparatus, &c. and with frequent interruptions; and yet I think
+they are to be depended upon.
+
+My first remark is, that nitrous air does not give water a sensibly acid
+impregnation, unless it comes into contact, or is mixed with a portion
+of common or atmospherical air: and my second, that nitrous air
+principally consists of the nitrous acid itself, reduced to the state of
+a _permanent_ vapour not condensable by cold, like other vapours, but
+which requires the presence and admixture of common air to restore it to
+its primitive state of a liquid. I am beholden for this idea, you will
+perceive, to your own very curious discovery of the true nature of Mr.
+Cavendish's _marine_ vapour.
+
+When I first repeated your experiment of impregnating water with nitrous
+air, the water, I must own tasted acid; as it did in one, or perhaps two
+trials afterwards; but, to my great astonishment, in all the following
+experiments, though some part of the factitious air, or vapour, was
+visibly absorbed by the water, I could not perceive the latter to have
+acquired any sensible acidity. I at length found, however, that I could
+render this same water _very_ acid, by means only of the nitrous air
+already included in the phial with it. Taking the inverted phial out of
+the water, I remove my finger from the mouth of it, to admit a little
+of the common air, and instantly replace my finger. The redness,
+effervescence, and diminution take place. Again taking off my finger,
+and instantly replacing it, more common, air rushes in, and the same
+phenomena recur. The process sometimes requires to be seven or eight
+times repeated, before the whole of the nitrous _vapour_ (as I shall
+venture to call it) is condensed into nitrous _acid_, by the successive
+entrance of fresh parcels of common air after each effervescence; and
+the water becomes evidently more and more acid after every such fresh
+admission of the external air, which at length ceases to enter, when the
+whole of the vapour has been condensed. No agitation of the water is
+requisite, except a gentle motion, just sufficient to rince the sides of
+the phial, in order to wash off the condensed vapour.
+
+The acidity which you (and I likewise, at first) observed in the water
+agitated with nitrous air _alone_, I account for thus. On bringing the
+phial to the mouth, the common air meeting with the nitrous vapour in
+the neck of the phial, condenses it, and impregnates the water with the
+acid, in the very act of receiving it upon the tongue. On stopping the
+mouth of the phial with my tongue for a short time and afterwards
+withdrawing it a very little, to suffer the common air to rush past it
+into the phial, the sensation of acidity has been sometimes intolerable:
+but taking a large gulph of the water at the same time, it has been
+found very slightly acid.--The following is one of the methods by which
+I have given water a very strong acid impregnation, by means of a
+mixture of nitrous and common air.
+
+Into a small phial, containing only common air, I force a quantity of
+nitrous air at random, out of a bladder, and instantly clap my finger on
+the mouth of the bottle. I then immerse the neck of it into water, a
+small quantity of which I suffer to enter, which squirts into it with
+violence; and immediately replacing my finger, remove the phial. The
+water contained in it is already _very_ acid, and it becomes more and
+more so (if a sufficient quantity of nitrous air was at first thrown in)
+on alternately stopping the mouth of the phial, and opening it, as often
+as fresh air will enter.
+
+Since I wrote the above, I have frequently converted a small portion of
+water in an ounce phial into a weak _Aqua fortis_, by repeated mixtures
+of common and nitrous air; throwing in alternately the one or the other,
+according to the circumstances; that is, as long as there was a
+superabundance of nitrous air, suffering the common air to enter and
+condense it; and, when that was effected, forcing in more nitrous air
+from the bladder, to the common air which now predominated in the
+phial--and so alternately. I have wanted leisure, and conveniences, to
+carry on this process to its _maximum_, or to execute it in a different
+and better manner; but from what I have done, I think we may conclude
+that nitrous air consists principally of the nitrous acid,
+phlogisticated, or otherwise so modified, by a previous commenstruation
+with metals, inflammable spirits, &c. as to be reduced into a durably
+elastic vapour: and that, in order to deprive it of its elasticity, and
+restore it to its former state, an addition of common air is requisite,
+and, as I suspect, of water likewise, or some other fluid: as in the
+course of my few trials, I have not yet been able to condense it in a
+perfectly dry bottle.
+
+
+NUMBER VI.
+
+_A Letter from_ Dr. FRANKLIN.
+
+                              Craven Street, April 10, 1774.
+
+     Dear Sir,
+
+In compliance with your request, I have endeavoured to recollect the
+circumstances of the American experiments I formerly mentioned to you,
+of raising a flame on the surface of some waters there.
+
+When I passed through New Jersey in 1764, I heard it several times
+mentioned, that by applying a lighted candle near the surface of some of
+their rivers, a sudden flame Would catch and spread on the water,
+continuing to burn for near half a minute. But the accounts I received
+were so imperfect that I could form no guess at the cause of such an
+effect, and rather doubted the truth of it. I had no opportunity of
+seeing the experiment; but calling to see a friend who happened to be
+just returned home from making it himself, I learned from him the manner
+of it; which was to choose a shallow place, where the bottom could be
+reached by a walking-stick, and was muddy; the mud was first to be
+stirred with the stick, and when a number of small bubbles began to
+arise from it, the candle was applied. The flame was so sudden and so
+strong, that it catched his ruffle and spoiled it, as I saw. New-Jersey
+having many pine-trees in different parts of it, I then imagined that
+something like a volatile oil of turpentine might be mixed with the
+waters from a pine-swamp, but this supposition did not quite satisfy me.
+I mentioned the fact to some philosophical friends on my return to
+England, but it was not much attended to. I suppose I was thought a
+little too credulous.
+
+In 1765, the Reverend Dr. Chandler received a letter from Dr. Finley,
+President of the College in that province, relating the same experiment.
+It was read at the Royal Society, Nov. 21, of that year, but not printed
+in the Transactions; perhaps because it was thought too strange to be
+true, and some ridicule might be apprehended if any member should
+attempt to repeat it in order to ascertain or refute it. The following
+is a copy of that account.
+
+"A worthy gentleman, who lives at a few miles distance, informed me that
+in a certain small cove of a mill-pond, near his house, he was surprized
+to see the surface of the water blaze like inflamed spirits. I soon
+after went to the place, and made the experiment with the same success.
+The bottom of the creek was muddy, and when stirred up, so as to cause a
+considerable curl on the surface, and a lighted candle held within two
+or three inches of it, the whole surface was in a blaze, as instantly as
+the vapour of warm inflammable spirits, and continued, when strongly
+agitated, for the space of several seconds. It was at first imagined to
+be peculiar to that place; but upon trial it was soon found, that such a
+bottom in other places exhibited the same phenomenon. The discovery was
+accidentally made by one belonging to the mill."
+
+I have tried the experiment twice here in England, but without success.
+The first was in a slow running water with a muddy bottom. The second in
+a stagnant water at the bottom of a deep ditch. Being some time employed
+in stirring this water, I ascribed an intermitting fever, which seized
+me a few days after, to my breathing too much of that foul air which I
+stirred up from the bottom, and which I could not avoid while I stooped
+in endeavouring to kindle it.--The discoveries you have lately made of
+the manner in which inflammable air is in some cases produced, may throw
+light on this experiment, and explain its succeeding in some cases, and
+not in others. With the highest esteem and respect,
+
+     I am, Dear Sir,
+
+       Your most obedient humble servant,
+
+         B. FRANKLIN.
+
+
+NUMBER VII.
+
+_Extract of a Letter from_ Mr. HENRY _of_ Manchester.
+
+It is with great pleasure I hear of your intended publication _on air_,
+and I beg leave to communicate to you an experiment or two which I
+lately made.
+
+Dr. Percival had tried, without effect, to dissolve lead in water
+impregnated with fixed air. I however thought it probable, that the
+experiment might succeed with nitrous air. Into a quantity of water
+impregnated with it, I put several pieces of sheet-lead, and suffered
+them, after agitation, to continue immersed about two hours. A few drops
+of vol. tincture of sulphur changed the water to a deep orange colour,
+but not so deep as when the same tincture was added to a glass of the
+same water, into which one drop of a solution of sugar of lead had been
+instilled. The precipitates of both in the morning, were exactly of the
+same kind; and the water in which the lead had been infused all night,
+being again tried by the same test, gave signs of a still stronger
+saturnine impregnation--Whether the nitrous air acts as an acid on the
+lead, or in the same manner that fixed air dissolves iron, I do not
+pretend to determine. Syrup of violets added to the nitrous water became
+of a pale red, but on standing about an hour, grew of a turbid brown
+cast.
+
+Though the nitrous acid is not often found, except produced by art, yet
+as there is a probability that nitre may be formed in the earth in large
+towns, and indeed fossile nitre has been actually found in such
+situations, it should be an additional caution against the use of leaden
+pumps.
+
+I tried to dissolve mercury by the same means, but without success.
+
+     I am, with the most sincere esteem,
+
+       Dear Sir,
+
+         Your obliged and obedient servant,
+
+           THO. HENRY.
+
+
+_FINIS._
+
+FOOTNOTES:
+
+[15] See Dr. Falconer's very useful and ingenious treatise on the Bath
+water, 2d edit. p. 313.
+
+[16] May, 1772.
+
+[17] Vid. Mr. White's useful treatise on the management of pregnant and
+lying-in women, p. 279.
+
+[18] See the author's observations on the efficacy of external
+applications in the ulcerous sore throats, Essays medical and
+experimental, Vol. I. 2d edit. p. 377.
+
+[19] The author of these observations.
+
+[20] Directions for impregnating water with fixed air, in order to
+communicate to it the peculiar spirit and virtues of Pyrmont water, and
+other mineral waters of a similar nature.
+
+[21] Referring to the case communicated by Mr. Hey.
+
+[22] He languished about a week, and then died.
+
+[23] The vegetables which are most efficacious in the cure of the
+scurvy, possess some degree of a stimulating power.
+
+[24] This refers, to an experiment mentioned in the first publication of
+these papers in the Philosophical Transactions, but omitted in this
+volume.
+
+[25] The first account of this curious process was, I believe, given in
+the Mem. de l'Ac. de Sc. de Paris for 1742. Though seemingly less
+volatile than the vitriolic ether, it boils with a much smaller degree
+of heat. One day last summer, it boiled in the coolest room of my house;
+as it gave me notice by the explosion attending its driving out the
+cork. To save the bottle, and to prevent the total loss of the liquor by
+evaporation, I found myself obliged instantly to carry it down to my
+cellar.
+
+
+
+
+ERRATA.
+
+
+     P. 15. l. 13.  _for_  it to  _read_  to it
+
+     p. 24. l. 20.    ----       has      ----      had
+
+     p. 60. l. 22.    ----     inflammable ----     in inflammable
+
+     p. 84. l. 5.     ----     experiments ----     experiment
+
+     p. 145. l. 16.   ----     with        ----     of
+
+     p. 153. l. 1.    ----     that is     ----     this air
+
+     p. 199. l. 17.   ----     ingenious   ----     ingenuous
+
+     p. 211. l. 23.   ----     of          ----     , if
+
+     p. 243. l. 27.   ----     diminishing ----     diminished
+
+     p. 272. l. 21.   ----     seem        ----     seems
+
+     p. 301. l. 31.   ----     ----        ----     one end
+
+     p. 303. l. 5.    ----     ----        ----     the nitrous
+
+     p. 304. l. 21.   ----     deslrium    ----     delirium
+
+     p. 306. l. 2.    ----     recet.      ----     recent.
+
+     p. 308. l. 7.    ----     per         ----     Peruv.
+
+     p. 313. l. 27.   ----     usual       ----     useful
+
+     p. 300. to 314.  passim   ----        Diarrhaea ---- Diarrhoea
+
+     p. 316. l. 11.   ----     remains     ----     remainder
+
+     p. 524. l. 15.   ----     it          ----     iron.
+
+
+
+
+A CATALOGUE of BOOKS written by
+
+JOSEPH PRIESTLEY, LL.D. F.R.S.,
+
+_And printed for_
+
+J. JOHNSON, BOOKSELLER, at No. 72,
+
+St. Paul's Church-Yard, London.
+
+
+1. The HISTORY and PRESENT STATE of ELECTRICITY, with original
+Experiments, illustrated with Copper Plates. 4th Edit, corrected and
+enlarged, 4to. 1l. 1s.
+
+2. A FAMILIAR INTRODUCTION to the STUDY of ELECTRICITY, 2d Edit. 8vo.
+2s. 6d.
+
+3. The HISTORY and PRESENT STATE of DISCOVERIES relating to VISION,
+LIGHT, and COLOURS, 2 vols. 4to. illustrated with a great Number of
+Copper Plates, 1l. 11s. 6d. in Boards.
+
+4. A FAMILIAR INTRODUCTION to the THEORY and PRACTICE of PERSPECTIVE,
+with Copper Plates, 5s. in Boards.
+
+5. DIRECTIONS for impregnating Water with FIXED AIR, in order to
+communicate to it the peculiar Spirit and Virtues of PYRMONT WATER, and
+other Mineral Waters of a similar Nature, 1s.
+
+6. Experiments and Observations on different Kinds of Air, with Copper
+Plates, 2d Edit. 5s. in Boards.
+
+7. A NEW CHART of HISTORY, containing a View of the principal
+Revolutions of Empire that have taken Place in the World; with a Book
+describing it, containing an Epitome of Universal History, 10s. 6d.
+
+8. A CHART of BIOGRAPHY, with a Book, containing an Explanation of it,
+and a Catalogue of all the Names inserted in it, 4th Edit, very much
+improved, 10s. 6d.
+
+9. An Essay on a Course of liberal Education for Civil and Active Life;
+with Plans of Lectures on, 1. The Study of History and general Policy.
+2. The History of England. 3. The Constitution and Laws of England. To
+which are added Remarks on Dr. Browne's proposed Code of Education.
+
+10. The RUDIMENTS of ENGLISH GRAMMAR, adapted to the Use of Schools, 1s.
+6d.
+
+11. The above GRAMMAR, with Notes and Observations, for the Use of those
+who have made some Proficiency in the Language, 4th Ed. 3s.
+
+12. An ESSAY on the FIRST PRINCIPLES of GOVERNMENT, and on the Nature of
+POLITICAL, CIVIL, and RELIGIOUS LIBERTY, 2d Edit, much enlarged, 5s.
+
+13. INSTITUTES of NATURAL and REVEALED RELIGION, Vol. I. containing the
+Elements of Natural Religion; to which is prefixed, An Essay on the best
+Method of communicating religious Knowledge to the Members of Christian
+Societies, 2s. 6d. sewed.--Vol. II. containing the Evidences of the
+Jewish and Christian Revelation, 3s. sewed.--Vol. III. containing the
+Doctrines of Revelation, 2s. 6d. sewed.--Preparing for the Press (March
+1775) the fourth and last Part of this Work, containing a View of the
+Corruptions of Christianity.
+
+14. An Examination of Dr. Reid's Enquiry into the Human Mind, on the
+Principles of Common Sense, Dr. Beattie's Essay on the Nature and
+Immutability of Truth, and Dr. Oswald's Appeal to Common Sense in behalf
+of Religion. To which is added the Correspondence of Dr. Beattie and Dr.
+Oswald with the Author, 2d Edit. 5s. unbound.
+
+15. A FREE ADDRESS to PROTESTANT DISSENTERS, on the Subject of the
+Lord's Supper, the third Edition with Additions, 2s.
+
+16. The Additions to the Above may be had alone, 1s.
+
+17. An ADDRESS to PROTESTANT DISSENTERS, on the Subject of giving the
+Lord's Supper to Children, 1s.
+
+18. CONSIDERATIONS on DIFFERENCES of OPINION among Christians; with a
+Letter to the Rev. Mr. VENN, in Answer to his Examination of the Address
+to Protestant Dissenters, 1s. 6d.
+
+19. A CATECHISM for CHILDREN and YOUNG PERSONS, 2d Edit. 3d.
+
+20. A SCRIPTURE CATECHISM, consisting of a Series of Questions, with
+References to the Scriptures instead of Answers, 3d.
+
+21. A Serious ADDRESS to MASTERS of FAMILIES, with Forms of Family
+Prayer, 2d Edit. 6d.
+
+22. A View of the PRINCIPLES and CONDUCT of the PROTESTANT DISSENTERS,
+with respect to the Civil and Ecclesiastical Constitution of England, 2d
+Edit. 1s. 6d.
+
+23. A Free ADDRESS to PROTESTANT DISSENTERS, on the Subject of CHURCH
+DISCIPLINE; with a Preliminary Discourse concerning the Spirit of
+Christianity, and the Corruption of it by false Notions of Religion, 2s.
+6d.
+
+24. A SERMON preached before the Congregation of PROTESTANT DISSENTERS,
+at Mill Hill Chapel, in Leeds, May 16, 1773, on Occasion of his
+resigning the Pastoral Office among them, 1s.
+
+25. A FREE ADDRESS to PROTESTANT DISSENTERS, as such. By a Dissenter. A
+new Edition, enlarged and corrected, 1s. 6d.--An Allowance is made to
+those who buy this Pamphlet to give away.
+
+26. Letters to the Author of _Remarks on several late Publications
+relative to the Dissenters, in a Letter to Dr. Priestley_, 1s.
+
+27. An APPEAL to the serious and candid Professors of Christianity on
+the following Subjects, viz. 1. The Use of Reason in Matters of
+Religion. 2. The Power of Man to do the Will of God. 3. Original Sin. 4.
+Election and Reprobation. 5. The Divinity of Christ. And, 6. Atonement
+for Sin by the Death of Christ, 4th Edit. 1d.
+
+28. A FAMILIAR ILLUSTRATION of certain Passages of Scripture relating to
+the same Subject. 4d. or 3s. 6d. per Dozen.
+
+29. The TRIUMPH of TRUTH; being an Account of the Trial of Mr. E.
+Elwall, for Heresy and Blasphemy, at Stafford Assizes, before Judge
+Denton, &c. 2d Edit. 1d.
+
+30. CONSIDERATIONS for the USE of YOUNG MEN, and the Parents of YOUNG
+MEN, 2d.
+
+
+_Also, published under the Direction of Dr. PRIESTLEY_,
+
+THE THEOLOGICAL REPOSITORY.
+
+    Consisting of original Essays, Hints, Queries, &c. calculated to
+    promote religious Knowledge, in 3 Volumes, 8vo, Price 18s. in
+    Boards.
+
+Among other Articles, too many to be enumerated in an Advertisement,
+these three Volumes will be found to contain such original and truly
+valuable Observations on the Doctrine of the _Atonement_, the
+_Pre-existence of Christ_, and the _Inspiration of the Scriptures_, more
+especially respecting the _Harmony of the Evangelists_, and the
+Reasoning of the Apostle Paul, as cannot fail to recommend them to those
+Persons, who wish to make a truly free Enquiry into these important
+Subjects.
+
+In the First Volume, which is now reprinted, several Articles are added,
+particularly TWO LETTERS from Dr. THOMAS SHAW to Dr. BENSON, relating to
+the Passage of the Israelites through the Red Sea.
+
+[Illustration: _To face the last page._]
+
+
+
+
+
+
+End of the Project Gutenberg EBook of Experiments and Observations on
+Different Kinds of Air, by Joseph Priestley
+
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