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diff --git a/.gitattributes b/.gitattributes new file mode 100644 index 0000000..d7b82bc --- /dev/null +++ b/.gitattributes @@ -0,0 +1,4 @@ +*.txt text eol=lf +*.htm text eol=lf +*.html text eol=lf +*.md text eol=lf diff --git a/LICENSE.txt b/LICENSE.txt new file mode 100644 index 0000000..6312041 --- /dev/null +++ b/LICENSE.txt @@ -0,0 +1,11 @@ +This eBook, including all associated images, markup, improvements, +metadata, and any other content or labor, has been confirmed to be +in the PUBLIC DOMAIN IN THE UNITED STATES. + +Procedures for determining public domain status are described in +the "Copyright How-To" at https://www.gutenberg.org. + +No investigation has been made concerning possible copyrights in +jurisdictions other than the United States. Anyone seeking to utilize +this eBook outside of the United States should confirm copyright +status under the laws that apply to them. diff --git a/README.md b/README.md new file mode 100644 index 0000000..1b76065 --- /dev/null +++ b/README.md @@ -0,0 +1,2 @@ +Project Gutenberg (https://www.gutenberg.org) public repository for +eBook #55266 (https://www.gutenberg.org/ebooks/55266) diff --git a/old/55266-0.txt b/old/55266-0.txt deleted file mode 100644 index a572d15..0000000 --- a/old/55266-0.txt +++ /dev/null @@ -1,3908 +0,0 @@ -The Project Gutenberg EBook of The Art of Glass-Blowing, by T. P. Danger - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world 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. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Art of Glass-Blowing - Plain Instruction for the Making of Chemical and - Philosophical Instruments Which are Formed of Glass - -Author: T. P. Danger - -Release Date: August 4, 2017 [EBook #55266] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE ART OF GLASS-BLOWING *** - - - - -Produced by Wayne Hammond and The Online Distributed -Proofreading Team at http://www.pgdp.net (This file was -produced from images generously made available by The -Internet Archive) - - - - - - - -[Illustration: - - _Pl. 1._ - -_Published by Bumpus & Griffin London, 1831._] - - - - - THE - - ART OF GLASS-BLOWING, - - OR - - PLAIN INSTRUCTIONS - - FOR MAKING THE - - CHEMICAL AND PHILOSOPHICAL - INSTRUMENTS - - WHICH ARE FORMED OF GLASS; - - SUCH AS - - BAROMETERS, THERMOMETERS, HYDROMETERS, - - _Hour-Glasses_, _Funnels_, _Syphons_, - - TUBE VESSELS FOR CHEMICAL EXPERIMENTS, - - TOYS FOR RECREATIVE PHILOSOPHY, &c. - - - BY A FRENCH ARTIST. - - - ILLUSTRATED BY ENGRAVINGS. - - LONDON: - - PUBLISHED BY BUMPUS AND GRIFFIN, 3, SKINNER-STREET; - AND RICHARD GRIFFIN AND CO. GLASGOW: - SOLD ALSO BY STILLIES, BROTHERS, EDINBURGH. - - 1831. - - -W. WILSON, PRINTER, 57, SKINNER-STREET, LONDON. - - - - -THE POLYTECHNIC LIBRARY. - - -The design of the Publishers of the POLYTECHNIC LIBRARY is to produce -a Series of highly-instructive Works, which the Public may be tempted -to _buy_, because they will be cheap,--be induced to _read_, because -they will be brief,--be competent to _understand_, because they will -be clearly written,--and be able to _profit by_, because they will be -WORKS OF PRACTICAL UTILITY. Every volume, therefore, will contain _a -complete Treatise_ relating to one of the useful arts or sciences, or -the chemical or mechanical trades. - - - JUST PUBLISHED, PRICE HALF-A-CROWN, - VOL. I. OF THE POLYTECHNIC LIBRARY, - - _Neatly printed in_ 18mo. _and bound in_ Cloth, _containing_ - - THE ART OF GLASS-BLOWING, - - _Or Plain Instructions for Making the_ - - CHEMICAL & PHILOSOPHICAL INSTRUMENTS - WHICH ARE FORMED OF GLASS; - - Such as - - BAROMETERS, THERMOMETERS, HYDROMETERS, - _Hour-Glasses_, _Funnels_, _Syphons_, - TUBE-VESSELS FOR CHEMICAL EXPERIMENTS, - TOYS FOR RECREATIVE PHILOSOPHY, &c. - - BY A FRENCH ARTIST. - - ILLUSTRATED BY UPWARDS OF ONE HUNDRED FIGURES, - _Elegantly engraved on Copper plates_. - -Artists and Students of the Experimental Sciences will find this work -adapted to aid them effectually in the economical preparation of their -Apparatus; and persons who would willingly occupy their leisure hours -in practising the charming art of working Glass and Enamels with the -Blowpipe, but who have hitherto been deterred by the anticipated -expense of the instruments, and the imaginary difficulties of the -undertaking, are taught herein the simplest, most expeditious, least -expensive, and most effectual methods of working Glass into every -variety of useful or fanciful device. - - - PUBLISHED BY BUMPUS & GRIFFIN, SKINNER-STREET, LONDON; - R. GRIFFIN AND CO. GLASGOW; - AND STILLIES, BROTHERS, EDINBURGH. - - - - - THE FOLLOWING WORKS, INTENDED TO FORM PART OF - THE POLYTECHNIC LIBRARY, - _Are nearly ready for Publication_. - - THE - DOMESTIC CHEMIST; - _Comprising Instructions for_ - THE DETECTION OF ADULTERATIONS - In numerous Articles employed in - DOMESTIC ECONOMY & THE ARTS. - - _To which is prefixed_, - THE ART OF DETECTING POISONS IN FOOD AND - ORGANIC MIXTURES. - - -_Contents._ - - PART I.--INSTRUCTIONS FOR THE DETECTION OF MINERAL POISONS IN - VEGETABLE OR ANIMAL MIXTURES.--Copper, Lead, Antimony, Arsenic, - Mercury, Iron, Barytes, Lime, Alumina, Potash, Soda, Sulphuric - Acid, Nitric Acid, Muriatic Acid. - - PART II.--INSTRUCTIONS FOR THE EXAMINATION OF ARTICLES SUPPOSED - TO BE ADULTERATED.--Alcohol, Ale, Anchovy Sauce, Arrow-Root, - Beer, Brandy, Bread, Calomel, Carmine, Cayenne Pepper, Cheese, - Chocolate, Chrome Yellow, Cinnamon, Cloves, Cochineal, Coffee, - Confectionery, Crabs' Eyes, Cream, Cream of Tartar, Epsom - Salts, Flour, Gin, Gum Arabic, Spirits of Hartshorn, Honey, - Hops, Ipecacuanha, Isinglass, Ketchup, Lakes, Leeches, Lemon - Acid, Litharge, Magnesia, Milk, Mushrooms, Mustard, Olive Oil, - Parsley, Pepper, Peruvian Bark, Pickles, Porter, Red Oxide of - Mercury, Rhubarb, Sal Ammoniac, Salt, Saltpetre, Soap, Soluble - Tartar, Spanish Liquorice, Spirits, Sugar, Sulphur, Tamarinds, - Tapioca, Tartaric Acid, Tartar Emetic, Tea, Ultramarine, - Verdigris, Vermilion, Vinegar, Volatile Oils, Wax, White Lead, - Wine, Water,(including directions for testing the purity of all - descriptions of Rain, River, or Spring Water.) - - PART III.--INSTRUCTIONS FOR THE PREPARATION OF THE TESTS EMPLOYED - IN DOMESTIC CHEMISTRY AND FOR THE PERFORMANCE OF VARIOUS CHEMICAL - OPERATIONS; WITH DESCRIPTION OF THE GLASSES AND APPARATUS PROPER - TO BE EMPLOYED. - -⁂ The work is written in a popular manner, and intended for the use of -Families, Publicans, Wine and Spirit Merchants, Oilmen, Manufacturers, -Apothecaries, Physicians, Coroners, and Jurymen.--_Price Three -Shillings._ - - - - -THE PERFUMER’S ORACLE. - - -The object of this work is to present a comprehensive and practical -account of the Preparation of PERFUMES and COSMETICS, according to -the newest, most successful, and most economical processes. It will -be adapted either for Professional Persons, or for Ladies who may -wish to amuse themselves with this elegant branch of experimental -science.--_Price Three Shillings._ - -[Illustration: - - _Pl. 2._ - -_Published by Bumpus & Griffin London, 1831._] - -[Illustration: - - _Pl. 3._ - -_Published by Bumpus & Griffin London, 1831._] - -[Illustration: - - _Pl. 4._ - -_Published by Bumpus & Griffin London, 1831._] - - - - -TRANSLATOR’S PREFACE. - - -The scientific instruments prepared by the glass-blower are numerous -and highly useful: barometers, thermometers, syphons, and many other -vessels constructed of tubes, are indispensable to the student of -physics or chemistry. Some of these instruments are high in price, -and liable to frequent destruction; and those by whom they are much -employed are subject to considerable expense in procuring or replacing -them. It is therefore advisable that he who desires to occupy himself -in the pursuit of experimental science, should know how to prepare -such instruments himself; that, in short, he should become his own -glass-blower. “The attainment of a ready practice in the blowing and -bending of glass,” says Mr. Faraday, “is one of those experimental -acquirements which render the chemist most independent of large towns -and of instrument-makers.” - -Unquestionably the best method of learning to work glass is to obtain -personal instructions from one who is conversant with the art: but -such instructions are not easily obtained. The best operators are not -always the best teachers; and to find a person equally qualified and -willing to teach the art, is a matter of considerable difficulty. In -large towns, workmen are too much engaged with their ordinary business -to step aside for such a purpose; and in small towns glass-blowers -are seldom to be found. In most cases, also, they are too jealous of -their supposed _secrets_ to be willing to communicate their methods of -operating to strangers, even when paid to do so. - -The following Treatise is a free translation of _L’Art du Souffleur -à la Lampe, par_ T. P. DANGER. The author is employed, in Paris, in -preparing glass instruments for sale, and in teaching others the art -of preparing them. He has presented in this work the most minute -instructions for the working of glass which have ever been offered to -the public. The general processes of the art are so fully explained, -and the experimental illustrations are so numerous, that nothing -remains except the reducing of these instructions to practice to enable -the student to become an adept in the blowing of glass. I trust that, -in publishing this work in an English dress, I may be considered as -aiding in some degree the progress of physical science. - -This work contains a description of a cheap blowpipe and a very -convenient lamp; both of them the invention of the author: but any -other kind of lamp or blowpipe may be employed instead of these. The -reader who wishes for a description of the blowpipes generally employed -in England, may consult Mr. GRIFFIN’S _Practical Treatise on the Use of -the Blowpipe in Chemical and Mineral Analysis_. - - _London, September 1831._ - - - - -AUTHOR’S PREFACE. - - -The flame of a lamp, or candle, condensed and directed by a current -of air, is exceedingly useful in a great number of arts. The -instrument which is employed to modify flame is the BLOWPIPE. This -is an indispensable agent for jewellers, watch-makers, enamellers, -glass-blowers, natural philosophers, chemists, mineralogists, and, -indeed, for all persons who are occupied with the sciences, or their -application to the arts. Its employment offers immense advantages in -a multitude of circumstances; and the best method of making use of so -powerful an agent ought to be well known to every person who is likely -to be called upon to adopt it. - -Students, especially those who desire to exercise themselves in -chemical manipulation, must feel the want of a simple and economical -process, by means of which they could give to glass tubes, of which -they make great use, the various forms that are necessary for -particular operations. How much reason have they to complain of the -high price of the instruments of which they make continual use! The -studies of a great number are shackled from want of opportunity to -exercise themselves in manipulation; and many, not daring to be at -the expense of a machine of which they doubt their ability to make -an advantageous use, figure to themselves the employment of the -glass-blower’s apparatus as being beset with difficulties, and so rest -without having even an idea of the numberless instruments which can be -made by its means. - -Many persons would very willingly occupy their leisure time in -practising the charming art of working glass and enamels with the -blowpipe; but the anticipated expense of the apparatus, and the -difficulties which they imagine to foresee in the execution of work of -this kind, always repels them. - -The new species of blowpipe which we have offered to the public, and -which has received the approbation of the Society for the Encouragement -of Arts, obviates all these inconveniences: its moderate price, its -portability, and the facility with which it can be used, adapt it to -general employment. - -But we should not believe that we had attained the end which we -had proposed to ourselves if we had not placed young students in a -situation to repeat at their own houses, at little cost, and with the -greatest facility, the experiments which are necessary to familiarise -them with the sciences. It is with such a view that we present to them -this little Treatise, which is destined to teach them the simplest, the -most expeditious, the least expensive, and the most effectual methods -of constructing themselves the various instruments which they require -in the prosecution of their studies. - -The word _glass-blower_, generally speaking, signifies a workman who -occupies himself in making of glass and enamel, the instruments, -vessels, and ornaments, which are fabricated on a larger scale in -the glass-houses: but the domain of the sciences having laid the art -of glass-blowing under contribution, the artists of the lamp have -divided the labours thereof. Some apply themselves particularly to the -construction of philosophical and chemical instruments; others occupy -themselves with little ornamental objects, such as flowers, &c.; and, -among the latter, some manufacture nothing but pearls, and others only -artificial eyes. Finally, a few artists confine themselves to drawing -and painting on enamel, which substance is previously applied to -metallic surfaces by means of the fire of a muffle. - -As we intend to treat separately of these different branches of the -art, we commence with that of which the manipulation is the simplest. - - _Paris, 1829._ - - - - -CONTENTS. - - - Page - - I.--_Instruments employed in Glass-Blowing_ 1 - - The Blowpipe 1 - - The Glass-Blower’s Table 3 - - The Eolipyle 5 - - Blowpipe with Continued Current 5 - - The Lamp 8 - - The Candlestick 9 - - Combustibles 9 - - Oil, Tallow, &c. 9 - - The Wicks 10 - - Relation between the Diameter of the - Beaks of the Blowpipe and the Wicks - of the Lamp 12 - - II. _Preliminary Notions of the Art of Glass-Blowing_ 16 - - The Flame 16 - - Places fit to work in 19 - - Means of obtaining a Good Fire 19 - - Choice and Preservation of Glass 22 - - Preparation of Glass Tubes before heating them 25 - - Method of presenting Tubes to the Fire, and of working them - therein 26 - - III. _Fundamental Operations in Glass-Blowing_ 30 - - 1. Cutting 31 - 2. Bordering 34 - 3. Widening 36 - 4. Drawing-out 36 - 5. Choking 37 - 6. Sealing 38 - 7. Blowing 39 - 8. Piercing 46 - 9. Bending 48 - 10. Soldering 49 - - IV. _Construction of Chemical and Philosophical Instruments_ 54 - - Adapters 55 - - Apparatus for various Instruments 55 - - Archimedes’s Screw 57 - - Areometers 71 - - Barker’s Mill 57 - - Barometers 58 - - Cistern Barometer 58 - - Dial Barometer 58 - - Syphon Barometer 59 - - Stop-cock Barometer 59 - - Compound Barometers 59 - - Gay-Lussac’s Barometer 60 - - Bunten’s Barometer 61 - - Barometer pierced laterally for Demonstrations 61 - - Bell Glasses for Experiments 61 - - Blowpipe 62 - - Capsules 63 - - Cartesian Devils 64 - - Communicating Vases 65 - - Cryophorus 55 - - Dropping Tubes 65 - - Fountains 66 - - Fountain of Circulation 66 - - Fountain of Compression 67 - - Intermitting Fountain 68 - - Hero’s Fountain 68 - - Funnels 68 - - Hour Glasses 70 - - Hydraulic Ram 70 - - Hydrometers 71 - - Baumé’s Hydrometer 71 - - Nicholson’s Hydrometer 73 - - Hydrometers with two, three, or four branches 74 - - Manometers 74 - - Mariotte’s Tube 75 - - Phosphoric Fire-bottle 75 - - Pulsometer 75 - - Pump 76 - - Retorts for Chemical Experiments 76 - - Rumford’s Thermoscope 77 - - Syphons 78 - - Spoons 80 - - Spirit Level 80 - - Test Glass with a foot 80 - - Thermometers 81 - - Ordinary Thermometer 81 - - Dial Thermometer 83 - - Chemical Thermometer 84 - - Spiral Thermometer 85 - - Pocket Thermometer 86 - - Maximum Thermometer 86 - - Minimum Thermometer 86 - - Bellani’s Maximum Thermometer 87 - - Differential Thermometer 87 - - Thermoscope 77 - - Tubes bent for various purposes 88 - - Vial of the four Elements 90 - - Water Hammer 91 - - Welter’s Safety Tubes 92 - - - V. _Graduation of Chemical and Philosophical Instruments_ 93 - - Of the substances employed in the preparation of these - instruments 93 - - Of Graduation in general 94 - - Examination of the Bore of Tubes 95 - - Division of Capillary Tubes into parts of equal Capacity 95 - - Graduation of Gas Jars, Test Tubes, &c. 97 - - Graduation of Hydrometers 99 - - Graduation of Barometers 103 - - Graduation of the Manometer 105 - - Graduation of Thermometers 105 - - Graduation of Rumford’s Thermoscope 112 - - Graduation of Mariotte’s Tube 112 - - - - -THE - -ART OF GLASS-BLOWING. - -I.--_Instruments employed in Glass-Blowing._ - - -On seeing, for the first time, a glass-blower at work, we are -astonished at the multitude and the variety of the modifications to -which he can make the glass submit. The small number and the simplicity -of the instruments he employs, is also surprising. The blowpipe, or, in -its place, the glass-blower’s bellows and a lamp, are indeed all that -are indispensable. - - -THE BLOWPIPE. - -Originally, the blowpipe was only a simple, conical tube, more or less -curved towards its point, and terminated by a very small circular -opening. By means of this, a current of air was carried against the -flame of a candle, and the inflamed matter was directed upon small -objects, of which it was desirable to elevate the temperature. Workers -in metal still derive immense advantages from the use of this little -instrument: they employ it in the soldering of very small articles, -as well as for heating the extremities of delicate tools, in order -to temper them. But since the blowpipe has passed into the hands of -mineralogical chemists, its form has been subjected to a series of -very curious and important modifications. In spite, however, of these -ameliorations, which rendered the instrument better adapted for the -uses to which it was successively applied, we are far from having -drawn from it all the advantages to which we might attain, were its -employment not as fatiguing as it is difficult. We require no other -proof of this than the small number of those who know well how to make -use of the blowpipe. - -The most economical blowpipe is a tube of glass, bent near one end, -and pointed at its extremity. A bulb is blown near that part of the -tube which corresponds with the curvature (pl. 3, fig. 7.) This bulb -serves as a reservoir for moisture deposited by the air blown into the -tube from the mouth. If you employ a tube without a bulb, the moisture -is projected in drops into the flame, and upon the objects heated by -it--an effect which is very inconvenient in practice. To put this -instrument into action, accustom yourself to hold the mouth full of -air, and to keep the cheeks well inflated, during a pretty long series -of alternate inspirations and expirations; then, seizing lightly with -the lips the mouth of the blowpipe, suffer the air compressed by the -muscles of the cheeks, which act the part of a bellows, to escape by -the beak of the blowpipe, which you will be able to do without being -put to the least inconvenience with regard to respiration. When the -air contained in the mouth is pretty nearly expended, you must take -advantage of an inspiration, to inflate the lungs afresh; and thus -the operation is continued. You must never blow through the tube by -means of the lungs; first, because air which has been in the lungs is -less proper for combustion than that which has merely passed through -the nose and mouth; secondly, because the effort which it would be -necessary to make, to sustain the blast for only a short time, would by -its frequent repetition become very injurious to your health. - -The jet of flame produced by the mouth-blowpipe can only be used to -heat small objects: when instruments of a considerable bulk have to be -worked, it is customary to employ the _lamp_, or _glass-blower’s table_. - - -THE GLASS-BLOWER’S TABLE. - -Artists give this name to an apparatus which consists of the following -articles:-- - -1. A _Table_, below which is disposed a _double bellows_, capable of -being put in motion by means of a pedal. This bellows furnishes a -continued current of air, which can be directed at pleasure by making -it pass through a tube terminating above the table in a sharp beak. The -bellows with which the glass-blower’s tables are commonly furnished -have very great defects. The irregular form which is given to the -pannels diminishes the capacity of the instruments, without augmenting -their advantages. If we reflect an instant on the angle, more or less -open, which these pannels form when in motion, we instantly perceive -that the weight with which the upper surface of a bellows is charged, -and which always affords a vertical pressure, acts very unequally on -the arm of a lever which is continually changing its position. This -faulty disposition of the parts of the machine has the effect of -varying every instant the intensity of the current of air directed upon -the flame. All these inconveniences would disappear, were the upper -pannel, like that in the middle, disposed in such a manner as to be -always horizontal. It ought to be elevated and depressed, in its whole -extent, in the same manner; so that, when charged with a weight, the -pressure should be constantly the same, and the current of air uniform. - -2. A _lamp_, of copper or tin plate.--The construction of this article, -sufficiently imperfect until the present time, has varied according to -the taste of those who have made use of it. We shall give, farther on, -the description of a lamp altogether novel in its construction. - -3. The glass-blower’s table is generally furnished with little -_drawers_ for holding the tools employed in modelling the softened -glass. Careful artists have the surface of their table coated with -sheet iron, in order that it may not be burned by the hot substances -that fall, or are laid upon it. As glass-blowers have frequent occasion -to take measures, it is convenient to have the front edge of the table -divided into a certain number of equal parts, marked with copper nails. -This enables the workman to take, at a glance of the eye, the half, -third, or fourth of a tube, or to give the same length to articles -of the same kind, without having perpetual recourse to the rule and -compasses. But when it is desirable to have the tubes, or the work, -measured with _greater exactness_ than it can be measured by this -method, the rule and the compasses can be applied to. - - -THE EOLIPYLE. - -We shall merely make mention of this instrument. It is a globular -vessel, commonly formed of brass. If filled with a very combustible -liquor, such as alcohol, and strongly heated, it affords a rapid -current of vapour, which, if directed by means of a fine beak into -the middle of a flame, produces the same effect as the air which -issues from a blowpipe. The eolipyle is a pretty toy, but not a good -instrument for a workman, its action being too irregular. - - -BLOWPIPE WITH CONTINUED CURRENT. - -It is after having, during a long period, made use of the instruments -of which we have spoken, and fully experienced their inconveniences, -that, aware of the indispensable necessity for such instruments in the -arts and sciences, we have thought it our duty to make known to the -public _a New Apparatus_, which is, not only calculated to fulfil the -same purposes, but presents advantages which it is easy to appreciate. -The price of it is only the sixth part of that of the glass-blower’s -table[1]. It is very portable, and capable of being attached to any -table whatever. It unites the advantages of not fatiguing the workman, -of leaving his hands free, and of rendering him absolute master of the -current of air, which he can direct on the flame either of the lamp or -the candle,--advantages which are not offered in the same degree even -by the table of the glass-blower. - -[1] In Paris, the blowpipe which is here described is sold for six -francs (five shillings English); or, with the improved lamp and -candlestick, twelve francs. - -The instrument which we have presented is, properly speaking, nothing -but a simple blowpipe, C, (pl. 1, fig. 19) communicating with a -bladder, or leather bag, fixed on E, which is kept full of air by -means of a bent tube, D, through which the operator blows occasionally -with the mouth. This tube is closed at its inferior extremity, F, by a -valve, which permits the passage of air into the reservoir, but not of -its return, so that the air can only escape by the beak of the blowpipe. - -The valve at F is constructed in the following manner:--At about two -inches from the end of the tube a contraction is made, as represented -at _a_, pl. 1, fig. 24. This reduces the internal diameter of the -tube about one-third. A small conical piece of cork or wood is now -introduced into the tube in the manner represented by _c_. The base of -the cone must be large enough to close the tube at the point where it -is contracted; it must, however, not be so large as to close the tube -at the wide part. A brass pin is inserted in the point of the cone, as -is shewn in the figure. Between the cone and the end of the tube, the -piece of wood, _b_, is fixed; the shape of this piece of wood is best -shewn by figure 25, on the same plate. There is a hole in the centre, -in which the pin of the cork cone can move easily. The cone or valve -is therefore at liberty to move between the contraction _a_, and the -fixture _b_. Consequently, when air is blown into the tube at _e_, the -valve is forced from the contraction, falls into the position indicated -by the dotted lines _d_, and allows the air to pass by its sides. -When, on the contrary, the operator ceases to blow, the valve is acted -upon by the air in the bladder, which, pressing back at _f_, drives -the valve close against the contraction, and effectually closes the -aperture. A slight hissing is heard, but when the contraction is well -made, and the cork is good, an extremely small quantity of air escapes. - -The workman, seated before the table where he has fixed his instrument, -blows from time to time, to feed the reservoir or bladder, which, -being pressed by a system of strings stretched by a weight, produces -an uniform current of air. The force of this current of air can be -modified at pleasure, by pressing the reservoir more or less between -the knees. (Fig. 22 represents a blowpipe complete, formed not of -glass, but of brass tubes. Fig. 22, _bis_, represents the bladder or -reservoir appertaining to this blowpipe.) - -M. GAULTIER DE CLAUBRY, who was charged by the Committee of Chemical -Arts of the Society of Encouragement (of Paris) to make a report on -this instrument, was astonished at the facility with which the author, -in his presence, reduced the oxide of cobalt to the metallic state, and -fused the metal to a globule; an experiment which even M. Berzelius -could not perform with the simple blowpipe, since he expressly says, -in his work on that instrument, that oxide of cobalt suffers no change -when heated before the blowpipe. The results obtained with cast iron, -oxide of tin, &c.--experiments which are exhibited every day at the -public lectures given by the author--evidently prove the superiority of -this apparatus over all the blowpipes that have hitherto been contrived. - -A detailed account of the glass tubes belonging to this improved -blowpipe will be found in the fourth part of this work, at the article -_Blowpipe_. - - -THE LAMP. - -While occupied in rendering popular, if we may so speak, the use of the -_blowpipe_--an instrument which is so advantageous in a great number -of circumstances--we have also endeavoured to improve _the lamp_, -which has, until the present time, been used by all those who employ -the glass-blower’s table. The lamp which we recommend (pl. 1, fig. -23) is of a very simple construction. It possesses the advantages of -giving much less smoke than the old lamp, and of being cleaned with -the greatest facility. It also gives sensibly more heat; because the -portion of flame which, in the common lamps, rises perpendicularly, -and is not used, is, in this case, beaten down by a cap or hood, and -made to contribute to the force of the jet. This cap also keeps the -flame from injuring the eyes of the operator, and destroys the smoke to -such an extent, that the large hoods with which glass-blowers commonly -garnish their work table, to carry off the smoke, become unnecessary. -This is a peculiar advantage in the chamber of a student, where a large -hood or chimney can seldom be conveniently prepared. - - -THE CANDLESTICK. - -For mineralogical researches, chemical assays, and the soldering of -small objects, as in jewellery, we recommend the use of a little -candlestick, which, by means of a spring fixed to the bottom, maintains -the candle always at the same height. A reservoir, or shallow cup, -formed at the top of the candlestick, to hinder the running away of the -tallow or wax, allows the operator to consume the fragments of tallow -or grease which are ordinarily lost in domestic economy. There is a -little hole in the centre of the cup or upper part of the candlestick, -through which the wick of the candle passes. _o_, pl. 1, fig. 22, is a -representation of this candlestick. - - -COMBUSTIBLES. - -_Oil_, _Tallow_, _&c._--Among the substances which have been employed -to feed the fire of the glass-blower’s lamp, those to which the -preference is to be given are wax, olive oil, rape oil, poppy oil, and -tallow. Animal oils, such as bone oil and fish oil, are much esteemed -by some glass-blowers, who pretend that with these substances they -obtain better results than with other combustibles. Nevertheless, -animal oils, generally speaking, do not give so much heat as purified -rape oil, while they exhale an odour which is extremely disagreeable. - -As to alcohol, which is sometimes used with the eolipyle, its -combustion furnishes so feeble a degree of heat that its employment -cannot be recommended. - -Purified rape oil is that of which the use is the most general. Next -to olive oil and wax, it affords the greatest heat, and the least -smoke. But, in a word, as in the working of glass, the operator has -more need of a bright flame without smoke, than of a high temperature, -any combustible may be employed which is capable of furnishing a flame -possessing these two qualities. The vegetable oils thicken, and suffer -alterations more or less sensible, when they are long exposed to the -action of the air. They should be chosen very limpid, and they may be -preserved in that state by being enclosed in bottles, which should be -kept quite full and well corked. - -_The Wicks._--There has never been any substance so generally used for -wicks as cotton; some glass-blowers, indeed, have employed wicks of -asbestus, but without deriving from them the advantages which might -have been expected; the greater number, therefore, keep to cotton. - -But it has been observed that cotton which has been for some time -exposed to the air no longer possesses the good properties for which -glass-blowers esteem it. The alteration of the cotton is probably -brought about by the dust and water which the air always holds in -suspension. Such cotton burns badly, forms a bulky coal, and permits -with much difficulty the capillary ascension of the liquid which serves -to support the flame; so that it is impossible to obtain a good fire, -and necessary to be incessantly occupied in snuffing the wick. Cotton -is equally subject to alteration when lying in the lamp, even though -impregnated with oil. You should avoid making use of wicks that are too -old. When you foresee that you will remain a long time without having -occasion to employ the lamp, pour the oil into a bottle, which can be -corked up, and let the wick be destroyed, previously squeezing from it -the oil which it contains. - -It is indispensable to make use of none but new and good cotton; it -should be clean, soft, fine, and not twisted. It is best to preserve -it in boxes, after having folded it in many double papers, to exclude -dust and moisture. When you wish to make wicks, take a skein of cotton -and cut it into four or six pieces, dispose them side by side in such a -manner as to make a bundle, more or less thick, and eight or ten inches -in length; pass a large comb lightly through the bundle, to lay the -threads even, and tie it gently at each end, to keep the threads from -getting entangled. - -_Relation between the diameters of the beaks of the blowpipe, and the -wicks of the lamp._--We believe that we cannot place better than here -a few observations respecting the size of the opening in the beak of -the blowpipe, considered in relation to the size of the wick of the -lamp. These observations will probably be superfluous to those who are -already conversant with the use of the blowpipe; but as every thing is -interesting to beginners, who are frequently stopped in their progress -by very slight difficulties, and as this Treatise is particularly -designed for beginners, we do not hesitate to enter into the minutest -details on subjects which we deem interesting. - -The point of your blowpipe should be formed in such a manner, that you -can fix upon it various little beaks or caps, the orifices in which, -always perfectly round, ought to vary in size according to the bulk -of the flame upon which you desire to act. You cannot, without this -precaution, obtain the maximum of heat which the combustion of the oil -is capable of affording. This employment of little moveable caps offers -the facility of establishing a current of air, greater or smaller, -according to the object you wish to effect; above all, it allows you to -clean with ease the cavity or orifice of the beak, as often as it may -be necessary. - -These caps can be made of different materials. It is most advisable to -have them made of copper or brass; those which are formed of tin plate -(white iron), and which are commonly used in chemical laboratories, are -the worst kind of all. They soon become covered with grease or soot, -which either completely closes up the orifices, or, at least, very soon -alters the circular form which is necessary to the production of a good -fire. Glass caps are less liable to get dirty, and are much cheaper -than the above; but, on the other hand, they have the disadvantage -of being easily melted. This can to a certain extent be remedied by -making the points of very thick glass, and by always keeping them at -some distance from the flame. Moreover, as you can make them yourself -when you are at leisure, their use is very commodious. If they are to -be used with the blowpipe described in this work, they must be fixed -in the cork that closes the passage through which the current of air -arrives. _C c_ and _C´ c_ (pl. 1, fig. 19) are two glass beaks, _c c_ -are the corks, which can indifferently be adapted to _c_, in the wooden -vice, by which the various parts of the blowpipe are connected when it -is in action. - -Of whatever material the beak may be made, its orifice must be -perfectly round, and the _size_ of the orifice, as we have before -observed, must have a relation to the size of the wick which is to -be used with it. You can ascertain the diameters of the orifices by -inserting into them a little plate of brass, having the form of a long -isoceles triangle, such as is represented by pl. 1, fig. 2. It should -be an inch long, the twelfth of an inch wide at one end, and diminish -to nothing at the other. When divided into eight equal parts, it will -give, at the divisions, the respective proportions of 1, 2, 3, 4, 5, -6, 7 _eighths_ of the diameter at the wide end, as is exemplified by -the figure above referred to. We have stated in the following table -the relative diameters which long experience has recommended to us, -as being adapted to produce the greatest effect; yet it is not to -be imagined that these proportions are mathematically correct and -indispensable for the obtaining of good results. A sensible difference -of effect would be perceived, however, were these proportions departed -from in a notable manner. - - +-----------------+---------------------------+------------------+ - | | | | - | Diameter of the | Diameter of the |Height of the wick| - | wick, | orifice of the |above the surface | - | _in inches_. | beak, | of the oil, | - | | _in parts of an inch_. | _in inches_. | - | | | | - +-----------------+---------------------------+------------------+ - | ¼ | 96th | ½ | - | ½ | 48th | ½ | - | 1 | 24th | ¾ | - | 1½ | 16th | 1 | - | 2 | 12th | 1¼ | - +-----------------+---------------------------+------------------+ - -It must be mentioned, that this table has been formed from experiments -made with a glass-blower’s lamp of the ordinary construction; so that, -with the new lamp with the hood, described in this work, it will not -be necessary to employ wicks of so great a bulk, nor yet to elevate -them so much above the level of the oil, in order to produce the same -effect. Hence there will be a very considerable saving in oil. - -The wicks of a quarter of an inch in diameter are only adapted -for mineralogieal examinations, for soldering very fine metallic -substances, and for working very small tubes. When the objects are -of considerable bulk, it is in general necessary to have a flame -sufficiently large to cover the whole instrument, or at least all the -portion of the instrument which is operated upon at once. For working -tubes, of which the sides are not more than the twelfth of an inch in -thickness, you should have a wick at least as wide as the tube that is -worked upon. The diameter of the lamp-wick usually employed is _one -inch_; a wick of this size is sufficient for all the glass instruments -which are in common use. - - - - -THE - -ART OF GLASS-BLOWING. - -II.--_Preliminary Notions of the Art._ - - -THE FLAME. - -It is only by long habitude, and a species of routine, that workmen -come to know, not only the kind of flame which is most proper for -each object they wish to make, but the exact point of the jet where -they ought to expose their glass. By analysing the flame, upon the -knowledge of which depends the success of the work, we can immediately -obtain results, which, without that, could only be the fruit of long -experience. - -Flame is a gaseous matter, of which a portion is heated to the point of -becoming luminous; its form depends upon the mode of its disengagement, -and upon the force and direction of the current of air which either -supports its combustion or acts upon it mechanically. (Pl. 1, fig. 1.) - -The flame of a candle, burning freely in still air, presents in -general the form of a pyramid, of which the base is supported on -a hemisphere. It consists of four distinct parts: the immediate -products of the decomposition of the combustible by the heat which is -produced, occupy the centre, _o_, where they exist in the state of an -obscure gaseous matter, circumscribed by a brilliant and very luminous -envelope, _s_; the latter is nothing but the obscure matter itself, in -the circumstances where, on coming into contact with the atmosphere, -it combines with the oxygen which exists therein, and forms what is -properly called _flame_. - -The blueish light which characterises the inferior part of the flame, -_s_, is produced by a current of cold air, which, passing from below -_upwards_, hinders the combustion from taking place at the bottom of -the flame, at the _same_ temperature that exists in the parts of the -flame not immediately subject to this influence. - -Finally, on observing attentively, we perceive a fourth part, which -is but slightly luminous, and exists as an envelope of all the other -parts of the flame. The greatest thickness of this envelope corresponds -with the summit of the flame. From this point it gradually becomes -thinner, till it arrives at the lowest part of the blueish light, where -it altogether disappears. It is in this last-described portion of the -flame that the combustion of the gas is finished, and there it is that -we find the seat of the most intense heat which the flame of the candle -affords. If we compare the temperature of the different parts of the -flame, we find that the _maximum_ of heat forms a ring corresponding to -the zone of insertion, A A; a point which is the limit of the superior -extremity of the blueish light. - -When the flame is acted upon by the blowpipe, it is subject to two -principal modifications:-- - -1. If, by means of a blowpipe with a very fine orifice, you direct a -current of air through the middle of the flame, you project a portion -of the flame in the direction of the blast. The jet thus formed appears -like a tongue of fire, blueish, cylindrical, straight, and very long; -the current of air occupies its interior. This flame is enveloped on -all sides by an almost invisible light, which, extending beyond the -blue flame, forms a jet, A´ B, very little luminous, but possessing an -extremely high temperature. It is at the point A´, which corresponds -with the extremity of the blue flame, that the _maximum_ of heat is -found. The extreme point of the jet B possesses a less degree of heat. -This flame is adapted for mineralogical assays, for soldering, for -working enamels, and in general for all small objects. - -2. When the orifice of the blowpipe is somewhat large, or when (the -orifice being capillary) the current of air is very strong, or the -beak is somewhat removed from the flame, the jet of fire, instead of -being prolonged into a pointed tongue, is blown into a brush. It makes -then a roaring noise, and spreads into an irregular figure, wherein -the different parts of the flame are confounded beyond the possibility -of discrimination. This flame is very proper for the working of -glass, and particularly of glass tubes; it ought to be clear and very -brilliant, and above all should not deposit soot upon cold bodies -suddenly plunged into it. The _maximum_ of temperature in this flame is -not well marked; we can say, however, that in general it will be found -at about two-thirds of the whole length of the jet. As this roaring -flame contains a great quantity of carburetted hydrogen, and even of -vapour of oil, escaped from combustion, it possesses a disoxidizing or -reducing property in a very high degree. - - -PLACES FIT TO WORK IN. - -Every place is adapted for a workshop, provided it is not too light -and the air is tranquil. The light of the lamp enables one to work -with more safety than day-light, which does not permit the dull-red -colour of hot glass to be seen. Currents of cold air are to be avoided, -because they occasion the fracture of glass exposed to them on coming -out of the flame. - - -MEANS OF OBTAINING A GOOD FIRE. - -The lamp should be firmly seated upon a steady and perfectly horizontal -table, and should be kept continually full of oil. The oil which -escapes during the operation, from the lamp into the tin-stand placed -below it, should be taken up with a glass tube having a large bulb, and -returned to the lamp. - -When you set to work, the first thing you have to do is to examine the -orifice of the beak. If it is closed, or altered in form, by adhering -soot, you must carefully clean it, and open the canal by means of a -needle or fine wire. In the next place, you freshen the wick by cutting -it squarely, and carrying off with the scissars the parts which are -carbonised. You then divide it into two principal bundles, such as C, K -(pl. 1, fig. 21), which you separate sufficiently to permit a current -of air, directed between the two, to touch their surfaces lightly, -without being interrupted in its progress. By pushing the bundles -more or less close to one another, and by snuffing them, you arrive -at length at obtaining a convenient jet. It is a good plan to allow, -between the two principal bundles and at their inferior part, a little -portion of the wick to remain: you bend this down in the direction of -the jet, and make it lie immediately beneath the current of air. - -The wick must be prevented from touching the rim of the lamp, in order -to avoid the running of the oil into the stand of the lamp. This is -easily managed by means of a bent iron-wire, disposed as it is in the -lamp described in this work; see pl. 1, fig. 23, where the wire is -seen in an elevated position. When the wick is in the lamp, the wire -is brought down round the wick and level with the surface of the lamp. -A few drops of oil of turpentine, spread on the wick, makes it take -fire immediately, over its whole extent, on the approach of an inflamed -substance. - -To obtain a good fire, it is necessary to place the lamp in such a -position that the orifice of the blowpipe shall just touch the exterior -part of the flame. The beak must not enter the flame, as it can then -throw into the jet only an inconsiderable portion of the ignited -matter. See pl. 1, fig. 20. On the other hand, if the lamp be too far -away from the blowpipe, the flame becomes trembling, appears blueish, -and possesses a very low degree of heat. - -For mineralogical experiments, and for operations connected with -watch-making and jewellery, the current of air should project the flame -horizontally. For glass-blowing, the flame should be projected in the -direction intimated by the arrow in pl. 1, fig. 20--that is to say, -under an angle of twenty or twenty-five degrees. - -The current of air ought to be constant, uniform, and sufficiently -powerful to carry the flame in its direction. When it is not strong -enough to produce this effect, it is necessary to add weights to the -bellows or the bladder, according as the glass-blowers' table or our -lamp is employed. The point to which you should apply, in the use of -these instruments, is to enable yourself to produce a current of air -so uniform in its course that the projected flame be without the least -variation. - -Finally, when you leave off working you should extinguish the flame, by -cutting off the inflamed portion of the wick with the scissars. This -has the double advantage of avoiding the production of a mass of smoke -and of leaving the lamp in a fit state for another operation. - - -CHOICE AND PRESERVATION OF GLASS. - -The only materials employed in the fabrication of the objects described -in this Treatise, are tubes of common glass or of flint-glass. They -can be had of all diameters, and of every variety of substance. They -are commonly about three feet long, but some are found in commerce -which are six feet in length. You should choose tubes that are very -uniform--that is to say, straight and perfectly cylindrical, both -inside and outside. A good tube should have the same diameter from one -end to the other, and the sides or substance of the glass should be of -equal thickness in every part. This is indispensable when the tubes -are to have spherical bulbs blown upon them. We shall describe, in the -article _Graduation_, the method of ascertaining whether or not a tube -is uniform in the bore. - -The substance of the glass should be perfectly clear, without bulbs, or -specks, or stripes. The tubes are so much the more easy of use, as the -glass of which they are made is the more homogeneous. Under this point -of view, the white glass, known in commerce by the name of crystal or -flint-glass, is preferable to common glass: it is more fusible, less -fragile, and less liable to break under the alternations of heat and -cold; but it is dearer and heavier, and has the serious disadvantage -of becoming permanently black when exposed to a certain part of the -flame. This is an effect, the causes and consequences of which will be -explained in a subsequent chapter. - -You must take care never to employ flint-glass for instruments -which are to be submitted to the action of certain fluids--such as -sulphuretted and phosphuretted hydrogen, and the hydro-sulphurets; for -these compounds are capable of decomposing flint-glass, in consequence -of its containing oxide of lead. In general, hard common glass is -preferable to flint-glass for all instruments which are to be employed -in chemistry. Flint-glass should only be used for ornamental objects, -and for the barometers, thermometers, and other instruments employed in -philosophical researches. - -It sometimes happens that glass tubes lose their transparence and -ductility, and suddenly become almost infusible, in the fire of the -lamp: this effect takes place when they have been kept for some time -in a melted state. It is then almost impossible to bring them back to -their original condition; it can only be done by exposing them for a -long time to an exceedingly high temperature. You can prevent this -accident by working such kind of glass with considerable rapidity, -and in a pretty brisk fire. There are tubes, however, which vitrify -so promptly that it is only a person well versed in the art who can -make good use of them. It is best not to employ such glass. But how -can it be discriminated before-hand? It is experience, sooner than -any characters capable of description, that will teach you how to -make choice of good glass; nevertheless we have observed, that, -among the glass tubes which occur in commerce, those possessing a -very _white colour_ manifest this bad quality most particularly. It -may be observed, that, for tubes which are to have thin sides, this -vitrifiable sort of glass is better than any other. - -For certain philosophical instruments it is necessary to employ flat -tubes. These are formed of flint-glass, are very small, and have a -canal or bore, which, instead of being round, as in common tubes, -has the form of a long and very flat oval. This disposition has the -advantage of rendering more perceptible the column of liquid that may -be introduced, and which in a round canal would scarcely be visible. In -choosing this sort of tubes, carefully avoid those of which the canal -is twisted, and not found to be in the same plane, in the whole length -of the tube. - -The tubes should be sorted, according to their sizes and qualities, -and should be deposited in large drawers or on long shelves, in such -a manner as to be equally supported through their whole extent. They -should also be sheltered from dust and from moisture. If you cannot -conveniently warehouse them in this manner, you should tie them up in -parcels, and support them in a perpendicular position. It is a very -bad plan to place them in an inclined direction, or to support them by -their extremities on wooden brackets, as it is the fashion to do in -chemical laboratories; because, as the tubes are then supported only -at certain points, they bend, in course of time, under the influence -of their own weight, and contract a curvature which is extremely -prejudicial in certain instruments, and which it is almost impossible -to correct. - - -PREPARATION OF TUBES BEFORE HEATING THEM. - -Before presenting a tube to the flame, you should clean it well both -within and without, in order to remove all dust and humidity. If -you neglect to take this precaution, you run the risk of cracking -or staining the glass. When the diameter of the tube is too small -to permit of your passing a plug of cloth or paper to clean its -interior, you can accomplish the object by the introduction of water, -which must, many times alternately, be sucked in and blown out, until -the tube is deemed clean. One end of it must then be closed at the -lamp, and it must be gradually exposed to a charcoal fire, where, by -raising successively all parts of the tube to a sufficiently high -temperature, you endeavour to volatilize and expel all the water it -contains. In all cases you considerably facilitate the disengagement -of moisture by renewing the air in the tube by means of a bottle of -Indian-rubber fastened to the end of a long narrow tube, which you -keep in the interior of the tube to be dried during the time that it -is being heated. You can here advantageously substitute alcohol for -water, as being much more volatile, and as dissolving greasy matters; -but these methods of cleansing should only be employed for valuable -objects, because it is extremely difficult fully to expel moisture from -a tube wherein you have introduced water, and because alcohol is too -expensive to be employed where there is no particular necessity. - -When the tubes no longer contain dust, or moisture, you measure them, -and mark the divisions according to the sort of work which you propose -to execute. - - -METHOD OF PRESENTING TUBES TO THE FIRE, AND OF WORKING THEM THEREIN. - -The two arms are supported on the front edge of the table, and the -tube is held with the hands either above or below, according as it may -be necessary to employ more or less force, more or less lightness. -You ought, in general, to hold the tube _horizontally_, and in such a -manner that its direction may be perpendicular to that of the flame. -Yet, when you wish to heat at once a large portion of the tube, or to -soften it so that it shall sink together in a particular manner, as in -the operation of sealing, you will find it convenient to _incline_ the -tube, the direction of which, however, must always be such as to turn -the heated part continually towards you. - -We are about to give a general rule, upon the observance of which we -cannot too strongly insist, as the success of almost every operation -entirely depends upon it. The rule is, _never to present a tube to the -flame without_ CONTINUALLY TURNING _it_; and turning it, too, with -such a degree of rapidity that every part of its circumference may be -heated and softened to the same degree. As melted glass necessarily -tends to descend, there is no method of preventing a heated tube from -becoming deformed but that of continually turning it, so as to bring -the softened part very frequently uppermost. When you heat a tube -near the middle, the movement of the two hands must be _uniform_ and -_simultaneous_, or the tube will be twisted and spoiled. - -When the tubes have thick sides, they must not be plunged _into_ the -flame until they have previously been strongly heated. You expose them -at first to the current of hot air, at some inches from the extremity -of the jet; you keep them there some time, taking care to turn them -continually, and then you gradually bring them towards, and finally -into, the flame. The thicker the sides of the tubes are, the greater -precaution must be taken to elevate the temperature gradually: this is -the only means of avoiding the fractures which occur when the glass -is too rapidly heated. Though it is necessary to take so much care -with large and thick tubes, there are, on the contrary, some tubes -so small and so thin that the most sudden application of the fire is -insufficient to break them. Practice soon teaches the rule which is to -be followed with regard to tubes that come between these extremes. - -Common glass ought to be fused at the _maximum_ point of heat; but -glass that contains oxides capable of being reduced at that temperature -(such as flint-glass) require to be worked in that part of the flame -which possesses the highest oxidating power. If you operate without -taking this precaution, you run the risk of decomposing the glass. -Thus, for example, in the case of flint-glass, you may reduce the oxide -of lead, which is one of its constituents, to the state of metallic -lead. The consequence of such a reduction is the production of a black -and opaque stain upon the work, which can only be removed by exposing -the glass, during a very long time, to the extremity of the jet. - -You must invariably take the greatest care to keep the flame from -passing into the interior of the tube; for when it gets there it -deposits a greasy vapour, which is the ordinary cause of the dirt -which accumulates in instruments that have been constructed without -sufficient precaution as to this matter. - -In order that you may not blacken your work, you should take care to -snuff the wick of the lamp whenever you perceive the flame to deposit -soot. - -You can judge of the _consistence_ of the tubes under operation as -much by the _feel_ as by the _look_ of the glass. The degree of heat -necessary to be applied to particular tubes, depends entirely upon -the objects for which they are destined. As soon as the glass begins -to feel soft, at a _brownish-red heat_, for example, you are at the -temperature most favourable to good _bending_. But is it intended to -_blow a bulb_? The glass must, in this case, be completely melted, -and subjected to a full _reddish-white heat_. We shall take care, -when speaking hereafter of the different operations to be performed, -to mention the temperature at which _each_ can be performed with most -success. - -When an instrument upon which you have been occupied is finished, you -should remove it from the flame _gradually_, taking care to _turn_ it -continually, until the glass has acquired sufficient consistence to -support its own weight without becoming deformed. Every instrument -formed thus of glass requires to undergo a species of _annealing_, -to enable it to be preserved and employed. To give the instrument -this annealing, it is only necessary to remove it from the flame very -gradually, allowing it to repose some time in each _cooler_ place to -which you successively remove it. The thicker or the more equal the -sides of the glass, the more carefully it requires to be annealed. No -instrument should be permitted to touch cold or wet bodies while it is -warm. - - - - -THE - -ART OF GLASS-BLOWING. - -III.--_Fundamental Operations in Glass-Blowing_. - - -All the modifications of shape and size which can be given to tubes in -the construction of various instruments, are produced by a very small -number of dissimilar operations. We have thought it best to unite -the description of these operations in one article, both to avoid -repetitions and to place those who are desirous to exercise this art -in a state to proceed, without embarrassment, to the construction of -any instrument of which they may be provided with a model or a drawing; -for those who attend properly to the instructions given here, with -respect to the fundamental operations of glass-blowing, will need no -other instructions to enable them to succeed in the construction of all -kinds of instruments capable of being made of tubes. These fundamental -operations can be reduced to ten, which may be named as follows:-- - - 1. Cutting. - 2. Bordering. - 3. Widening. - 4. Drawing out. - 5. Choking. - 6. Sealing. - 7. Blowing. - 8. Piercing. - 9. Bending. - 10. Soldering. - -We proceed to give a detailed account of these different operations. - - -1.--CUTTING. - -The different methods of cutting of glass tubes which have been -contrived, are all founded on two principles; one of these is the -division of the surface of glass by cutting instruments, the other the -effecting of the same object by a sudden change of temperature; and -sometimes these two principles are combined in one process. - -The first method consists in notching the tube, at the point where it -is to be divided, with the edge of a file, or of a thin plate of hard -steel, or with a diamond; after which, you press upon the two ends of -the tube, as if to enlarge the notch, or, what is better, you give the -tube a slight smart blow. This method is sufficient for the breaking -of small tubes. Many glass-blowers habitually employ an agate, or a -common flint, which they hold in one hand, while with the other they -rub the tube over the sharp edge of the stone, taking the precaution -of securing the tube by the help of the thumb. For tubes of a greater -diameter, you can employ a fine iron wire stretched in a bow, or, still -better, the glass-cutters' wheel; with either of these, assisted by a -mixture of emery and water, you can cut a circular trace round a large -tube, and then divide it with ease. - -When the portion which is to be removed from a tube is so small that -you cannot easily lay hold of it, you cut a notch with a file, and -expose the notch to the point of the blowpipe flame: the cut then flies -round the tube. - -This brings us to the second method of cutting tubes--a method which -has been modified in a great variety of ways. It is founded on the -property possessed by vitrified matters, of breaking when exposed to a -sudden change of temperature. Acting upon this principle, some artists -apply to the tube, at the point where they desire to cut it, a band -of fused glass. If the tube does not immediately separate into two -pieces, they give it a slight smart blow on the extremity, or they drop -a little water on the heated ring. Other glass-blowers make use of a -piece of iron heated to redness, an angle or a corner of which they -apply to the tube at the point where it is to be cut, and then, if the -fracture is not at once effected by the action of the hot iron, they -plunge the tube suddenly into cold water. - -The two methods here described can be combined. After having made a -notch with a file, or the edge of a flint, you introduce into it a -little water, and bring close upon it the point of a very little tube -previously heated to the melting point. This double application of heat -and moisture obliges the notch to fly right round the tube. - -When the object to be cut has a large diameter, and very thin -sides--when it is such a vessel as a drinking-glass, a cup, or a gas -tube--you may divide it with much neatness by proceeding as follows. -After having well cleaned the vessel, both within and without, pour -oil into it till it rises to the point, or very nearly to the point, -where you desire to cut it. Place the vessel, so prepared, in an airy -situation; then take a rod of iron, of about an inch in diameter, make -the extremity brightly red-hot, and plunge it into the vessel until the -extremity of the iron is half an inch below the surface of the oil: -there is immediately formed a great quantity of very hot oil, which -assembles in a thin stratum at the surface of the cold oil, and forms -a circular crack where it touches the sides of the glass. If you take -care to place the object in a horizontal position, and to plunge the -hot iron without communicating much agitation to the oil, the parts -so separated will be as neat and as uniform as you could desire them -to be. By means of this method we have always perfectly succeeded in -cutting very regular zones from ordinary glass. - -The method which is described in some works, of cutting a tube by -twisting round it a thread saturated with oil of turpentine, and then -inflaming the thread, we have found to be unfit for objects which have -thick sides. - -Some persons employ cotton wicks dipped in sulphur. By the burning of -these, the glass is strongly heated in a given line, or very narrow -space, which is instantly cooled by a wet feather or a wet stick. So -soon as a crack is produced, it can be led in any required direction -by a red-hot iron, or an inflamed piece of charcoal. - -Finally, you may cut small portions from glass tubes in a state of -fusion, by means of common scissars. - - -2.--BORDERING. - -To whatever use you may destine the tubes which you cut, they ought, -almost always, to be bordered. If you merely desire that the edges -shall not be sharp, you can smoothen them with the file, or, what is -better, you can expose them to the flame of the lamp until they are -rounded. If you fear the sinking in of the edges when they are in a -softened state, you can hinder this by working in the interior of the -tube a round rod of iron, such as pl. 1, fig. 5. The rod of iron should -be one-sixth of an inch thick; one end of it should be filed to a -conical point, and the other end be inserted into a thin, round, wooden -handle. You will find it convenient to have a similar rod with a slight -bend in the middle. - -When you desire to make the edges of the tube project, bring the end -to a soft state, then insert in it a metallic rod, and move it about -in such a manner as to widen a little the opening. While the end of -the tube is still soft, place it suddenly upon a horizontal surface, -or press it by means of a very flat metallic plate. The object of -this operation is to make the end of the tube flat and uniform. The -metallic rod which you employ may be the same as we have described -in the preceding paragraph. Instead of agitating the rod in the tube, -you may hold it in a fixed oblique position, and turn the tube round -with the other hand, taking care to press it continually and regularly -against the rod. See pl. 1, fig. 6. Very small tubes can be bordered -by approaching their extremities to a flame not acted upon by the -blowpipe; particularly the flame of a spirit-lamp. - -When the edges of a tube are to be rendered capable of suffering -considerable pressure, you can very considerably augment their -strength by soldering a rib or string of glass all round the end of -the tube--see pl. 1, fig. 12. Holding the tube in the left hand, and -the string of glass in the right, you expose them both at once to the -flame. When their extremities are sufficiently softened, you attach -the end of the rib of glass to the tube at a very short distance from -its extremity; you then continue gradually to turn the tube, so as to -cause the rib of glass to adhere to it, in proportion as it becomes -softened. When the rib has made the entire circumference of the tube, -you separate the surplus by suddenly darting a strong jet of fire upon -the point where it should be divided; and you continue to expose the -tube to the flame, always turning it round, until the ring of glass -is fully incorporated with the glass it was applied to. You then -remove the instrument from the flame, taking care to anneal it in so -doing. During this operation you must take care to prevent the sinking -together of the sides of the tube, by now and then turning the iron -rod in its interior. It is a _red heat_, or a _brownish red heat_, that -is best adapted to this operation. - - -3.--WIDENING. - -When you desire to enlarge the diameter of the end of a tube, it is -necessary, after having brought it to a soft state, to remove it from -the flame, and to press the sides of the glass outwards by means of -a large rod of iron with a conical point. The tube must be again -heated, and again pressed with the conical iron rod, until the proper -enlargement is effected. This operation is much the same as that of -bordering a tube with projecting edges. - - -4.--DRAWING OUT. - -You can _draw out_ or _contract_ a tube either in the middle or at the -end. Let us in the first place consider that a tube is to be drawn out -in the middle. If the tube is long, you support it with the right hand -_below_, and the left hand _above_, by which means you secure the force -that is necessary, as well as the position which is commodious, for -turning it continually and uniformly in the flame. It must be kept in -the jet till it has acquired a _cherry red heat_. You then remove it -from the flame, and always continuing gently to turn it, you gradually -separate the hands from each other, and draw the tube in a straight -line. In this manner you produce a long thin tube in the centre of -the original tube, which ought to exhibit two uniform cones where it -joins the thin tube, and to have the points of these cones in the -prolongation of the axis of the tube. See pl. 1, fig. 3. - -To draw out a tube at its extremity, you heat the extremity till it is -in fusion, and then remove it from the flame; you immediately seize -this extremity with the pliers, and at the same time separate the two -hands. The more rapidly this operation is performed, the glass being -supposed to be well softened, the more capillary will the drawn-out -point of the tube be rendered. Instead of pinching the fused end with -the pliers, it is simpler to bring to it the end of a little auxiliary -tube, which should be previously heated, to fuse the two together, and -then to draw out the end of the original tube by means of the auxiliary -tube--see pl. 1, fig. 4 and 11. In all cases, the smaller the portion -of tube softened, the more abrupt is the part drawn out. - -When you desire to draw out a point from the side of a tube, you must -heat that portion alone, by holding it fixedly at the extremity of the -jet of flame. When it is sufficiently softened, solder to it the end of -an auxiliary tube, and then draw it out. Pl. 1, fig. 18, exhibits an -example of a tube drawn out laterally. A _red heat_, or a _cherry red -heat_, is best adapted to this operation. - - -5.--CHOKING. - -We do not mean by _choking_, the closing or stopping of the tube, but -simply a diminution of the interior passage, or bore. It is a sort of -contraction. For examples, see pl. 2, fig. 15, 20, 29. You perform the -operation by presenting to the flame a zone of the tube at the point -where the contraction is to be effected. When the glass is softened, -you draw out the tube, or push it together, according as you desire to -produce a hollow in the surface of the tube, or to have the surface -even, or to cause a ridge to rise above it. A _cherry red heat_ is the -proper temperature to employ. - - -6.--SEALING. - -If the sides of the tube to be sealed are thin, and its diameter is -small, it is sufficient to expose the end that you wish to close to -the flame of the lamp. When the glass is softened it sinks of itself, -in consequence of the rotatory motion given to it, towards the axis -of the tube, and becomes rounded. The application of no instrument is -necessary. - -If the tube is of considerable diameter, or if the sides are thick, you -must soften the end, and then, with a metallic rod or a flat pair of -pliers, mould the sides to a hemisphere, by bringing the circumference -towards the centre, and continuing to turn the tube in the flame, until -the extremity is well sealed, and perfectly round. Examples of the -figure are to be seen in pl. 2, fig. 3 and 5. Instead of this method, -it is good, when the extremity is sufficiently softened, to employ an -auxiliary tube, with the help of which you can abruptly draw out the -point of the original tube, which becomes by that means cut and closed -by the flame. In order that this part may be well rounded, you may, -as soon as the tube is sealed, close the other extremity with a little -wax, and continue to expose the sealed part to the flame, until it has -assumed the form of a _drop of tallow_. See pl. 2, fig. 15. You can -also seal in this fashion, by blowing, with precaution, in the open end -of the tube, while the sealed end is in a softened state. - -If you desire the sealed part to be flat, like pl. 3, fig. 30, you -must press it, while it is soft, against a flat substance. If you wish -it to be concave, like the bottom of a bottle, or pl. 3, fig. 2, you -must suck air from the tube with the mouth; or, instead of that, force -the softened end inwards with a metallic rod. You may also draw out -the end till it be conical, as pl. 2, fig. 4, or terminate it with a -little button, as pl. 2, fig. 6. In some cases the sealed end is bent -laterally; in others it is twirled into a ring, having previously been -drawn out and stopped in the bore. In short, the form given to the -sealed end of a tube can be modified in an infinity of ways, according -to the object for which the tube may be destined. - -You should take care not to accumulate too much glass at the place -of sealing. If you allow it to be too thick there, you run the risk -of seeing it crack during the cooling. Some farther observations on -sealing will be found at the article _Water Hammer_, in a subsequent -section. The operation of sealing succeeds best at a _cherry-red heat_. - - -7.--BLOWING. - -The construction of a great number of philosophical instruments -requires that he who would make them should exercise himself in the art -of blowing _bulbs_ possessing a figure exactly spherical. This is one -of the most difficult operations. - -To blow a bulb at the extremity of a tube, you commence by sealing it; -after which, you collect at the sealed extremity more or less glass, -according to the size and the solidity which you desire to give to -the bulb. When the end of the tube is made thick, completely sealed, -and well rounded, you elevate the temperature to a _reddish white_ -heat, taking care to turn the tube continually and rapidly between -your fingers. When the end is perfectly soft you remove it from the -flame, and, holding the tube horizontally, you blow quickly with the -mouth into the open end, without discontinuing for a single moment the -movement of rotation. If the bulb does not by this operation acquire -the necessary size, you soften it again in the flame, while under the -action of which you turn it very rapidly, lest it should sink together -at the sides, and become deformed. When it is sufficiently softened you -introduce, in the same manner as before, a fresh quantity of air. It -is of importance to observe that, if the tube be of a large diameter, -it is necessary to contract the end by which you are to blow, in order -that it may be turned round with facility while in the mouth. - -When the bulb which you desire to make is to be somewhat large, it is -necessary, after having sealed the tube, to soften it for the space of -about half an inch from its extremity, and then, with the aid of a -flat piece of metal, to press moderately and repeatedly on the softened -portion, until the sides of the tube which are thus pressed upon, -sink together, and acquire a certain degree of thickness. During this -operation, however, you must take care to blow, now and then, into the -tube, in order to retain a hollow space in the midst of the little mass -of glass, and to hinder the bore of the tube from being closed up. When -you have thus, at the expense of the length of the tube, accumulated -at its extremity a quantity of glass sufficient to produce a bulb, you -have nothing more to do than to heat the matter till it is raised to a -temperature marked by a _reddish-white_ colour, and then to expand it -by blowing. - -Instead of accumulating the glass thus, it is more expedient to blow on -the tube a series of little bulbs close to one another (see pl. 1, fig. -8), and then, by heating the intervals, and blowing, to unite these -little bulbs into a large one of convenient dimensions. - -We have already observed, and we repeat here, that it is indispensably -necessary to hold the glass _out_ of the flame during the act -of blowing. This is the only means of maintaining uniformity of -temperature in the whole softened parts of the tube, without which it -is impossible to produce bulbs with sides of equal thickness in all -their extent. - -When you desire to form a bulb at the extremity of a capillary tube, -that is to say, of a tube which has a bore of very small diameter, -such as the tubes which are commonly employed to form thermometers, -it would be improper to blow it with the mouth; were you to do so, -the vapour which would be introduced, having a great affinity for the -glass, would soon obstruct the little canal, and present to the passage -of the air a resistance, which, with the tubes of smallest interior -diameter, would often be insurmountable. But, even when the tubes you -employ have not so very small an internal diameter, you should still -take care to avoid blowing with the mouth; because the introduction of -moisture always injures fine instruments, and it is impossible to dry -the interior of a capillary tube when once it has become wet. It is -better to make use of a bottle of Indian rubber, which can be fixed on -the open end of the tube by means of a cork with a hole bored through -it. You press the bottle in the hand, taking care to hold the tube -vertically, with the hot part _upwards_; if you were not to take this -precaution, the bulb would be turned on one side, or would exhibit the -form of a pear, because it is impossible, in this case, to give to the -mass in fusion that rotatory motion which is necessary, when the tube -is held horizontally, to the production of a globe perfectly spherical -in its form, and with sides of equal thickness. - -Whenever you blow into a tube you should keep the eye fixed on the -dilating bulb, in order to be able to arrest the passage of air at the -proper moment. If you were not to attend to this, you would run the -risk of giving to the bulb too great an extension, by which the sides -would be rendered so thin that it would be liable to be broken by the -touch of the lightest bodies. This is the reason that, when you desire -to obtain a large bulb, it is necessary to thicken the extremity of the -tube, or to combine many small bulbs in one, that it may possess more -solidity. - -In general, when you blow a bulb with the mouth, it is better to -introduce the air a little at a time, forcing in the small portions -very rapidly one after the other; rather than to attempt to produce the -whole expansion of the bulb at once: you are then more certain of being -able to arrest the blowing at the proper time. - -When you desire to produce a moderate expansion, either at the -extremity or in any other part of a tube, you are enabled easily to -effect it by the following process, which is founded on the property -possessed by all bodies, and especially by fluids, of expanding when -heated; a property which characterises air in a very high degree. After -having sealed one end of the tube and drawn out the other, allow it -to become cold, in order that it may be quite filled with air; close -the end which has been drawn out, and prevent the air within the tube -from communicating with that at its exterior; then gradually heat the -part which you desire to have expanded, by turning it gently in the -flame of a lamp. In a short time the softened matter is acted on by the -tension of the air which is enclosed and heated in the interior of the -tube; the glass expands, and produces a bulb or swelling more or less -extensive, according as you expose the glass to a greater or lesser -degree of heat. - -To blow a bulb in the middle of a tube, it is sufficient to seal it at -one of its extremities, to heat the part that you wish to inflate, and, -when it is at a _cherry-red_ heat, to blow in the tube, which must be -held horizontally and turned with both hands, of which, for the sake of -greater facility, the left may be held above and the right below. - -If the bulb is to be large, the matter must previously be thickened -or accumulated, or, instead of that, a series of small bulbs first -produced, and these subsequently blown into a single larger bulb, as we -have already mentioned. See pl. 1, fig. 8. - -For some instruments, the tubes of which must be capillary, it is -necessary to blow the bulbs separately, and then to solder them to -the requisite adjuncts. The reason of this is, that it would be too -difficult to produce, from a very fine tube, a bulb of sufficient size -and solidity to answer the intended purpose. - -You make choice of a tube which is not capillary, but of a sufficient -diameter, very cylindrical, with equal sides, and tolerably -substantial: it may generally be from the twentieth to the twelfth of -an inch thick in the glass. You soften two zones in this tube, more -or less near to each other, according to the bulk you desire to give -to the bulb, and you draw out the melted part in points. The talent -consists in _well-centering_--that is to say, in drawing out the melted -tube in such a manner that the thin parts or points shall be situated -exactly in the prolongation of the axis of the little portion of the -original tube remaining between them. This operation is technically -termed drawing _a cylinder between two points_. The tube so drawn out -is exhibited by pl. 1, fig. 4. You cut these points at some distance -from the central or thick part, and seal one end; you next completely -soften the little thick tube and expand it into a bulb, by blowing -with the precautions which have already been described. You must keep -the glass in continual motion, if you desire to be successful in this -experiment. Much rapidity of movement, and at the same time lightness -of touch, are requisite in the operation here described. It is termed -_blowing a bulb between two points_. Pl. 1, fig. 10, exhibits a bulb -blown between two points. - -To obtain a _round_ bulb, you should hold the tube horizontally; to -obtain a _flattened_ bulb, you should hold it perpendicularly, with -the fused extremity turned above; to obtain a _pear-shaped_ bulb, you -should hold the fused extremity downwards. - -When you are working upon a bulb between two points, or in the middle -of a tube, you should hold the tube horizontally, in the ordinary -manner; but you are to push the softened portion together, or to draw -it out, according as you desire to produce a ridge or a prolongation. - -When you are at liberty to choose the point from which you are to blow, -you should prefer, 1st, that where the moisture of the breath can be -the least prejudicial to the instrument which is to be made; 2dly, that -which brings the part which is to be expanded nearest to your eye; -3dly, that which presents the fewest difficulties in the execution. -When bulbs are to be formed in complicated apparatus, it is good to -reflect a little on the best means of effecting the object. It is easy -to understand that contrivances which may appear very simple on paper, -present difficulties in the practical execution which often call for -considerable management. - - -8.--PIERCING. - -You first seal the tube at one extremity, and then direct the point of -the flame on the part which you desire to pierce. When the tube has -acquired a _reddish-white_ heat, you suddenly remove it from the flame, -and forcibly blow into it. The softened portion of the tube gives way -before the pressure of the air, and bursts into a hole. You expose the -tube again to the flame, and border the edges of the hole. - -It is scarcely necessary to observe, that, if it be a sealed extremity -which you desire to pierce, it is necessary to turn the tube between -the fingers while in the fire; but if, on the contrary, you desire to -pierce a hole in the side of a tube, you should keep the glass in a -fixed position, and direct the jet upon a single point. - -If the side of the tube is thin, you may dispense with blowing. The -tube is sealed and allowed to cool; then, accurately closing the open -extremity with the finger, or a little wax, you expose to the jet the -part which you desire to have pierced. When the glass is sufficiently -softened, the air enclosed in the tube being expanded by the heat, -and not finding at the softened part a sufficient resistance, bursts -through the tube, and thus pierces a hole. - -You may generally dispense with the sealing of the tube, by closing the -ends with wax, or with the fingers. - -There is still another method of performing this operation, which is -very expeditious, and constantly succeeds with objects which have thin -sides. You raise to a _reddish white_ heat a little cylinder of glass, -of the diameter of the hole that you desire to make, and you instantly -apply it to the tube or globe, to which it will strongly adhere. You -allow the whole to cool, and then give the auxiliary cylinder a sharp -slight knock; the little cylinder drops off, and carries with it the -portion of the tube to which it had adhered. On presenting the hole to -a slight degree of heat, you remove the sharpness of its edges. - -When you purpose to pierce a tube laterally, for the purpose of joining -to it another tube, it is always best to pierce it by blowing many -times, and only a little at a time, and with that view, to soften the -glass but moderately. By this means the tube preserves more thickness, -and is in a better state to support the subsequent operation of -soldering. - -There are circumstances in which you can pierce tubes by forcibly -sucking the air out of them; and this method sometimes presents -advantages that can be turned to good account. Finally, the orifices -which are produced by cutting off the lateral point of a tube drawn out -at the side, may also be reckoned as an operation belonging to this -article. - - -9.--BENDING. - -If the tube is narrow, and the sides are pretty thick, this operation -presents no difficulty. You heat the tube, but not too much, lest it -become deformed; a _reddish-brown_ heat is sufficient, for at that -temperature it gives way to the slightest effort you make to bend it. -You should, as much as possible, avoid making the bend too abrupt. For -this purpose, you heat a zone of one or two inches in extent at once, -by moving the tube backwards and forwards in the flame, and you take -care to bend it very gradually. - -But if the tube is large, or its sides are thin, and you bend it -without proper precautions, the force you employ entirely destroys -its cylindrical form, and the bent part exhibits nothing but a double -flattening,--a canal, more or less compressed. To avoid this deformity -it is necessary, first, to seal the tube at one extremity, and then, -while giving it a certain curvature, to blow cautiously by the other -extremity, which for convenience sake should previously be drawn out. -When tubes have been deformed by bad bending, as above described, you -may, by following this method, correct the fault; that is to say, upon -sealing one extremity of the deformed tube, heating the flattened -part, and blowing into the other extremity, you can with care reproduce -the round form. - -In general, that a curvature may be well-made, it is necessary that -the side of the tube which is to form the concave part be sufficiently -softened by heat to sink of itself equally in every part during the -operation, while the other side be only softened to such a degree as -to enable it to give way under the force applied to bend it. On this -account, after having softened in a _cherry-red heat_ one side of the -tube, you should turn the other side, which is to form the exterior of -the curvature, towards you, and then, exposing it to the point of the -jet, you should bend the tube immediately upon its beginning to sink -under the heat. - -When you desire to bend the extremity of a tube into a ring you must -employ a metallic rod, with which, by pressing on the tube, you -separate with a curve, C, (see pl. 1, fig. 14) all the portion A C -which is necessary to produce the desired curl. You then successively -soften all parts of this curve, and gradually twist it in the direction -indicated by the arrow, pressing the iron rod constantly upon the -extremity of the curve. When the end A comes into contact with bend C -you solder them together at this point, and thus complete the ring. Pl. -2, fig. 27, and pl. 3, fig. 27, exhibit examples of rings formed by -this process. - - -10.--SOLDERING. - -If the tubes which you propose to solder are of a small diameter, -pretty equal in size, and have thick sides, it is sufficient, before -joining them together, to widen them equally at their extremities, by -agitating a metallic rod within them. (Pl. 1, fig. 17.) - -But if they have thin sides, or are of a large diameter, the bringing -of their sides into juxta-position is very difficult, and the method -of soldering just indicated becomes insufficient. In this case you are -obliged to seal, and subsequently to pierce, the two ends which you -desire to join. The disposition which this operation gives to their -sides very much facilitates the soldering. - -Finally, when the tubes are of a very different diameter, you must draw -out the extremity of the larger and cut it where the part drawn out -corresponds in diameter to the tube which it is to be joined to. Pl. 1, -fig. 9 and 15, exhibit examples of this mode of adapting tubes to one -another. - -For lateral solderings you must dispose the tubes in such a manner that -the sides of the orifices which you desire to join together coincide -with each other completely. See pl. 1, fig. 7. - -When the holes are well prepared, you heat at the same time the two -parts that are to be soldered together, and join them at the moment -when they enter into fusion. You must push them slightly together, and -continue to heat successively all their points of contact; whereupon -the two tubes soon unite perfectly. As it is almost always necessary, -when you desire the soldering to be neatly done, or the joint to be -imperceptible, to terminate the operation by blowing, it is proper to -prepare the extreme ends of the tubes before-hand. That end of the tube -by which you intend to blow should be carefully drawn out, provided it -be so large as to render drawing out necessary; and the other end of -the tube, if large, should be closed with wax, as in pl. 1, fig. 9, -or if small, should be sealed at the lamp (pl. 1, fig. 15). When the -points of junction are perfectly softened, and completely incorporated -with each other, you introduce a little air into the tube, which -produces a swelling at the joint. As soon as this has taken place, -you must gently pull the two ends of the joined tube in different -directions, by which means the swelled portion at the joint is brought -down to the size of the other parts of the tube, so that the whole -surface becomes continuous. The soldering is then finished. - -To solder a bulb or a cylinder between two points, to the extremity -of a capillary tube, you cut and seal one of the points at a short -distance from the bulb (pl. 1, fig. 16), and at the moment when this -extremity is in fusion you pierce it by blowing strongly at the other -extremity. By this means the opening of the reservoir is terminated -by edges very much widened, which facilitates considerably its being -brought into juxta-position with the little tube. In order that the -ends of the two tubes may be well incorporated the one with the -other, you should keep the soldered joint for some time in the flame, -and ought to blow in the tube, push the ends together and draw them -asunder, until the protuberance is no longer perceptible. - -If, after having joined two tubes, it should be found that there still -exists an opening too considerable to be closed by simply pushing the -two tubes upon one another, you can close such an opening by means of -a morsel of glass, applied by presenting the fused end of an auxiliary -tube. - -You should avoid soldering together two different species of glass--for -example, a tube of ordinary glass with a tube of flint-glass; because -these two species of glass experience a different degree of contraction -upon cooling, and, if joined together while in a fused state, are -so violently pulled from one another as they become cool, that the -cohesion of the point of soldering is infallibly overcome, and the -tube breaks. You ought also, for a similar reason, to take care not to -accumulate a greater mass of glass in one place than in another. - -If the first operation has not been sufficient to complete the -soldering, the tube must be again presented to the flame, and again -pushed together at the joint, or drawn asunder, or blown into, -according as it may appear to be necessary. In all cases the soldering -is not truly solid, but inasmuch as the two masses of glass are well -incorporated together, and present a surface continuous in all points. - -The mineralogical flame (pl. 1, fig. 1, A´ B) is that which is to be -employed in preference to the larger flame, when you desire to effect a -good joining: it is sufficient to proportion the size of the flame to -the object you wish to execute. - - - - -THE - -ART OF GLASS-BLOWING. - -IV.--_Construction of Chemical and Philosophical Instruments._ - - -When a person is well acquainted with the fundamental operations which -we have just described, the preparation of the instruments of which we -are about to speak can present scarcely any difficulty. Indeed, some of -them are so extremely simple, and are so easy of execution, that it is -sufficient to cast a glance upon the figures which represent them, to -seize at once the method which must be followed in their construction. -Of such instruments we shall not stop to give a detailed description, -but shall content ourselves with presenting the design. - -On the other hand, it is of importance to observe that a certain -number of instruments are _graduated_ or furnished with pieces, or -_mountings_, of which it is not the object of our art to teach the -construction, and which demand a more or less extensive knowledge -of the sciences. We shall treat of these mountings but summarily, -referring the student, for more detailed instructions, to the works -on natural philosophy and chemistry, in which these instruments are -especially treated of. Our reason for this is, that we do not wish -to abandon the plan we had adopted of describing simply the art of -glass-blowing. To describe the use and application of philosophical -instruments, or to explain the principles on which they act, would be -passing quite out of our province. - -ADAPTERS.--These are tubes of glass of various forms, employed in -chemistry to connect together the different pieces constituting an -apparatus--as, for example, to join a retort to a receiver during -the operation of distillation. You should take care to border the -extremities of an adapter; or you may widen them into the form of the -mouth of a bottle, when they are to be closed air-tight by corks. -Besides this, there is nothing particular to be observed in the -preparation of adapters. - - * * * * * - -APPARATUS FOR BOILING IN VACUO.--Represented by pl. 3, fig. 19. Employ -a tube about a quarter of an inch in diameter. Blow two bulbs; give the -tube the necessary curvature; fill one of the bulbs with nitric ether; -boil the ether to expel the atmospheric air from the apparatus, then -seal the opening in the other bulb. - - * * * * * - -APPARATUS FOR FREEZING IN VACUO. _The Cryophorus._--Take a tube -one-third of an inch or rather more in diameter, and pretty thick in -the sides. Blow a bulb at each end; the first at the sealed part of the -tube, the other at the open point; then give to the tube the curvature -represented by pl. 3, fig. 32. Introduce as much water as will half -fill one of the bulbs; make the water boil, and draw off the point and -seal the apparatus during the ebullition. - - * * * * * - -APPARATUS FOR CONDUCTING WATER IN BENT TUBES.--Solder a funnel (see -FUNNELS) to the end of a tube; pierce two holes in this tube in the -same line, and solder to each a little addition proper to receive a -cork. Finish the instrument by bending it in the manner indicated by -pl. 4, fig. 18. - - * * * * * - -APPARATUS FOR EXPERIMENTS ON RUNNING LIQUIDS.--A tube bent once at a -right angle, mounted with a funnel, pierced laterally, and soldered at -the same point to a smaller tube. See pl. 3, fig. 17. - - * * * * * - -APPARATUS FOR EXHIBITING THE PHENOMENA OF CAPILLARY TUBES.--This -apparatus consists of a capillary tube soldered to another tube of a -more considerable diameter. Sometimes it is bent like the letter U. Pl. -3, fig. 15. - - * * * * * - -APPARATUS FOR THE PREPARATION OF PHOSPHURET OF LIME.--An apparatus that -can be employed for the preparation of phosphuret of lime, as well as -in a variety of other chemical experiments, consists of a tube sealed -at one extremity, slightly bent and choked at two inches and a half -from the sealed part, and drawn out (after the introduction of the -substances to be operated upon) at the other extremity. This little -distillatory apparatus is represented by pl. 3, fig. 29. - - * * * * * - -ARCHIMEDES’S SCREW.--There is no particular process for the making of -this instrument. It is, however, necessary for one who would succeed in -making it, to exercise himself in the art of well bending a tube. After -a few attempts, you may finish by producing a pretty-regular spiral. -The tube chosen for this instrument should be six or seven feet long, -and about one-third of an inch in diameter. You commence by making -a bend, nearly at a right angle, about four inches from one of its -extremities. This bent portion serves afterwards as a handle, and very -much facilitates the operation; it represents the prolongation of the -rational axis which may be conceived to pass through the centre of the -spiral. See pl. 4, fig. 10. - - * * * * * - -BARKER’S MILL.--_Apparatus for exhibiting the rotatory motion produced -by the running of liquids._--Contract a tube at its two extremities, -pierce it laterally about the middle of its length, and solder to the -hole an additional tube, terminated by a funnel. Soften the principal -tube at the side opposite to the part that was pierced, and form there -a conical cavity by pressing the softened glass inward with the aid -of a metallic rod. This cavity must be so carefully made that the -whole apparatus can be supported on a pivot. Bend the contracted ends -of the tube horizontally, and in different directions, cut off their -extremities at a proper length, and slightly border the edges of the -orifices. See pl. 3, fig. 33. - -You may produce this apparatus under a different form, as may be seen -at pl. 3, fig. 5. - - * * * * * - -BAROMETERS.--Barometers serve to measure the pressure of the -atmosphere. The following are the varieties most in use. - - * * * * * - -CISTERN BAROMETER.--Take a tube about thirty-two inches long, and at -least one-third of an inch in diameter, internally; seal one of its -extremities, free it with most particular care from moisture, fill -it with mercury, and make the mercury boil in the tube, by heat, in -order to drive out every particle of air which might be present. When -the tube is full of mercury, and the boiling has taken place, turn it -upside down, and plunge the open end into a cistern also filled with -mercury which has been boiled. See pl. 2, fig. 4. - - * * * * * - -DIAL (or WHEEL) BAROMETER.--The tube intended for this barometer should -be very regular in the bore. It should be thirty-nine inches long. -Close it at one end, and bend it like the letter U at about thirty-two -inches from the sealed extremity. See pl. 2, fig. 5, and _Graduation of -the Dial Barometer_. - -SYPHON BAROMETER.--Make use of such a tube as might be employed -for a _Cistern Barometer_; solder to its open end a cylindrical or -spherical reservoir, and bend the tube close to the point of junction -in such a manner as to bring the cylinder parallel with the tube. -If the reservoir is to be closed with a cover of leather, cut off -the remaining point of the cylinder, slightly widen the orifice, and -then border it. If no leather is to be applied, but the point of the -cylinder left open, it is necessary, after the introduction of the -mercury, to draw off the point abruptly, and to leave an opening so -small that mercury cannot pass by it. Pl. 2, fig. 6. - - * * * * * - -STOP-COCK BAROMETER.--This differs from the preceding barometer only by -having a stop-cock mounted in iron between the reservoir and the tube. - - * * * * * - -COMPOUND BAROMETERS.--Blow a bulb at each end of a barometer tube -of about thirty-three inches in length. Solder a small and almost -capillary tube to the point which terminates one of the bulbs, and bend -the great tube very near this bulb. This must be done in such a manner -that the centre of one bulb shall be thirty inches from the centre of -the other bulb. Introduce a quantity of mercury sufficient to fill the -great tube and half the two bulbs; fill the remaining space in the last -bulb with alcohol. - -You may give a different disposition to this instrument. Divide a -barometer tube into two, three, or four pieces, and reunite the pieces -by intermediate capillary tubes, so as to form a series of large and -small tubes, soldered alternately the one at the end of the other. Then -communicate to this compound tube the form exhibited by pl. 3, fig. 25, -and join, at each superior bend, a little tube, for the convenience of -easily filling the instrument with mercury: seal these tubes as soon -as the mercury is introduced. The graduation of compound barometers is -made by bringing them into comparison with a good standard barometer. -After taking two or three fixed points, it is easy to continue the -scale. - - * * * * * - -GAY LUSSAC’S BAROMETER.--Take a tube which is very regular in the bore, -four-tenths of an inch in diameter, and thirty-five inches and a half -in length. Seal one of its extremities and draw out the other; then -cut the tube at about two-thirds of its whole length from the sealed -end, and reunite the two pieces by means of a capillary tube soldered -between them, the whole being kept in a line. See pl. 2, fig. 1. Pierce -laterally the part of the tube which is drawn out, at some inches -from the base of the point, and force the margin of the hole into the -interior of the tube, by means of a conical point of metal, in such a -manner as to form a little sunk funnel, of which the orifice must be -very small. After having introduced the proper quantity of mercury into -the instrument, boil it, and assist the disengagement of the bubbles -of air by agitating a fine iron wire within the tube. Then remove the -part of the tube which was drawn out, by sealing the end of the wide -part. Give to the whole instrument the curvature indicated by pl. 2, -fig. 3. - - * * * * * - -BUNTEN’S BAROMETER.--This instrument differs from the preceding but in -one point, namely, that the capillary tube is formed of two soldered -pieces, of which the one, passing into the other, is terminated by a -capillary point. This arrangement is exhibited by pl. 2, fig. 2. - - * * * * * - -BAROMETER PIERCED LATERALLY FOR DEMONSTRATIONS.--Take a tube -thirty-nine inches long, with thick sides, and two-tenths of an inch -internal diameter. Seal it at one end, and choke it at the distance -of eight inches therefrom. Pierce a hole in the tube about twelve -or sixteen inches from the choked part, and solder to the hole an -additional piece, which can be closed by a cork or covered by a piece -of bladder. The instrument is represented by pl. 2, fig. 15. - - * * * * * - -BELL-GLASSES FOR EXPERIMENTS.--These are pieces of tube sealed at one -end, and widened or bordered at the other. They are extremely useful, -and much employed in chemical experiments. They also supply the place -of bottles for preserving small quantities of substances. Sometimes -they are required to be straight, as pl. 3, fig. 12. Sometimes they -need to be curved, as pl. 3, fig. 29. This is particularly the case -when they are to be employed as retorts, for which purpose the sealed -part should be made thin. Pl. 3, fig. 6, exhibits a retort with a -tubulure. - - * * * * * - -BLOWPIPE.--We shall give in this article an account of the various -pieces of glass which form part of the blowpipe described in the early -part of this work. See pl. 1, fig. 19. - -The beak C, which is employed with the candlestick, is merely a bent -tube, at the extremity of which a bulb is blown. The bulb is terminated -by a point, the thickness of the sides of which is augmented by turning -it for a long time in the flame. - -As for the beak used with the lamp, it is simply a bent tube C´, of -which the orifice has been diminished by turning it round in the flame. -The point of this beak is not drawn out like that of the beak described -in the preceding paragraph, but is allowed to be thick, that it may not -melt in the flame of the lamp. - -The tube D F has four-tenths of an inch internal diameter, and is -pretty thick in the sides. You must commence by bordering and slightly -widening one of its extremities, and then proceed to choke it at about -two inches from its other extremity, taking care to give to the choked -part a figure as perfectly conical as possible, in order that the valve -may act well. We have described the valve at length at p. 6. - -The tube _d_ is as much narrower than the tube D F as is necessary -to permit it to pass up and down within the latter. Its use is to -lengthen or shorten the tube for the convenience of the blower. The -lower end is wound round with waxed thread, to make it fit air-tight. -The mouth-piece is executed by widening the end of the tube, and -then, while the widened part is still soft, by pressing the two sides -obliquely, one against the other. By this means you give to the -mouth-piece a flattened form, which adapts it better to the lips. The -tube is finished by slightly bending this extremity. - -In order that the bladder, or air reservoir, may be conveniently and -securely attached to the tube E, you must take care to widen the end of -this tube, and to turn up the edges strongly, by pressing the soft end -against a flat metallic surface. - - * * * * * - -CAPSULES.--These are very small mercury funnels, of which the opening -or neck has been closed. To transform these funnels into capsules, you -must cut the neck as close as possible, and then soften, close, and -flatten the opening. In performing this operation, hold the capsule by -the edge with your pincers, and employ a piece of metal to press the -glass together and make it close the hole and form the flat bottom of -the capsule. See pl. 2, fig. 23. - -_Another Method._--After having blown a bulb at the end of a point, -soften a narrow zone of the bulb, and then blow suddenly and strongly -into it; by which means you separate the bulb into two capsules, which -only need to be bordered. If you find any difficulty in presenting -to the flame the capsule which forms the part of the bulb opposed to -the point, you can attach to it a little rod of glass, which you can -afterwards easily separate by a slight smart blow. - -Occasionally you will have to make _capsules with double sides_, which -will be described at the article _Nicholson’s Hydrometer_. - - * * * * * - -CARTESIAN DEVILS.--Blow a bulb at the extremity of a very small tube, -and heat a portion of the bulb, for the purpose of prolonging it into -a beak. This can be effected with the aid of an auxiliary tube, which, -on being joined to the heated part of the bulb, carries away with it -the portion of glass which adheres. This portion of the bulb becomes -thus prolonged into a little point, which must be cut at its extremity, -so as to leave a small opening. The principal tube must be cut at -the distance of half an inch from the bulb, and the ends of it must -be drawn out and twisted into a ring. Instead of forming laterally a -little beak to the bulb, you may pierce the tail, after twisting it -into the form of a ring, or you may manage in such a manner as not to -obliterate the canal of the twisted part. In general, little enamel -figures are suspended to the ring of these globes, as is represented -by pl. 2, fig. 22. A simple bulb, blown at the extremity of a small -portion of tube, can supply the place of the Ludion or Cartesian devil. -See pl. 2, fig. 8. - - * * * * * - -COMMUNICATING VASES.--Employ a tube of a large diameter; terminate one -of its extremities with a funnel, fashion the other like the neck of a -bottle; and bend the tube into the shape shewn by pl. 4, fig. 11. Then -twist some other tubes into various forms, according to the end you -propose to attain, and adjust these tubes to the neck of the large tube -by means of corks, which have holes bored through them. In this manner -an exchange of tubes is provided for various experiments. - - * * * * * - -DROPPING TUBES.--The name _dropping tube_ is given to an instrument -of glass which is very much employed in chemistry, for the purpose of -transferring small quantities of liquor from one vessel into another, -without disturbing either of the vessels. Dropping tubes are made of a -great variety of forms and sizes, according to the purposes to which -they are intended to be applied. - -Blow a bulb between two points, and then, before the glass has regained -its consistence, lengthen the bulb into an oval form. Cut and border -the two points. - -If the bulb, or reservoir, is to be so large that it cannot be formed -at the expense of the thickness of the tube, and yet be sufficiently -strong, it must be blown separately from a larger tube, and then -soldered to two smaller tubes, one of which should have a certain -curvature given to it. See pl. 2, fig. 20. - -Sometimes a dropping tube is employed to measure small quantities of -liquid. In this case the point should be drawn off abruptly, and the -scale should be marked on the shank or tube with spots of black enamel. - -Pl. 2, fig. 21, represents a peculiar variety of dropping tube employed -in some experiments. It is made in the same manner as the common -dropping tubes, excepting that, when the tail is formed, it is sealed -at the extremity, bent there into a ring, and then pierced at A. - -Pl. 3, fig. 26, represents another variety of dropping tube, a -description of which is unnecessary. - - * * * * * - -FOUNTAINS.--It will readily be understood by those acquainted with the -construction of hydraulic apparatus, that, by means of a judicious -arrangement of glass tubes, a great variety of fountains may be -produced. The following are given as examples. - - * * * * * - -FOUNTAIN OF CIRCULATION.--Take a tube, twenty-four or thirty inches -long, nearly half an inch in diameter, and with pretty thick sides; -blow a bulb at one of its extremities, and bend the other into a U, -after having drawn it out as indicated by pl. 3, fig. 4. Pierce the -tube at B, and join there a short piece adapted to receive a cork. Then -prepare a bulb of the same size as the first bulb, and solder it to the -extremity of a very long and almost capillary tube, which you must -bend in zig-zag, in such a manner as to make it represent a Maltese -cross, a star, a rose, or any other figure that may be suggested. The -side of the bulb opposite to that which is attached to this twisted -tube, ought to be formed like the neck of a bottle, in order that it -may receive the drawn-out part of the larger tube, which should enter -the bulb until the point of the large tube nearly touches the neck of -the little tube at its junction with the bulb. This disposition is -shewn in the figure. Seal now the other end of the little tube to the -bulb of the large tube; then, with a little cement or sealing-wax, -close the space between the bulb of the little tube and the point of -the large tube. The instrument being thus prepared, as much alcohol, -previously coloured red, must be inserted by the neck _b_ as is -sufficient to fill one of the bulbs. The neck is then closed with a -cork, and a little cement or sealing-wax. Or, instead of forming this -neck to the instrument, the additional piece may be drawn out to a -point, which permits it to be sealed hermetically. - - * * * * * - -FOUNTAIN OF COMPRESSION.--Introduce into a tube of large diameter a -piece of capillary tube with thick sides. This must pass a little -beyond the extremity of the large tube, which is to be softened and -soldered to the other, so that it shall be fixed concentrically. The -common point is then to be drawn out. When the tube is quite cold, and -the small tube properly fixed in the centre of the large one, cut the -latter at a proper distance, border it, and choke it near the end, -which must be fashioned in such a manner as to be capable of being -completely closed by a cork. See pl. 2, fig. 29. - - * * * * * - -INTERMITTING FOUNTAIN.--This apparatus is represented by pl. 3, fig. -16. Solder a cylindrical reservoir to the extremity of a capillary -tube, pierced at _a_, and sealed at its extremity. Draw out abruptly -the point of the reservoir, and give it a very small orifice; then give -to the capillary tube the form indicated by the figure. Prepare next a -funnel resembling a mercury-funnel, but much larger; choke the neck of -this funnel, and bend the tube into the form of a syphon. - - * * * * * - -HERO’S FOUNTAIN.--Solder a bulb to the extremity of a tube, and -transform the bulb into a funnel. Close the funnel with a cork, and -solder to the other end of the tube a bulb similar to the first. Next, -solder a third bulb between two tubes, of which one must be twice as -long the other; solder the longer of these tubes to the bulb of the -first tube, and draw out the point of the shorter tube. You have now a -long tube, with a funnel at one end, a contracted point at the other, -and two bulbs in its length. Give to the whole apparatus the form -indicated by pl. 3, fig. 21. - - * * * * * - -FUNNELS.--It will be seen, upon looking over the engravings, that -funnels require to be made for a great variety of instruments; you -ought therefore to acquire as soon as possible the art of making them -well. The following are those most frequently required. - - * * * * * - -RETORT FUNNEL.--Blow a bulb at the extremity of a tube; present -the superior hemisphere of the bulb to the flame, and when it is -sufficiently softened, blow strongly into the other end of the tube. -The air will force its way through the bulb, making a hole which will -be larger or smaller according to the extent of surface which may -have been softened. The opening of the funnel being made thus, there -is nothing more to do than to adjust the edges, which, in the present -state, are both fragile and irregular. This it is very easy to do. -The edges are softened, the most prominent parts are cut off with the -scissars, and the parts which are thin are bent back on themselves, -that they may become thicker. Upon turning the funnel round in the -flame, the smaller irregularities give way, and the edges become -rounded. See pl. 2, fig. 24. - -When the funnel is desired to be very large in proportion to the size -of the tube, a bulb is made from a larger tube, and afterwards soldered -to the small tube, and transformed into a funnel in the manner above -described. - - * * * * * - -FUNNEL FOR INTRODUCING MERCURY INTO NARROW TUBES.--The mercury-funnel -is represented by pl. 2, fig. 25. Blow a bulb between two points; cut -off one of the points, and open the bulb at that place, in the manner -described in the preceding article. - - * * * * * - -HYDROSTATIC FUNNEL.--This is represented by pl. 3, fig. 31. It is an -instrument of constant use in chemical experiments. Form a funnel -at the extremity of a tube in the manner described above, having -previously blown a bulb near the middle of the tube. When this has been -done, bend the tube into the form shown by the figure. - - * * * * * - -HOUR-GLASSES.--Blow four bulbs on a tube close to each other; open the -two end bulbs like funnels, and then form them into flat supports or -pedestals, according to the method described at the article _Test-glass -with a foot_. Obstruct entirely the canal which separates one of these -feet; choke to a certain extent the passage between the two remaining -bulbs; and close the canal between the other foot and the bulbs, after -introducing the quantity of sand which you have found to be necessary. -See pl. 3, fig. 13. - - * * * * * - -HYDRAULIC RAM.--This instrument is represented by pl. 4, fig. 15. -Employ a tube about six feet long, with thick sides and of large -diameter. Seal it at one extremity, _k_, and border it at the other; -solder at _p_ an additional piece, choked so as to receive a valve. -Pierce the tube at _l_; draw it out, and fix a funnel there; then -twist the tube into a spiral. Form, on the other hand, a fountain of -compression, _o_, and a funnel, _m_; and fix both of these pieces by -means of sealing-wax, as soon as the two valves _p_ and _l_ have been -put into their places. - - * * * * * - -HYDROMETERS.--_Hydrometers_ are instruments which, on being plunged -into liquids, indicate immediately their density or specific gravity. -_Areometers_ differ from hydrometers sometimes in graduation, sometimes -merely in name. The following are examples of hydrometers, of which a -great many varieties are in use. - - * * * * * - -BAUMÉ’S HYDROMETER.--Make a cylinder between two points, and solder -it to the extremity of a tube with thin sides, and which must be very -regular on the outside. Close the open part which is to form the stalk -of the hydrometer with a little wax. See pl. 1, fig. 9 and 15. When the -soldering, which must be well done, is complete, and the stalk well -centered, choke the reservoir at a little distance from the base of the -point, by drawing it out in such a manner as considerably to diminish -the canal in this part. Remove then the ball of wax which closed the -tube, draw off the point of the cylinder, and make the part which was -pulled away from the cylinder by the choking, into a bulb, by blowing -with precaution into the tube. If the reservoir is required to be -spherical instead of cylindrical, it must be softened and expanded by -blowing. When it is intended to ballast the instrument with mercury, -the canal must be completely stopped at the point where it is choked. -In this case, the part drawn away from the cylinder is expanded into a -bulb by blowing through the extreme point, which is to be cut off after -the instrument is completed. - -In the first case, you ballast the instrument with lead shot, which you -fix in the lower bulb by means of a little wax, which closes the canal -at the choked part. In the second case, after having proved the ballast -by putting it first into the large reservoir, it is removed into the -little bulb, and the latter is immediately sealed. - -One of the essential conditions of a good hydrometer is that the stalk -should keep a perfectly vertical position when the instrument is -plunged in water. If, therefore, on proving the ballast, you perceive -the stalk to rest obliquely, you must take care, on retiring it from -the water, to wipe it dry, and to present the choked part between the -cylinder and the little bulb to the flame; when it is softened, it is -easy, by giving it a slight bend in the direction where the stalk of -the hydrometer passes from the vertical, to rectify the defect. - -Finally, when the instrument is ballasted, you must seal the stalk, -after having fixed in its interior the strip of paper which bears the -graduated division. - -This method of operation serves equally for all the areometers known -under the names of _areometer of Baumé_, _pèse-sels_, _pèse-liqueurs_, -_pèse-acides_, and _hydrometers_, which differ only in the scheme of -their graduation. As to the _size_ and the _length_ of the stalks, -they depend upon the _dimensions_ you desire to give to the degrees of -the scale, and upon the _use_ to which the instruments are destined. -For the areometer of Baumé, and for the _pèse-sels_, the stalks are -generally thicker and shorter than for hydrometers. Pl. 4, fig. 19, 20, -and 21, represent different hydrometers. - - * * * * * - -NICHOLSON’S HYDROMETER.--Solder a bulb to the extremity of a capillary -tube; open it so as to form a very wide funnel, or rather capsule; -border the edges, and melt the point of junction with the tube so as to -close the opening of the latter. Solder the other extremity of the tube -to a cylindrical reservoir. Soften the point at the lower extremity of -the cylinder, and obstruct the canal so as to convert the point into a -glass rod; bend this rod into a hook. Now blow a bulb at the end of a -point, as if to make a mercury funnel; but, after having softened the -hemisphere of the bulb opposite to the point, and placed the latter in -the mouth, instead of blowing into the bulb so as to make a funnel, -strongly suck air from the bulb: by this means the softened part of the -glass is drawn inwards, and you obtain a capsule with double sides, -as exhibited by pl. 2, fig. 17. This capsule must have a small handle -fastened across it, by which it may be hung to the hook formed at the -bottom of the cylinder described above. - -This hydrometer being always brought to the same level, the point to -which it must be sunk in the liquid experimented with, is marked on -the stalk by applying a little spot of black enamel. The instrument is -represented by pl. 4, fig. 23. A variation in form is shewn by pl. 4, -fig. 22. - - * * * * * - -HYDROMETER WITH TWO BRANCHES.--To measure the relative density of two -liquids which have no action on each other, you employ a simple tube, -bent in the middle and widened at its two extremities. See pl. 2, fig. -11. - - * * * * * - -HYDROMETER WITH THREE BRANCHES.--This consists of a tube bent in such -a manner that the two branches become parallel. To this tube another -is soldered at the point of curvature, and is bent in the direction -exhibited by pl. 2, fig. 12. When the two branches are put into -different liquids, and the operator sucks air from the third branch, -the two liquids rise in their respective tubes to heights which are in -the inverse ratio of their specific gravities. - - * * * * * - -HYDROMETER WITH FOUR BRANCHES.--This is merely a tube bent three times, -and widened at its extremities. Pl. 2, fig. 13. - -To graduate hydrometers with two, three, and four branches, you have to -divide their tubes into a certain number of equal parts. - - * * * * * - -MANOMETERS.--Make choice of a tube nearly capillary, very regular in -the bore, and with sides more or less thick, according to the degree -of pressure which it is to support. Seal this tube at one end, blow a -bulb with thick sides near the middle, and curl it in S, just as is -represented by pl. 2, fig. 9. For manometers which serve to measure -the elasticity of the air under the receiver of the air-pump, what is -generally employed is a tube closed at one end and bent into a U. Pl. -2, fig. 10. You should take care to contract these at some distance -from the sealed part, in order to avoid the breaking of the instrument -on the sudden admission of air. Manometers are graduated, as will be -explained in the sequel. - - * * * * * - -MARIOTTE’S TUBE.--This is represented by pl. 2, fig. 7. It consists of -a tube thirty-nine inches long, closed at one end, bordered and widened -at the other, and bent into a U at the distance of eight inches from -its sealed end. The graduation of this instrument will be described -hereafter. - - * * * * * - -PHOSPHORIC FIRE-BOTTLE.--This is a short piece of tube closed at one -end, and widened and bordered at the other, in such a manner as to -receive a cork. Pl. 3, fig. 34. It is in this little vessel that the -phosphorus is enclosed. Glasses of this form can be employed in a great -variety of chemical experiments. - - * * * * * - -PULSOMETER.--This instrument consists of a tube, of which each -extremity is terminated by a bulb; it is partly filled with nitric -ether, and sealed at the moment when the ebullition of the ether has -chased the atmospheric air wholly from the interior of the vessel. Pl. -2, fig. 16. - - * * * * * - -PUMP.--Solder a cylinder, B (pl. 4, fig. 12), to the extremity of a -small tube, C, and form their point of coincidence into a funnel, to -which you will adapt a valve. Pierce the wide tube or body of the pump -at D, and solder there a piece of tube bent into an elbow and widened -at the other end into a funnel, which is to be furnished with a second -valve, as is represented in the figure. Prepare then the fountain of -compression E, and, by means of a cork and a little sealing-wax, fix it -upon the branch D. To prepare the piston, A, blow a bulb at the end of -a tube, flatten the end of the bulb, and choke it across the middle, -in order to form a place round which tow can be twisted, to make it -fit the tube air-tight. Finish the piston by twisting the other end of -the tube into a ring, as at A. The valves are formed of small cones of -cork, or wood, having in the centre an iron wire of sufficient size and -weight to enable them to play well. - - * * * * * - -RETORT FOR CHEMICAL EXPERIMENTS.--Plate 3, fig. 9, represents a -combination of a large and a small tube, forming a retort, which can -be employed with much advantage in many chemical experiments. When a -gas is to be distilled by means of such a vessel, the ingredients are -put into the wide tube, which is previously closed at one end, and then -the other end of the tube is either drawn out or soldered to a narrow -tube. Pl. 3, fig. 8 and 29, represent such vessels under different -forms. Very often a sort of retort can be formed by joining a wide tube -to a long bent narrow tube, by means of a cork. - - * * * * * - -TUBULATED RETORT.--This is represented by pl. 3, fig. 6. Prepare a -retort, such as is described in the preceding article, but one which -is bent near the closed end; pierce it at A (fig. 6), and solder -there a little piece of tube previously drawn out and sealed, such -as is represented by pl. 1, fig. 11. When the soldering is finished, -soften the end of the little tube, pierce it, and fashion it into a -bottle neck, so that it can be closed by a cork. Finish the instrument -by forming the open end according to the purpose to which it may be -destined. In the figure, the end is represented as drawn out for the -convenience of blowing into the retort to pierce the tubulure. - - * * * * * - -RUMFORD’S THERMOSCOPE.--This instrument is represented by pl. 3, fig. -35. It is necessary to take a tube almost capillary, to solder a bulb -at each extremity, to pierce it laterally at _b_, and to solder there a -piece of tube previously drawn out, but of which you open the point for -the purpose of finishing the sealing of the bulb A. After doing this, -you bend the two branches, as shewn in the figure. When the liquid has -been introduced into the instrument, you must seal the little piece of -tube which serves as a reservoir. - -This instrument can be made in another manner. Take two pieces of tube, -one of them twice as long as the other; solder a bulb at one end of -each of these tubes, and at about the third part of the length of the -long tube, parting from the bulb, bend it at a right angle; pierce the -little tube at a corresponding distance, and solder to the hole the end -of the long tube. The soldering being finished, and the whole system -having the form indicated by pl. 3, fig. 35, introduce, by the open end -of the short tube, a small quantity of coloured acid, and then seal the -end of the short tube, which serves as a reservoir. - -The interior diameter of the tubes which are generally employed as -thermoscopes, is one-eighth or one-twelfth of an inch. The mode of -graduation is described in a subsequent chapter. - - * * * * * - -SYPHONS.--The _simple syphon_ is a glass tube bent, at a little -distance from the middle, into a form which is intermediate between -those of ⋂ and ⋀, the legs being stretched apart like those of the -latter, but the bend being rounded like that of the former. The tube -is bent _near_ the middle, and _not exactly at_ the middle, in order -that the legs may be of unequal lengths; an arrangement which is -indispensable. Syphons are made of different lengths and diameters, for -various purposes. They can be made of tubes so capillary that it is -sufficient to put them into water to make them act: the liquid rises in -them by capillary attraction, and does not require to be sucked through -the tube, as it does when large syphons are employed. - - * * * * * - -WIRTEMBERG SYPHON.--This syphon is the same as the simple syphon, -excepting that the two branches are of equal length, and are bent in U -at both extremities. Pl. 3, fig. 22. - - * * * * * - -SYPHON WITH THREE BRANCHES.--This instrument is represented by pl. 2, -fig. 19. Close a tube at one end and draw it out at the other; pierce -it at some inches from the contracted extremity, and solder to the -hole a little tube of which the other end has been closed with wax. -Give the tube the bend necessary to constitute a syphon, and open the -two branches. The soldering of the two tubes is facilitated by giving -to the extremity of the little tube a bend which adapts it to be -applied parallel to the large tube. When the syphon is desired to be -well finished, the mouth-piece of the little tube must be bordered and -widened, and a bulb must be blown near the mouth-piece. - - * * * * * - -SYPHON WITH JET OF WATER.--This instrument is represented by pl. 3, -fig. 1. Take a tube of a large diameter, close it at one end, and draw -it out at the other. Cut the contracted part in such a manner as to -be able to introduce, through the orifice, the extremity, also drawn -out, of another tube, which should be almost capillary. Solder these -together in such a manner that the point of the small tube shall remain -fixed about an inch within the interior of the reservoir. Pierce again -the latter, at B, and solder there another branch of the same diameter -as the former; but fix it in such a manner that its side shall be -contiguous to the side of the reservoir. Finally, give to the branches -the bend represented by the figure. - - * * * * * - -SPOONS.--Solder a bulb to the extremity of a capillary tube; open the -bulb as for a funnel, but make the opening laterally. Cut with scissars -the edges of the part blown open, and in such a manner as to form a -spoon or a ladle, according as the bulb had the form of a sphere or an -olive. This instrument is useful for taking small quantities of acids. -Pl. 3, fig. 11. - - * * * * * - -SPIRIT LEVEL.--The spirit level is represented by pl. 2, fig. 28. -Choose a piece of tube very straight, and with sides precisely of -the same thickness in all parts. Seal it at one end, and draw it out -abruptly at the other. Fill it almost entirely with alcohol, and seal -the point by the jet of a candle. - - * * * * * - -TEST GLASS WITH A FOOT.--Take a tube drawn out at one end; choke it at -an inch from the base, in such a manner as to obstruct the canal almost -entirely. Pl. 1, fig. 12. Cut off the point, close the opening, and -soften the whole end completely; then blow it into a bulb and burst -it into a funnel. Now present the contracted part to the fire, so as -totally to close the passage. Border and soften the funnel, and by -pressing it against a flat plate of metal give it the form of a foot, -or pedestal. Cut the tube at the length which you desire the test-glass -to have, and border the edges of the opening. This is a very useful -little chemical instrument. It is represented by pl. 3, fig. 10. - - * * * * * - -THERMOMETERS.--Thermometers are instruments employed for appreciating -changes of temperature, either in the atmosphere or in substances which -we have occasion to examine. The following are the principal varieties -now employed. - - * * * * * - -ORDINARY THERMOMETER.--If you desire to make standard thermometers, -you must have capillary tubes of perfect accuracy in the bore. You are -assured of regularity in the diameter of a tube when a drop of mercury, -made to pass along the canal by means of a gentle inclination, or by -air blown from an Indian-rubber bottle, gives everywhere a metallic -column of the same length. - -For ordinary thermometers this precaution is superfluous. In all cases -you employ a tube more or less capillary, at one of the extremities -of which you blow or solder a spherical or cylindrical reservoir. -See pl. 4, fig. 1 and 2. You fill the instrument with well-purified -mercury, or alcohol, which you boil in the tube, in order to chase the -air from it. As it is necessary to heat the instrument throughout its -whole length, you must place it on a railing of iron wire, inclined -in the manner represented by pl. 4, fig. 14, and covered with burning -charcoal, or red-hot wood ashes. It is better, however, to employ a -kind of muff, formed of two concentric wire grates, between which you -put burning charcoal, and reserve the centre for the instrument. The -tube is thus kept in a vertical position, which allows the bubbles -of air to escape with more facility. An iron wire is made use of to -fasten the tube precisely in the centre of the column of fire. The -operation is considerably promoted by soldering a little funnel to the -upper extremity of the thermometer tube; and, in order to avoid the -interruption of the column of liquid by bubbles of air, it is better -to give to the superior part of the reservoir the form of a cone (pl. -4, fig. 3), rather than to preserve the completely spherical form -indicated by pl. 4, fig. 2. - -When the ebullition has expelled all the air which was contained in the -mercury, or alcohol, you immediately plunge the open extremity of the -instrument into a vessel filled with one or the other of these liquids; -or, instead of this, you pour the liquid into the funnel, in order that -the instrument may be quite filled at the common temperature. You then -cut off the funnel, if one has been used, and, by properly elevating -the temperature of the reservoir, you expel so much of the liquid -that the summit of the column rests at the point which you desire to -make choice of for the mean temperature: this operation is termed -_regulating the course of the thermometer_. - -There are two methods of closing thermometers: you may either produce -a vacuum above the column of mercury, or you may allow air to remain -there. In the first case, after having drawn out the end of the tube, -you heat the liquid until a single drop passes out of the opening; you -then instantly bring the point into the jet, and seal it. - -In the second case, you seal the instrument at the ordinary -temperature, and having previously raised to a reddish-white heat the -button of glass which is formed by the sealing, you suddenly elevate -the temperature of the mercury. The liquid, on rising, compresses -the enclosed air, which dilates the red-hot button at the summit of -the tube, and produces a species of reservoir. This reservoir is -indispensably necessary when you leave air above the column of liquid, -in order to provide against the bursting of the instrument on those -occasions when the temperature of the mercury comes to be considerably -elevated. See pl. 4, fig. 13. - - * * * * * - -DIAL THERMOMETER.--Terminate a piece of tube, of six-tenths of an inch -in diameter, with two points, and solder to one of these points a tube -one-eighth of an inch in diameter and six inches long; close the end of -this small tube, and, heating a zone of the reservoir, near the base of -the other point, blow a bulb there. Cut off the point by which you have -blown, at a little distance from the bulb; open and border the end of -the narrow tube, and bend it into a U. See pl. 4, fig. 16. - -Fill the bulb and the reservoir with alcohol, and add a drop of mercury -which fills a certain space in the narrow tube. This mercury bears -on its surface a little iron weight, to which a thread is fastened; -the other end of this thread passes over a pulley, whose axis turns a -needle. The expansion or contraction of the alcohol causes the mercury -to rise and fall, and consequently produces a movement of the needle or -index of the dial. This thermometer is graduated like the others, by -being brought into comparison with a standard thermometer. - - * * * * * - -CHEMICAL THERMOMETER.--This instrument is merely a common thermometer, -the divisions of which, graduated on paper, are enclosed in a very -thin glass tube, to hinder them from being altered or destroyed when -the instrument is plunged into liquids. Pl. 4, fig. 4, 5, 6, and 7, -represent chemical thermometers of various kinds. - -The case of the thermometer can be made in two different ways. -According to the first, you take a tube of a pretty large diameter, and -with very thin sides; you draw out one end and obliterate the point, -which you bend into a ring, in a direction perpendicular to that of -the case; you pass through this ring the stalk of the thermometer, -which is thus placed parallel to the large tube. After having fixed -the graduated scale in the interior of the case, by means of a small -drop of sealing-wax, which has been dropped on the slip of paper, and -which, being supported against the side of the case, needs only to be -warmed to adhere there and fix the scale securely to its envelope, you -close the upper extremity of the case by drawing it out, obliterating -the canal and soldering it to the thermometer tube which has been -introduced into the ring at the lower end of the case. You heat the -connecting piece till it is soft, and then push the thermometer up and -down until the zero marked on its tube corresponds with the zero marked -on the scale within the case. See pl. 4, fig. 6 and 7. - -The second method of making the case is as follows:--You take a -tube with thin sides, and sufficiently large to contain the entire -thermometer; you draw out the tube at one end, and choke it at some -distance from the point of the contracted part. This you must do in -such a manner as to form a little bulb, which is to be ballasted -in the manner described at the article _Hydrometers_. After having -introduced into the case a little ball of cotton, you place therein the -thermometer, furnished with its scale, and in such a manner that the -reservoir rests on the cotton. You terminate the upper end of the case -either with a ring or by a contraction which permits the instrument to -be suspended by a cord. See pl. 4, fig. 4 and 5. - - * * * * * - -SPIRAL THERMOMETER.--Take a tube which is not capillary, but which has -thin sides; close one of its ends, and bend it round by pressing it -with a metallic rod; continue to bend it round till it has made several -turns, all in the same plane. See pl. 1, fig. 13. The latter turns -may be managed with the fingers instead of the metallic rod. When the -reservoir so formed is sufficiently large, solder to the end of it a -capillary tube, which you point in a direction perpendicular to that of -the axis of the spiral. The instrument is represented by pl. 4, fig. 8. - - * * * * * - -POCKET THERMOMETER.--The pocket thermometer differs in nothing from the -thermometer just described, except that the capillary tube, instead of -passing away from the spiral in a straight line, is turned round, so as -to form a continuation of the spiral. See pl. 4, fig. 17. - - * * * * * - -MAXIMUM THERMOMETER.--This instrument consists of an ordinary mercurial -thermometer, bent at a right angle near the origin of the reservoir, -and in the horizontal column of which a little steel or iron rod has -been introduced: this rod, by gliding in the tube, where it experiences -very little friction, serves as an index. Since this index does not -permit the instrument to be sealed with the vacuum above the mercury, -you must terminate the sealing by a little reservoir, as we have -described at the article on the second method of closing thermometers. -The instrument is represented by pl. 4, fig. 24. - - * * * * * - -MINIMUM THERMOMETER.--This instrument is constructed pretty nearly in -the same manner as the preceding. The liquid, however, must be alcohol, -and the index a little rod of enamel, which ought not to be quite so -large as the bore of the thermometer tube. You seal the tube by making -a vacuum above the column. - - * * * * * - -BELLANI’S MAXIMUM THERMOMETER.--This thermometer is represented by pl. -4, fig. 9. Take a tube which is very regular, and about one-eighth or -one-twelfth of an inch diameter in the bore; solder a reservoir at each -end, one of them much larger than the other; make a bend near the large -reservoir, and then fill the instrument with alcohol to A. Above that, -place the first index, which consists of a very small piece of tube -closed at one end and cut off square at the other. In the interior of -this tube the two ends of a hair are fixed, by means of a little rod of -iron, which is pushed into the tube. Introduce a quantity of mercury -above this index, make the bend B, add again mercury as far as C, then -another index similar to the first. Finally, fill the rest of the tube -and the half the little reservoir with alcohol, and seal the point. - - * * * * * - -DIFFERENTIAL THERMOMETER.--This instrument is represented by pl. 3, -fig. 14. Take a tube ten or twelve inches long, and one-eighth or -one-twelfth of an inch internal diameter; blow a bulb at one end, and -bend the tube at a right angle towards the fourth part of its length. -Prepare a second tube in the same manner, and solder the bent ends -together, so as to form a single tube with a bulb at each end, having -previously poured into one of the bulbs a small quantity of sulphuric -acid tinged red. - -Instead of following the above method, you may take a single tube of -twenty or twenty-four inches in length, and of the above-mentioned -diameter; you solder a bulb at each end, bend the tube twice till it -represents the figure, pour in the acid, and then seal the open points. -The graduation of the differential thermometer, as well as of all the -other thermometers, is described in a subsequent section. - - * * * * * - -TUBE FOR CRYSTALLIZING SPERMACETI.--Take a little capillary tube; curl -one of its ends into a ring, and solder the other to a cylindrical -reservoir, two-thirds of the capacity of which you fill with very pure -spermaceti dissolved in sulphuric ether; you then seal the point of the -reservoir. See pl. 3, fig. 27. - - * * * * * - -TUBE FOR DEMONSTRATING THE NON-CONDUCTABILITY OF HEAT BY LIQUIDS.--This -is represented by pl. 2, fig. 26. It is a tube sealed at one end, -bordered at the other, and bent in such a manner as conveniently to -permit the upper part of a column of liquid to be exposed to heat. - - * * * * * - -TUBE FOR ESTIMATING THE DENSITY OF VAPOURS.--Represented by pl. 2, fig. -14. It is merely a tube sealed at one end, bordered at the other, and -bent as shewn by the figure. - - * * * * * - -TUBES FOR EXPOSING SUBSTANCES TO HEAT AND GASES.--This instrument -consists of a tube bent in the middle into a U. Pl. 3, fig. 3. It is -much employed in chemistry, for containing substances which we wish at -the same time to expose to an elevated temperature and to the action -of certain gases. This tube can also be employed for cooling gases, or -liquids, in distillation; the bent part being, in this case, dipped -into water or a freezing mixture, or enveloped in wet paper or cloth. - - * * * * * - -TUBES FOR THE PRESERVATION OF OBJECTS OF NATURAL HISTORY, OR OF -CHEMICAL PREPARATIONS.--Take a tube of which the width and length -corresponds with the object which is to be enclosed; draw it out at -one end, and, after having obstructed the point, twist it into a ring. -Introduce the object by the open extremity, which you must afterwards -draw out; fill the tube with the liquid necessary to preserve the -object, and then seal the point. See pl. 2, fig. 27. - -If you desire to have the power of taking out the object at will--as, -for example, when grain is preserved, or when, in chemistry, the tube -is employed to contain salts and other compounds, of which small -quantities are now and then required for use--you do not seal the end -of the receiver, but border it in such a manner that it can be closed -by a cork. - -In some cases a cork is not sufficient to secure the substance from -the action of air: it must then be assisted with a little cement. By -melting together two parts of yellow wax, one part of turpentine, and a -small quantity of Venetian red, a very useful cement for such purposes -is obtained. - -It is sometimes necessary to _suspend_ the objects enclosed within the -tube: you then introduce a little glass hook, the tail of which you -solder to the upper extremity of the tube; managing this operation at -the same time that you make the external ring for the support of the -instrument. By turning the hook round cautiously, which is done when -the end of the tube is in a soft state, and by cooling the whole with -care, you may succeed in fixing the hook in the centre of the tube. See -pl. 3, fig. 20. - - * * * * * - -TUBE FOR EMPTYING EGGS.--It is a simple tube, drawn out to a capillary -point at one end, and bent there into a V. See pl. 3, fig. 23. - -The application which the author has made of this instrument, and of -the tube represented by pl. 3, fig. 26, has been shewn in a memoir -inserted in the _Annales des Sciences Naturelles, Tom. XV. Novembre_ -1828, concerning a new method of preparing and rendering durable -collections of eggs destined for cabinets of Natural History. - - * * * * * - -VIAL OF THE FOUR ELEMENTS.--This instrument is represented by pl. 2, -fig. 27. Take a tube drawn out at one end, obstruct the canal two -inches from the extremity, and twist the contracted part into a ring. -Draw out the other end of the tube, introduce the proper liquids, -remove the point of the tube, and seal it. The liquids generally -employed for filling the vial of the four elements are, 1. Mercury; -2. A very concentrated solution of carbonate of potash; 3. Oil of -turpentine; 4. Alcohol. A portion of air is also allowed to remain in -the tube. - - * * * * * - -WATER HAMMER.--Pl. 2, fig. 18, is a representation of this instrument. -Choose a tube of a good diameter, and with thick sides; seal it at -one end and draw it out at the other. Blow a bulb at the base of the -contracted part; then, having put a quantity of water in the tube, let -it boil therein, to expel the atmospherical air. When you imagine that -all the air has been expelled, and that nothing remains in the tube but -steam and water, seal the open point. - -When you have to seal a tube in this manner, you should be careful -to draw out the extremity of the tube somewhat abruptly, and leave -a very small opening, so that it shall be sufficient to expose the -point to the jet of a candle blown by a mouth blowpipe, to have the -sealing completely and suddenly effected. You can afterwards round -this sealed part by turning it in the flame of the lamp, provided, -however, that you have preserved a sufficient thickness of glass at the -sides of the point. If you omit to take this precaution, the pressure -of the atmosphere, acting with great force on the softened glass when -it is unsupported by the partial vacuum within the tube, is capable -of producing such a flattening, or even sinking in of the matter, -as could not subsequently be rectified; except, indeed, by heating -simultaneously the liquid contained in the tube and the glass to be -mended, which is an operation of a very delicate description. - - * * * * * - -WELTER’S SAFETY TUBES.--After having closed a tube at one end and -drawn it out at the other, give it the curvature exhibited by plate 3, -fig. 18. Pierce it then laterally, in the middle of the part _a b_, -and solder there the extremity of a tube, to the other end of which a -funnel has been soldered: it is necessary that the funnel be closed by -a cork. The soldering being terminated, a bulb must be blown and the -tube bent in S, in the manner shewn by the figure. Then open the closed -end, and cut off the contracted point. - - - - -THE - -ART OF GLASS-BLOWING. - -V.--_Graduation of Chemical and Philosophical Instruments._ - - -OF THE SUBSTANCES EMPLOYED IN THE PREPARATION OF THESE INSTRUMENTS. - -Before proceeding to the subject of _graduation_, it is necessary -to say a few words respecting the substances which are generally -employed to fill a variety of instruments, particularly barometers and -thermometers. - -_Mercury._--It ought to be completely purified from all foreign -substances. You can separate it from the dust it may contain by passing -it through a piece of chamois leather; you tie a very hard knot, -and by pressure oblige the mercury to pass out in a fine rain. This -process is sufficient for the purification of mercury which merely -contains extraneous bodies in suspension; but it is not sufficient -when the mercury to be purified contains tin, lead, or other metals, -in solution. It is then necessary to distil the mercury; upon which -the fixed metals remain behind. The oxide of mercury produced by the -distillation is removed by agitating the distilled metal with sulphuric -acid, and subsequently washing it with a large quantity of water, till -all the acid is removed; it is then dried as completely as possible -with blotting-paper, and afterwards is moderately warmed. - -_Alcohol_ ought to be very pure and well rectified. It is necessary to -colour it, because, being colourless of itself, it could not be seen -in capillary tubes. To colour alcohol, you infuse carmine in it, and, -after some time, decant or filter the clear solution. The liquid should -be perfectly transparent, and free from all extraneous substances. -It is not proper to employ alcohol in the construction of standard -thermometers; mercury being much preferable. - -_Sulphuric Acid._--It is made use of for the differential thermometer, -and the thermoscope of Rumford. It has the advantage of being lighter -than mercury, and very slightly volatile: these two qualities, joined -to its tendency to absorb the vapour of water, render it very proper to -be employed for various instruments. It must be very concentrated, and -tinged red by carmine. - -_Ether._--Sulphuric and nitric ether, with which some small instruments -are filled, are merely employed to shew with what facility these -liquids are brought to their boiling point. - - * * * * * - -OF GRADUATION IN GENERAL.--Graduation, generally speaking, consists -in dividing lines, surfaces, and capacities, into a certain number -of equal or proportional parts. It is not our intention to treat here -of the methods furnished by practical geometry for effecting such -divisions with mathematical accuracy; these methods are known to -every body. We shall confine ourselves to describing the processes of -graduation which are peculiar to the instruments constructed by the -glass-blower. - - * * * * * - -EXAMINATION OF THE BORE OF TUBES.--We have already observed, that, for -standard thermometers and other instruments which require to be made -very accurate, it is necessary to employ tubes which are extremely -regular in the bore. When a drop of mercury, passed successively along -all parts of the tube, forms everywhere a column of the same length, -the examiner is assured of the goodness of the tube. - -That a tube may be regular in the bore, it is not necessary that the -bore be cylindrical; it is sufficiently accurate when equal lengths -correspond to equal capacities. A tube with a flat canal, for example, -can be perfectly accurate without at all approaching the cylindrical -form. It is only necessary that a drop of mercury occupy everywhere -the same length. We may observe, by,the way, that, in flat canals, the -flattening should be always in the same plane. - - * * * * * - -DIVISION OF CAPILLARY TUBES INTO PARTS OF EQUAL CAPACITY.--As it is -very difficult to meet with capillary tubes which are exactly regular -in the bore, it happens that the tubes which glass-blowers are obliged -to employ have different capacities in parts of equal length. You -commence the division of these tubes into parts of equal capacity by -a process described by M. Gay-Lussac. You introduce a quantity of -mercury, sufficient to fill rather more than half the tube, and make a -mark at the extremity of the column. You then pass the mercury to the -other end of the tube, and again mark the extremity of the column. If -you so manage that the distance between the two marks is very small, -you may consider the enclosed space as concentric, and a mark made -in the middle of the division will divide the tube into two parts of -evidently equal capacity. You divide one of these parts, by the same -process, into two equal capacities, and each of these into two others; -and in this manner you continue to graduate the tube until you have -pushed the division as far as you judge proper. - -But it is still more simple to introduce a drop of mercury into the -tube, so as to form a little cylinder, and then to mark the two -extremities of the cylinder. If it were possible to push the drop of -mercury from one end of the tube to the other, in such a manner as to -make it coincide, at every removal, with the last mark, it would be -very easy to divide the tube accurately; but as it is very difficult, -not to say impossible, to attain this precision of result in moving the -column of mercury, you must endeavour to approach exactness as nigh -as may be. You measure, every time you move the mercury, the length -of the cylinder it produces, and carry this length to the last mark, -presuming the small space which is found between the mark and the -commencement of the column to be fairly represented by the same space -after the column. You thus obtain a series of small and corresponding -capacities. - - * * * * * - -GRADUATION OF GAS JARS, TEST TUBES, &C.--If the tube is regular in the -bore, close one end, either by sealing it at the lamp, or by inserting -a cork, and pour into the interior two or three small and equal -portions of mercury, in order to have an opportunity of observing the -irregularities produced by the sealed part. Take care to mark, with a -writing diamond, the height of the mercury, after the addition of each -portion. When equal portions of mercury are perceived to fill equal -spaces, take with the compass the length of the last portion, and mark -it successively along the side of the tube, where you must previously -trace a line parallel to its axis. - -For tubes which are irregular in the bore, and where equal lengths -indicate unequal capacities, it is necessary to continue the graduation -in the same manner that you commenced it--that is to say, to fill the -tubes by adding successively many small and equal portions of mercury, -and marking the height of the metallic column after every addition. -These divisions will of course represent parts of an ounce or of a -cubic inch according to the measure which you make use of. When you -have thus traced on the tube a certain number of equal parts, you can, -by means of the compasses, divide each of them into two other parts of -equal length. The first divisions being very close to one another, the -small portion of tube between every two may be considered without much -risk of error as being sensibly of equal diameter in its whole extent. - -When the tube which you desire to graduate is long and has thin sides, -it would be difficult to fill it with mercury without running the risk -of seeing it break under the weight of the metal. In this case, you -must use water instead of mercury. - -Bell-glasses of large dimensions are graduated by filling them with -water, placing them in an inverted position on a smooth and horizontal -surface, which is slightly covered with water, and passing under them -a series of equal measures of air. But it is then necessary to operate -constantly at the same temperature and under the same atmospheric -pressure, because air is very elastic and capable of being greatly -expanded. - -In all cases, tubes, bell-glasses, &c. ought to be held in a position -perfectly vertical. The most convenient measure is a dropping-tube, -on the stalk of which a mark has been made, or a small piece of tube, -sealed at one end, and ground flat at the other; the latter can be -accurately closed by a plate of glass. - -The marks which are traced on tubes being generally very close to one -another, you facilitate the reading of the scale by giving a greater -length to those marks which represent every fifth division, and by -writing the figures merely to every tenth division. See pl. 4, fig. 8. -The number of divisions is somewhat arbitrary; nevertheless, 100, 120, -360, 1000, are divisions which, in practice, offer most advantages. - - * * * * * - -GRADUATION OF HYDROMETERS.--Cut a band of paper on which the graduation -of the instrument can be traced, and let fall upon it a little drop -of sealing-wax; then roll the paper upon a little glass tube, and -introduce it into the stalk of the hydrometer. The instrument is -afterwards to be plunged into distilled water, which is carefully kept -at the temperature of 40° F. above zero. Give the instrument sufficient -ballast to make it sink till the point (_a_, pl. 4, fig. 20,) which -you desire to make to represent the density of water, touches the -surface of the water. Mark this point with much precision; it is the -zero of the instrument. The other degrees are taken by plunging the -hydrometer into distilled water to which you have added 1, 2, 3, 4, 5, -&c. _tenths_, or 1, 2, 3, 4, 5, &c. _hundredths_, of the substance for -which you wish to construct the hydrometer, according as you desire the -scale to indicate tenths or hundredths. - -When you have thus marked the degrees on the stalk of the instrument, -transfer them to the paper with the help of the compasses. The scale -being completed, replace it in the tube of the hydrometer, where it -must be fixed; in so doing, take care to make the degrees on the scale -coincide precisely with those marked on the stalk. - -You can thus procure hydrometers for alcohol, acids, salts, &c. which -are instruments that indicate the _proportion_ of alcohol, acid, salt, -&c. contained in a given mass of water. - -But if it were necessary to plunge the hydrometer in a hundred -different solutions in order to produce the scale, it is easy to -conceive that that would be extremely troublesome, especially for -hydrometers which are employed in commerce, and which do not need to be -so extremely accurate. When the density of the mixtures or solutions -is a mean between those of the substances which enter into them, you -may content yourself with marking the zero and one other fixed point, -(_a_ and _b_, pl. 4, fig. 20.) Then, as the stalk of the hydrometer is -evidently of equal diameter in all its extent, you can divide the space -which separates the two fixed points into a certain number of equal -parts. One of these, being taken for unity, represents a particular -quantity of the substance which you have added to a determined weight -of distilled water. By means of this unity you can carry the scale -up and down the stalk of the instrument. It is thus, that, to obtain -a Baumé’s hydrometer, after having obtained the zero by immersion in -distilled water, you plunge the instrument into a solution containing -a hundred parts of water and fifteen of common salt, to have the 15th -degree, or containing a hundred water and thirty salt, to have the 30th -degree. Upon dividing the interval into fifteen or thirty equal parts, -according as you have employed one or the other solution, you obtain -the value of the degree, which you can carry upwards or downwards as -far as you wish. - -Among the substances for which hydrometers are required in commerce, -are some which it is impossible to obtain free from water--such are -alcohol, the acids, &c. In this case it is necessary to employ the -substances in their purest state, and deprived of as much water as -possible. - -The employment of hydrometers is very extensive: they are used to -estimate the strength of lyes, of soap solutions, of wines, milk, &c. -There is, in short, no branch of commerce in which these instruments -are not required for the purpose of ascertaining the goodness of the -articles which are bought and sold. The employment of hydrometers -would be still more general, if they could be made to give immediately -the absolute specific gravity of the liquids into which they might be -plunged, the specific gravity of water being considered as unity. It is -possible to graduate a thermometer of this description by proceeding as -follows:-- - -Make choice of a hydrometer of which the exterior part of the stalk is -very regular. Introduce the band of paper on which the scale is to be -written, and then ballast the instrument. Make a mark where the surface -of the distilled water touches the stalk. Remove the hydrometer from -the water, wipe it perfectly dry, and weigh it very accurately with a -sensible balance. Then pour into it a quantity of mercury equal to its -own weight; plunge it again into the water, and again mark the point -where the stalk touches the surface of the water. Pour the mercury out -of the instrument, transfer the two marks to the scale, and divide -this fixed distance into fifty equal parts. Having by this operation -obtained the value of the degree, you carry it upwards and downwards, -to augment the scale. If you take the first point near the reservoir, -the hydrometer will be proper to indicate the density of liquids which -are heavier than water; if you take it towards the middle of the tube, -the contrary will be the case. - -If you destine the hydrometer for liquids much heavier than water--such -as acids, for example--you might, after having determined the first -point, add to the original ballast as much mercury as is equal to the -weight of the whole instrument; then the point where the stalk would -touch the surface of the water, and which would be represented by 100, -would be very high, and the second point, which would be found below, -would be represented by 200. On dividing the space into a hundred equal -parts, you would have the value of the degree, which could be carried -up and down for the extension of the scale. - -The specific gravities being in the inverse ratio of the volumes -plunged into the liquid, the numbers of the scale which mark the -specific gravities diminish from below; so that, on marking the lowest -point 100, you have, on proceeding upwards, the successive degrees -0·99, 0·98, 0·97, 0·96, &c. - -The hydrometers with two, three, and four branches, are graduated by -having their tubes divided into a hundred or a thousand equal parts. -The divisions on each branch must correspond with those on the other -branches. - - * * * * * - -GRADUATION OF BAROMETERS.--The graduation of this instrument consists -in dividing a piece of metal, wood, or ivory, into inches and parts of -inches. The divided rod is then employed to measure the height of the -mercury in the tube. As the rule is moveable, the operation presents no -sort of difficulty: all that is necessary is to make the zero of the -scale coincide with the inferior level of the mercury; the point which -corresponds with the superior level of the mercury, seen in the tube, -indicates the height of the barometric column. It is in this manner -that the cistern barometer is graduated. - -But if the barometer is one of those in which the surface of the -mercury is variable, such as the barometer of Gay-Lussac, it is -necessary to have recourse to a different process of graduation. If -the two branches of the instrument are very regular, and of equal -diameter, you first measure with precision the height of the column of -mercury, then divide it in the middle, and fix the scale, which must be -graduated in such a manner that the mark of fifteen inches corresponds -exactly with the middle point. This mode of graduation serves to -indicate merely the apparent height of the barometric column. If you -desire that the scale should immediately indicate the real height, you -must fix the zero at the middle of the column, and then double the -figure which marks each degree. - -When you do not wish to write the real height, you make two divisions, -of which one proceeds upwards, the other downwards. You do not, in this -case, double the value of each division, but in observations made with -such a barometer scale you add the degree marked by the two surfaces, -in order to find the real height. - -It is in an analogous manner that you graduate the gauges or short -barometers which are employed to measure the density of air under -the recipient of the air-pump. You take the height of the mercury in -the gauge, and fix at the middle of the column the zero of a double -scale, of which one division proceeds upwards, the other downwards; -or, instead of this, if you choose to have only one scale, and that an -ascending scale, you double the value of every degree. - -The zero of the barometric scale can be fixed below the inferior -surface of the mercury; but then, to have the real height, it is -necessary to measure precisely the height of the mercury in the two -branches of the instrument, and to deduct the smaller from the larger. - -_Dial (or Wheel) Barometer._--The disposition which should be given -to this instrument is precisely the same as that of the _Dial -Thermometer_, described in a preceding section. You make a small iron -weight float on the inferior surface of the mercury, and fix to this -weight a silk thread, which is stretched by a counterpoise, and rolls -over a very moveable pulley. The axis of this pulley carries a needle, -which turns backwards or forwards according as the column of mercury -augments or diminishes. You arrange the whole in such a manner that the -extreme variations of this column cannot make the needle describe more -than one circumference; with this view you give the pulley a diameter -of nearly an inch. - -The dial barometer being rather an object of luxury than an instrument -of precision, you graduate it by inscribing the following words, at -full length, on the scale. In pl. 4, fig. 16, for example, you write, - - At the point _a_ Tempest. - ... _b_ Much rain. - ... _c_ Rain or Wind. - ... _d_ Temperate. - ... _e_ Fine Weather. - ... _f_ Fixed Fair. - ... _g_ Very Dry. - -You write nothing at the inferior division. - - * * * * * - -GRADUATION OF THE MANOMETER.--The graduation of this instrument -consists in dividing the tube where the air is to be compressed, into a -given number of parts of equal capacity; but as, in general, such tubes -are employed as are nearly capillary and very regular, the operation -is reduced to a linear division, where every degree occupies an equal -space. - - * * * * * - -GRADUATION OF THERMOMETERS. _Construction of Standard -Thermometers._--Having constructed your instrument with a very regular -tube, or one which has been divided into parts of equal capacity, and -having filled it with the proper liquid, according to the instructions -given in a preceding section, the graduation is to be effected as -follows. Procure very pure ice, break it into small pieces, and fill -a vessel with it. When the ice begins to melt, plunge the thermometer -into the middle of it, in such a manner that, without touching the -sides of the vessel, the whole thermometer, or at least that part -of it which contains the liquid, may be covered with ice. Allow the -instrument to remain in this state until, in spite of the gradual -melting of the ice, the surface of the column of liquid remains at -a fixed point, and neither falls nor rises. Mark this point very -carefully on the stalk of the thermometer, either with a thread or a -little drop of sealing-wax, or with the trace of a diamond or a flint. -This is the _freezing point_, the _zero_ of the centigrade scale, the -thirty-second degree of Fahrenheit’s scale. - -As for the second fixed point, it is marked during an experiment with -boiling water, performed as follows:--You employ a vessel of tin plate -sufficiently high to enclose the whole thermometer; you pour into this -vessel distilled water, till it is about an inch deep, and then you -heat it. The vessel is surmounted by a cover pierced with two holes, -one of which is intended to receive the stalk of the thermometer, the -other to allow the steam to escape. When, on continuing the ebullition, -you observe that the mercury ceases to rise in the tube, you mark -the point at which it has stopped, just as you marked the first -point. The last mark indicates the _boiling point_; the one hundredth -degree of the centigrade scale, the two hundred and twelfth degree -of Fahrenheit’s scale. You transfer to paper the distance which is -found between the first point and the second point determined, and you -divide this distance into one hundred equal parts, or degrees, for -the centigrade thermometer, into eighty parts for the thermometer of -Réaumur, and into one hundred and eighty for that of Fahrenheit. If -the tube of the instrument is very regular in the bore, the degrees -should be equal in length; if, on the contrary, you have been obliged -to divide it into parts of equal capacity, you find how many of these -parts or little spaces it is necessary to take to constitute one of the -above degrees. You find this by dividing their whole number by 100, or -80, or 180, according to the degrees of the scale which you intend to -make use of. Thus, if you find between the two points fixed by melting -ice and boiling water, three hundred divisions of equal capacity, it is -necessary to include _three_ of these divisions in every _degree_ of -the centigrade scale. - -The vessel employed to take the boiling point must be of metal, and its -surface should be perfectly clean and well polished, and have no rough -points. If sand, or other matters, were permitted to repose on the -vessel, and to form asperities, the water would enter into ebullition -at an inferior temperature. - -This operation should, moreover, be performed under an atmospherical -pressure, which is indicated by the barometer when the mercury stands -at twenty-nine inches and a half. But as this pressure is different -according to the elevation of the place of operation, and, indeed, -suffers continual variations even in the same place, it follows that -the temperature of boiling water is subject to continual changes, -and that, in the graduation of the thermometer, it is indispensably -necessary to take notice of the height of the barometer at the very -moment that the point denoting the degree of boiling-water is fixed -upon. You succeed in making the necessary corrections by the help of -the following table, which is founded on the experiments of Sir G. -Shuckburg and of the Committee of the Royal Society. - -[See the Table on the opposite page.] - -_Common Thermometers._--Having, by the method which we have just -described, obtained a _Standard Thermometer_, you may procure with -facility as many ordinary thermometers as you desire. It is proper -to employ the most regular tubes which you can obtain, and when the -instruments are ready to be graduated, you must bring them into -comparison with your standard thermometer. You place them together into -a liquid of which you gradually raise the temperature, and you mark -several points on the scale of the new thermometer, the intervals -between which are subsequently divided into as many degrees as are -marked on the scale of the standard thermometer. Thus, for example, -you mark the 10° and 15°, and afterwards divide the interval into five -equal parts. This gives you the length of a degree on the stalk of the -new instrument. The more you multiply these fixed points, the more you -insure the precision of the thermometer. When you have taken a certain -number of points, you measure the remainder with the compasses. - - * * * * * - - +-----------------------------------+------------------------+ - |Height of the Barometer in Inches. | | - +-----------------+-----------------+ Correction in | - |When the boiling |When the boiling | 1000ths of the | - | point is found | point is found | interval between | - | by immersing | by immersing | the freezing | - | the Instrument | the Instrument | and boiling points | - | in _Steam_. | in _Water_. | of Water. | - +-----------------+-----------------+------------------------+ - | ... | 30.60 | 10 } | - | ... | 30.50 | 9 } | - | 30.71 | 30.41 | 8 } | - | 30.50 | 30.29 | 7 } | - | 30.48 | 30.18 | 6 } | - | 30.37 | 30.07 | 5 } Lower. | - | 30.25 | 30.95 | 4 } | - | 30.14 | 30.84 | 3 } | - | 30.03 | 30.73 | 2 } | - | 29.91 | 30.61 | 1 } | - | 29.80 | 30.50 | 0 } | - | | | | - | 29.69 | 29.39 | 1 } | - | 29.58 | 29.28 | 2 } | - | 29.47 | 29.17 | 3 } | - | 29.36 | 29.06 | 4 } | - | 29.25 | 28.95 | 5 } Higher. | - | 29.14 | 28.84 | 6 } | - | 29.03 | 28.73 | 7 } | - | 28.92 | 28.62 | 8 } | - | 28.81 | 28.51 | 9 } | - | 28.70 | | 10 } | - | | |The boiling point to be | - | | |marked so much higher or| - | | |lower than the stand of | - | | |the mercury during the | - | | |experiment. | - +-----------------+-----------------+------------------------+ - -The zero, 0°, of the thermometer of Fahrenheit, is taken by means of a -mixture of snow and common salt, and its maximum point is, like that of -the preceding thermometer, taken by means of boiling water; but this -interval is divided into 212 degrees; so that the scale marks 32° where -the centigrade and Réaumur’s scales mark 0°. - -The thermometer of Delisle has but one fixed point, which is the heat -of boiling water; this is the zero of the instrument. The inferior -degrees are 0,0001 (one ten-thousandth part) of the capacity of -the bulb and stalk of the thermometer. It marks 150° at 0° of the -centigrade, or 32° of Fahrenheit’s thermometer. - -The dial, the maximum and the minimum thermometers, are graduated -according to the same principles as the common thermometers. - -You can, with a mercurial thermometer, make the centigrade scale rise -to 300 or 400 degrees above zero; but with an alcohol thermometer, -you must never go beyond the heat of boiling water. On the contrary, -the inferior degrees of the alcohol thermometer can be carried to the -very lowest point, while those of the mercurial thermometer should -be stopped at thirty or thirty-five degrees below the zero of the -centigrade scale, as the mercury then approaches very near the point -of its congelation. In all cases, the degrees of thermometer scales -are indicated by the sign - when they are below zero, and by the sign -+ when they are above it; the -is always marked, but the + generally -omitted. See pl. 4, fig. 6. - -We may observe here that it is proper from time to time to plunge the -standard thermometer into melting ice, for the purpose of verifying -its exactness. It has been found that thermometers constructed with a -vacuum above the column of mercury gradually become inaccurate, the -0° ascending, until it corresponds with + 1° or + 2°. This singular -effect is attributable to the constant pressure of the atmosphere, -which, being supported merely by the resistance of the very thin sides -of the thermometer, finally presses them together, and diminishes -the capacity of the reservoir. It is partly for the sake of avoiding -this inconvenience that we consider it good not to make an entire -vacuum above the mercury, but to leave a portion of air in the tube, -and at the same time to form a little reservoir at the summit of the -instrument. - -_Differential Thermometer._--To graduate this instrument, you first -maintain the two bulbs at an equal temperature, by which you determine -the first fixed point, which is zero. Then, enveloping one of the -two bulbs with melting snow, and elevating the other by means of a -vessel with warm water, to a known temperature--to 20° Centigrade, -for example--you fix a certain space, which you afterwards divide -into 20 equal parts or degrees. The scale is continued by carrying -successively to each side the known value of a degree. - - * * * * * - -GRADUATION OF RUMFORD’S THERMOSCOPE.--This instrument is graduated by -dividing the tube which separates the two bulbs into equal parts, the -number of which is arbitrary, though, in general, the thermoscope tube -is divided into nine or eleven parts. There is always an odd number of -degrees, and you manage so that the odd degree is found in the middle -of the tube. It carries the mark of zero at each end, and the figures -1, 2, 3, &c. proceed from each end of this middle degree, and form two -corresponding scales. - - * * * * * - -GRADUATION OF MARIOTTE’S TUBE.--You divide the little branch which is -sealed at the end into a certain number of parts of equal capacity, -and the large branch into inches and parts of inches. It is necessary -to take care that the zero of the two ascending scales correspond, and -are situated above the inferior bend formed by the two branches of the -instrument. - - -THE END. - -W. WILSON, PRINTER, 57, SKINNER-STREET, LONDON. - - - - - -End of Project Gutenberg's The Art of Glass-Blowing, by T. P. 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P. Danger - -This eBook is for the use of anyone anywhere in the United States and most -other parts of the world 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. If you are not located in the United States, you'll have -to check the laws of the country where you are located before using this ebook. - -Title: The Art of Glass-Blowing - Plain Instruction for the Making of Chemical and - Philosophical Instruments Which are Formed of Glass - -Author: T. P. Danger - -Release Date: August 4, 2017 [EBook #55266] - -Language: English - -Character set encoding: UTF-8 - -*** START OF THIS PROJECT GUTENBERG EBOOK THE ART OF GLASS-BLOWING *** - - - - -Produced by Wayne Hammond and The Online Distributed -Proofreading Team at http://www.pgdp.net (This file was -produced from images generously made available by The -Internet Archive) - - - - - - -</pre> - -<hr class="chap" /> - -<div class="figcenter"> -<img id="cover" src="images/cover.jpg" alt="" /> -</div> - -<div class="figcenter"> -<p class="copyleft"><i>Pl. 1.</i></p> -<img id="pl_1" src="images/pl_1.jpg" alt="" /> -<p class="copy"><i>Published by Bumpus & Griffin London, 1831.</i></p> -</div> - -<hr class="chap" /> - -<h1> -<span class="medium">THE</span><br /> - -ART OF GLASS-BLOWING,<br /> - -<small>OR</small><br /> - -<span class="large">PLAIN INSTRUCTIONS</span><br /> - -<small>FOR MAKING THE</small><br /> - -<span class="x-large">CHEMICAL AND PHILOSOPHICAL<br /> -INSTRUMENTS</span><br /> - -<span class="large">WHICH ARE FORMED OF GLASS;</span><br /> - -<small>SUCH AS</small><br /> - -<span class="large">BAROMETERS, THERMOMETERS, HYDROMETERS,</span><br /> - -<small><i>Hour-Glasses</i>, <i>Funnels</i>, <i>Syphons</i>,</small><br /> - -<span class="medium">TUBE VESSELS FOR CHEMICAL EXPERIMENTS,</span><br /> - -<small>TOYS FOR RECREATIVE PHILOSOPHY, &c.</small><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span class="large">BY A FRENCH ARTIST.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span class="large">ILLUSTRATED BY ENGRAVINGS.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span class="large">LONDON:</span><br /> - -<span class="small table">PUBLISHED BY BUMPUS AND GRIFFIN, 3, SKINNER-STREET;<br /> -AND RICHARD GRIFFIN AND CO. GLASGOW:<br /> -SOLD ALSO BY STILLIES, BROTHERS, EDINBURGH.</span> - -<span class="large">1831.</span> -</h1> - -<p class="copy">W. WILSON, PRINTER, 57, SKINNER-STREET, LONDON. -<span class="pagenum" id="Page_i">i</span></p> - -<hr class="chap" /> - -<h2 class="xx-large"><small>THE</small><br /> -POLYTECHNIC LIBRARY.</h2> - -<hr class="tb" /> - -<p>The design of the Publishers of the <span class="smcap">Polytechnic Library</span> -is to produce a Series of highly-instructive Works, which -the Public may be tempted to <i>buy</i>, because they will be -cheap,—be induced to <i>read</i>, because they will be brief,—be -competent to <i>understand</i>, because they will be clearly written,—and -be able to <i>profit by</i>, because they will be <small>WORKS -OF PRACTICAL UTILITY</small>. Every volume, therefore, will -contain <i>a complete Treatise</i> relating to one of the useful arts -or sciences, or the chemical or mechanical trades.</p> - -<p><img class="figcenter" src="images/hr.jpg" alt="" /></p> - -<h2 class="xx-large"> -<span class="medium">JUST PUBLISHED, PRICE HALF-A-CROWN,</span><br /> -<span class="x-large"><span class="smcap">VOL. I. of the POLYTECHNIC LIBRARY</span>,</span><br /> - -<small><i>Neatly printed in</i> 18mo. <i>and bound in</i> Cloth, <i>containing</i></small><br /> - -THE ART OF GLASS-BLOWING,<br /> - -<span class="medium"><i>Or Plain Instructions for Making the</i></span><br /> - -<span class="x-large">CHEMICAL & PHILOSOPHICAL INSTRUMENTS</span><br /> -<span class="medium">WHICH ARE FORMED OF GLASS;</span><br /> - -<small>Such as</small><br /> - -<span class="large">BAROMETERS, THERMOMETERS, HYDROMETERS,</span><br /> -<small><i>Hour-Glasses</i>, <i>Funnels</i>, <i>Syphons</i>,</small><br /> -<span class="large">TUBE-VESSELS FOR CHEMICAL EXPERIMENTS,</span><br /> -<span class="medium">TOYS FOR RECREATIVE PHILOSOPHY, &c.</span><br /> -<img class="figcenter" src="images/hr.jpg" alt="" /> -BY A FRENCH ARTIST.<br /> -<img class="figcenter" src="images/hr.jpg" alt="" /> -<span class="medium table">ILLUSTRATED BY UPWARDS OF ONE HUNDRED FIGURES,<br /> -<i>Elegantly engraved on Copper plates</i>.</span><br /> -</h2> - -<hr class="tb" /> - -<p>Artists and Students of the Experimental Sciences will find this -work adapted to aid them effectually in the economical preparation -of their Apparatus; and persons who would willingly occupy -their leisure hours in practising the charming art of working -Glass and Enamels with the Blowpipe, but who have hitherto been -deterred by the anticipated expense of the instruments, and the imaginary -difficulties of the undertaking, are taught herein the simplest, -most expeditious, least expensive, and most effectual methods -of working Glass into every variety of useful or fanciful device.</p> - -<p><img class="figcenter" src="images/hr.jpg" alt="" /></p> - -<p class="copy"> -PUBLISHED BY BUMPUS & GRIFFIN, SKINNER-STREET, LONDON;<br /> -R. GRIFFIN AND CO. GLASGOW;<br /> -AND STILLIES, BROTHERS, EDINBURGH.<span class="pagenum" id="Page_ii">ii</span></p> - -<hr class="chap" /> - -<h2> -<span class="medium">THE FOLLOWING WORKS, INTENDED TO FORM PART OF</span><br /> -THE POLYTECHNIC LIBRARY,<br /> -<span class="medium"><i>Are nearly ready for Publication</i>.</span><br /> - -<span class="medium">THE</span><br /> -DOMESTIC CHEMIST;<br /> -<small><i>Comprising Instructions for</i></small><br /> -THE DETECTION OF ADULTERATIONS<br /> -<span class="medium">In numerous Articles employed in</span><br /> -<span class="x-large">DOMESTIC ECONOMY & THE ARTS.</span><br /> - -<span class="medium"><i>To which is prefixed</i>,</span><br /> -<span class="large table">THE ART OF DETECTING POISONS IN FOOD AND<br /> -ORGANIC MIXTURES.</span><br /> -</h2> - -<hr class="tb" /> - -<h4><i>Contents.</i></h4> - -<blockquote> - -<p>PART I.—<span class="smcap">Instructions for the Detection of Mineral -Poisons in Vegetable or Animal Mixtures.</span>—Copper, Lead, -Antimony, Arsenic, Mercury, Iron, Barytes, Lime, Alumina, -Potash, Soda, Sulphuric Acid, Nitric Acid, Muriatic Acid.</p> - -<p>PART II.—<span class="smcap">Instructions for the Examination of Articles -supposed to be Adulterated.</span>—Alcohol, Ale, Anchovy Sauce, -Arrow-Root, Beer, Brandy, Bread, Calomel, Carmine, Cayenne -Pepper, Cheese, Chocolate, Chrome Yellow, Cinnamon, Cloves, -Cochineal, Coffee, Confectionery, Crabs’ Eyes, Cream, Cream of -Tartar, Epsom Salts, Flour, Gin, Gum Arabic, Spirits of Hartshorn, -Honey, Hops, Ipecacuanha, Isinglass, Ketchup, Lakes, -Leeches, Lemon Acid, Litharge, Magnesia, Milk, Mushrooms, -Mustard, Olive Oil, Parsley, Pepper, Peruvian Bark, Pickles, -Porter, Red Oxide of Mercury, Rhubarb, Sal Ammoniac, Salt, -Saltpetre, Soap, Soluble Tartar, Spanish Liquorice, Spirits, -Sugar, Sulphur, Tamarinds, Tapioca, Tartaric Acid, Tartar Emetic, -Tea, Ultramarine, Verdigris, Vermilion, Vinegar, Volatile Oils, -Wax, White Lead, Wine, Water,(including directions for testing -the purity of all descriptions of Rain, River, or Spring Water.)</p> - -<p>PART III.—<span class="smcap">Instructions for the Preparation of the Tests -employed in Domestic Chemistry and for the Performance -of various Chemical Operations; with Description -of the Glasses and Apparatus proper to be employed.</span></p></blockquote> - -<p>⁂ The work is written in a popular manner, and intended for the use of -Families, Publicans, Wine and Spirit Merchants, Oilmen, Manufacturers, -Apothecaries, Physicians, Coroners, and Jurymen.—<i>Price Three Shillings.</i></p> - -<hr class="tb" /> - -<h2 id="THE_PERFUMERS_ORACLE">THE PERFUMER’S ORACLE.</h2> - -<p>The object of this work is to present a comprehensive and practical -account of the Preparation of PERFUMES and COSMETICS, -according to the newest, most successful, and most economical -processes. It will be adapted either for Professional Persons, or -for Ladies who may wish to amuse themselves with this elegant -branch of experimental science.—<i>Price Three Shillings.</i></p> - -<div class="figcenter"> -<p class="copyleft"><i>Pl. 2.</i></p> -<img id="pl_2" src="images/pl_2.jpg" alt="" /> -<p class="copy"><i>Published by Bumpus & Griffin London, 1831.</i></p> -</div> - -<div class="figcenter"> -<p class="copyright"><i>Pl. 3.</i></p> -<img id="pl_3" src="images/pl_3.jpg" alt="" /> -<p class="copy"><i>Published by Bumpus & Griffin London, 1831.</i></p> -</div> - -<div class="figcenter"> -<p class="copyright"><i>Pl. 4.</i></p> -<img id="pl_4" src="images/pl_4.jpg" alt="" /> -<p class="copy"><i>Published by Bumpus & Griffin London, 1831.</i>] -<span class="pagenum" id="Page_iii">iii</span></p> -</div> - -<hr class="chap" /> - -<h2 id="TRANSLATORS_PREFACE">TRANSLATOR’S PREFACE.</h2> - -<hr class="tb" /> - -<p>The scientific instruments prepared by the glass-blower -are numerous and highly useful: barometers, -thermometers, syphons, and many other -vessels constructed of tubes, are indispensable to -the student of physics or chemistry. Some of these -instruments are high in price, and liable to frequent -destruction; and those by whom they are much -employed are subject to considerable expense in -procuring or replacing them. It is therefore advisable -that he who desires to occupy himself in the -pursuit of experimental science, should know how -to prepare such instruments himself; that, in short, -he should become his own glass-blower. “The -attainment of a ready practice in the blowing and -bending of glass,” says Mr. Faraday, “is one of -those experimental acquirements which render the -chemist most independent of large towns and of -instrument-makers.”</p> - -<p>Unquestionably the best method of learning to -work glass is to obtain personal instructions from -one who is conversant with the art: but such instructions -are not easily obtained. The best operators -are not always the best teachers; and to -find a person equally qualified and willing to teach -the art, is a matter of considerable difficulty. In -large towns, workmen are too much engaged with -their ordinary business to step aside for such a -purpose; and in small towns glass-blowers are -<span class="pagenum" id="Page_iv">iv</span> -seldom to be found. In most cases, also, they are -too jealous of their supposed <i>secrets</i> to be willing -to communicate their methods of operating to -strangers, even when paid to do so.</p> - -<p>The following Treatise is a free translation of -<i>L’Art du Souffleur à la Lampe, par</i> <span class="smcap">T. P. -Danger</span>. The author is employed, in Paris, in -preparing glass instruments for sale, and in teaching -others the art of preparing them. He has presented -in this work the most minute instructions -for the working of glass which have ever been -offered to the public. The general processes of -the art are so fully explained, and the experimental -illustrations are so numerous, that nothing remains -except the reducing of these instructions to practice -to enable the student to become an adept in -the blowing of glass. I trust that, in publishing -this work in an English dress, I may be considered -as aiding in some degree the progress of physical -science.</p> - -<p>This work contains a description of a cheap blowpipe -and a very convenient lamp; both of them -the invention of the author: but any other kind -of lamp or blowpipe may be employed instead of -these. The reader who wishes for a description of -the blowpipes generally employed in England, may -consult Mr. <span class="smcap">Griffin’s</span> <i>Practical Treatise on the -Use of the Blowpipe in Chemical and Mineral -Analysis</i>.</p> - -<blockquote> - -<p><i>London, September 1831.</i></p></blockquote> - -<p><span class="pagenum" id="Page_v">v</span></p> - -<hr class="chap" /> - -<h2 id="AUTHORS_PREFACE">AUTHOR’S PREFACE.</h2> - -<hr class="tb" /> - -<p>The flame of a lamp, or candle, condensed and -directed by a current of air, is exceedingly useful -in a great number of arts. The instrument which -is employed to modify flame is the <span class="smcap">Blowpipe</span>. This -is an indispensable agent for jewellers, watch-makers, -enamellers, glass-blowers, natural philosophers, -chemists, mineralogists, and, indeed, for all -persons who are occupied with the sciences, or -their application to the arts. Its employment -offers immense advantages in a multitude of circumstances; -and the best method of making use -of so powerful an agent ought to be well known to -every person who is likely to be called upon to -adopt it.</p> - -<p>Students, especially those who desire to exercise -themselves in chemical manipulation, must feel the -want of a simple and economical process, by means -of which they could give to glass tubes, of which -they make great use, the various forms that are -necessary for particular operations. How much -reason have they to complain of the high price of -the instruments of which they make continual use! -The studies of a great number are shackled from -want of opportunity to exercise themselves in -<span class="pagenum" id="Page_vi">vi</span> -manipulation; and many, not daring to be at the -expense of a machine of which they doubt their -ability to make an advantageous use, figure to -themselves the employment of the glass-blower’s -apparatus as being beset with difficulties, and so -rest without having even an idea of the numberless -instruments which can be made by its means.</p> - -<p>Many persons would very willingly occupy -their leisure time in practising the charming art of -working glass and enamels with the blowpipe; -but the anticipated expense of the apparatus, and -the difficulties which they imagine to foresee in the -execution of work of this kind, always repels them.</p> - -<p>The new species of blowpipe which we have -offered to the public, and which has received the -approbation of the Society for the Encouragement -of Arts, obviates all these inconveniences: its -moderate price, its portability, and the facility -with which it can be used, adapt it to general -employment.</p> - -<p>But we should not believe that we had attained -the end which we had proposed to ourselves if we -had not placed young students in a situation to -repeat at their own houses, at little cost, and with -the greatest facility, the experiments which are -necessary to familiarise them with the sciences. -It is with such a view that we present to them this -little Treatise, which is destined to teach them the -simplest, the most expeditious, the least expensive, -<span class="pagenum" id="Page_vii">vii</span> -and the most effectual methods of constructing -themselves the various instruments which they require -in the prosecution of their studies.</p> - -<p>The word <i>glass-blower</i>, generally speaking, -signifies a workman who occupies himself in -making of glass and enamel, the instruments, -vessels, and ornaments, which are fabricated on a -larger scale in the glass-houses: but the domain of -the sciences having laid the art of glass-blowing -under contribution, the artists of the lamp have -divided the labours thereof. Some apply themselves -particularly to the construction of philosophical -and chemical instruments; others occupy -themselves with little ornamental objects, such as -flowers, &c.; and, among the latter, some manufacture -nothing but pearls, and others only artificial -eyes. Finally, a few artists confine themselves -to drawing and painting on enamel, which substance -is previously applied to metallic surfaces -by means of the fire of a muffle.</p> - -<p>As we intend to treat separately of these different -branches of the art, we commence with that -of which the manipulation is the simplest.</p> - -<blockquote> - -<p><i>Paris, 1829.</i></p></blockquote> - -<p><span class="pagenum" id="Page_viii">viii</span></p> - -<hr class="chap" /> - -<h2 id="CONTENTS">CONTENTS.</h2> - -<hr class="tb" /> - -<table id="toc"> - <tr> - <td /> - <td /> - <td class="tdr small">Page</td> - </tr> - <tr> - <td>I.—</td> - <td><a href="#I"><i>Instruments employed in Glass-Blowing</i></a></td> - <td class="tdr">1</td> - </tr> - <tr> - <td /> - <td><a href="#THE_BLOWPIPE">The Blowpipe</a></td> - <td class="tdr">1</td> - </tr> - <tr> - <td /> - <td><a href="#THE_GLASS_BLOWERS_TABLE">The Glass-Blower’s Table</a></td> - <td class="tdr">3</td> - </tr> - <tr> - <td /> - <td><a href="#THE_EOLIPYLE">The Eolipyle</a></td> - <td class="tdr">5</td> - </tr> - <tr> - <td /> - <td><a href="#BLOWPIPE_WITH_CONTINUED_CURRENT">Blowpipe with Continued Current</a></td> - <td class="tdr">5</td> - </tr> - <tr> - <td /> - <td><a href="#THE_LAMP">The Lamp</a></td> - <td class="tdr">8</td> - </tr> - <tr> - <td /> - <td><a href="#THE_CANDLESTICK">The Candlestick</a></td> - <td class="tdr">9</td> - </tr> - <tr> - <td /> - <td><a href="#COMBUSTIBLES">Combustibles</a></td> - <td class="tdr">9</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#OIL_TALLOW">Oil, Tallow, &c.</a></td> - <td class="tdr">9</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#THE_WICKS">The Wicks</a></td> - <td class="tdr">10</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#RELATION_BETWEEN_THE_DIAMETER">Relation between the Diameter of the -Beaks of the Blowpipe and the Wicks -of the Lamp</a></td> - <td class="tdr">12</td> - </tr> - <tr> - <td>II.—</td> - <td><a href="#II"><i>Preliminary Notions of the Art of Glass-Blowing</i></a></td> - <td class="tdr">16</td> - </tr> - <tr> - <td /> - <td><a href="#THE_FLAME">The Flame</a></td> - <td class="tdr">16</td> - </tr> - <tr> - <td /> - <td><a href="#PLACES_FIT_TO_WORK_IN">Places fit to work in</a></td> - <td class="tdr">19</td> - </tr> - <tr> - <td /> - <td><a href="#MEANS_OF_OBTAINING_A_GOOD_FIRE">Means of obtaining a Good Fire</a></td> - <td class="tdr">19</td> - </tr> - <tr> - <td /> - <td><a href="#CHOICE_AND_PRESERVATION_OF_GLASS">Choice and Preservation of Glass</a></td> - <td class="tdr">22</td> - </tr> - <tr> - <td /> - <td><a href="#PREPARATION_OF_GLASS_TUBES_BEFORE_HEATING_THEM">Preparation of Glass Tubes before heating them</a></td> - <td class="tdr">25</td> - </tr> - <tr> - <td /> - <td><a href="#METHOD_OF_PRESENTING_TUBES_TO_THE_FIRE_AND_OF_WORKING_THEM_THEREIN">Method of presenting Tubes to the Fire, and of working them therein</a></td> - <td class="tdr">26</td> - </tr> - <tr> - <td>III.—</td> - <td><a href="#III"><i>Fundamental Operations in Glass-Blowing</i></a></td> - <td class="tdr">30</td> - </tr> - <tr> - <td /> - <td><a href="#CUTTING">1. Cutting</a></td> - <td class="tdr">31</td> - </tr> - <tr> - <td /> - <td><a href="#BORDERING">2. Bordering</a></td> - <td class="tdr">34</td> - </tr> - <tr> - <td /> - <td><a href="#WIDENING">3. Widening</a></td> - <td class="tdr">36</td> - </tr> - <tr> - <td /> - <td><a href="#DRAWING_OUT">4. Drawing-out</a></td> - <td class="tdr">36</td> - </tr> - <tr> - <td /> - <td><a href="#CHOKING">5. Choking</a></td> - <td class="tdr">37</td> - </tr> - <tr> - <td /> - <td><a href="#SEALING">6. Sealing</a></td> - <td class="tdr">38</td> - </tr> - <tr> - <td /> - <td><a href="#BLOWING">7. Blowing</a></td> - <td class="tdr">39</td> - </tr> - <tr> - <td /> - <td><a href="#PIERCING">8. Piercing</a></td> - <td class="tdr">46</td> - </tr> - <tr> - <td /> - <td><a href="#BENDING">9. Bending</a></td> - <td class="tdr">48</td> - </tr> - <tr> - <td /> - <td><a href="#SOLDERING">10. Soldering</a></td> - <td class="tdr">49</td> - </tr> - <tr> - <td>IV.—</td> - <td><a href="#IV"><i>Construction of Chemical and Philosophical Instruments</i></a></td> - <td class="tdr">54</td> - </tr> - <tr> - <td /> - <td><a href="#ADAPTERS">Adapters</a></td> - <td class="tdr">55</td> - </tr> - <tr> - <td /> - <td><a href="#APPARATUS_FOR_VARIOUS_INSTRUMENTS">Apparatus for various Instruments</a></td> - <td class="tdr">55</td> - </tr> - <tr> - <td /> - <td><a href="#ARCHIMEDESS_SCREW">Archimedes’s Screw</a></td> - <td class="tdr">57<span class="pagenum" id="Page_ix">ix</span></td> - </tr> - <tr> - <td /> - <td><a href="#AREOMETERS">Areometers</a></td> - <td class="tdr">71</td> - </tr> - <tr> - <td /> - <td><a href="#BARKERS_MILL">Barker’s Mill</a></td> - <td class="tdr">57</td> - </tr> - <tr> - <td /> - <td><a href="#BAROMETERS">Barometers</a></td> - <td class="tdr">58</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#CISTERN_BAROMETER">Cistern Barometer</a></td> - <td class="tdr">58</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#DIAL_BAROMETER">Dial Barometer</a></td> - <td class="tdr">58</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#SYPHON_BAROMETER">Syphon Barometer</a></td> - <td class="tdr">59</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#STOP_COCK_BAROMETER">Stop-cock Barometer</a></td> - <td class="tdr">59</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#COMPOUND_BAROMETERS">Compound Barometers</a></td> - <td class="tdr">59</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#GAY_LUSSACS_BAROMETER">Gay-Lussac’s Barometer</a></td> - <td class="tdr">60</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#BUNTENS_BAROMETER">Bunten’s Barometer</a></td> - <td class="tdr">61</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#BAROMETER_PIERCED_LATERALLY_FOR_DEMONSTRATIONS">Barometer pierced laterally for Demonstrations</a></td> - <td class="tdr">61</td> - </tr> - <tr> - <td /> - <td><a href="#BELL_GLASSES_FOR_EXPERIMENTS">Bell Glasses for Experiments</a></td> - <td class="tdr">61</td> - </tr> - <tr> - <td /> - <td><a href="#BLOWPIPE">Blowpipe</a></td> - <td class="tdr">62</td> - </tr> - <tr> - <td /> - <td><a href="#CAPSULES">Capsules</a></td> - <td class="tdr">63</td> - </tr> - <tr> - <td /> - <td><a href="#CARTESIAN_DEVILS">Cartesian Devils</a></td> - <td class="tdr">64</td> - </tr> - <tr> - <td /> - <td><a href="#COMMUNICATING_VASES">Communicating Vases</a></td> - <td class="tdr">65</td> - </tr> - <tr> - <td /> - <td><a href="#CRYOPHORUS">Cryophorus</a></td> - <td class="tdr">55</td> - </tr> - <tr> - <td /> - <td><a href="#DROPPING_TUBES">Dropping Tubes</a></td> - <td class="tdr">65</td> - </tr> - <tr> - <td /> - <td><a href="#FOUNTAINS">Fountains</a></td> - <td class="tdr">66</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#FOUNTAIN_OF_CIRCULATION">Fountain of Circulation</a></td> - <td class="tdr">66</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#FOUNTAIN_OF_COMPRESSION">Fountain of Compression</a></td> - <td class="tdr">67</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#INTERMITTING_FOUNTAIN">Intermitting Fountain</a></td> - <td class="tdr">68</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#HEROS_FOUNTAIN">Hero’s Fountain</a></td> - <td class="tdr">68</td> - </tr> - <tr> - <td /> - <td><a href="#FUNNELS">Funnels</a></td> - <td class="tdr">68</td> - </tr> - <tr> - <td /> - <td><a href="#HOUR_GLASSES">Hour Glasses</a></td> - <td class="tdr">70</td> - </tr> - <tr> - <td /> - <td><a href="#HYDRAULIC_RAM">Hydraulic Ram</a></td> - <td class="tdr">70</td> - </tr> - <tr> - <td /> - <td><a href="#HYDROMETERS">Hydrometers</a></td> - <td class="tdr">71</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#BAUMÉS_HYDROMETER">Baumé’s Hydrometer</a></td> - <td class="tdr">71</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#NICHOLSONS_HYDROMETER">Nicholson’s Hydrometer</a></td> - <td class="tdr">73</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#HYDROMETER_WITH_TWO_BRANCHES">Hydrometers with two,</a> <a href="#HYDROMETER_WITH_THREE_BRANCHES"> three,</a> or <a href="#HYDROMETER_WITH_FOUR_BRANCHES">four branches</a></td> - <td class="tdr">74</td> - </tr> - <tr> - <td /> - <td><a href="#MANOMETERS">Manometers</a></td> - <td class="tdr">74</td> - </tr> - <tr> - <td /> - <td><a href="#MARIOTTES_TUBE">Mariotte’s Tube</a></td> - <td class="tdr">75</td> - </tr> - <tr> - <td /> - <td><a href="#PHOSPHORIC_FIRE_BOTTLE">Phosphoric Fire-bottle</a></td> - <td class="tdr">75</td> - </tr> - <tr> - <td /> - <td><a href="#PULSOMETER">Pulsometer</a></td> - <td class="tdr">75</td> - </tr> - <tr> - <td /> - <td><a href="#PUMP">Pump</a></td> - <td class="tdr">76</td> - </tr> - <tr> - <td /> - <td><a href="#RETORTS_FOR_CHEMICAL_EXPERIMENTS">Retorts for Chemical Experiments</a></td> - <td class="tdr">76</td> - </tr> - <tr> - <td /> - <td><a href="#RUMFORDS_THERMOSCOPE">Rumford’s Thermoscope</a></td> - <td class="tdr">77</td> - </tr> - <tr> - <td /> - <td><a href="#SYPHONS">Syphons</a></td> - <td class="tdr">78</td> - </tr> - <tr> - <td /> - <td><a href="#SPOONS">Spoons</a></td> - <td class="tdr">80</td> - </tr> - <tr> - <td /> - <td><a href="#SPIRIT_LEVEL">Spirit Level</a></td> - <td class="tdr">80</td> - </tr> - <tr> - <td /> - <td><a href="#TEST_GLASS_WITH_A_FOOT">Test Glass with a foot</a></td> - <td class="tdr">80</td> - </tr> - <tr> - <td /> - <td><a href="#THERMOMETERS">Thermometers</a></td> - <td class="tdr">81</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#ORDINARY_THERMOMETER">Ordinary Thermometer</a></td> - <td class="tdr">81<span class="pagenum" id="Page_x">x</span></td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#DIAL_THERMOMETER">Dial Thermometer</a></td> - <td class="tdr">83</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#CHEMICAL_THERMOMETER">Chemical Thermometer</a></td> - <td class="tdr">84</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#SPIRAL_THERMOMETER">Spiral Thermometer</a></td> - <td class="tdr">85</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#POCKET_THERMOMETER">Pocket Thermometer</a></td> - <td class="tdr">86</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#MAXIMUM_THERMOMETER">Maximum Thermometer</a></td> - <td class="tdr">86</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#MINIMUM_THERMOMETER">Minimum Thermometer</a></td> - <td class="tdr">86</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#BELLANIS_MAXIMUM_THERMOMETER">Bellani’s Maximum Thermometer</a></td> - <td class="tdr">87</td> - </tr> - <tr> - <td /> - <td class="i4"><a href="#DIFFERENTIAL_THERMOMETER">Differential Thermometer</a></td> - <td class="tdr">87</td> - </tr> - <tr> - <td /> - <td><a href="#RUMFORDS_THERMOSCOPE">Thermoscope</a></td> - <td class="tdr">77</td> - </tr> - <tr> - <td /> - <td><a href="#TUBES_BENT_FOR_VARIOUS_PURPOSES">Tubes bent for various purposes</a></td> - <td class="tdr">88</td> - </tr> - <tr> - <td /> - <td><a href="#VIAL_OF_THE_FOUR_ELEMENTS">Vial of the four Elements</a></td> - <td class="tdr">90</td> - </tr> - <tr> - <td /> - <td><a href="#WATER_HAMMER">Water Hammer</a></td> - <td class="tdr">91</td> - </tr> - <tr> - <td /> - <td><a href="#WELTERS_SAFETY_TUBES">Welter’s Safety Tubes</a></td> - <td class="tdr">92</td> - </tr> - <tr> - <td>V.—</td> - <td><a href="#V"><i>Graduation of Chemical and Philosophical Instruments</i></a></td> - <td class="tdr">93</td> - </tr> - <tr> - <td /> - <td><a href="#OF_THE_SUBSTANCES_EMPLOYED_IN_THE_PREPARATION_OF_THESE_INSTRUMENTS">Of the substances employed in the preparation of these instruments</a></td> - <td class="tdr">93</td> - </tr> - <tr> - <td /> - <td><a href="#OF_GRADUATION_IN_GENERAL">Of Graduation in general</a></td> - <td class="tdr">94</td> - </tr> - <tr> - <td /> - <td><a href="#EXAMINATION_OF_THE_BORE_OF_TUBES">Examination of the Bore of Tubes</a></td> - <td class="tdr">95</td> - </tr> - <tr> - <td /> - <td><a href="#DIVISION_OF_CAPILLARY_TUBES_INTO_PARTS_OF_EQUAL_CAPACITY">Division of Capillary Tubes into parts of equal Capacity</a></td> - <td class="tdr">95</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_GAS_JARS_TEST_TUBES">Graduation of Gas Jars, Test Tubes, &c.</a></td> - <td class="tdr">97</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_HYDROMETERS">Graduation of Hydrometers</a></td> - <td class="tdr">99</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_BAROMETERS">Graduation of Barometers</a></td> - <td class="tdr">103</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_THE_MANOMETER">Graduation of the Manometer</a></td> - <td class="tdr">105</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_THERMOMETERS">Graduation of Thermometers</a></td> - <td class="tdr">105</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_RUMFORDS_THERMOSCOPE">Graduation of Rumford’s Thermoscope</a></td> - <td class="tdr">112</td> - </tr> - <tr> - <td /> - <td><a href="#GRADUATION_OF_MARIOTTES_TUBE">Graduation of Mariotte’s Tube</a></td> - <td class="tdr">112</td> - </tr></table> - -<p><span class="pagenum" id="Page_1">1</span></p> - -<hr class="chap" /> - -<h2><small>THE</small><br /> - -<span class="xx-large">ART OF GLASS-BLOWING.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span id="I">I.—<i>Instruments employed in Glass-Blowing.</i></span></h2> - -<hr class="tb" /> - -<p>On seeing, for the first time, a glass-blower at -work, we are astonished at the multitude and -the variety of the modifications to which he can -make the glass submit. The small number and -the simplicity of the instruments he employs, is -also surprising. The blowpipe, or, in its place, -the glass-blower’s bellows and a lamp, are indeed -all that are indispensable.</p> - -<h3 id="THE_BLOWPIPE">THE BLOWPIPE.</h3> - -<p>Originally, the blowpipe was only a simple, -conical tube, more or less curved towards its point, -and terminated by a very small circular opening. -By means of this, a current of air was carried -against the flame of a candle, and the inflamed -matter was directed upon small objects, of -which it was desirable to elevate the temperature. -Workers in metal still derive immense -advantages from the use of this little instrument: -they employ it in the soldering of very small -articles, as well as for heating the extremities -<span class="pagenum" id="Page_2">2</span> -of delicate tools, in order to temper them. -But since the blowpipe has passed into the -hands of mineralogical chemists, its form has -been subjected to a series of very curious and -important modifications. In spite, however, -of these ameliorations, which rendered the instrument -better adapted for the uses to which -it was successively applied, we are far from -having drawn from it all the advantages to -which we might attain, were its employment -not as fatiguing as it is difficult. We require -no other proof of this than the small number -of those who know well how to make use of -the blowpipe.</p> - -<p>The most economical blowpipe is a tube of -glass, bent near one end, and pointed at its -extremity. A bulb is blown near that part of -the tube which corresponds with the curvature -(<a href="#pl_3">pl. 3</a>, fig. 7.) This bulb serves as a reservoir -for moisture deposited by the air blown into -the tube from the mouth. If you employ a -tube without a bulb, the moisture is projected -in drops into the flame, and upon the objects -heated by it—an effect which is very inconvenient -in practice. To put this instrument -into action, accustom yourself to hold the mouth -full of air, and to keep the cheeks well inflated, -during a pretty long series of alternate inspirations -and expirations; then, seizing lightly -with the lips the mouth of the blowpipe, suffer -the air compressed by the muscles of the cheeks, -which act the part of a bellows, to escape by -the beak of the blowpipe, which you will be -able to do without being put to the least inconvenience -<span class="pagenum" id="Page_3">3</span> -with regard to respiration. When -the air contained in the mouth is pretty nearly -expended, you must take advantage of an inspiration, -to inflate the lungs afresh; and thus -the operation is continued. You must never -blow through the tube by means of the lungs; -first, because air which has been in the lungs -is less proper for combustion than that which -has merely passed through the nose and mouth; -secondly, because the effort which it would be -necessary to make, to sustain the blast for only -a short time, would by its frequent repetition -become very injurious to your health.</p> - -<p>The jet of flame produced by the mouth-blowpipe -can only be used to heat small objects: -when instruments of a considerable bulk -have to be worked, it is customary to employ -the <i>lamp</i>, or <i>glass-blower’s table</i>.</p> - -<h3 id="THE_GLASS_BLOWERS_TABLE">THE GLASS-BLOWER’S TABLE.</h3> - -<p>Artists give this name to an apparatus which -consists of the following articles:—</p> - -<p>1. A <i>Table</i>, below which is disposed a -<i>double bellows</i>, capable of being put in motion -by means of a pedal. This bellows furnishes a -continued current of air, which can be directed -at pleasure by making it pass through a tube -terminating above the table in a sharp beak. -The bellows with which the glass-blower’s -tables are commonly furnished have very great -defects. The irregular form which is given to -the pannels diminishes the capacity of the instruments, -without augmenting their advantages. -If we reflect an instant on the angle, more or -<span class="pagenum" id="Page_4">4</span> -less open, which these pannels form when in -motion, we instantly perceive that the weight -with which the upper surface of a bellows is -charged, and which always affords a vertical -pressure, acts very unequally on the arm of a -lever which is continually changing its position. -This faulty disposition of the parts of the machine -has the effect of varying every instant -the intensity of the current of air directed upon -the flame. All these inconveniences would disappear, -were the upper pannel, like that in the -middle, disposed in such a manner as to be -always horizontal. It ought to be elevated and -depressed, in its whole extent, in the same manner; -so that, when charged with a weight, the -pressure should be constantly the same, and the -current of air uniform.</p> - -<p>2. A <i>lamp</i>, of copper or tin plate.—The -construction of this article, sufficiently imperfect -until the present time, has varied according to -the taste of those who have made use of it. -We shall give, farther on, the description of a -lamp altogether novel in its construction.</p> - -<p>3. The glass-blower’s table is generally furnished -with little <i>drawers</i> for holding the tools -employed in modelling the softened glass. -Careful artists have the surface of their table -coated with sheet iron, in order that it may not -be burned by the hot substances that fall, or -are laid upon it. As glass-blowers have frequent -occasion to take measures, it is convenient -to have the front edge of the table divided into -a certain number of equal parts, marked with -copper nails. This enables the workman to -<span class="pagenum" id="Page_5">5</span> -take, at a glance of the eye, the half, third, or -fourth of a tube, or to give the same length to -articles of the same kind, without having perpetual -recourse to the rule and compasses. But -when it is desirable to have the tubes, or the -work, measured with <i>greater exactness</i> than it -can be measured by this method, the rule and -the compasses can be applied to.</p> - -<h3 id="THE_EOLIPYLE">THE EOLIPYLE.</h3> - -<p>We shall merely make mention of this instrument. -It is a globular vessel, commonly -formed of brass. If filled with a very combustible -liquor, such as alcohol, and strongly -heated, it affords a rapid current of vapour, -which, if directed by means of a fine beak into -the middle of a flame, produces the same effect -as the air which issues from a blowpipe. The -eolipyle is a pretty toy, but not a good instrument -for a workman, its action being too -irregular.</p> - -<h3 id="BLOWPIPE_WITH_CONTINUED_CURRENT">BLOWPIPE WITH CONTINUED CURRENT.</h3> - -<p>It is after having, during a long period, made -use of the instruments of which we have spoken, -and fully experienced their inconveniences, -that, aware of the indispensable necessity for -such instruments in the arts and sciences, we -have thought it our duty to make known to the -public <i>a New Apparatus</i>, which is, not only -calculated to fulfil the same purposes, but -presents advantages which it is easy to appreciate. -The price of it is only the sixth part of -<span class="pagenum" id="Page_6">6</span> -that of the glass-blower’s table<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">1</a>. It is very -portable, and capable of being attached to any -table whatever. It unites the advantages of -not fatiguing the workman, of leaving his hands -free, and of rendering him absolute master of -the current of air, which he can direct on the -flame either of the lamp or the candle,—advantages -which are not offered in the same degree -even by the table of the glass-blower.</p> - -<div class="footnote"> - -<p><a id="Footnote_1" href="#FNanchor_1" class="label">1</a> -In Paris, the blowpipe which is here described is -sold for six francs (five shillings English); or, with the -improved lamp and candlestick, twelve francs.</p></div> - -<p>The instrument which we have presented is, -properly speaking, nothing but a simple blowpipe, -C, (<a href="#pl_1">pl. 1</a>, fig. 19) communicating with a -bladder, or leather bag, fixed on E, which is -kept full of air by means of a bent tube, D, -through which the operator blows occasionally -with the mouth. This tube is closed at its inferior -extremity, F, by a valve, which permits -the passage of air into the reservoir, but not of -its return, so that the air can only escape by -the beak of the blowpipe.</p> - -<p>The valve at F is constructed in the following -manner:—At about two inches from the -end of the tube a contraction is made, as represented -at <i>a</i>, <a href="#pl_1">pl. 1</a>, fig. 24. This reduces the -internal diameter of the tube about one-third. -A small conical piece of cork or wood is now -introduced into the tube in the manner represented -by <i>c</i>. The base of the cone must be -large enough to close the tube at the point where -it is contracted; it must, however, not be so -<span class="pagenum" id="Page_7">7</span> -large as to close the tube at the wide part. A -brass pin is inserted in the point of the cone, as -is shewn in the figure. Between the cone and -the end of the tube, the piece of wood, <i>b</i>, is -fixed; the shape of this piece of wood is best -shewn by figure 25, on the same plate. There -is a hole in the centre, in which the pin of the -cork cone can move easily. The cone or valve -is therefore at liberty to move between the contraction -<i>a</i>, and the fixture <i>b</i>. Consequently, -when air is blown into the tube at <i>e</i>, the valve is -forced from the contraction, falls into the position -indicated by the dotted lines <i>d</i>, and allows -the air to pass by its sides. When, on the -contrary, the operator ceases to blow, the valve -is acted upon by the air in the bladder, which, -pressing back at <i>f</i>, drives the valve close -against the contraction, and effectually closes -the aperture. A slight hissing is heard, but -when the contraction is well made, and the -cork is good, an extremely small quantity of -air escapes.</p> - -<p>The workman, seated before the table where -he has fixed his instrument, blows from time to -time, to feed the reservoir or bladder, which, -being pressed by a system of strings stretched -by a weight, produces an uniform current of -air. The force of this current of air can be -modified at pleasure, by pressing the reservoir -more or less between the knees. (Fig. 22 represents -a blowpipe complete, formed not of -glass, but of brass tubes. Fig. 22, <i>bis</i>, represents -the bladder or reservoir appertaining to -this blowpipe.) -<span class="pagenum" id="Page_8">8</span></p> - -<p><span class="smcap">M. Gaultier de Claubry</span>, who was charged -by the Committee of Chemical Arts of the -Society of Encouragement (of Paris) to make -a report on this instrument, was astonished at -the facility with which the author, in his presence, -reduced the oxide of cobalt to the metallic -state, and fused the metal to a globule; an -experiment which even M. Berzelius could not -perform with the simple blowpipe, since he -expressly says, in his work on that instrument, -that oxide of cobalt suffers no change when -heated before the blowpipe. The results obtained -with cast iron, oxide of tin, &c.—experiments -which are exhibited every day at the -public lectures given by the author—evidently -prove the superiority of this apparatus over all -the blowpipes that have hitherto been contrived.</p> - -<p>A detailed account of the glass tubes belonging -to this improved blowpipe will be found in the -fourth part of this work, at the article <i>Blowpipe</i>.</p> - -<h3 id="THE_LAMP">THE LAMP.</h3> - -<p>While occupied in rendering popular, if we -may so speak, the use of the <i>blowpipe</i>—an instrument -which is so advantageous in a great -number of circumstances—we have also endeavoured -to improve <i>the lamp</i>, which has, -until the present time, been used by all those -who employ the glass-blower’s table. The -lamp which we recommend (<a href="#pl_1">pl. 1</a>, fig. 23) is of -a very simple construction. It possesses the -advantages of giving much less smoke than -the old lamp, and of being cleaned with the -greatest facility. It also gives sensibly more -<span class="pagenum" id="Page_9">9</span> -heat; because the portion of flame which, in -the common lamps, rises perpendicularly, and -is not used, is, in this case, beaten down by a -cap or hood, and made to contribute to the -force of the jet. This cap also keeps the flame -from injuring the eyes of the operator, and -destroys the smoke to such an extent, that the -large hoods with which glass-blowers commonly -garnish their work table, to carry off the smoke, -become unnecessary. This is a peculiar advantage -in the chamber of a student, where a -large hood or chimney can seldom be conveniently -prepared.</p> - -<h3 id="THE_CANDLESTICK">THE CANDLESTICK.</h3> - -<p>For mineralogical researches, chemical assays, -and the soldering of small objects, as in jewellery, -we recommend the use of a little candlestick, -which, by means of a spring fixed to the -bottom, maintains the candle always at the -same height. A reservoir, or shallow cup, -formed at the top of the candlestick, to hinder -the running away of the tallow or wax, allows -the operator to consume the fragments of tallow -or grease which are ordinarily lost in domestic -economy. There is a little hole in the centre -of the cup or upper part of the candlestick, -through which the wick of the candle passes. -<i>o</i>, <a href="#pl_1">pl. 1</a>, fig. 22, is a representation of this -candlestick.</p> - -<h3 id="COMBUSTIBLES">COMBUSTIBLES.</h3> - -<p><i id="OIL_TALLOW">Oil</i>, <i>Tallow</i>, <i>&c.</i>—Among the substances -which have been employed to feed the fire of -<span class="pagenum" id="Page_10">10</span> -the glass-blower’s lamp, those to which the -preference is to be given are wax, olive oil, -rape oil, poppy oil, and tallow. Animal oils, -such as bone oil and fish oil, are much esteemed -by some glass-blowers, who pretend that with -these substances they obtain better results than -with other combustibles. Nevertheless, animal -oils, generally speaking, do not give so much -heat as purified rape oil, while they exhale an -odour which is extremely disagreeable.</p> - -<p>As to alcohol, which is sometimes used with -the eolipyle, its combustion furnishes so feeble -a degree of heat that its employment cannot be -recommended.</p> - -<p>Purified rape oil is that of which the use is -the most general. Next to olive oil and wax, -it affords the greatest heat, and the least smoke. -But, in a word, as in the working of glass, the -operator has more need of a bright flame without -smoke, than of a high temperature, any -combustible may be employed which is capable -of furnishing a flame possessing these two -qualities. The vegetable oils thicken, and -suffer alterations more or less sensible, when -they are long exposed to the action of the air. -They should be chosen very limpid, and they -may be preserved in that state by being enclosed -in bottles, which should be kept quite full and -well corked.</p> - -<p id="THE_WICKS"><i>The Wicks.</i>—There has never been any -substance so generally used for wicks as -cotton; some glass-blowers, indeed, have employed -wicks of asbestus, but without deriving -from them the advantages which might have -<span class="pagenum" id="Page_11">11</span> -been expected; the greater number, therefore, -keep to cotton.</p> - -<p>But it has been observed that cotton which -has been for some time exposed to the air no -longer possesses the good properties for which -glass-blowers esteem it. The alteration of the -cotton is probably brought about by the dust -and water which the air always holds in suspension. -Such cotton burns badly, forms a -bulky coal, and permits with much difficulty -the capillary ascension of the liquid which -serves to support the flame; so that it is impossible -to obtain a good fire, and necessary to be -incessantly occupied in snuffing the wick. -Cotton is equally subject to alteration when -lying in the lamp, even though impregnated -with oil. You should avoid making use of -wicks that are too old. When you foresee -that you will remain a long time without having -occasion to employ the lamp, pour the oil into -a bottle, which can be corked up, and let the -wick be destroyed, previously squeezing from -it the oil which it contains.</p> - -<p>It is indispensable to make use of none but -new and good cotton; it should be clean, soft, -fine, and not twisted. It is best to preserve it -in boxes, after having folded it in many double -papers, to exclude dust and moisture. When -you wish to make wicks, take a skein of cotton -and cut it into four or six pieces, dispose them -side by side in such a manner as to make a -bundle, more or less thick, and eight or ten -inches in length; pass a large comb lightly -through the bundle, to lay the threads even, and -<span class="pagenum" id="Page_12">12</span> -tie it gently at each end, to keep the threads -from getting entangled.</p> - -<p id="RELATION_BETWEEN_THE_DIAMETER"><i>Relation between the diameters of the -beaks of the blowpipe, and the wicks of the -lamp.</i>—We believe that we cannot place -better than here a few observations respecting -the size of the opening in the beak of the blowpipe, -considered in relation to the size of the -wick of the lamp. These observations will -probably be superfluous to those who are -already conversant with the use of the blowpipe; -but as every thing is interesting to beginners, -who are frequently stopped in their progress by -very slight difficulties, and as this Treatise is -particularly designed for beginners, we do not -hesitate to enter into the minutest details on -subjects which we deem interesting.</p> - -<p>The point of your blowpipe should be formed -in such a manner, that you can fix upon it -various little beaks or caps, the orifices in -which, always perfectly round, ought to vary in -size according to the bulk of the flame upon -which you desire to act. You cannot, without -this precaution, obtain the maximum of heat -which the combustion of the oil is capable of -affording. This employment of little moveable -caps offers the facility of establishing a current -of air, greater or smaller, according to the object -you wish to effect; above all, it allows you -to clean with ease the cavity or orifice of the -beak, as often as it may be necessary.</p> - -<p>These caps can be made of different materials. -It is most advisable to have them made of -copper or brass; those which are formed of -<span class="pagenum" id="Page_13">13</span> -tin plate (white iron), and which are commonly -used in chemical laboratories, are the worst -kind of all. They soon become covered with -grease or soot, which either completely closes -up the orifices, or, at least, very soon alters the -circular form which is necessary to the production -of a good fire. Glass caps are less liable -to get dirty, and are much cheaper than the -above; but, on the other hand, they have the -disadvantage of being easily melted. This -can to a certain extent be remedied by making -the points of very thick glass, and by always -keeping them at some distance from the flame. -Moreover, as you can make them yourself when -you are at leisure, their use is very commodious. -If they are to be used with the blowpipe described -in this work, they must be fixed in the -cork that closes the passage through which the -current of air arrives. <i>C c</i> and <i>C´ c</i> (<a href="#pl_1">pl. 1</a>, -fig. 19) are two glass beaks, <i>c c</i> are the -corks, which can indifferently be adapted to <i>c</i>, -in the wooden vice, by which the various parts -of the blowpipe are connected when it is in -action.</p> - -<p>Of whatever material the beak may be made, -its orifice must be perfectly round, and the -<i>size</i> of the orifice, as we have before observed, -must have a relation to the size of the wick -which is to be used with it. You can ascertain -the diameters of the orifices by inserting -into them a little plate of brass, having the -form of a long isoceles triangle, such as is represented -by <a href="#pl_1">pl. 1</a>, fig. 2. It should be an inch -long, the twelfth of an inch wide at one end, -<span class="pagenum" id="Page_14">14</span> -and diminish to nothing at the other. When -divided into eight equal parts, it will give, at the -divisions, the respective proportions of 1, 2, 3, -4, 5, 6, 7 <i>eighths</i> of the diameter at the wide -end, as is exemplified by the figure above -referred to. We have stated in the following -table the relative diameters which long experience -has recommended to us, as being adapted -to produce the greatest effect; yet it is not to -be imagined that these proportions are mathematically -correct and indispensable for the obtaining -of good results. A sensible difference -of effect would be perceived, however, were -these proportions departed from in a notable -manner.</p> - -<table class="bbox"> - <tr> - <th>Diameter of the<br />wick,<br /><i>in inches</i>.</th> - <th>Diameter of the<br />orifice of the<br />beak,<br /><i>in parts of an inch</i>.</th> - <th>Height of the wick<br />above the surface<br />of the oil,<br /><i>in inches</i>.</th> - </tr> - <tr> - <td class="tdc">¼</td> - <td class="tdc">96th</td> - <td class="tdc">½</td> - </tr> - <tr> - <td class="tdc">½</td> - <td class="tdc">48th</td> - <td class="tdc">½</td> - </tr> - <tr> - <td class="tdc">1</td> - <td class="tdc">24th</td> - <td class="tdc">¾</td> - </tr> - <tr> - <td class="tdc">1½</td> - <td class="tdc">16th</td> - <td class="tdc">1</td> - </tr> - <tr> - <td class="tdc">2</td> - <td class="tdc">12th</td> - <td class="tdc">1¼</td> - </tr></table> - -<p>It must be mentioned, that this table has been -formed from experiments made with a glass-blower’s -lamp of the ordinary construction; so -that, with the new lamp with the hood, described -in this work, it will not be necessary to -employ wicks of so great a bulk, nor yet to -elevate them so much above the level of the oil, -<span class="pagenum" id="Page_15">15</span> -in order to produce the same effect. Hence -there will be a very considerable saving in oil.</p> - -<p>The wicks of a quarter of an inch in diameter -are only adapted for mineralogieal examinations, -for soldering very fine metallic substances, and -for working very small tubes. When the objects -are of considerable bulk, it is in general -necessary to have a flame sufficiently large to -cover the whole instrument, or at least all the -portion of the instrument which is operated upon -at once. For working tubes, of which the sides -are not more than the twelfth of an inch in -thickness, you should have a wick at least as -wide as the tube that is worked upon. The -diameter of the lamp-wick usually employed is -<i>one inch</i>; a wick of this size is sufficient for -all the glass instruments which are in common -use. -<span class="pagenum" id="Page_16">16</span></p> - -<hr class="chap" /> - -<h2><small>THE</small><br /> - -<span class="xx-large">ART OF GLASS-BLOWING.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span id="II">II.—<i>Preliminary Notions of the Art.</i></span></h2> - -<hr class="tb" /> - -<h3 id="THE_FLAME">THE FLAME.</h3> - -<p>It is only by long habitude, and a species of -routine, that workmen come to know, not only -the kind of flame which is most proper for each -object they wish to make, but the exact point of -the jet where they ought to expose their glass. -By analysing the flame, upon the knowledge of -which depends the success of the work, we can -immediately obtain results, which, without that, -could only be the fruit of long experience.</p> - -<p>Flame is a gaseous matter, of which a portion -is heated to the point of becoming luminous; -its form depends upon the mode of its -disengagement, and upon the force and direction -of the current of air which either supports -its combustion or acts upon it mechanically. -(<a href="#pl_1">Pl. 1</a>, fig. 1.)</p> - -<p>The flame of a candle, burning freely in still -air, presents in general the form of a pyramid, -of which the base is supported on a hemisphere. -It consists of four distinct parts: the immediate -<span class="pagenum" id="Page_17">17</span> -products of the decomposition of the combustible -by the heat which is produced, occupy -the centre, <i>o</i>, where they exist in the state of -an obscure gaseous matter, circumscribed by a -brilliant and very luminous envelope, <i>s</i>; the -latter is nothing but the obscure matter itself, -in the circumstances where, on coming into -contact with the atmosphere, it combines with -the oxygen which exists therein, and forms -what is properly called <i>flame</i>.</p> - -<p>The blueish light which characterises the inferior -part of the flame, <i>s</i>, is produced by a -current of cold air, which, passing from below -<i>upwards</i>, hinders the combustion from taking -place at the bottom of the flame, at the <i>same</i> -temperature that exists in the parts of the flame -not immediately subject to this influence.</p> - -<p>Finally, on observing attentively, we perceive -a fourth part, which is but slightly luminous, -and exists as an envelope of all the -other parts of the flame. The greatest thickness -of this envelope corresponds with the -summit of the flame. From this point it gradually -becomes thinner, till it arrives at the -lowest part of the blueish light, where it altogether -disappears. It is in this last-described -portion of the flame that the combustion of the -gas is finished, and there it is that we find the -seat of the most intense heat which the flame -of the candle affords. If we compare the temperature -of the different parts of the flame, we -find that the <i>maximum</i> of heat forms a ring -corresponding to the zone of insertion, A A; -<span class="pagenum" id="Page_18">18</span> -a point which is the limit of the superior extremity -of the blueish light.</p> - -<p>When the flame is acted upon by the blowpipe, -it is subject to two principal modifications:—</p> - -<p>1. If, by means of a blowpipe with a very -fine orifice, you direct a current of air through -the middle of the flame, you project a portion -of the flame in the direction of the blast. The -jet thus formed appears like a tongue of fire, -blueish, cylindrical, straight, and very long; -the current of air occupies its interior. This -flame is enveloped on all sides by an almost invisible -light, which, extending beyond the blue -flame, forms a jet, A´ B, very little luminous, -but possessing an extremely high temperature. -It is at the point A´, which corresponds with -the extremity of the blue flame, that the <i>maximum</i> -of heat is found. The extreme point of -the jet B possesses a less degree of heat. This -flame is adapted for mineralogical assays, for -soldering, for working enamels, and in general -for all small objects.</p> - -<p>2. When the orifice of the blowpipe is -somewhat large, or when (the orifice being capillary) -the current of air is very strong, or the -beak is somewhat removed from the flame, the -jet of fire, instead of being prolonged into a -pointed tongue, is blown into a brush. It -makes then a roaring noise, and spreads into -an irregular figure, wherein the different parts -of the flame are confounded beyond the possibility -of discrimination. This flame is very -<span class="pagenum" id="Page_19">19</span> -proper for the working of glass, and particularly -of glass tubes; it ought to be clear and -very brilliant, and above all should not deposit -soot upon cold bodies suddenly plunged into -it. The <i>maximum</i> of temperature in this flame -is not well marked; we can say, however, that -in general it will be found at about two-thirds -of the whole length of the jet. As this roaring -flame contains a great quantity of carburetted -hydrogen, and even of vapour of oil, escaped -from combustion, it possesses a disoxidizing -or reducing property in a very high degree.</p> - -<h3 id="PLACES_FIT_TO_WORK_IN">PLACES FIT TO WORK IN.</h3> - -<p>Every place is adapted for a workshop, provided -it is not too light and the air is tranquil. -The light of the lamp enables one to work with -more safety than day-light, which does not permit -the dull-red colour of hot glass to be seen. -Currents of cold air are to be avoided, because -they occasion the fracture of glass exposed to -them on coming out of the flame.</p> - -<h3 id="MEANS_OF_OBTAINING_A_GOOD_FIRE">MEANS OF OBTAINING A GOOD FIRE.</h3> - -<p>The lamp should be firmly seated upon a -steady and perfectly horizontal table, and -should be kept continually full of oil. The oil -which escapes during the operation, from the -lamp into the tin-stand placed below it, should -be taken up with a glass tube having a large -bulb, and returned to the lamp.</p> - -<p>When you set to work, the first thing you -have to do is to examine the orifice of the beak. -<span class="pagenum" id="Page_20">20</span> -If it is closed, or altered in form, by adhering -soot, you must carefully clean it, and open the -canal by means of a needle or fine wire. In -the next place, you freshen the wick by cutting -it squarely, and carrying off with the scissars -the parts which are carbonised. You then -divide it into two principal bundles, such as -C, K (<a href="#pl_1">pl. 1</a>, fig. 21), which you separate -sufficiently to permit a current of air, directed -between the two, to touch their surfaces lightly, -without being interrupted in its progress. By -pushing the bundles more or less close to one -another, and by snuffing them, you arrive at -length at obtaining a convenient jet. It is a -good plan to allow, between the two principal -bundles and at their inferior part, a little portion -of the wick to remain: you bend this -down in the direction of the jet, and make it lie -immediately beneath the current of air.</p> - -<p>The wick must be prevented from touching -the rim of the lamp, in order to avoid the running -of the oil into the stand of the lamp. This -is easily managed by means of a bent iron-wire, -disposed as it is in the lamp described in this -work; see <a href="#pl_1">pl. 1</a>, fig. 23, where the wire is seen -in an elevated position. When the wick is in -the lamp, the wire is brought down round the -wick and level with the surface of the lamp. -A few drops of oil of turpentine, spread on the -wick, makes it take fire immediately, over its -whole extent, on the approach of an inflamed -substance.</p> - -<p>To obtain a good fire, it is necessary to -<span class="pagenum" id="Page_21">21</span> -place the lamp in such a position that the orifice -of the blowpipe shall just touch the exterior -part of the flame. The beak must not enter -the flame, as it can then throw into the jet only -an inconsiderable portion of the ignited matter. -See <a href="#pl_1">pl. 1</a>, fig. 20. On the other hand, if the -lamp be too far away from the blowpipe, the -flame becomes trembling, appears blueish, and -possesses a very low degree of heat.</p> - -<p>For mineralogical experiments, and for operations -connected with watch-making and -jewellery, the current of air should project the -flame horizontally. For glass-blowing, the -flame should be projected in the direction intimated -by the arrow in <a href="#pl_1">pl. 1</a>, fig. 20—that is to -say, under an angle of twenty or twenty-five -degrees.</p> - -<p>The current of air ought to be constant, -uniform, and sufficiently powerful to carry the -flame in its direction. When it is not strong -enough to produce this effect, it is necessary -to add weights to the bellows or the bladder, -according as the glass-blowers’ table or our -lamp is employed. The point to which you -should apply, in the use of these instruments, -is to enable yourself to produce a current of -air so uniform in its course that the projected -flame be without the least variation.</p> - -<p>Finally, when you leave off working you -should extinguish the flame, by cutting off the -inflamed portion of the wick with the scissars. -This has the double advantage of avoiding the -production of a mass of smoke and of leaving -the lamp in a fit state for another operation. -<span class="pagenum" id="Page_22">22</span></p> - -<h3 id="CHOICE_AND_PRESERVATION_OF_GLASS">CHOICE AND PRESERVATION OF GLASS.</h3> - -<p>The only materials employed in the fabrication -of the objects described in this Treatise, are -tubes of common glass or of flint-glass. They -can be had of all diameters, and of every variety -of substance. They are commonly about -three feet long, but some are found in commerce -which are six feet in length. You should choose -tubes that are very uniform—that is to say, straight -and perfectly cylindrical, both inside and outside. -A good tube should have the same diameter -from one end to the other, and the sides -or substance of the glass should be of equal -thickness in every part. This is indispensable -when the tubes are to have spherical bulbs -blown upon them. We shall describe, in the -article <i>Graduation</i>, the method of ascertaining -whether or not a tube is uniform in the bore.</p> - -<p>The substance of the glass should be perfectly -clear, without bulbs, or specks, or -stripes. The tubes are so much the more easy -of use, as the glass of which they are made is -the more homogeneous. Under this point of -view, the white glass, known in commerce by -the name of crystal or flint-glass, is preferable -to common glass: it is more fusible, less fragile, -and less liable to break under the alternations -of heat and cold; but it is dearer and -heavier, and has the serious disadvantage of -becoming permanently black when exposed to -a certain part of the flame. This is an effect, -the causes and consequences of which will be -explained in a subsequent chapter. -<span class="pagenum" id="Page_23">23</span></p> - -<p>You must take care never to employ flint-glass -for instruments which are to be submitted to -the action of certain fluids—such as sulphuretted -and phosphuretted hydrogen, and the hydro-sulphurets; -for these compounds are capable -of decomposing flint-glass, in consequence of -its containing oxide of lead. In general, hard -common glass is preferable to flint-glass for all -instruments which are to be employed in chemistry. -Flint-glass should only be used for -ornamental objects, and for the barometers, -thermometers, and other instruments employed -in philosophical researches.</p> - -<p>It sometimes happens that glass tubes lose -their transparence and ductility, and suddenly -become almost infusible, in the fire of the lamp: -this effect takes place when they have been -kept for some time in a melted state. It is -then almost impossible to bring them back to -their original condition; it can only be done -by exposing them for a long time to an exceedingly -high temperature. You can prevent this -accident by working such kind of glass with -considerable rapidity, and in a pretty brisk -fire. There are tubes, however, which vitrify -so promptly that it is only a person well versed -in the art who can make good use of them. -It is best not to employ such glass. But how -can it be discriminated before-hand? It is experience, -sooner than any characters capable -of description, that will teach you how to -make choice of good glass; nevertheless we -have observed, that, among the glass tubes -which occur in commerce, those possessing a -<span class="pagenum" id="Page_24">24</span> -very <i>white colour</i> manifest this bad quality -most particularly. It may be observed, that, -for tubes which are to have thin sides, this -vitrifiable sort of glass is better than any other.</p> - -<p>For certain philosophical instruments it is -necessary to employ flat tubes. These are -formed of flint-glass, are very small, and have -a canal or bore, which, instead of being round, -as in common tubes, has the form of a long and -very flat oval. This disposition has the advantage -of rendering more perceptible the column -of liquid that may be introduced, and -which in a round canal would scarcely be visible. -In choosing this sort of tubes, carefully -avoid those of which the canal is twisted, and -not found to be in the same plane, in the whole -length of the tube.</p> - -<p>The tubes should be sorted, according to -their sizes and qualities, and should be deposited -in large drawers or on long shelves, in -such a manner as to be equally supported -through their whole extent. They should also -be sheltered from dust and from moisture. If -you cannot conveniently warehouse them in -this manner, you should tie them up in parcels, -and support them in a perpendicular position. -It is a very bad plan to place them in an inclined -direction, or to support them by their -extremities on wooden brackets, as it is the -fashion to do in chemical laboratories; because, -as the tubes are then supported only at certain -points, they bend, in course of time, under -the influence of their own weight, and contract -a curvature which is extremely prejudicial in -<span class="pagenum" id="Page_25">25</span> -certain instruments, and which it is almost impossible -to correct.</p> - -<h3 id="PREPARATION_OF_GLASS_TUBES_BEFORE_HEATING_THEM">PREPARATION OF TUBES BEFORE HEATING THEM.</h3> - -<p>Before presenting a tube to the flame, you -should clean it well both within and without, -in order to remove all dust and humidity. If -you neglect to take this precaution, you run -the risk of cracking or staining the glass. -When the diameter of the tube is too small to -permit of your passing a plug of cloth or paper -to clean its interior, you can accomplish the object -by the introduction of water, which must, -many times alternately, be sucked in and -blown out, until the tube is deemed clean. -One end of it must then be closed at the lamp, -and it must be gradually exposed to a charcoal -fire, where, by raising successively all parts of -the tube to a sufficiently high temperature, you -endeavour to volatilize and expel all the water -it contains. In all cases you considerably facilitate -the disengagement of moisture by renewing -the air in the tube by means of a bottle of -Indian-rubber fastened to the end of a long narrow -tube, which you keep in the interior of -the tube to be dried during the time that it is -being heated. You can here advantageously -substitute alcohol for water, as being much -more volatile, and as dissolving greasy matters; -but these methods of cleansing should only be -employed for valuable objects, because it is -extremely difficult fully to expel moisture from -a tube wherein you have introduced water, -<span class="pagenum" id="Page_26">26</span> -and because alcohol is too expensive to be employed -where there is no particular necessity.</p> - -<p>When the tubes no longer contain dust, or -moisture, you measure them, and mark the -divisions according to the sort of work which -you propose to execute.</p> - -<h3 id="METHOD_OF_PRESENTING_TUBES_TO_THE_FIRE_AND_OF_WORKING_THEM_THEREIN">METHOD OF PRESENTING TUBES TO THE FIRE, AND OF WORKING THEM THEREIN.</h3> - -<p>The two arms are supported on the front -edge of the table, and the tube is held with the -hands either above or below, according as it -may be necessary to employ more or less force, -more or less lightness. You ought, in general, -to hold the tube <i>horizontally</i>, and in such a -manner that its direction may be perpendicular -to that of the flame. Yet, when you wish to -heat at once a large portion of the tube, or to -soften it so that it shall sink together in a particular -manner, as in the operation of sealing, -you will find it convenient to <i>incline</i> the tube, -the direction of which, however, must always -be such as to turn the heated part continually -towards you.</p> - -<p>We are about to give a general rule, upon -the observance of which we cannot too strongly -insist, as the success of almost every operation -entirely depends upon it. The rule is, <i>never to -present a tube to the flame without</i> <small>CONTINUALLY -TURNING</small> <i>it</i>; and turning it, too, with such a -degree of rapidity that every part of its circumference -may be heated and softened to the -same degree. As melted glass necessarily -tends to descend, there is no method of preventing -<span class="pagenum" id="Page_27">27</span> -a heated tube from becoming deformed -but that of continually turning it, so as to bring -the softened part very frequently uppermost. -When you heat a tube near the middle, the -movement of the two hands must be <i>uniform</i> -and <i>simultaneous</i>, or the tube will be twisted -and spoiled.</p> - -<p>When the tubes have thick sides, they must -not be plunged <i>into</i> the flame until they have -previously been strongly heated. You expose -them at first to the current of hot air, at some -inches from the extremity of the jet; you keep -them there some time, taking care to turn them -continually, and then you gradually bring them -towards, and finally into, the flame. The -thicker the sides of the tubes are, the greater -precaution must be taken to elevate the temperature -gradually: this is the only means of -avoiding the fractures which occur when the -glass is too rapidly heated. Though it is -necessary to take so much care with large and -thick tubes, there are, on the contrary, some -tubes so small and so thin that the most sudden -application of the fire is insufficient to break -them. Practice soon teaches the rule which -is to be followed with regard to tubes that come -between these extremes.</p> - -<p>Common glass ought to be fused at the -<i>maximum</i> point of heat; but glass that contains -oxides capable of being reduced at that -temperature (such as flint-glass) require to be -worked in that part of the flame which -possesses the highest oxidating power. If you -operate without taking this precaution, you run -<span class="pagenum" id="Page_28">28</span> -the risk of decomposing the glass. Thus, for -example, in the case of flint-glass, you may reduce -the oxide of lead, which is one of its constituents, -to the state of metallic lead. The consequence -of such a reduction is the production of a black -and opaque stain upon the work, which can only -be removed by exposing the glass, during a -very long time, to the extremity of the jet.</p> - -<p>You must invariably take the greatest care -to keep the flame from passing into the interior -of the tube; for when it gets there it deposits a -greasy vapour, which is the ordinary cause of -the dirt which accumulates in instruments that -have been constructed without sufficient precaution -as to this matter.</p> - -<p>In order that you may not blacken your -work, you should take care to snuff the -wick of the lamp whenever you perceive the -flame to deposit soot.</p> - -<p>You can judge of the <i>consistence</i> of the -tubes under operation as much by the <i>feel</i> as by -the <i>look</i> of the glass. The degree of heat -necessary to be applied to particular tubes, depends -entirely upon the objects for which they -are destined. As soon as the glass begins to -feel soft, at a <i>brownish-red heat</i>, for example, -you are at the temperature most favourable to -good <i>bending</i>. But is it intended to <i>blow a -bulb</i>? The glass must, in this case, be completely -melted, and subjected to a full <i>reddish-white -heat</i>. We shall take care, when speaking -hereafter of the different operations to be -performed, to mention the temperature at which -<i>each</i> can be performed with most success. -<span class="pagenum" id="Page_29">29</span></p> - -<p>When an instrument upon which you have -been occupied is finished, you should remove it -from the flame <i>gradually</i>, taking care to <i>turn</i> -it continually, until the glass has acquired sufficient -consistence to support its own weight -without becoming deformed. Every instrument -formed thus of glass requires to undergo a -species of <i>annealing</i>, to enable it to be preserved -and employed. To give the instrument -this annealing, it is only necessary to remove it -from the flame very gradually, allowing it to -repose some time in each <i>cooler</i> place to which -you successively remove it. The thicker or the -more equal the sides of the glass, the more -carefully it requires to be annealed. No instrument -should be permitted to touch cold or -wet bodies while it is warm. -<span class="pagenum" id="Page_30">30</span></p> - -<hr class="chap" /> - -<h2><small>THE</small><br /> - -<span class="xx-large">ART OF GLASS-BLOWING.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span id="III">III.—<i>Fundamental Operations in Glass-Blowing</i>.</span></h2> - -<p>All the modifications of shape and size which -can be given to tubes in the construction of various -instruments, are produced by a very small -number of dissimilar operations. We -have thought it best to unite the description of -these operations in one article, both to avoid -repetitions and to place those who are desirous -to exercise this art in a state to proceed, -without embarrassment, to the construction of -any instrument of which they may be provided -with a model or a drawing; for those who attend -properly to the instructions given here, -with respect to the fundamental operations of -glass-blowing, will need no other instructions -to enable them to succeed in the construction -of all kinds of instruments capable of being -made of tubes. These fundamental operations -can be reduced to ten, which may be named as -follows:— -<span class="pagenum" id="Page_31">31</span></p> - -<p class="table"> -1. Cutting.<br /> -2. Bordering.<br /> -3. Widening.<br /> -4. Drawing out.<br /> -5. Choking.<br /> -6. Sealing.<br /> -7. Blowing.<br /> -8. Piercing.<br /> -9. Bending.<br /> -10. Soldering.<br /> -</p> - -<p>We proceed to give a detailed account of -these different operations.</p> - -<h3 id="CUTTING">1.—<small>CUTTING.</small></h3> - -<p>The different methods of cutting of glass -tubes which have been contrived, are all founded -on two principles; one of these is the -division of the surface of glass by cutting -instruments, the other the effecting of the same -object by a sudden change of temperature; and -sometimes these two principles are combined in -one process.</p> - -<p>The first method consists in notching the -tube, at the point where it is to be divided, with -the edge of a file, or of a thin plate of hard -steel, or with a diamond; after which, you -press upon the two ends of the tube, as if to -enlarge the notch, or, what is better, you give -the tube a slight smart blow. This method is -sufficient for the breaking of small tubes. -Many glass-blowers habitually employ an agate, -or a common flint, which they hold in one hand, -while with the other they rub the tube over the -sharp edge of the stone, taking the precaution -of securing the tube by the help of the thumb. -For tubes of a greater diameter, you can employ -a fine iron wire stretched in a bow, or, -still better, the glass-cutters’ wheel; with either -of these, assisted by a mixture of emery -<span class="pagenum" id="Page_32">32</span> -and water, you can cut a circular trace round -a large tube, and then divide it with ease.</p> - -<p>When the portion which is to be removed -from a tube is so small that you cannot easily -lay hold of it, you cut a notch with a file, and -expose the notch to the point of the blowpipe -flame: the cut then flies round the tube.</p> - -<p>This brings us to the second method of cutting -tubes—a method which has been modified -in a great variety of ways. It is founded on -the property possessed by vitrified matters, of -breaking when exposed to a sudden change of -temperature. Acting upon this principle, some -artists apply to the tube, at the point where -they desire to cut it, a band of fused glass. -If the tube does not immediately separate into -two pieces, they give it a slight smart blow on -the extremity, or they drop a little water on -the heated ring. Other glass-blowers make -use of a piece of iron heated to redness, an -angle or a corner of which they apply to the -tube at the point where it is to be cut, and -then, if the fracture is not at once effected by -the action of the hot iron, they plunge the tube -suddenly into cold water.</p> - -<p>The two methods here described can be -combined. After having made a notch with a -file, or the edge of a flint, you introduce into -it a little water, and bring close upon it the -point of a very little tube previously heated to -the melting point. This double application of -heat and moisture obliges the notch to fly right -round the tube.</p> - -<p>When the object to be cut has a large diameter, -<span class="pagenum" id="Page_33">33</span> -and very thin sides—when it is such a -vessel as a drinking-glass, a cup, or a gas -tube—you may divide it with much neatness by -proceeding as follows. After having well -cleaned the vessel, both within and without, -pour oil into it till it rises to the point, or very -nearly to the point, where you desire to cut it. -Place the vessel, so prepared, in an airy situation; -then take a rod of iron, of about an inch -in diameter, make the extremity brightly red-hot, -and plunge it into the vessel until the extremity -of the iron is half an inch below the -surface of the oil: there is immediately formed -a great quantity of very hot oil, which assembles -in a thin stratum at the surface of the -cold oil, and forms a circular crack where it -touches the sides of the glass. If you take -care to place the object in a horizontal position, -and to plunge the hot iron without communicating -much agitation to the oil, the parts so -separated will be as neat and as uniform as you -could desire them to be. By means of this -method we have always perfectly succeeded in -cutting very regular zones from ordinary glass.</p> - -<p>The method which is described in some -works, of cutting a tube by twisting round it -a thread saturated with oil of turpentine, and -then inflaming the thread, we have found to be -unfit for objects which have thick sides.</p> - -<p>Some persons employ cotton wicks dipped in -sulphur. By the burning of these, the glass is -strongly heated in a given line, or very narrow -space, which is instantly cooled by a wet feather -or a wet stick. So soon as a crack is produced, -<span class="pagenum" id="Page_34">34</span> -it can be led in any required direction -by a red-hot iron, or an inflamed piece of charcoal.</p> - -<p>Finally, you may cut small portions from -glass tubes in a state of fusion, by means of -common scissars.</p> - -<h3 id="BORDERING">2.—<small>BORDERING.</small></h3> - -<p>To whatever use you may destine the tubes -which you cut, they ought, almost always, to -be bordered. If you merely desire that the -edges shall not be sharp, you can smoothen -them with the file, or, what is better, you can -expose them to the flame of the lamp until they -are rounded. If you fear the sinking in of the -edges when they are in a softened state, you -can hinder this by working in the interior of -the tube a round rod of iron, such as <a href="#pl_1">pl. 1</a>, -fig. 5. The rod of iron should be one-sixth of -an inch thick; one end of it should be filed -to a conical point, and the other end be inserted -into a thin, round, wooden handle. You -will find it convenient to have a similar rod -with a slight bend in the middle.</p> - -<p>When you desire to make the edges of the -tube project, bring the end to a soft state, then -insert in it a metallic rod, and move it about in -such a manner as to widen a little the opening. -While the end of the tube is still soft, place it -suddenly upon a horizontal surface, or press it -by means of a very flat metallic plate. The object -of this operation is to make the end of the -tube flat and uniform. The metallic rod which -you employ may be the same as we have described -<span class="pagenum" id="Page_35">35</span> -in the preceding paragraph. Instead -of agitating the rod in the tube, you may hold -it in a fixed oblique position, and turn the tube -round with the other hand, taking care to -press it continually and regularly against the -rod. See <a href="#pl_1">pl. 1</a>, fig. 6. Very small tubes can -be bordered by approaching their extremities -to a flame not acted upon by the blowpipe; -particularly the flame of a spirit-lamp.</p> - -<p>When the edges of a tube are to be rendered -capable of suffering considerable pressure, you -can very considerably augment their strength -by soldering a rib or string of glass all round -the end of the tube—see <a href="#pl_1">pl. 1</a>, fig. 12. Holding -the tube in the left hand, and the string of -glass in the right, you expose them both at once -to the flame. When their extremities are sufficiently -softened, you attach the end of the rib -of glass to the tube at a very short distance -from its extremity; you then continue gradually -to turn the tube, so as to cause the rib of glass -to adhere to it, in proportion as it becomes -softened. When the rib has made the entire -circumference of the tube, you separate the -surplus by suddenly darting a strong jet of fire -upon the point where it should be divided; -and you continue to expose the tube to the -flame, always turning it round, until the ring -of glass is fully incorporated with the glass it -was applied to. You then remove the instrument -from the flame, taking care to anneal it in -so doing. During this operation you must -take care to prevent the sinking together of -the sides of the tube, by now and then turning -<span class="pagenum" id="Page_36">36</span> -the iron rod in its interior. It is a <i>red heat</i>, -or a <i>brownish red heat</i>, that is best adapted to -this operation.</p> - -<h3 id="WIDENING">3.—<small>WIDENING.</small></h3> - -<p>When you desire to enlarge the diameter of -the end of a tube, it is necessary, after having -brought it to a soft state, to remove it from the -flame, and to press the sides of the glass outwards -by means of a large rod of iron with a -conical point. The tube must be again heated, -and again pressed with the conical iron rod, -until the proper enlargement is effected. This -operation is much the same as that of bordering -a tube with projecting edges.</p> - -<h3 id="DRAWING_OUT">4.—<small>DRAWING OUT.</small></h3> - -<p>You can <i>draw out</i> or <i>contract</i> a tube either -in the middle or at the end. Let us in the -first place consider that a tube is to be drawn -out in the middle. If the tube is long, you -support it with the right hand <i>below</i>, and the -left hand <i>above</i>, by which means you secure -the force that is necessary, as well as the position -which is commodious, for turning it continually -and uniformly in the flame. It must be -kept in the jet till it has acquired a <i>cherry red -heat</i>. You then remove it from the flame, and -always continuing gently to turn it, you gradually -separate the hands from each other, and -draw the tube in a straight line. In this manner -you produce a long thin tube in the centre -of the original tube, which ought to exhibit two -uniform cones where it joins the thin tube, and -<span class="pagenum" id="Page_37">37</span> -to have the points of these cones in the prolongation -of the axis of the tube. See <a href="#pl_1">pl. 1</a>, fig. 3.</p> - -<p>To draw out a tube at its extremity, you heat -the extremity till it is in fusion, and then remove -it from the flame; you immediately seize -this extremity with the pliers, and at the same -time separate the two hands. The more rapidly -this operation is performed, the glass being supposed -to be well softened, the more capillary -will the drawn-out point of the tube be rendered. -Instead of pinching the fused end with -the pliers, it is simpler to bring to it the end of -a little auxiliary tube, which should be previously -heated, to fuse the two together, and -then to draw out the end of the original tube -by means of the auxiliary tube—see <a href="#pl_1">pl. 1</a>, -fig. 4 and 11. In all cases, the smaller the -portion of tube softened, the more abrupt is -the part drawn out.</p> - -<p>When you desire to draw out a point from -the side of a tube, you must heat that portion -alone, by holding it fixedly at the extremity of -the jet of flame. When it is sufficiently -softened, solder to it the end of an auxiliary -tube, and then draw it out. <a href="#pl_1">Pl. 1</a>, fig. 18, exhibits -an example of a tube drawn out laterally. -A <i>red heat</i>, or a <i>cherry red heat</i>, is best adapted -to this operation.</p> - -<h3 id="CHOKING">5.—<small>CHOKING.</small></h3> - -<p>We do not mean by <i>choking</i>, the closing or -stopping of the tube, but simply a diminution -of the interior passage, or bore. It is a sort of -contraction. For examples, see <a href="#pl_2">pl. 2</a>, fig. 15, -<span class="pagenum" id="Page_38">38</span> -20, 29. You perform the operation by presenting -to the flame a zone of the tube at the -point where the contraction is to be effected. -When the glass is softened, you draw out the -tube, or push it together, according as you -desire to produce a hollow in the surface of -the tube, or to have the surface even, or to -cause a ridge to rise above it. A <i>cherry red -heat</i> is the proper temperature to employ.</p> - -<h3 id="SEALING">6.—<small>SEALING.</small></h3> - -<p>If the sides of the tube to be sealed are thin, -and its diameter is small, it is sufficient to expose -the end that you wish to close to the -flame of the lamp. When the glass is softened -it sinks of itself, in consequence of the rotatory -motion given to it, towards the axis of the -tube, and becomes rounded. The application -of no instrument is necessary.</p> - -<p>If the tube is of considerable diameter, or -if the sides are thick, you must soften the end, -and then, with a metallic rod or a flat pair of -pliers, mould the sides to a hemisphere, by -bringing the circumference towards the centre, -and continuing to turn the tube in the flame, -until the extremity is well sealed, and perfectly -round. Examples of the figure are to be seen -in <a href="#pl_2">pl. 2</a>, fig. 3 and 5. Instead of this method, -it is good, when the extremity is sufficiently -softened, to employ an auxiliary tube, with -the help of which you can abruptly draw -out the point of the original tube, which becomes -by that means cut and closed by the -flame. In order that this part may be well -<span class="pagenum" id="Page_39">39</span> -rounded, you may, as soon as the tube is sealed, -close the other extremity with a little wax, and -continue to expose the sealed part to the flame, -until it has assumed the form of a <i>drop of tallow</i>. -See <a href="#pl_2">pl. 2</a>, fig. 15. You can also seal in this -fashion, by blowing, with precaution, in the -open end of the tube, while the sealed end is -in a softened state.</p> - -<p>If you desire the sealed part to be flat, like -<a href="#pl_3">pl. 3</a>, fig. 30, you must press it, while it is -soft, against a flat substance. If you wish it to -be concave, like the bottom of a bottle, or <a href="#pl_3">pl. 3</a>, -fig. 2, you must suck air from the tube with the -mouth; or, instead of that, force the softened -end inwards with a metallic rod. You may -also draw out the end till it be conical, as -<a href="#pl_2">pl. 2</a>, fig. 4, or terminate it with a little button, -as <a href="#pl_2">pl. 2</a>, fig. 6. In some cases the sealed end -is bent laterally; in others it is twirled into a -ring, having previously been drawn out and -stopped in the bore. In short, the form given -to the sealed end of a tube can be modified in -an infinity of ways, according to the object for -which the tube may be destined.</p> - -<p>You should take care not to accumulate too -much glass at the place of sealing. If you -allow it to be too thick there, you run the risk -of seeing it crack during the cooling. Some -farther observations on sealing will be found at -the article <i>Water Hammer</i>, in a subsequent -section. The operation of sealing succeeds -best at a <i>cherry-red heat</i>.</p> - -<h3 id="BLOWING">7.—<small>BLOWING.</small></h3> - -<p>The construction of a great number of philosophical -<span class="pagenum" id="Page_40">40</span> -instruments requires that he who would -make them should exercise himself in the art -of blowing <i>bulbs</i> possessing a figure exactly -spherical. This is one of the most difficult -operations.</p> - -<p>To blow a bulb at the extremity of a tube, -you commence by sealing it; after which, -you collect at the sealed extremity more or less -glass, according to the size and the solidity -which you desire to give to the bulb. When -the end of the tube is made thick, completely -sealed, and well rounded, you elevate the temperature -to a <i>reddish white</i> heat, taking care -to turn the tube continually and rapidly between -your fingers. When the end is perfectly soft -you remove it from the flame, and, holding the -tube horizontally, you blow quickly with the -mouth into the open end, without discontinuing -for a single moment the movement of rotation. -If the bulb does not by this operation acquire -the necessary size, you soften it again in the -flame, while under the action of which you turn -it very rapidly, lest it should sink together at -the sides, and become deformed. When it is -sufficiently softened you introduce, in the same -manner as before, a fresh quantity of air. It is -of importance to observe that, if the tube be of -a large diameter, it is necessary to contract the -end by which you are to blow, in order that -it may be turned round with facility while in the -mouth.</p> - -<p>When the bulb which you desire to make is -to be somewhat large, it is necessary, after -having sealed the tube, to soften it for the space -of about half an inch from its extremity, and -<span class="pagenum" id="Page_41">41</span> -then, with the aid of a flat piece of metal, to -press moderately and repeatedly on the softened -portion, until the sides of the tube which are -thus pressed upon, sink together, and acquire a -certain degree of thickness. During this operation, -however, you must take care to blow, -now and then, into the tube, in order to retain -a hollow space in the midst of the little mass -of glass, and to hinder the bore of the tube from -being closed up. When you have thus, at the -expense of the length of the tube, accumulated -at its extremity a quantity of glass sufficient -to produce a bulb, you have nothing more to -do than to heat the matter till it is raised to a -temperature marked by a <i>reddish-white</i> colour, -and then to expand it by blowing.</p> - -<p>Instead of accumulating the glass thus, it is -more expedient to blow on the tube a series of -little bulbs close to one another (see <a href="#pl_1">pl. 1</a>, fig. 8), -and then, by heating the intervals, and blowing, -to unite these little bulbs into a large one of -convenient dimensions.</p> - -<p>We have already observed, and we repeat -here, that it is indispensably necessary to hold -the glass <i>out</i> of the flame during the act of -blowing. This is the only means of maintaining -uniformity of temperature in the whole -softened parts of the tube, without which it is -impossible to produce bulbs with sides of equal -thickness in all their extent.</p> - -<p>When you desire to form a bulb at the extremity -of a capillary tube, that is to say, of a -tube which has a bore of very small diameter, -such as the tubes which are commonly employed -<span class="pagenum" id="Page_42">42</span> -to form thermometers, it would be improper to -blow it with the mouth; were you to do so, the -vapour which would be introduced, having a -great affinity for the glass, would soon obstruct -the little canal, and present to the passage of -the air a resistance, which, with the tubes of -smallest interior diameter, would often be insurmountable. -But, even when the tubes you -employ have not so very small an internal -diameter, you should still take care to avoid -blowing with the mouth; because the introduction -of moisture always injures fine instruments, -and it is impossible to dry the interior of a -capillary tube when once it has become wet. -It is better to make use of a bottle of Indian -rubber, which can be fixed on the open end -of the tube by means of a cork with a hole -bored through it. You press the bottle in the -hand, taking care to hold the tube vertically, -with the hot part <i>upwards</i>; if you were not to -take this precaution, the bulb would be turned -on one side, or would exhibit the form of a -pear, because it is impossible, in this case, to -give to the mass in fusion that rotatory motion -which is necessary, when the tube is held horizontally, -to the production of a globe perfectly -spherical in its form, and with sides of equal -thickness.</p> - -<p>Whenever you blow into a tube you should -keep the eye fixed on the dilating bulb, in -order to be able to arrest the passage of air -at the proper moment. If you were not to -attend to this, you would run the risk of giving -to the bulb too great an extension, by which -<span class="pagenum" id="Page_43">43</span> -the sides would be rendered so thin that it -would be liable to be broken by the touch of -the lightest bodies. This is the reason that, -when you desire to obtain a large bulb, it is -necessary to thicken the extremity of the tube, -or to combine many small bulbs in one, that it -may possess more solidity.</p> - -<p>In general, when you blow a bulb with the -mouth, it is better to introduce the air a little at -a time, forcing in the small portions very -rapidly one after the other; rather than to attempt -to produce the whole expansion of the -bulb at once: you are then more certain of being -able to arrest the blowing at the proper time.</p> - -<p>When you desire to produce a moderate expansion, -either at the extremity or in any other -part of a tube, you are enabled easily to effect -it by the following process, which is founded on -the property possessed by all bodies, and -especially by fluids, of expanding when heated; -a property which characterises air in a -very high degree. After having sealed one end -of the tube and drawn out the other, allow it -to become cold, in order that it may be quite -filled with air; close the end which has been -drawn out, and prevent the air within the tube -from communicating with that at its exterior; -then gradually heat the part which you desire -to have expanded, by turning it gently in the -flame of a lamp. In a short time the softened -matter is acted on by the tension of the air -which is enclosed and heated in the interior of -the tube; the glass expands, and produces a -bulb or swelling more or less extensive, according -<span class="pagenum" id="Page_44">44</span> -as you expose the glass to a greater or -lesser degree of heat.</p> - -<p>To blow a bulb in the middle of a tube, it is -sufficient to seal it at one of its extremities, to -heat the part that you wish to inflate, and, -when it is at a <i>cherry-red</i> heat, to blow in the -tube, which must be held horizontally and -turned with both hands, of which, for the -sake of greater facility, the left may be held -above and the right below.</p> - -<p>If the bulb is to be large, the matter must -previously be thickened or accumulated, or, -instead of that, a series of small bulbs first -produced, and these subsequently blown into a -single larger bulb, as we have already mentioned. -See <a href="#pl_1">pl. 1</a>, fig. 8.</p> - -<p>For some instruments, the tubes of which -must be capillary, it is necessary to blow the -bulbs separately, and then to solder them to -the requisite adjuncts. The reason of this is, -that it would be too difficult to produce, from -a very fine tube, a bulb of sufficient size and -solidity to answer the intended purpose.</p> - -<p>You make choice of a tube which is not -capillary, but of a sufficient diameter, very -cylindrical, with equal sides, and tolerably -substantial: it may generally be from the -twentieth to the twelfth of an inch thick in the -glass. You soften two zones in this tube, -more or less near to each other, according to -the bulk you desire to give to the bulb, and -you draw out the melted part in points. The -talent consists in <i>well-centering</i>—that is to -say, in drawing out the melted tube in such a -<span class="pagenum" id="Page_45">45</span> -manner that the thin parts or points shall be -situated exactly in the prolongation of the axis -of the little portion of the original tube remaining -between them. This operation is -technically termed drawing <i>a cylinder between -two points</i>. The tube so drawn out is exhibited -by <a href="#pl_1">pl. 1</a>, fig. 4. You cut these points at -some distance from the central or thick part, -and seal one end; you next completely soften -the little thick tube and expand it into a bulb, -by blowing with the precautions which have -already been described. You must keep the -glass in continual motion, if you desire to be -successful in this experiment. Much rapidity -of movement, and at the same time lightness -of touch, are requisite in the operation here -described. It is termed <i>blowing a bulb between -two points</i>. <a href="#pl_1">Pl. 1</a>, fig. 10, exhibits a -bulb blown between two points.</p> - -<p>To obtain a <i>round</i> bulb, you should hold -the tube horizontally; to obtain a <i>flattened</i> -bulb, you should hold it perpendicularly, with -the fused extremity turned above; to obtain a -<i>pear-shaped</i> bulb, you should hold the fused -extremity downwards.</p> - -<p>When you are working upon a bulb between -two points, or in the middle of a tube, you -should hold the tube horizontally, in the ordinary -manner; but you are to push the softened -portion together, or to draw it out, according as -you desire to produce a ridge or a prolongation.</p> - -<p>When you are at liberty to choose the point -from which you are to blow, you should prefer, -<span class="pagenum" id="Page_46">46</span> -1st, that where the moisture of the breath can -be the least prejudicial to the instrument which -is to be made; 2dly, that which brings the -part which is to be expanded nearest to your -eye; 3dly, that which presents the fewest difficulties -in the execution. When bulbs are -to be formed in complicated apparatus, it is -good to reflect a little on the best means of -effecting the object. It is easy to understand -that contrivances which may appear very -simple on paper, present difficulties in the -practical execution which often call for considerable -management.</p> - -<h3 id="PIERCING">8.—<small>PIERCING.</small></h3> - -<p>You first seal the tube at one extremity, and -then direct the point of the flame on the part -which you desire to pierce. When the tube -has acquired a <i>reddish-white</i> heat, you suddenly -remove it from the flame, and forcibly -blow into it. The softened portion of the tube -gives way before the pressure of the air, and -bursts into a hole. You expose the tube again -to the flame, and border the edges of the hole.</p> - -<p>It is scarcely necessary to observe, that, if -it be a sealed extremity which you desire to -pierce, it is necessary to turn the tube between -the fingers while in the fire; but if, on the contrary, -you desire to pierce a hole in the side of -a tube, you should keep the glass in a fixed -position, and direct the jet upon a single point.</p> - -<p>If the side of the tube is thin, you may dispense -with blowing. The tube is sealed and -allowed to cool; then, accurately closing the -<span class="pagenum" id="Page_47">47</span> -open extremity with the finger, or a little wax, -you expose to the jet the part which you desire -to have pierced. When the glass is sufficiently -softened, the air enclosed in the tube being expanded -by the heat, and not finding at the -softened part a sufficient resistance, bursts -through the tube, and thus pierces a hole.</p> - -<p>You may generally dispense with the sealing -of the tube, by closing the ends with wax, or -with the fingers.</p> - -<p>There is still another method of performing -this operation, which is very expeditious, and -constantly succeeds with objects which have -thin sides. You raise to a <i>reddish white</i> heat -a little cylinder of glass, of the diameter of the -hole that you desire to make, and you instantly -apply it to the tube or globe, to which it will -strongly adhere. You allow the whole to cool, -and then give the auxiliary cylinder a sharp -slight knock; the little cylinder drops off, and -carries with it the portion of the tube to which -it had adhered. On presenting the hole to a -slight degree of heat, you remove the sharpness -of its edges.</p> - -<p>When you purpose to pierce a tube laterally, -for the purpose of joining to it another -tube, it is always best to pierce it by blowing -many times, and only a little at a time, and -with that view, to soften the glass but moderately. -By this means the tube preserves -more thickness, and is in a better state to support -the subsequent operation of soldering.</p> - -<p>There are circumstances in which you can -pierce tubes by forcibly sucking the air out -<span class="pagenum" id="Page_48">48</span> -of them; and this method sometimes presents -advantages that can be turned to good account. -Finally, the orifices which are produced by -cutting off the lateral point of a tube drawn -out at the side, may also be reckoned as an -operation belonging to this article.</p> - -<h3 id="BENDING">9.—<small>BENDING.</small></h3> - -<p>If the tube is narrow, and the sides are -pretty thick, this operation presents no difficulty. -You heat the tube, but not too much, lest it become -deformed; a <i>reddish-brown</i> heat is sufficient, -for at that temperature it gives way to -the slightest effort you make to bend it. You -should, as much as possible, avoid making the -bend too abrupt. For this purpose, you heat -a zone of one or two inches in extent at once, -by moving the tube backwards and forwards in -the flame, and you take care to bend it very -gradually.</p> - -<p>But if the tube is large, or its sides are thin, -and you bend it without proper precautions, -the force you employ entirely destroys its cylindrical -form, and the bent part exhibits nothing -but a double flattening,—a canal, more or less -compressed. To avoid this deformity it is -necessary, first, to seal the tube at one extremity, -and then, while giving it a certain -curvature, to blow cautiously by the other extremity, -which for convenience sake should previously -be drawn out. When tubes have been -deformed by bad bending, as above described, -you may, by following this method, correct the -fault; that is to say, upon sealing one extremity -<span class="pagenum" id="Page_49">49</span> -of the deformed tube, heating the flattened -part, and blowing into the other extremity, -you can with care reproduce the round form.</p> - -<p>In general, that a curvature may be well-made, -it is necessary that the side of the tube -which is to form the concave part be sufficiently -softened by heat to sink of itself equally in -every part during the operation, while the other -side be only softened to such a degree as to -enable it to give way under the force applied to -bend it. On this account, after having softened -in a <i>cherry-red heat</i> one side of the tube, you -should turn the other side, which is to form the -exterior of the curvature, towards you, and -then, exposing it to the point of the jet, you -should bend the tube immediately upon its beginning -to sink under the heat.</p> - -<p>When you desire to bend the extremity of a -tube into a ring you must employ a metallic -rod, with which, by pressing on the tube, you -separate with a curve, C, (see <a href="#pl_1">pl. 1</a>, fig. 14) all -the portion A C which is necessary to produce -the desired curl. You then successively soften -all parts of this curve, and gradually twist it in -the direction indicated by the arrow, pressing -the iron rod constantly upon the extremity of -the curve. When the end A comes into contact -with bend C you solder them together -at this point, and thus complete the ring. -<a href="#pl_2">Pl. 2</a>, fig. 27, and <a href="#pl_3">pl. 3</a>, fig. 27, exhibit examples -of rings formed by this process.</p> - -<h3 id="SOLDERING">10.—<small>SOLDERING.</small></h3> - -<p>If the tubes which you propose to solder -<span class="pagenum" id="Page_50">50</span> -are of a small diameter, pretty equal in size, -and have thick sides, it is sufficient, before -joining them together, to widen them equally at -their extremities, by agitating a metallic rod -within them. (<a href="#pl_1">Pl. 1</a>, fig. 17.)</p> - -<p>But if they have thin sides, or are of a large -diameter, the bringing of their sides into juxta-position -is very difficult, and the method of -soldering just indicated becomes insufficient. -In this case you are obliged to seal, and subsequently -to pierce, the two ends which you -desire to join. The disposition which this operation -gives to their sides very much facilitates -the soldering.</p> - -<p>Finally, when the tubes are of a very different -diameter, you must draw out the extremity -of the larger and cut it where the part -drawn out corresponds in diameter to the tube -which it is to be joined to. <a href="#pl_1">Pl. 1</a>, fig. 9 and -15, exhibit examples of this mode of adapting -tubes to one another.</p> - -<p>For lateral solderings you must dispose the -tubes in such a manner that the sides of the -orifices which you desire to join together coincide -with each other completely. See <a href="#pl_1">pl. 1</a>, -fig. 7.</p> - -<p>When the holes are well prepared, you heat -at the same time the two parts that are to be -soldered together, and join them at the moment -when they enter into fusion. You must -push them slightly together, and continue to -heat successively all their points of contact; -whereupon the two tubes soon unite perfectly. -As it is almost always necessary, when you desire -<span class="pagenum" id="Page_51">51</span> -the soldering to be neatly done, or the joint -to be imperceptible, to terminate the operation -by blowing, it is proper to prepare the extreme -ends of the tubes before-hand. That -end of the tube by which you intend to blow -should be carefully drawn out, provided it be -so large as to render drawing out necessary; -and the other end of the tube, if large, should -be closed with wax, as in <a href="#pl_1">pl. 1</a>, fig. 9, or if -small, should be sealed at the lamp (<a href="#pl_1">pl. 1</a>, -fig. 15). When the points of junction are perfectly -softened, and completely incorporated -with each other, you introduce a little air into -the tube, which produces a swelling at the -joint. As soon as this has taken place, you -must gently pull the two ends of the joined -tube in different directions, by which means -the swelled portion at the joint is brought down -to the size of the other parts of the tube, so that -the whole surface becomes continuous. The -soldering is then finished.</p> - -<p>To solder a bulb or a cylinder between two -points, to the extremity of a capillary tube, you -cut and seal one of the points at a short distance -from the bulb (<a href="#pl_1">pl. 1</a>, fig. 16), and at the -moment when this extremity is in fusion you -pierce it by blowing strongly at the other extremity. -By this means the opening of the -reservoir is terminated by edges very much -widened, which facilitates considerably its being -brought into juxta-position with the little -tube. In order that the ends of the two tubes -may be well incorporated the one with the -<span class="pagenum" id="Page_52">52</span> -other, you should keep the soldered joint for -some time in the flame, and ought to blow in -the tube, push the ends together and draw them -asunder, until the protuberance is no longer -perceptible.</p> - -<p>If, after having joined two tubes, it should -be found that there still exists an opening -too considerable to be closed by simply -pushing the two tubes upon one another, you -can close such an opening by means of a -morsel of glass, applied by presenting the fused -end of an auxiliary tube.</p> - -<p>You should avoid soldering together two -different species of glass—for example, a tube -of ordinary glass with a tube of flint-glass; -because these two species of glass experience -a different degree of contraction upon cooling, -and, if joined together while in a fused state, -are so violently pulled from one another as they -become cool, that the cohesion of the point of -soldering is infallibly overcome, and the tube -breaks. You ought also, for a similar reason, -to take care not to accumulate a greater mass -of glass in one place than in another.</p> - -<p>If the first operation has not been sufficient -to complete the soldering, the tube must be -again presented to the flame, and again pushed -together at the joint, or drawn asunder, or blown -into, according as it may appear to be necessary. -In all cases the soldering is not truly -solid, but inasmuch as the two masses of -glass are well incorporated together, and present -a surface continuous in all points. -<span class="pagenum" id="Page_53">53</span></p> - -<p>The mineralogical flame (<a href="#pl_1">pl. 1</a>, fig. 1, A´ B) -is that which is to be employed in preference to -the larger flame, when you desire to effect a -good joining: it is sufficient to proportion the -size of the flame to the object you wish to -execute. -<span class="pagenum" id="Page_54">54</span></p> - -<hr class="chap" /> - -<h2><small>THE</small><br /> - -<span class="xx-large">ART OF GLASS-BLOWING.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span id="IV">IV.—<i>Construction of Chemical and Philosophical -Instruments.</i></span></h2> - -<hr class="tb" /> - -<p>When a person is well acquainted with the -fundamental operations which we have just -described, the preparation of the instruments -of which we are about to speak can present -scarcely any difficulty. Indeed, some of them -are so extremely simple, and are so easy of -execution, that it is sufficient to cast a glance -upon the figures which represent them, to seize -at once the method which must be followed in -their construction. Of such instruments we -shall not stop to give a detailed description, -but shall content ourselves with presenting the -design.</p> - -<p>On the other hand, it is of importance to observe -that a certain number of instruments are -<i>graduated</i> or furnished with pieces, or <i>mountings</i>, -of which it is not the object of our art to -teach the construction, and which demand a -more or less extensive knowledge of the sciences. -<span class="pagenum" id="Page_55">55</span> -We shall treat of these mountings but -summarily, referring the student, for more detailed -instructions, to the works on natural philosophy -and chemistry, in which these instruments -are especially treated of. Our reason -for this is, that we do not wish to abandon the -plan we had adopted of describing simply the -art of glass-blowing. To describe the use and -application of philosophical instruments, or to -explain the principles on which they act, would -be passing quite out of our province.</p> - -<hr class="tb" /> - -<p><span id="ADAPTERS" class="smcap">Adapters.</span>—These are tubes of glass of various -forms, employed in chemistry to connect -together the different pieces constituting an -apparatus—as, for example, to join a retort to -a receiver during the operation of distillation. -You should take care to border the extremities -of an adapter; or you may widen them into -the form of the mouth of a bottle, when they -are to be closed air-tight by corks. Besides this, -there is nothing particular to be observed in -the preparation of adapters.</p> - -<hr class="tb" /> - -<p><span id="APPARATUS_FOR_VARIOUS_INSTRUMENTS" class="smcap">Apparatus for Boiling in Vacuo.</span>—Represented -by <a href="#pl_3">pl. 3</a>, fig. 19. Employ a tube about -a quarter of an inch in diameter. Blow two -bulbs; give the tube the necessary curvature; -fill one of the bulbs with nitric ether; boil the -ether to expel the atmospheric air from the apparatus, -then seal the opening in the other bulb.</p> - -<hr class="tb" /> - -<p><span id="CRYOPHORUS" class="smcap">Apparatus for Freezing in Vacuo.</span> <i>The -Cryophorus.</i>—Take a tube one-third of an inch -or rather more in diameter, and pretty thick in -<span class="pagenum" id="Page_56">56</span> -the sides. Blow a bulb at each end; the first -at the sealed part of the tube, the other at the -open point; then give to the tube the curvature -represented by <a href="#pl_3">pl. 3</a>, fig. 32. Introduce as -much water as will half fill one of the bulbs; -make the water boil, and draw off the point -and seal the apparatus during the ebullition.</p> - -<hr class="tb" /> - -<p><span id="APPARATUS_FOR_CONDUCTING_WATER_IN_BENT_TUBES" class="smcap">Apparatus for conducting Water in bent -Tubes.</span>—Solder a funnel (see <span class="smcap">Funnels</span>) to the -end of a tube; pierce two holes in this tube in -the same line, and solder to each a little addition -proper to receive a cork. Finish the instrument -by bending it in the manner indicated by -<a href="#pl_4">pl. 4</a>, fig. 18.</p> - -<hr class="tb" /> - -<p><span class="smcap">Apparatus for Experiments on Running -Liquids.</span>—A tube bent once at a right angle, -mounted with a funnel, pierced laterally, and -soldered at the same point to a smaller tube. -See <a href="#pl_3">pl. 3</a>, fig. 17.</p> - -<hr class="tb" /> - -<p><span class="smcap">Apparatus for Exhibiting the Phenomena -of Capillary Tubes.</span>—This apparatus consists -of a capillary tube soldered to another tube of -a more considerable diameter. Sometimes it is -bent like the letter U. <a href="#pl_3">Pl. 3</a>, fig. 15.</p> - -<hr class="tb" /> - -<p><span class="smcap">Apparatus for the Preparation of Phosphuret -of Lime.</span>—An apparatus that can be -employed for the preparation of phosphuret of -lime, as well as in a variety of other chemical -experiments, consists of a tube sealed at one -extremity, slightly bent and choked at two -<span class="pagenum" id="Page_57">57</span> -inches and a half from the sealed part, and -drawn out (after the introduction of the substances -to be operated upon) at the other extremity. -This little distillatory apparatus is -represented by <a href="#pl_3">pl. 3</a>, fig. 29.</p> - -<hr class="tb" /> - -<p><span id="ARCHIMEDESS_SCREW" class="smcap">Archimedes’s Screw.</span>—There is no particular -process for the making of this instrument. -It is, however, necessary for one who would -succeed in making it, to exercise himself in -the art of well bending a tube. After a few -attempts, you may finish by producing a pretty-regular -spiral. The tube chosen for this instrument -should be six or seven feet long, and -about one-third of an inch in diameter. You -commence by making a bend, nearly at a right -angle, about four inches from one of its extremities. -This bent portion serves afterwards -as a handle, and very much facilitates the -operation; it represents the prolongation of -the rational axis which may be conceived to -pass through the centre of the spiral. See -<a href="#pl_4">pl. 4</a>, fig. 10.</p> - -<hr class="tb" /> - -<p><span id="BARKERS_MILL" class="smcap">Barker’s Mill.</span>—<i>Apparatus for exhibiting -the rotatory motion produced by the running -of liquids.</i>—Contract a tube at its two extremities, -pierce it laterally about the middle of -its length, and solder to the hole an additional -tube, terminated by a funnel. Soften the principal -tube at the side opposite to the part that -was pierced, and form there a conical cavity -by pressing the softened glass inward with the -<span class="pagenum" id="Page_58">58</span> -aid of a metallic rod. This cavity must be so -carefully made that the whole apparatus can be -supported on a pivot. Bend the contracted -ends of the tube horizontally, and in different -directions, cut off their extremities at a proper -length, and slightly border the edges of the -orifices. See <a href="#pl_3">pl. 3</a>, fig. 33.</p> - -<p>You may produce this apparatus under a -different form, as may be seen at <a href="#pl_3">pl. 3</a>, fig. 5.</p> - -<hr class="tb" /> - -<p><span id="BAROMETERS" class="smcap">Barometers.</span>—Barometers serve to measure -the pressure of the atmosphere. The following -are the varieties most in use.</p> - -<hr class="tb" /> - -<p><span id="CISTERN_BAROMETER" class="smcap">Cistern Barometer.</span>—Take a tube about -thirty-two inches long, and at least one-third of -an inch in diameter, internally; seal one of its -extremities, free it with most particular care -from moisture, fill it with mercury, and make -the mercury boil in the tube, by heat, in order -to drive out every particle of air which might -be present. When the tube is full of mercury, -and the boiling has taken place, turn it upside -down, and plunge the open end into a cistern -also filled with mercury which has been boiled. -See <a href="#pl_2">pl. 2</a>, fig. 4.</p> - -<hr class="tb" /> - -<p><span id="DIAL_BAROMETER" class="smcap">Dial</span> (or <span class="smcap">Wheel</span>) <span class="smcap">Barometer.</span>—The tube -intended for this barometer should be very regular -in the bore. It should be thirty-nine -inches long. Close it at one end, and bend it -like the letter U at about thirty-two inches from -the sealed extremity. See <a href="#pl_2">pl. 2</a>, fig. 5, and -<i>Graduation of the Dial Barometer</i>. -<span class="pagenum" id="Page_59">59</span></p> - -<hr class="tb" /> - -<p><span id="SYPHON_BAROMETER" class="smcap">Syphon Barometer.</span>—Make use of such a -tube as might be employed for a <i>Cistern Barometer</i>; -solder to its open end a cylindrical -or spherical reservoir, and bend the tube close -to the point of junction in such a manner as to -bring the cylinder parallel with the tube. If -the reservoir is to be closed with a cover of -leather, cut off the remaining point of the cylinder, -slightly widen the orifice, and then -border it. If no leather is to be applied, but -the point of the cylinder left open, it is necessary, -after the introduction of the mercury, to -draw off the point abruptly, and to leave an -opening so small that mercury cannot pass by -it. <a href="#pl_2">Pl. 2</a>, fig. 6.</p> - -<hr class="tb" /> - -<p><span id="STOP_COCK_BAROMETER" class="smcap">Stop-Cock Barometer.</span>—This differs from -the preceding barometer only by having a stop-cock -mounted in iron between the reservoir -and the tube.</p> - -<hr class="tb" /> - -<p><span id="COMPOUND_BAROMETERS" class="smcap">Compound Barometers.</span>—Blow a bulb at -each end of a barometer tube of about thirty-three -inches in length. Solder a small and -almost capillary tube to the point which terminates -one of the bulbs, and bend the great -tube very near this bulb. This must be done -in such a manner that the centre of one bulb -shall be thirty inches from the centre of the -other bulb. Introduce a quantity of mercury -sufficient to fill the great tube and half the two -bulbs; fill the remaining space in the last bulb -with alcohol.</p> - -<p>You may give a different disposition to this -<span class="pagenum" id="Page_60">60</span> -instrument. Divide a barometer tube into -two, three, or four pieces, and reunite the -pieces by intermediate capillary tubes, so as to -form a series of large and small tubes, soldered -alternately the one at the end of the other. -Then communicate to this compound tube the -form exhibited by <a href="#pl_3">pl. 3</a>, fig. 25, and join, at -each superior bend, a little tube, for the convenience -of easily filling the instrument with -mercury: seal these tubes as soon as the mercury -is introduced. The graduation of compound -barometers is made by bringing them -into comparison with a good standard barometer. -After taking two or three fixed points, -it is easy to continue the scale.</p> - -<hr class="tb" /> - -<p><span id="GAY_LUSSACS_BAROMETER" class="smcap">Gay Lussac’s Barometer.</span>—Take a tube -which is very regular in the bore, four-tenths -of an inch in diameter, and thirty-five inches -and a half in length. Seal one of its extremities -and draw out the other; then cut the tube -at about two-thirds of its whole length from the -sealed end, and reunite the two pieces by -means of a capillary tube soldered between -them, the whole being kept in a line. See -<a href="#pl_2">pl. 2</a>, fig. 1. Pierce laterally the part of the -tube which is drawn out, at some inches from -the base of the point, and force the margin of -the hole into the interior of the tube, by means -of a conical point of metal, in such a manner as -to form a little sunk funnel, of which the orifice -must be very small. After having introduced -the proper quantity of mercury into the -instrument, boil it, and assist the disengagement -<span class="pagenum" id="Page_61">61</span> -of the bubbles of air by agitating a fine -iron wire within the tube. Then remove the -part of the tube which was drawn out, by -sealing the end of the wide part. Give to the -whole instrument the curvature indicated by -<a href="#pl_2">pl. 2</a>, fig. 3.</p> - -<hr class="tb" /> - -<p><span id="BUNTENS_BAROMETER" class="smcap">Bunten’s Barometer.</span>—This instrument differs -from the preceding but in one point, -namely, that the capillary tube is formed of -two soldered pieces, of which the one, passing -into the other, is terminated by a capillary -point. This arrangement is exhibited by <a href="#pl_2">pl. 2</a>, -fig. 2.</p> - -<hr class="tb" /> - -<p><span id="BAROMETER_PIERCED_LATERALLY_FOR_DEMONSTRATIONS" class="smcap">Barometer pierced laterally for Demonstrations.</span>—Take -a tube thirty-nine inches -long, with thick sides, and two-tenths of an -inch internal diameter. Seal it at one end, -and choke it at the distance of eight inches -therefrom. Pierce a hole in the tube about -twelve or sixteen inches from the choked part, -and solder to the hole an additional piece, -which can be closed by a cork or covered by -a piece of bladder. The instrument is represented -by <a href="#pl_2">pl. 2</a>, fig. 15.</p> - -<hr class="tb" /> - -<p><span id="BELL_GLASSES_FOR_EXPERIMENTS" class="smcap">Bell-Glasses for Experiments.</span>—These -are pieces of tube sealed at one end, and -widened or bordered at the other. They are -extremely useful, and much employed in chemical -experiments. They also supply the -place of bottles for preserving small quantities -of substances. Sometimes they are required -<span class="pagenum" id="Page_62">62</span> -to be straight, as <a href="#pl_3">pl. 3</a>, fig. 12. Sometimes -they need to be curved, as <a href="#pl_3">pl. 3</a>, fig. 29. This -is particularly the case when they are to be -employed as retorts, for which purpose the -sealed part should be made thin. <a href="#pl_3">Pl. 3</a>, fig. 6, -exhibits a retort with a tubulure.</p> - -<hr class="tb" /> - -<p><span id="BLOWPIPE" class="smcap">Blowpipe.</span>—We shall give in this article an -account of the various pieces of glass which -form part of the blowpipe described in the -early part of this work. See <a href="#pl_1">pl. 1</a>, fig. 19.</p> - -<p>The beak C, which is employed with the -candlestick, is merely a bent tube, at the extremity -of which a bulb is blown. The bulb is -terminated by a point, the thickness of the -sides of which is augmented by turning it for a -long time in the flame.</p> - -<p>As for the beak used with the lamp, it is -simply a bent tube C´, of which the orifice has -been diminished by turning it round in the flame. -The point of this beak is not drawn out like -that of the beak described in the preceding paragraph, -but is allowed to be thick, that it may -not melt in the flame of the lamp.</p> - -<p>The tube D F has four-tenths of an inch internal -diameter, and is pretty thick in the sides. -You must commence by bordering and slightly -widening one of its extremities, and then proceed -to choke it at about two inches from its -other extremity, taking care to give to the -choked part a figure as perfectly conical as -possible, in order that the valve may act well. -We have described the valve at length at p. 6.</p> - -<p>The tube <i>d</i> is as much narrower than the -<span class="pagenum" id="Page_63">63</span> -tube D F as is necessary to permit it to pass up -and down within the latter. Its use is to -lengthen or shorten the tube for the convenience -of the blower. The lower end is wound -round with waxed thread, to make it fit air-tight. -The mouth-piece is executed by widening -the end of the tube, and then, while the -widened part is still soft, by pressing the two -sides obliquely, one against the other. By this -means you give to the mouth-piece a flattened -form, which adapts it better to the lips. The -tube is finished by slightly bending this extremity.</p> - -<p>In order that the bladder, or air reservoir, -may be conveniently and securely attached to -the tube E, you must take care to widen the -end of this tube, and to turn up the edges -strongly, by pressing the soft end against a -flat metallic surface.</p> - -<hr class="tb" /> - -<p><span id="CAPSULES" class="smcap">Capsules.</span>—These are very small mercury -funnels, of which the opening or neck has been -closed. To transform these funnels into capsules, -you must cut the neck as close as possible, -and then soften, close, and flatten the -opening. In performing this operation, hold -the capsule by the edge with your pincers, and -employ a piece of metal to press the glass together -and make it close the hole and form -the flat bottom of the capsule. See <a href="#pl_2">pl. 2</a>, -fig. 23.</p> - -<p><i>Another Method.</i>—After having blown a -bulb at the end of a point, soften a narrow -<span class="pagenum" id="Page_64">64</span> -zone of the bulb, and then blow suddenly and -strongly into it; by which means you separate -the bulb into two capsules, which only need to -be bordered. If you find any difficulty in presenting -to the flame the capsule which forms -the part of the bulb opposed to the point, you -can attach to it a little rod of glass, which you -can afterwards easily separate by a slight -smart blow.</p> - -<p>Occasionally you will have to make <i>capsules -with double sides</i>, which will be described at -the article <i>Nicholson’s Hydrometer</i>.</p> - -<hr class="tb" /> - -<p><span id="CARTESIAN_DEVILS" class="smcap">Cartesian Devils.</span>—Blow a bulb at the -extremity of a very small tube, and heat a portion -of the bulb, for the purpose of prolonging -it into a beak. This can be effected with the -aid of an auxiliary tube, which, on being joined -to the heated part of the bulb, carries away -with it the portion of glass which adheres. -This portion of the bulb becomes thus prolonged -into a little point, which must be cut at -its extremity, so as to leave a small opening. -The principal tube must be cut at the distance -of half an inch from the bulb, and the ends of -it must be drawn out and twisted into a ring. -Instead of forming laterally a little beak to the -bulb, you may pierce the tail, after twisting it -into the form of a ring, or you may manage in -such a manner as not to obliterate the canal of -the twisted part. In general, little enamel -figures are suspended to the ring of these -globes, as is represented by <a href="#pl_2">pl. 2</a>, fig. 22. A -<span class="pagenum" id="Page_65">65</span> -simple bulb, blown at the extremity of a small -portion of tube, can supply the place of the -Ludion or Cartesian devil. See <a href="#pl_2">pl. 2</a>, fig. 8.</p> - -<hr class="tb" /> - -<p><span id="COMMUNICATING_VASES" class="smcap">Communicating Vases.</span>—Employ a tube of -a large diameter; terminate one of its extremities -with a funnel, fashion the other like -the neck of a bottle; and bend the tube into -the shape shewn by <a href="#pl_4">pl. 4</a>, fig. 11. Then twist -some other tubes into various forms, according -to the end you propose to attain, and adjust -these tubes to the neck of the large tube by -means of corks, which have holes bored -through them. In this manner an exchange of -tubes is provided for various experiments.</p> - -<hr class="tb" /> - -<p><span id="DROPPING_TUBES" class="smcap">Dropping Tubes.</span>—The name <i>dropping tube</i> -is given to an instrument of glass which is very -much employed in chemistry, for the purpose -of transferring small quantities of liquor from -one vessel into another, without disturbing either -of the vessels. Dropping tubes are made of -a great variety of forms and sizes, according to -the purposes to which they are intended to -be applied.</p> - -<p>Blow a bulb between two points, and then, -before the glass has regained its consistence, -lengthen the bulb into an oval form. Cut and -border the two points.</p> - -<p>If the bulb, or reservoir, is to be so large -that it cannot be formed at the expense of the -thickness of the tube, and yet be sufficiently -strong, it must be blown separately from a -larger tube, and then soldered to two smaller -<span class="pagenum" id="Page_66">66</span> -tubes, one of which should have a certain curvature -given to it. See <a href="#pl_2">pl. 2</a>, fig. 20.</p> - -<p>Sometimes a dropping tube is employed to -measure small quantities of liquid. In this -case the point should be drawn off abruptly, -and the scale should be marked on the shank -or tube with spots of black enamel.</p> - -<p><a href="#pl_2">Pl. 2</a>, fig. 21, represents a peculiar variety -of dropping tube employed in some experiments. -It is made in the same manner as the -common dropping tubes, excepting that, when -the tail is formed, it is sealed at the extremity, -bent there into a ring, and then pierced at A.</p> - -<p><a href="#pl_3">Pl. 3</a>, fig. 26, represents another variety of -dropping tube, a description of which is unnecessary.</p> - -<hr class="tb" /> - -<p><span id="FOUNTAINS" class="smcap">Fountains.</span>—It will readily be understood -by those acquainted with the construction of -hydraulic apparatus, that, by means of a judicious -arrangement of glass tubes, a great variety -of fountains may be produced. The following -are given as examples.</p> - -<hr class="tb" /> - -<p><span id="FOUNTAIN_OF_CIRCULATION" class="smcap">Fountain of Circulation.</span>—Take a tube, -twenty-four or thirty inches long, nearly half an -inch in diameter, and with pretty thick sides; -blow a bulb at one of its extremities, and bend -the other into a U, after having drawn it out as -indicated by <a href="#pl_3">pl. 3</a>, fig. 4. Pierce the tube at -B, and join there a short piece adapted to receive -a cork. Then prepare a bulb of the -same size as the first bulb, and solder it to the -extremity of a very long and almost capillary -<span class="pagenum" id="Page_67">67</span> -tube, which you must bend in zig-zag, in such -a manner as to make it represent a Maltese -cross, a star, a rose, or any other figure that -may be suggested. The side of the bulb opposite -to that which is attached to this twisted -tube, ought to be formed like the neck of a -bottle, in order that it may receive the drawn-out -part of the larger tube, which should enter -the bulb until the point of the large tube nearly -touches the neck of the little tube at its junction -with the bulb. This disposition is shewn -in the figure. Seal now the other end of the -little tube to the bulb of the large tube; then, -with a little cement or sealing-wax, close the -space between the bulb of the little tube and -the point of the large tube. The instrument -being thus prepared, as much alcohol, previously -coloured red, must be inserted by the -neck <i>b</i> as is sufficient to fill one of the bulbs. -The neck is then closed with a cork, and a little -cement or sealing-wax. Or, instead of forming -this neck to the instrument, the additional -piece may be drawn out to a point, which permits -it to be sealed hermetically.</p> - -<hr class="tb" /> - -<p><span id="FOUNTAIN_OF_COMPRESSION" class="smcap">Fountain of Compression.</span>—Introduce into -a tube of large diameter a piece of capillary -tube with thick sides. This must pass a little -beyond the extremity of the large tube, which -is to be softened and soldered to the other, so -that it shall be fixed concentrically. The common -point is then to be drawn out. When the -tube is quite cold, and the small tube properly -fixed in the centre of the large one, cut the -<span class="pagenum" id="Page_68">68</span> -latter at a proper distance, border it, and choke -it near the end, which must be fashioned in -such a manner as to be capable of being completely -closed by a cork. See <a href="#pl_2">pl. 2</a>, fig. 29.</p> - -<hr class="tb" /> - -<p><span id="INTERMITTING_FOUNTAIN" class="smcap">Intermitting Fountain.</span>—This apparatus is -represented by <a href="#pl_3">pl. 3</a>, fig. 16. Solder a cylindrical -reservoir to the extremity of a capillary -tube, pierced at <i>a</i>, and sealed at its extremity. -Draw out abruptly the point of the reservoir, -and give it a very small orifice; then give to -the capillary tube the form indicated by the -figure. Prepare next a funnel resembling a -mercury-funnel, but much larger; choke the -neck of this funnel, and bend the tube into the -form of a syphon.</p> - -<hr class="tb" /> - -<p><span id="HEROS_FOUNTAIN" class="smcap">Hero’s Fountain.</span>—Solder a bulb to the extremity -of a tube, and transform the bulb into -a funnel. Close the funnel with a cork, and -solder to the other end of the tube a bulb similar -to the first. Next, solder a third bulb between -two tubes, of which one must be twice -as long the other; solder the longer of these -tubes to the bulb of the first tube, and draw -out the point of the shorter tube. You have -now a long tube, with a funnel at one end, a -contracted point at the other, and two bulbs in -its length. Give to the whole apparatus the -form indicated by <a href="#pl_3">pl. 3</a>, fig. 21.</p> - -<hr class="tb" /> - -<p><span id="FUNNELS" class="smcap">Funnels.</span>—It will be seen, upon looking -over the engravings, that funnels require to be -made for a great variety of instruments; you -<span class="pagenum" id="Page_69">69</span> -ought therefore to acquire as soon as possible -the art of making them well. The following -are those most frequently required.</p> - -<hr class="tb" /> - -<p><span id="RETORT_FUNNEL" class="smcap">Retort Funnel.</span>—Blow a bulb at the extremity -of a tube; present the superior hemisphere -of the bulb to the flame, and when it is -sufficiently softened, blow strongly into the -other end of the tube. The air will force its -way through the bulb, making a hole which -will be larger or smaller according to the extent -of surface which may have been softened. -The opening of the funnel being made thus, -there is nothing more to do than to adjust the -edges, which, in the present state, are both -fragile and irregular. This it is very easy to -do. The edges are softened, the most prominent -parts are cut off with the scissars, and the -parts which are thin are bent back on themselves, -that they may become thicker. Upon -turning the funnel round in the flame, the -smaller irregularities give way, and the edges -become rounded. See <a href="#pl_2">pl. 2</a>, fig. 24.</p> - -<p>When the funnel is desired to be very large -in proportion to the size of the tube, a bulb is -made from a larger tube, and afterwards soldered -to the small tube, and transformed into a -funnel in the manner above described.</p> - -<hr class="tb" /> - -<p><span id="FUNNEL_FOR_INTRODUCING_MERCURY_INTO_NARROW_TUBES" class="smcap">Funnel for introducing Mercury into -narrow tubes.</span>—The mercury-funnel is represented -by <a href="#pl_2">pl. 2</a>, fig. 25. Blow a bulb between -two points; cut off one of the points, and -<span class="pagenum" id="Page_70">70</span> -open the bulb at that place, in the manner described -in the preceding article.</p> - -<hr class="tb" /> - -<p><span id="HYDROSTATIC_FUNNEL" class="smcap">Hydrostatic Funnel.</span>—This is represented -by <a href="#pl_3">pl. 3</a>, fig. 31. It is an instrument of constant -use in chemical experiments. Form a -funnel at the extremity of a tube in the manner -described above, having previously blown a -bulb near the middle of the tube. When this -has been done, bend the tube into the form -shown by the figure.</p> - -<hr class="tb" /> - -<p><span id="HOUR_GLASSES" class="smcap">Hour-Glasses.</span>—Blow four bulbs on a tube -close to each other; open the two end bulbs -like funnels, and then form them into flat supports -or pedestals, according to the method -described at the article <i>Test-glass with a foot</i>. -Obstruct entirely the canal which separates -one of these feet; choke to a certain extent the -passage between the two remaining bulbs; -and close the canal between the other foot and -the bulbs, after introducing the quantity of sand -which you have found to be necessary. See -<a href="#pl_3">pl. 3</a>, fig. 13.</p> - -<hr class="tb" /> - -<p><span id="HYDRAULIC_RAM" class="smcap">Hydraulic Ram.</span>—This instrument is represented -by <a href="#pl_4">pl. 4</a>, fig. 15. Employ a tube about -six feet long, with thick sides and of large -diameter. Seal it at one extremity, <i>k</i>, and -border it at the other; solder at <i>p</i> an additional -piece, choked so as to receive a valve. -Pierce the tube at <i>l</i>; draw it out, and fix a -funnel there; then twist the tube into a spiral. -<span class="pagenum" id="Page_71">71</span> -Form, on the other hand, a fountain of compression, -<i>o</i>, and a funnel, <i>m</i>; and fix both of -these pieces by means of sealing-wax, as soon -as the two valves <i>p</i> and <i>l</i> have been put into -their places.</p> - -<hr class="tb" /> - -<p><span id="HYDROMETERS" class="smcap">Hydrometers.</span>—<i>Hydrometers</i> are instruments -which, on being plunged into liquids, -indicate immediately their density or specific -gravity. <span id="AREOMETERS"><i>Areometers</i></span> differ from hydrometers -sometimes in graduation, sometimes merely in -name. The following are examples of hydrometers, -of which a great many varieties are in use.</p> - -<hr class="tb" /> - -<p><span id="BAUMÉS_HYDROMETER" class="smcap">Baumé’s Hydrometer.</span>—Make a cylinder -between two points, and solder it to the extremity -of a tube with thin sides, and which must -be very regular on the outside. Close the -open part which is to form the stalk of the -hydrometer with a little wax. See <a href="#pl_1">pl. 1</a>, fig. -9 and 15. When the soldering, which must -be well done, is complete, and the stalk well -centered, choke the reservoir at a little distance -from the base of the point, by drawing it out -in such a manner as considerably to diminish -the canal in this part. Remove then the ball -of wax which closed the tube, draw off the -point of the cylinder, and make the part which -was pulled away from the cylinder by the -choking, into a bulb, by blowing with precaution -into the tube. If the reservoir is required -to be spherical instead of cylindrical, it must -be softened and expanded by blowing. When -it is intended to ballast the instrument with -<span class="pagenum" id="Page_72">72</span> -mercury, the canal must be completely stopped -at the point where it is choked. In this case, -the part drawn away from the cylinder is expanded -into a bulb by blowing through the -extreme point, which is to be cut off after the -instrument is completed.</p> - -<p>In the first case, you ballast the instrument -with lead shot, which you fix in the lower bulb -by means of a little wax, which closes the -canal at the choked part. In the second case, -after having proved the ballast by putting it -first into the large reservoir, it is removed into -the little bulb, and the latter is immediately -sealed.</p> - -<p>One of the essential conditions of a good -hydrometer is that the stalk should keep a perfectly -vertical position when the instrument is -plunged in water. If, therefore, on proving -the ballast, you perceive the stalk to rest obliquely, -you must take care, on retiring it from -the water, to wipe it dry, and to present the -choked part between the cylinder and the little -bulb to the flame; when it is softened, it is -easy, by giving it a slight bend in the direction -where the stalk of the hydrometer passes from -the vertical, to rectify the defect.</p> - -<p>Finally, when the instrument is ballasted, -you must seal the stalk, after having fixed in its -interior the strip of paper which bears the graduated -division.</p> - -<p>This method of operation serves equally for -all the areometers known under the names of -<i>areometer of Baumé</i>, <i>pèse-sels</i>, <i>pèse-liqueurs</i>, -<i>pèse-acides</i>, and <i>hydrometers</i>, which differ only -<span class="pagenum" id="Page_73">73</span> -in the scheme of their graduation. As to the -<i>size</i> and the <i>length</i> of the stalks, they depend -upon the <i>dimensions</i> you desire to give to the -degrees of the scale, and upon the <i>use</i> to which -the instruments are destined. For the areometer -of Baumé, and for the <i>pèse-sels</i>, the stalks -are generally thicker and shorter than for hydrometers. -<a href="#pl_4">Pl. 4</a>, fig. 19, 20, and 21, represent -different hydrometers.</p> - -<hr class="tb" /> - -<p><span id="NICHOLSONS_HYDROMETER" class="smcap">Nicholson’s Hydrometer.</span>—Solder a bulb -to the extremity of a capillary tube; open it so -as to form a very wide funnel, or rather capsule; -border the edges, and melt the point of junction -with the tube so as to close the opening of -the latter. Solder the other extremity of the -tube to a cylindrical reservoir. Soften the -point at the lower extremity of the cylinder, -and obstruct the canal so as to convert the point -into a glass rod; bend this rod into a hook. -Now blow a bulb at the end of a point, as if -to make a mercury funnel; but, after having -softened the hemisphere of the bulb opposite to -the point, and placed the latter in the mouth, -instead of blowing into the bulb so as to make -a funnel, strongly suck air from the bulb: by -this means the softened part of the glass is -drawn inwards, and you obtain a capsule with -double sides, as exhibited by <a href="#pl_2">pl. 2</a>, fig. 17. -This capsule must have a small handle fastened -across it, by which it may be hung to the -hook formed at the bottom of the cylinder described -above.</p> - -<p>This hydrometer being always brought to -<span class="pagenum" id="Page_74">74</span> -the same level, the point to which it must be -sunk in the liquid experimented with, is marked -on the stalk by applying a little spot of black -enamel. The instrument is represented by -<a href="#pl_4">pl. 4</a>, fig. 23. A variation in form is shewn -by <a href="#pl_4">pl. 4</a>, fig. 22.</p> - -<hr class="tb" /> - -<p><span id="HYDROMETER_WITH_TWO_BRANCHES" class="smcap">Hydrometer with two Branches.</span>—To -measure the relative density of two liquids -which have no action on each other, you employ -a simple tube, bent in the middle and widened -at its two extremities. See <a href="#pl_2">pl. 2</a>, fig. 11.</p> - -<hr class="tb" /> - -<p><span id="HYDROMETER_WITH_THREE_BRANCHES" class="smcap">Hydrometer with three Branches.</span>—This -consists of a tube bent in such a manner that -the two branches become parallel. To this tube -another is soldered at the point of curvature, -and is bent in the direction exhibited by <a href="#pl_2">pl. 2</a>, -fig. 12. When the two branches are put into -different liquids, and the operator sucks air -from the third branch, the two liquids rise in -their respective tubes to heights which are -in the inverse ratio of their specific gravities.</p> - -<hr class="tb" /> - -<p><span id="HYDROMETER_WITH_FOUR_BRANCHES" class="smcap">Hydrometer with four Branches.</span>—This -is merely a tube bent three times, and widened -at its extremities. <a href="#pl_2">Pl. 2</a>, fig. 13.</p> - -<p>To graduate hydrometers with two, three, -and four branches, you have to divide their -tubes into a certain number of equal parts.</p> - -<hr class="tb" /> - -<p><span id="MANOMETERS" class="smcap">Manometers.</span>—Make choice of a tube nearly -capillary, very regular in the bore, and with -<span class="pagenum" id="Page_75">75</span> -sides more or less thick, according to the degree -of pressure which it is to support. Seal this -tube at one end, blow a bulb with thick sides -near the middle, and curl it in S, just as is represented -by <a href="#pl_2">pl. 2</a>, fig. 9. For manometers -which serve to measure the elasticity of the -air under the receiver of the air-pump, what -is generally employed is a tube closed at one -end and bent into a U. <a href="#pl_2">Pl. 2</a>, fig. 10. You -should take care to contract these at some distance -from the sealed part, in order to avoid -the breaking of the instrument on the sudden -admission of air. Manometers are graduated, -as will be explained in the sequel.</p> - -<hr class="tb" /> - -<p><span id="MARIOTTES_TUBE" class="smcap">Mariotte’s Tube.</span>—This is represented by -<a href="#pl_2">pl. 2</a>, fig. 7. It consists of a tube thirty-nine -inches long, closed at one end, bordered and -widened at the other, and bent into a U at the -distance of eight inches from its sealed end. -The graduation of this instrument will be described -hereafter.</p> - -<hr class="tb" /> - -<p><span id="PHOSPHORIC_FIRE_BOTTLE" class="smcap">Phosphoric Fire-Bottle.</span>—This is a short -piece of tube closed at one end, and widened -and bordered at the other, in such a manner as -to receive a cork. <a href="#pl_3">Pl. 3</a>, fig. 34. It is in this -little vessel that the phosphorus is enclosed. -Glasses of this form can be employed in a great -variety of chemical experiments.</p> - -<hr class="tb" /> - -<p><span id="PULSOMETER" class="smcap">Pulsometer.</span>—This instrument consists of a -tube, of which each extremity is terminated by -a bulb; it is partly filled with nitric ether, and -<span class="pagenum" id="Page_76">76</span> -sealed at the moment when the ebullition of the -ether has chased the atmospheric air wholly from -the interior of the vessel. <a href="#pl_2">Pl. 2</a>, fig. 16.</p> - -<hr class="tb" /> - -<p><span id="PUMP" class="smcap">Pump.</span>—Solder a cylinder, B (<a href="#pl_4">pl. 4</a>, fig. 12), to -the extremity of a small tube, C, and form their -point of coincidence into a funnel, to which you -will adapt a valve. Pierce the wide tube or -body of the pump at D, and solder there a -piece of tube bent into an elbow and widened -at the other end into a funnel, which is to be -furnished with a second valve, as is represented -in the figure. Prepare then the fountain of -compression E, and, by means of a cork and a -little sealing-wax, fix it upon the branch D. To -prepare the piston, A, blow a bulb at the end of -a tube, flatten the end of the bulb, and choke it -across the middle, in order to form a place -round which tow can be twisted, to make it fit -the tube air-tight. Finish the piston by twisting -the other end of the tube into a ring, as at -A. The valves are formed of small cones of -cork, or wood, having in the centre an iron -wire of sufficient size and weight to enable -them to play well.</p> - -<hr class="tb" /> - -<p><span id="RETORTS_FOR_CHEMICAL_EXPERIMENTS" class="smcap">Retort for Chemical Experiments.</span>—Plate -3, fig. 9, represents a combination of a large -and a small tube, forming a retort, which can be -employed with much advantage in many chemical -experiments. When a gas is to be distilled -by means of such a vessel, the ingredients are -put into the wide tube, which is previously -closed at one end, and then the other end of the -<span class="pagenum" id="Page_77">77</span> -tube is either drawn out or soldered to a narrow -tube. <a href="#pl_3">Pl. 3</a>, fig. 8 and 29, represent such -vessels under different forms. Very often a sort -of retort can be formed by joining a wide tube -to a long bent narrow tube, by means of a -cork.</p> - -<hr class="tb" /> - -<p><span id="TUBULATED_RETORT" class="smcap">Tubulated Retort.</span>—This is represented by -<a href="#pl_3">pl. 3</a>, fig. 6. Prepare a retort, such as is described -in the preceding article, but one which -is bent near the closed end; pierce it at A -(fig. 6), and solder there a little piece of tube -previously drawn out and sealed, such as is represented -by <a href="#pl_1">pl. 1</a>, fig. 11. When the soldering -is finished, soften the end of the little tube, -pierce it, and fashion it into a bottle neck, so that -it can be closed by a cork. Finish the instrument -by forming the open end according to the -purpose to which it may be destined. In the -figure, the end is represented as drawn out for -the convenience of blowing into the retort to -pierce the tubulure.</p> - -<hr class="tb" /> - -<p><span id="RUMFORDS_THERMOSCOPE" class="smcap">Rumford’s Thermoscope.</span>—This instrument -is represented by <a href="#pl_3">pl. 3</a>, fig. 35. It is necessary -to take a tube almost capillary, to solder a bulb -at each extremity, to pierce it laterally at <i>b</i>, and -to solder there a piece of tube previously drawn -out, but of which you open the point for the -purpose of finishing the sealing of the bulb A. -After doing this, you bend the two branches, -as shewn in the figure. When the liquid has -been introduced into the instrument, you must -<span class="pagenum" id="Page_78">78</span> -seal the little piece of tube which serves as a -reservoir.</p> - -<p>This instrument can be made in another manner. -Take two pieces of tube, one of them -twice as long as the other; solder a bulb at one -end of each of these tubes, and at about the -third part of the length of the long tube, parting -from the bulb, bend it at a right angle; pierce -the little tube at a corresponding distance, and -solder to the hole the end of the long tube. The -soldering being finished, and the whole system -having the form indicated by <a href="#pl_3">pl. 3</a>, fig. 35, introduce, -by the open end of the short tube, a -small quantity of coloured acid, and then seal -the end of the short tube, which serves as a -reservoir.</p> - -<p>The interior diameter of the tubes which are -generally employed as thermoscopes, is one-eighth -or one-twelfth of an inch. The mode -of graduation is described in a subsequent -chapter.</p> - -<hr class="tb" /> - -<p><span id="SYPHONS" class="smcap">Syphons.</span>—The <i>simple syphon</i> is a glass tube -bent, at a little distance from the middle, into a -form which is intermediate between those of -⋂ and ⋀, the legs being stretched apart like -those of the latter, but the bend being rounded -like that of the former. The tube is bent <i>near</i> -the middle, and <i>not exactly at</i> the middle, in -order that the legs may be of unequal lengths; -an arrangement which is indispensable. Syphons -are made of different lengths and diameters, -for various purposes. They can be made -<span class="pagenum" id="Page_79">79</span> -of tubes so capillary that it is sufficient to put -them into water to make them act: the liquid -rises in them by capillary attraction, and does -not require to be sucked through the tube, as -it does when large syphons are employed.</p> - -<hr class="tb" /> - -<p><span id="WIRTEMBERG_SYPHON" class="smcap">Wirtemberg Syphon.</span>—This syphon is the -same as the simple syphon, excepting that the -two branches are of equal length, and are bent -in U at both extremities. <a href="#pl_3">Pl. 3</a>, fig. 22.</p> - -<hr class="tb" /> - -<p><span id="SYPHON_WITH_THREE_BRANCHES" class="smcap">Syphon with three Branches.</span>—This instrument -is represented by <a href="#pl_2">pl. 2</a>, fig. 19. Close -a tube at one end and draw it out at the other; -pierce it at some inches from the contracted extremity, -and solder to the hole a little tube of -which the other end has been closed with wax. -Give the tube the bend necessary to constitute a -syphon, and open the two branches. The soldering -of the two tubes is facilitated by giving -to the extremity of the little tube a bend which -adapts it to be applied parallel to the large tube. -When the syphon is desired to be well finished, -the mouth-piece of the little tube must be bordered -and widened, and a bulb must be blown -near the mouth-piece.</p> - -<hr class="tb" /> - -<p><span id="SYPHON_WITH_JET_OF_WATER" class="smcap">Syphon with Jet of Water.</span>—This instrument -is represented by <a href="#pl_3">pl. 3</a>, fig. 1. Take a -tube of a large diameter, close it at one end, -and draw it out at the other. Cut the contracted -part in such a manner as to be able to introduce, -through the orifice, the extremity, also -drawn out, of another tube, which should be -<span class="pagenum" id="Page_80">80</span> -almost capillary. Solder these together in such -a manner that the point of the small tube shall -remain fixed about an inch within the interior of -the reservoir. Pierce again the latter, at B, -and solder there another branch of the same -diameter as the former; but fix it in such a -manner that its side shall be contiguous to the -side of the reservoir. Finally, give to the -branches the bend represented by the figure.</p> - -<hr class="tb" /> - -<p><span id="SPOONS" class="smcap">Spoons.</span>—Solder a bulb to the extremity of -a capillary tube; open the bulb as for a funnel, -but make the opening laterally. Cut with scissars -the edges of the part blown open, and in -such a manner as to form a spoon or a ladle, -according as the bulb had the form of a sphere -or an olive. This instrument is useful for -taking small quantities of acids. <a href="#pl_3">Pl. 3</a>, fig. 11.</p> - -<hr class="tb" /> - -<p><span id="SPIRIT_LEVEL" class="smcap">Spirit Level.</span>—The spirit level is represented -by <a href="#pl_2">pl. 2</a>, fig. 28. Choose a piece of -tube very straight, and with sides precisely of -the same thickness in all parts. Seal it at one -end, and draw it out abruptly at the other. -Fill it almost entirely with alcohol, and seal the -point by the jet of a candle.</p> - -<hr class="tb" /> - -<p><span id="TEST_GLASS_WITH_A_FOOT" class="smcap">Test Glass with a Foot.</span>—Take a tube -drawn out at one end; choke it at an inch -from the base, in such a manner as to obstruct -the canal almost entirely. <a href="#pl_1">Pl. 1</a>, fig. 12. Cut -off the point, close the opening, and soften the -whole end completely; then blow it into a -bulb and burst it into a funnel. Now present -<span class="pagenum" id="Page_81">81</span> -the contracted part to the fire, so as totally to -close the passage. Border and soften the funnel, -and by pressing it against a flat plate of -metal give it the form of a foot, or pedestal. -Cut the tube at the length which you desire the -test-glass to have, and border the edges of the -opening. This is a very useful little chemical -instrument. It is represented by <a href="#pl_3">pl. 3</a>, fig. 10.</p> - -<hr class="tb" /> - -<p><span id="THERMOMETERS" class="smcap">Thermometers.</span>—Thermometers are instruments -employed for appreciating changes of -temperature, either in the atmosphere or in substances -which we have occasion to examine. -The following are the principal varieties now -employed.</p> - -<hr class="tb" /> - -<p><span id="ORDINARY_THERMOMETER" class="smcap">Ordinary Thermometer.</span>—If you desire to -make standard thermometers, you must have -capillary tubes of perfect accuracy in the bore. -You are assured of regularity in the diameter -of a tube when a drop of mercury, made to -pass along the canal by means of a gentle inclination, -or by air blown from an Indian-rubber -bottle, gives everywhere a metallic column -of the same length.</p> - -<p>For ordinary thermometers this precaution is -superfluous. In all cases you employ a tube -more or less capillary, at one of the extremities -of which you blow or solder a spherical or cylindrical -reservoir. See <a href="#pl_4">pl. 4</a>, fig. 1 and 2. -You fill the instrument with well-purified mercury, -or alcohol, which you boil in the tube, in -order to chase the air from it. As it is necessary -to heat the instrument throughout its -whole length, you must place it on a railing of -<span class="pagenum" id="Page_82">82</span> -iron wire, inclined in the manner represented by -<a href="#pl_4">pl. 4</a>, fig. 14, and covered with burning charcoal, -or red-hot wood ashes. It is better, however, -to employ a kind of muff, formed of two -concentric wire grates, between which you put -burning charcoal, and reserve the centre for the -instrument. The tube is thus kept in a vertical -position, which allows the bubbles of air to -escape with more facility. An iron wire is -made use of to fasten the tube precisely in the -centre of the column of fire. The operation is -considerably promoted by soldering a little -funnel to the upper extremity of the thermometer -tube; and, in order to avoid the interruption -of the column of liquid by bubbles of air, -it is better to give to the superior part of the -reservoir the form of a cone (<a href="#pl_4">pl. 4</a>, fig. 3), rather -than to preserve the completely spherical -form indicated by <a href="#pl_4">pl. 4</a>, fig. 2.</p> - -<p>When the ebullition has expelled all the air -which was contained in the mercury, or alcohol, -you immediately plunge the open extremity of -the instrument into a vessel filled with one or the -other of these liquids; or, instead of this, you -pour the liquid into the funnel, in order that the -instrument may be quite filled at the common -temperature. You then cut off the funnel, if -one has been used, and, by properly elevating -the temperature of the reservoir, you expel so -much of the liquid that the summit of the column -rests at the point which you desire to -make choice of for the mean temperature: this -operation is termed <i>regulating the course of -the thermometer</i>.</p> - -<p>There are two methods of closing thermometers: -<span class="pagenum" id="Page_83">83</span> -you may either produce a vacuum above -the column of mercury, or you may allow air -to remain there. In the first case, after having -drawn out the end of the tube, you heat the -liquid until a single drop passes out of the -opening; you then instantly bring the point -into the jet, and seal it.</p> - -<p>In the second case, you seal the instrument -at the ordinary temperature, and having previously -raised to a reddish-white heat the -button of glass which is formed by the sealing, -you suddenly elevate the temperature of the -mercury. The liquid, on rising, compresses -the enclosed air, which dilates the red-hot -button at the summit of the tube, and produces -a species of reservoir. This reservoir is indispensably -necessary when you leave air above -the column of liquid, in order to provide -against the bursting of the instrument on those -occasions when the temperature of the mercury -comes to be considerably elevated. See <a href="#pl_4">pl. 4</a>, -fig. 13.</p> - -<hr class="tb" /> - -<p><span id="DIAL_THERMOMETER" class="smcap">Dial Thermometer.</span>—Terminate a piece of -tube, of six-tenths of an inch in diameter, with -two points, and solder to one of these points a -tube one-eighth of an inch in diameter and six -inches long; close the end of this small tube, -and, heating a zone of the reservoir, near the -base of the other point, blow a bulb there. -Cut off the point by which you have blown, at -a little distance from the bulb; open and border -the end of the narrow tube, and bend it -into a U. See <a href="#pl_4">pl. 4</a>, fig. 16. -<span class="pagenum" id="Page_84">84</span></p> - -<p>Fill the bulb and the reservoir with alcohol, -and add a drop of mercury which fills a certain -space in the narrow tube. This mercury -bears on its surface a little iron weight, to -which a thread is fastened; the other end of -this thread passes over a pulley, whose axis -turns a needle. The expansion or contraction -of the alcohol causes the mercury to rise and -fall, and consequently produces a movement of -the needle or index of the dial. This thermometer -is graduated like the others, by being -brought into comparison with a standard thermometer.</p> - -<hr class="tb" /> - -<p><span id="CHEMICAL_THERMOMETER" class="smcap">Chemical Thermometer.</span>—This instrument -is merely a common thermometer, the divisions -of which, graduated on paper, are enclosed in -a very thin glass tube, to hinder them from -being altered or destroyed when the instrument -is plunged into liquids. <a href="#pl_4">Pl. 4</a>, fig. 4, 5, 6, and -7, represent chemical thermometers of various -kinds.</p> - -<p>The case of the thermometer can be made -in two different ways. According to the first, -you take a tube of a pretty large diameter, and -with very thin sides; you draw out one end and -obliterate the point, which you bend into a -ring, in a direction perpendicular to that of the -case; you pass through this ring the stalk of -the thermometer, which is thus placed parallel -to the large tube. After having fixed the graduated -scale in the interior of the case, by -means of a small drop of sealing-wax, which -has been dropped on the slip of paper, and -<span class="pagenum" id="Page_85">85</span> -which, being supported against the side of the -case, needs only to be warmed to adhere there -and fix the scale securely to its envelope, you -close the upper extremity of the case by drawing -it out, obliterating the canal and soldering -it to the thermometer tube which has been introduced -into the ring at the lower end of the -case. You heat the connecting piece till it is -soft, and then push the thermometer up and -down until the zero marked on its tube corresponds -with the zero marked on the scale -within the case. See <a href="#pl_4">pl. 4</a>, fig. 6 and 7.</p> - -<p>The second method of making the case is as -follows:—You take a tube with thin sides, and -sufficiently large to contain the entire thermometer; -you draw out the tube at one end, and -choke it at some distance from the point of the -contracted part. This you must do in such a -manner as to form a little bulb, which is to be -ballasted in the manner described at the article -<i>Hydrometers</i>. After having introduced into -the case a little ball of cotton, you place therein -the thermometer, furnished with its scale, -and in such a manner that the reservoir rests on -the cotton. You terminate the upper end of -the case either with a ring or by a contraction -which permits the instrument to be suspended -by a cord. See <a href="#pl_4">pl. 4</a>, fig. 4 and 5.</p> - -<hr class="tb" /> - -<p><span id="SPIRAL_THERMOMETER" class="smcap">Spiral Thermometer.</span>—Take a tube which -is not capillary, but which has thin sides; close -one of its ends, and bend it round by pressing -it with a metallic rod; continue to bend it -round till it has made several turns, all in the -<span class="pagenum" id="Page_86">86</span> -same plane. See <a href="#pl_1">pl. 1</a>, fig. 13. The latter -turns may be managed with the fingers instead -of the metallic rod. When the reservoir so -formed is sufficiently large, solder to the end of -it a capillary tube, which you point in a direction -perpendicular to that of the axis of the -spiral. The instrument is represented by <a href="#pl_4">pl. 4</a>, -fig. 8.</p> - -<hr class="tb" /> - -<p><span id="POCKET_THERMOMETER" class="smcap">Pocket Thermometer.</span>—The pocket thermometer -differs in nothing from the thermometer -just described, except that the capillary tube, -instead of passing away from the spiral in a -straight line, is turned round, so as to form a -continuation of the spiral. See <a href="#pl_4">pl. 4</a>, fig. 17.</p> - -<hr class="tb" /> - -<p><span id="MAXIMUM_THERMOMETER" class="smcap">Maximum Thermometer.</span>—This instrument -consists of an ordinary mercurial thermometer, -bent at a right angle near the origin of the reservoir, -and in the horizontal column of which -a little steel or iron rod has been introduced: -this rod, by gliding in the tube, where it experiences -very little friction, serves as an index. -Since this index does not permit the instrument -to be sealed with the vacuum above the mercury, -you must terminate the sealing by a little -reservoir, as we have described at the article on -the second method of closing thermometers. -The instrument is represented by <a href="#pl_4">pl. 4</a>, fig. 24.</p> - -<hr class="tb" /> - -<p><span id="MINIMUM_THERMOMETER" class="smcap">Minimum Thermometer.</span>—This instrument -is constructed pretty nearly in the same manner -as the preceding. The liquid, however, -must be alcohol, and the index a little rod of -<span class="pagenum" id="Page_87">87</span> -enamel, which ought not to be quite so large as -the bore of the thermometer tube. You seal -the tube by making a vacuum above the column.</p> - -<hr class="tb" /> - -<p><span id="BELLANIS_MAXIMUM_THERMOMETER" class="smcap">Bellani’s Maximum Thermometer.</span>—This -thermometer is represented by <a href="#pl_4">pl. 4</a>, fig. 9. -Take a tube which is very regular, and about -one-eighth or one-twelfth of an inch diameter in -the bore; solder a reservoir at each end, one -of them much larger than the other; make a -bend near the large reservoir, and then fill the -instrument with alcohol to A. Above that, -place the first index, which consists of a very -small piece of tube closed at one end and cut -off square at the other. In the interior of this -tube the two ends of a hair are fixed, by means -of a little rod of iron, which is pushed into the -tube. Introduce a quantity of mercury above -this index, make the bend B, add again mercury -as far as C, then another index similar to -the first. Finally, fill the rest of the tube and -the half the little reservoir with alcohol, and -seal the point.</p> - -<hr class="tb" /> - -<p><span id="DIFFERENTIAL_THERMOMETER" class="smcap">Differential Thermometer.</span>—This instrument -is represented by <a href="#pl_3">pl. 3</a>, fig. 14. Take a -tube ten or twelve inches long, and one-eighth -or one-twelfth of an inch internal diameter; -blow a bulb at one end, and bend the tube at a -right angle towards the fourth part of its length. -Prepare a second tube in the same manner, and -solder the bent ends together, so as to form a -single tube with a bulb at each end, having previously -<span class="pagenum" id="Page_88">88</span> -poured into one of the bulbs a small -quantity of sulphuric acid tinged red.</p> - -<p>Instead of following the above method, you -may take a single tube of twenty or twenty-four -inches in length, and of the above-mentioned -diameter; you solder a bulb at each end, -bend the tube twice till it represents the figure, -pour in the acid, and then seal the open points. -The graduation of the differential thermometer, -as well as of all the other thermometers, is described -in a subsequent section.</p> - -<hr class="tb" /> - -<p><span id="TUBE_FOR_CRYSTALLIZING_SPERMACETI" class="smcap">Tube for Crystallizing Spermaceti.</span>—Take -a little capillary tube; curl one of its ends -into a ring, and solder the other to a cylindrical -reservoir, two-thirds of the capacity of -which you fill with very pure spermaceti dissolved -in sulphuric ether; you then seal the -point of the reservoir. See <a href="#pl_3">pl. 3</a>, fig. 27.</p> - -<hr class="tb" /> - -<p><span id="TUBES_BENT_FOR_VARIOUS_PURPOSES" class="smcap">Tube for demonstrating the non-conductability -of Heat by Liquids.</span>—This is represented -by <a href="#pl_2">pl. 2</a>, fig. 26. It is a tube sealed -at one end, bordered at the other, and bent in -such a manner as conveniently to permit the -upper part of a column of liquid to be exposed -to heat.</p> - -<hr class="tb" /> - -<p><span class="smcap">Tube for estimating the Density of -Vapours.</span>—Represented by <a href="#pl_2">pl. 2</a>, fig. 14. It -is merely a tube sealed at one end, bordered at -the other, and bent as shewn by the figure.</p> - -<hr class="tb" /> -<p><span class="pagenum" id="Page_89">89</span></p> - -<p><span class="smcap">Tubes for exposing Substances to Heat -and Gases.</span>—This instrument consists of a -tube bent in the middle into a U. <a href="#pl_3">Pl. 3</a>, fig. 3. -It is much employed in chemistry, for containing -substances which we wish at the same -time to expose to an elevated temperature and -to the action of certain gases. This tube can -also be employed for cooling gases, or liquids, -in distillation; the bent part being, in this case, -dipped into water or a freezing mixture, or enveloped -in wet paper or cloth.</p> - -<hr class="tb" /> - -<p><span class="smcap">Tubes for the Preservation of Objects -of Natural History, or of Chemical Preparations.</span>—Take -a tube of which the width -and length corresponds with the object which is -to be enclosed; draw it out at one end, and, -after having obstructed the point, twist it into a -ring. Introduce the object by the open extremity, -which you must afterwards draw out; -fill the tube with the liquid necessary to preserve -the object, and then seal the point. See -<a href="#pl_2">pl. 2</a>, fig. 27.</p> - -<p>If you desire to have the power of taking out -the object at will—as, for example, when grain -is preserved, or when, in chemistry, the tube is -employed to contain salts and other compounds, -of which small quantities are now and then required -for use—you do not seal the end of the -receiver, but border it in such a manner that it -can be closed by a cork.</p> - -<p>In some cases a cork is not sufficient to secure -the substance from the action of air: it -must then be assisted with a little cement. By -<span class="pagenum" id="Page_90">90</span> -melting together two parts of yellow wax, one -part of turpentine, and a small quantity of -Venetian red, a very useful cement for such -purposes is obtained.</p> - -<p>It is sometimes necessary to <i>suspend</i> the objects -enclosed within the tube: you then introduce -a little glass hook, the tail of which you -solder to the upper extremity of the tube; -managing this operation at the same time that -you make the external ring for the support of -the instrument. By turning the hook round -cautiously, which is done when the end of the -tube is in a soft state, and by cooling the whole -with care, you may succeed in fixing the hook -in the centre of the tube. See <a href="#pl_3">pl. 3</a>, fig. 20.</p> - -<hr class="tb" /> - -<p><span id="TUBE_FOR_EMPTYING_EGGS" class="smcap">Tube for emptying Eggs.</span>—It is a simple -tube, drawn out to a capillary point at one end, -and bent there into a V. See <a href="#pl_3">pl. 3</a>, fig. 23.</p> - -<p>The application which the author has made -of this instrument, and of the tube represented -by <a href="#pl_3">pl. 3</a>, fig. 26, has been shewn in a memoir -inserted in the <i>Annales des Sciences Naturelles, -Tom. XV. Novembre</i> 1828, concerning -a new method of preparing and rendering -durable collections of eggs destined for cabinets -of Natural History.</p> - -<hr class="tb" /> - -<p><span id="VIAL_OF_THE_FOUR_ELEMENTS" class="smcap">Vial of the Four Elements.</span>—This instrument -is represented by <a href="#pl_2">pl. 2</a>, fig. 27. Take a -tube drawn out at one end, obstruct the canal -two inches from the extremity, and twist the -contracted part into a ring. Draw out the -other end of the tube, introduce the proper -<span class="pagenum" id="Page_91">91</span> -liquids, remove the point of the tube, and seal -it. The liquids generally employed for filling -the vial of the four elements are, 1. Mercury; -2. A very concentrated solution of carbonate of -potash; 3. Oil of turpentine; 4. Alcohol. A -portion of air is also allowed to remain in the -tube.</p> - -<hr class="tb" /> - -<p><span id="WATER_HAMMER" class="smcap">Water Hammer.</span>—<a href="#pl_2">Pl. 2</a>, fig. 18, is a representation -of this instrument. Choose a tube -of a good diameter, and with thick sides; seal -it at one end and draw it out at the other. -Blow a bulb at the base of the contracted part; -then, having put a quantity of water in the -tube, let it boil therein, to expel the atmospherical -air. When you imagine that all the air -has been expelled, and that nothing remains in -the tube but steam and water, seal the open -point.</p> - -<p>When you have to seal a tube in this manner, -you should be careful to draw out the extremity -of the tube somewhat abruptly, and -leave a very small opening, so that it shall be -sufficient to expose the point to the jet of a -candle blown by a mouth blowpipe, to have the -sealing completely and suddenly effected. You -can afterwards round this sealed part by turning -it in the flame of the lamp, provided, however, -that you have preserved a sufficient thickness -of glass at the sides of the point. If you -omit to take this precaution, the pressure of the -atmosphere, acting with great force on the -softened glass when it is unsupported by the -partial vacuum within the tube, is capable of -<span class="pagenum" id="Page_92">92</span> -producing such a flattening, or even sinking in -of the matter, as could not subsequently be rectified; -except, indeed, by heating simultaneously -the liquid contained in the tube and the -glass to be mended, which is an operation of a -very delicate description.</p> - -<hr class="tb" /> - -<p><span id="WELTERS_SAFETY_TUBES" class="smcap">Welter’s Safety Tubes.</span>—After having -closed a tube at one end and drawn it out at -the other, give it the curvature exhibited by -plate 3, fig. 18. Pierce it then laterally, in the -middle of the part <i>a b</i>, and solder there the extremity -of a tube, to the other end of which a -funnel has been soldered: it is necessary that -the funnel be closed by a cork. The soldering -being terminated, a bulb must be blown and -the tube bent in S, in the manner shewn by the -figure. Then open the closed end, and cut off -the contracted point. -<span class="pagenum" id="Page_93">93</span></p> - -<hr class="chap" /> - -<h2><small>THE</small><br /> - -<span class="xx-large">ART OF GLASS-BLOWING.</span><br /> - -<img class="figcenter" src="images/hr.jpg" alt="" /> - -<span id="V">V.—<i>Graduation of Chemical and Philosophical -Instruments.</i></span></h2> - -<hr class="tb" /> - -<h3 id="OF_THE_SUBSTANCES_EMPLOYED_IN_THE_PREPARATION_OF_THESE_INSTRUMENTS">OF THE SUBSTANCES EMPLOYED IN THE PREPARATION -OF THESE INSTRUMENTS.</h3> - -<p>Before proceeding to the subject of <i>graduation</i>, -it is necessary to say a few words respecting -the substances which are generally employed -to fill a variety of instruments, particularly -barometers and thermometers.</p> - -<p><i>Mercury.</i>—It ought to be completely purified -from all foreign substances. You can -separate it from the dust it may contain by -passing it through a piece of chamois leather; -you tie a very hard knot, and by pressure oblige -the mercury to pass out in a fine rain. This -process is sufficient for the purification of mercury -which merely contains extraneous bodies -in suspension; but it is not sufficient when the -mercury to be purified contains tin, lead, or -other metals, in solution. It is then necessary -to distil the mercury; upon which the fixed -<span class="pagenum" id="Page_94">94</span> -metals remain behind. The oxide of mercury -produced by the distillation is removed by agitating -the distilled metal with sulphuric acid, -and subsequently washing it with a large quantity -of water, till all the acid is removed; it is -then dried as completely as possible with blotting-paper, -and afterwards is moderately -warmed.</p> - -<p><i>Alcohol</i> ought to be very pure and well rectified. -It is necessary to colour it, because, -being colourless of itself, it could not be seen -in capillary tubes. To colour alcohol, you infuse -carmine in it, and, after some time, decant -or filter the clear solution. The liquid should -be perfectly transparent, and free from all extraneous -substances. It is not proper to employ -alcohol in the construction of standard -thermometers; mercury being much preferable.</p> - -<p><i>Sulphuric Acid.</i>—It is made use of for the -differential thermometer, and the thermoscope -of Rumford. It has the advantage of being -lighter than mercury, and very slightly volatile: -these two qualities, joined to its tendency to -absorb the vapour of water, render it very -proper to be employed for various instruments. -It must be very concentrated, and tinged red -by carmine.</p> - -<p><i>Ether.</i>—Sulphuric and nitric ether, with -which some small instruments are filled, are -merely employed to shew with what facility -these liquids are brought to their boiling point.</p> - -<hr class="tb" /> - -<p><span id="OF_GRADUATION_IN_GENERAL" class="smcap">Of Graduation in general.</span>—Graduation, -generally speaking, consists in dividing lines, -<span class="pagenum" id="Page_95">95</span> -surfaces, and capacities, into a certain number -of equal or proportional parts. It is not our -intention to treat here of the methods furnished -by practical geometry for effecting such divisions -with mathematical accuracy; these -methods are known to every body. We shall -confine ourselves to describing the processes of -graduation which are peculiar to the instruments -constructed by the glass-blower.</p> - -<hr class="tb" /> - -<p><span id="EXAMINATION_OF_THE_BORE_OF_TUBES" class="smcap">Examination of the Bore of Tubes.</span>—We -have already observed, that, for standard -thermometers and other instruments which require -to be made very accurate, it is necessary -to employ tubes which are extremely regular in -the bore. When a drop of mercury, passed -successively along all parts of the tube, forms -everywhere a column of the same length, the -examiner is assured of the goodness of the -tube.</p> - -<p>That a tube may be regular in the bore, it is -not necessary that the bore be cylindrical; it -is sufficiently accurate when equal lengths correspond -to equal capacities. A tube with a flat -canal, for example, can be perfectly accurate -without at all approaching the cylindrical form. -It is only necessary that a drop of mercury occupy -everywhere the same length. We may -observe, by,the way, that, in flat canals, the -flattening should be always in the same plane.</p> - -<hr class="tb" /> - -<p><span id="DIVISION_OF_CAPILLARY_TUBES_INTO_PARTS_OF_EQUAL_CAPACITY" class="smcap">Division of Capillary Tubes into parts -of equal capacity.</span>—As it is very difficult to -meet with capillary tubes which are exactly regular -in the bore, it happens that the tubes -<span class="pagenum" id="Page_96">96</span> -which glass-blowers are obliged to employ have -different capacities in parts of equal length. -You commence the division of these tubes into -parts of equal capacity by a process described -by M. Gay-Lussac. You introduce a quantity -of mercury, sufficient to fill rather more than -half the tube, and make a mark at the extremity -of the column. You then pass the mercury -to the other end of the tube, and again -mark the extremity of the column. If you so -manage that the distance between the two -marks is very small, you may consider the enclosed -space as concentric, and a mark made -in the middle of the division will divide the -tube into two parts of evidently equal capacity. -You divide one of these parts, by the same -process, into two equal capacities, and each of -these into two others; and in this manner you -continue to graduate the tube until you have -pushed the division as far as you judge proper.</p> - -<p>But it is still more simple to introduce a drop -of mercury into the tube, so as to form a little -cylinder, and then to mark the two extremities -of the cylinder. If it were possible to push -the drop of mercury from one end of the tube -to the other, in such a manner as to make it -coincide, at every removal, with the last mark, -it would be very easy to divide the tube accurately; -but as it is very difficult, not to say -impossible, to attain this precision of result in -moving the column of mercury, you must endeavour -to approach exactness as nigh as may -be. You measure, every time you move the -mercury, the length of the cylinder it produces, -<span class="pagenum" id="Page_97">97</span> -and carry this length to the last mark, presuming -the small space which is found between -the mark and the commencement of the column -to be fairly represented by the same space after -the column. You thus obtain a series of small -and corresponding capacities.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_GAS_JARS_TEST_TUBES" class="smcap">Graduation of Gas Jars, Test Tubes, &c.</span>—If -the tube is regular in the bore, close one -end, either by sealing it at the lamp, or by inserting -a cork, and pour into the interior two -or three small and equal portions of mercury, -in order to have an opportunity of observing -the irregularities produced by the sealed part. -Take care to mark, with a writing diamond, -the height of the mercury, after the addition of -each portion. When equal portions of mercury -are perceived to fill equal spaces, take -with the compass the length of the last portion, -and mark it successively along the side of the -tube, where you must previously trace a line -parallel to its axis.</p> - -<p>For tubes which are irregular in the bore, -and where equal lengths indicate unequal capacities, -it is necessary to continue the graduation -in the same manner that you commenced -it—that is to say, to fill the tubes by adding -successively many small and equal portions of -mercury, and marking the height of the metallic -column after every addition. These divisions -will of course represent parts of an -ounce or of a cubic inch according to the measure -which you make use of. When you have -thus traced on the tube a certain number of -<span class="pagenum" id="Page_98">98</span> -equal parts, you can, by means of the compasses, -divide each of them into two other -parts of equal length. The first divisions being -very close to one another, the small portion of -tube between every two may be considered -without much risk of error as being sensibly of -equal diameter in its whole extent.</p> - -<p>When the tube which you desire to graduate -is long and has thin sides, it would be difficult -to fill it with mercury without running the risk -of seeing it break under the weight of the -metal. In this case, you must use water instead -of mercury.</p> - -<p>Bell-glasses of large dimensions are graduated -by filling them with water, placing them in -an inverted position on a smooth and horizontal -surface, which is slightly covered with water, -and passing under them a series of equal measures -of air. But it is then necessary to -operate constantly at the same temperature -and under the same atmospheric pressure, because -air is very elastic and capable of being -greatly expanded.</p> - -<p>In all cases, tubes, bell-glasses, &c. ought -to be held in a position perfectly vertical. The -most convenient measure is a dropping-tube, -on the stalk of which a mark has been made, -or a small piece of tube, sealed at one end, and -ground flat at the other; the latter can be accurately -closed by a plate of glass.</p> - -<p>The marks which are traced on tubes being -generally very close to one another, you facilitate -the reading of the scale by giving a greater -length to those marks which represent every -<span class="pagenum" id="Page_99">99</span> -fifth division, and by writing the figures merely -to every tenth division. See <a href="#pl_4">pl. 4</a>, fig. 8. The -number of divisions is somewhat arbitrary; -nevertheless, 100, 120, 360, 1000, are divisions -which, in practice, offer most advantages.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_HYDROMETERS" class="smcap">Graduation of Hydrometers.</span>—Cut a -band of paper on which the graduation of the -instrument can be traced, and let fall upon it a -little drop of sealing-wax; then roll the paper -upon a little glass tube, and introduce it into -the stalk of the hydrometer. The instrument -is afterwards to be plunged into distilled water, -which is carefully kept at the temperature of -40° F. above zero. Give the instrument sufficient -ballast to make it sink till the point -(<i>a</i>, <a href="#pl_4">pl. 4</a>, fig. 20,) which you desire to make to -represent the density of water, touches the -surface of the water. Mark this point with -much precision; it is the zero of the instrument. -The other degrees are taken by plunging -the hydrometer into distilled water to which -you have added 1, 2, 3, 4, 5, &c. <i>tenths</i>, or -1, 2, 3, 4, 5, &c. <i>hundredths</i>, of the substance -for which you wish to construct the hydrometer, -according as you desire the scale to indicate -tenths or hundredths.</p> - -<p>When you have thus marked the degrees on -the stalk of the instrument, transfer them to -the paper with the help of the compasses. The -scale being completed, replace it in the tube of -the hydrometer, where it must be fixed; in so -doing, take care to make the degrees on the -scale coincide precisely with those marked on -the stalk. -<span class="pagenum" id="Page_100">100</span></p> - -<p>You can thus procure hydrometers for -alcohol, acids, salts, &c. which are instruments -that indicate the <i>proportion</i> of alcohol, -acid, salt, &c. contained in a given mass of -water.</p> - -<p>But if it were necessary to plunge the hydrometer -in a hundred different solutions in -order to produce the scale, it is easy to conceive -that that would be extremely troublesome, -especially for hydrometers which are employed -in commerce, and which do not need to be so -extremely accurate. When the density of the -mixtures or solutions is a mean between those -of the substances which enter into them, you -may content yourself with marking the zero -and one other fixed point, (<i>a</i> and <i>b</i>, <a href="#pl_4">pl. 4</a>, fig. 20.) -Then, as the stalk of the hydrometer is evidently -of equal diameter in all its extent, you can divide -the space which separates the two fixed -points into a certain number of equal parts. -One of these, being taken for unity, represents -a particular quantity of the substance which -you have added to a determined weight of distilled -water. By means of this unity you can -carry the scale up and down the stalk of the -instrument. It is thus, that, to obtain a Baumé’s -hydrometer, after having obtained the zero by -immersion in distilled water, you plunge the -instrument into a solution containing a hundred -parts of water and fifteen of common salt, to -have the 15th degree, or containing a hundred -water and thirty salt, to have the 30th degree. -Upon dividing the interval into fifteen or thirty -equal parts, according as you have employed -one or the other solution, you obtain the value -<span class="pagenum" id="Page_101">101</span> -of the degree, which you can carry upwards -or downwards as far as you wish.</p> - -<p>Among the substances for which hydrometers -are required in commerce, are some which it is -impossible to obtain free from water—such are -alcohol, the acids, &c. In this case it is necessary -to employ the substances in their purest -state, and deprived of as much water as -possible.</p> - -<p>The employment of hydrometers is very extensive: -they are used to estimate the strength -of lyes, of soap solutions, of wines, milk, &c. -There is, in short, no branch of commerce in -which these instruments are not required for -the purpose of ascertaining the goodness of -the articles which are bought and sold. The -employment of hydrometers would be still -more general, if they could be made to give -immediately the absolute specific gravity of -the liquids into which they might be plunged, -the specific gravity of water being considered -as unity. It is possible to graduate a thermometer -of this description by proceeding as -follows:—</p> - -<p>Make choice of a hydrometer of which the -exterior part of the stalk is very regular. Introduce -the band of paper on which the scale -is to be written, and then ballast the instrument. -Make a mark where the surface of the -distilled water touches the stalk. Remove the -hydrometer from the water, wipe it perfectly -dry, and weigh it very accurately with a sensible -balance. Then pour into it a quantity of -mercury equal to its own weight; plunge it -<span class="pagenum" id="Page_102">102</span> -again into the water, and again mark the point -where the stalk touches the surface of the -water. Pour the mercury out of the instrument, -transfer the two marks to the scale, and -divide this fixed distance into fifty equal parts. -Having by this operation obtained the value of -the degree, you carry it upwards and downwards, -to augment the scale. If you take the -first point near the reservoir, the hydrometer -will be proper to indicate the density of liquids -which are heavier than water; if you -take it towards the middle of the tube, the contrary -will be the case.</p> - -<p>If you destine the hydrometer for liquids -much heavier than water—such as acids, for -example—you might, after having determined -the first point, add to the original ballast as -much mercury as is equal to the weight of the -whole instrument; then the point where the -stalk would touch the surface of the water, and -which would be represented by 100, would be -very high, and the second point, which would -be found below, would be represented by 200. -On dividing the space into a hundred equal -parts, you would have the value of the degree, -which could be carried up and down for the -extension of the scale.</p> - -<p>The specific gravities being in the inverse -ratio of the volumes plunged into the liquid, -the numbers of the scale which mark the specific -gravities diminish from below; so that, on -marking the lowest point 100, you have, on -proceeding upwards, the successive degrees -0·99, 0·98, 0·97, 0·96, &c. -<span class="pagenum" id="Page_103">103</span></p> - -<p>The hydrometers with two, three, and four -branches, are graduated by having their tubes -divided into a hundred or a thousand equal -parts. The divisions on each branch must -correspond with those on the other branches.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_BAROMETERS" class="smcap">Graduation of Barometers.</span>—The graduation -of this instrument consists in dividing a -piece of metal, wood, or ivory, into inches and -parts of inches. The divided rod is then employed -to measure the height of the mercury in -the tube. As the rule is moveable, the operation -presents no sort of difficulty: all that is -necessary is to make the zero of the scale coincide -with the inferior level of the mercury; the -point which corresponds with the superior level -of the mercury, seen in the tube, indicates the -height of the barometric column. It is in this -manner that the cistern barometer is graduated.</p> - -<p>But if the barometer is one of those in which -the surface of the mercury is variable, such as -the barometer of Gay-Lussac, it is necessary -to have recourse to a different process of graduation. -If the two branches of the instrument -are very regular, and of equal diameter, -you first measure with precision the height of -the column of mercury, then divide it in the -middle, and fix the scale, which must be graduated -in such a manner that the mark of fifteen -inches corresponds exactly with the middle -point. This mode of graduation serves to indicate -merely the apparent height of the barometric -column. If you desire that the scale -should immediately indicate the real height, you -<span class="pagenum" id="Page_104">104</span> -must fix the zero at the middle of the column, -and then double the figure which marks each -degree.</p> - -<p>When you do not wish to write the real -height, you make two divisions, of which one -proceeds upwards, the other downwards. You -do not, in this case, double the value of each -division, but in observations made with such a -barometer scale you add the degree marked by -the two surfaces, in order to find the real height.</p> - -<p>It is in an analogous manner that you graduate -the gauges or short barometers which are -employed to measure the density of air under -the recipient of the air-pump. You take the -height of the mercury in the gauge, and fix at -the middle of the column the zero of a double -scale, of which one division proceeds upwards, -the other downwards; or, instead of this, if -you choose to have only one scale, and that an -ascending scale, you double the value of every -degree.</p> - -<p>The zero of the barometric scale can be -fixed below the inferior surface of the mercury; -but then, to have the real height, it is necessary -to measure precisely the height of the mercury -in the two branches of the instrument, and to -deduct the smaller from the larger.</p> - -<p><i>Dial (or Wheel) Barometer.</i>—The disposition -which should be given to this instrument -is precisely the same as that of the <i>Dial Thermometer</i>, -described in a preceding section. -You make a small iron weight float on the inferior -surface of the mercury, and fix to this -weight a silk thread, which is stretched by a -<span class="pagenum" id="Page_105">105</span> -counterpoise, and rolls over a very moveable -pulley. The axis of this pulley carries a needle, -which turns backwards or forwards according -as the column of mercury augments or diminishes. -You arrange the whole in such a -manner that the extreme variations of this column -cannot make the needle describe more -than one circumference; with this view you -give the pulley a diameter of nearly an inch.</p> - -<p>The dial barometer being rather an object of -luxury than an instrument of precision, you graduate -it by inscribing the following words, at -full length, on the scale. In <a href="#pl_4">pl. 4</a>, fig. 16, for -example, you write,</p> - -<table> - <tr> - <td>At the point</td> - <td><i>a</i></td> - <td>......</td> - <td>Tempest.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>b</i></td> - <td>......</td> - <td>Much rain.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>c</i></td> - <td>......</td> - <td>Rain or Wind.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>d</i></td> - <td>......</td> - <td>Temperate.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>e</i></td> - <td>......</td> - <td>Fine Weather.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>f</i></td> - <td>......</td> - <td>Fixed Fair.</td> - </tr> - <tr> - <td class="tdc">...</td> - <td><i>g</i></td> - <td>......</td> - <td>Very Dry.</td> - </tr> -</table> - -<p>You write nothing at the inferior division.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_THE_MANOMETER" class="smcap">Graduation of the Manometer.</span>—The -graduation of this instrument consists in -dividing the tube where the air is to be compressed, -into a given number of parts of equal -capacity; but as, in general, such tubes are -employed as are nearly capillary and very regular, -the operation is reduced to a linear division, -where every degree occupies an equal space.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_THERMOMETERS" class="smcap">Graduation of Thermometers.</span> <i>Construction -of Standard Thermometers.</i>—Having -<span class="pagenum" id="Page_106">106</span> -constructed your instrument with a very regular -tube, or one which has been divided into -parts of equal capacity, and having filled it with -the proper liquid, according to the instructions -given in a preceding section, the graduation is -to be effected as follows. Procure very pure -ice, break it into small pieces, and fill a vessel -with it. When the ice begins to melt, plunge -the thermometer into the middle of it, in such -a manner that, without touching the sides -of the vessel, the whole thermometer, or at -least that part of it which contains the liquid, -may be covered with ice. Allow the instrument -to remain in this state until, in spite of -the gradual melting of the ice, the surface of -the column of liquid remains at a fixed point, -and neither falls nor rises. Mark this point -very carefully on the stalk of the thermometer, -either with a thread or a little drop of sealing-wax, -or with the trace of a diamond or a flint. -This is the <i>freezing point</i>, the <i>zero</i> of the centigrade -scale, the thirty-second degree of -Fahrenheit’s scale.</p> - -<p>As for the second fixed point, it is marked -during an experiment with boiling water, performed -as follows:—You employ a vessel of -tin plate sufficiently high to enclose the whole -thermometer; you pour into this vessel distilled -water, till it is about an inch deep, and then -you heat it. The vessel is surmounted by a -cover pierced with two holes, one of which is -intended to receive the stalk of the thermometer, -the other to allow the steam to escape. -When, on continuing the ebullition, you observe -<span class="pagenum" id="Page_107">107</span> -that the mercury ceases to rise in the tube, -you mark the point at which it has stopped, -just as you marked the first point. The last -mark indicates the <i>boiling point</i>; the one hundredth -degree of the centigrade scale, the two -hundred and twelfth degree of Fahrenheit’s -scale. You transfer to paper the distance -which is found between the first point and the -second point determined, and you divide this -distance into one hundred equal parts, or degrees, -for the centigrade thermometer, into -eighty parts for the thermometer of Réaumur, -and into one hundred and eighty for that of -Fahrenheit. If the tube of the instrument is -very regular in the bore, the degrees should be -equal in length; if, on the contrary, you have -been obliged to divide it into parts of equal -capacity, you find how many of these parts or -little spaces it is necessary to take to constitute -one of the above degrees. You find this -by dividing their whole number by 100, or 80, -or 180, according to the degrees of the scale -which you intend to make use of. Thus, if -you find between the two points fixed by melting -ice and boiling water, three hundred divisions -of equal capacity, it is necessary to include -<i>three</i> of these divisions in every <i>degree</i> -of the centigrade scale.</p> - -<p>The vessel employed to take the boiling -point must be of metal, and its surface should -be perfectly clean and well polished, and have -no rough points. If sand, or other matters, -were permitted to repose on the vessel, and to -<span class="pagenum" id="Page_108">108</span> -form asperities, the water would enter into -ebullition at an inferior temperature.</p> - -<p>This operation should, moreover, be performed -under an atmospherical pressure, which -is indicated by the barometer when the mercury -stands at twenty-nine inches and a half. But -as this pressure is different according to the -elevation of the place of operation, and, indeed, -suffers continual variations even in the same -place, it follows that the temperature of boiling -water is subject to continual changes, and that, -in the graduation of the thermometer, it is indispensably -necessary to take notice of the -height of the barometer at the very moment -that the point denoting the degree of boiling-water -is fixed upon. You succeed in making -the necessary corrections by the help of the -following table, which is founded on the experiments -of Sir G. Shuckburg and of the -Committee of the Royal Society.</p> - -<p class="copy">[See the Table on the opposite page.]</p> - -<hr class="tb" /> - -<p><i>Common Thermometers.</i>—Having, by the -method which we have just described, obtained -a <i>Standard Thermometer</i>, you may procure -with facility as many ordinary thermometers as -you desire. It is proper to employ the most -regular tubes which you can obtain, and when -the instruments are ready to be graduated, you -must bring them into comparison with your -standard thermometer. You place them together -into a liquid of which you gradually raise -the temperature, and you mark several points -on the scale of the new thermometer, the intervals -<span class="pagenum" id="Page_109">109</span> -between which are subsequently divided -into as many degrees as are marked on the scale -of the standard thermometer. Thus, for example, -you mark the 10° and 15°, and afterwards -divide the interval into five equal parts. This -gives you the length of a degree on the stalk -<span class="pagenum" id="Page_110">110</span> -of the new instrument. The more you multiply -these fixed points, the more you insure the -precision of the thermometer. When you have -taken a certain number of points, you measure -the remainder with the compasses.</p> - -<table class="bbox tdc"> - <tr> - <th colspan="2">Height of the Barometer in Inches.</th> - <th colspan="2" rowspan="2">Correction in<br />1000ths of the<br />interval between<br />the freezing<br />and boiling points<br />of Water.</th> - </tr> - <tr> - <th class="hang">When the boiling<br />point is found<br />by immersing<br />the Instrument<br />in <i>Steam</i>.</th> - <th class="hang">When the boiling<br />point is found<br />by immersing<br />the Instrument<br />in <i>Water</i>.</th> - </tr> - <tr> - <td>...</td> - <td>30.60</td> - <td>10</td> - <td rowspan="11" style="vertical-align: middle">Lower.</td> - </tr> - <tr> - <td>...</td> - <td>30.50</td> - <td>9</td> - </tr> - <tr> - <td>30.71</td> - <td>30.41</td> - <td>8</td> - </tr> - <tr> - <td>30.50</td> - <td>30.29</td> - <td>7</td> - </tr> - <tr> - <td>30.48</td> - <td>30.18</td> - <td>6</td> - </tr> - <tr> - <td>30.37</td> - <td>30.07</td> - <td>5</td> - </tr> - <tr> - <td>30.25</td> - <td>30.95</td> - <td>4</td> - </tr> - <tr> - <td>30.14</td> - <td>30.84</td> - <td>3</td> - </tr> - <tr> - <td>30.03</td> - <td>30.73</td> - <td>2</td> - </tr> - <tr> - <td>29.91</td> - <td>30.61</td> - <td>1</td> - </tr> - <tr> - <td>29.80</td> - <td>30.50</td> - <td>0</td> - </tr> - <tr> - <td colspan="4"> </td> - </tr> - <tr> - <td>29.69</td> - <td>29.39</td> - <td>1</td> - <td rowspan="10" style="vertical-align: middle">Higher.</td> - </tr> - <tr> - <td>29.58</td> - <td>29.28</td> - <td>2</td> - </tr> - <tr> - <td>29.47</td> - <td>29.17</td> - <td>3</td> - </tr> - <tr> - <td>29.36</td> - <td>29.06</td> - <td>4</td> - </tr> - <tr> - <td>29.25</td> - <td>28.95</td> - <td>5</td> - </tr> - <tr> - <td>29.14</td> - <td>28.84</td> - <td>6</td> - </tr> - <tr> - <td>29.03</td> - <td>28.73</td> - <td>7</td> - </tr> - <tr> - <td>28.92</td> - <td>28.62</td> - <td>8</td> - </tr> - <tr> - <td>28.81</td> - <td>28.51</td> - <td>9</td> - </tr> - <tr> - <td>28.70</td> - <td /> - <td>10</td> - </tr> - <tr> - <td /> - <td /> - <td colspan="2">The boiling point to be<br /> -marked so much higher or<br /> -lower than the stand of<br /> -the mercury during the<br /> -experiment.</td> - </tr></table> - -<p>The zero, 0°, of the thermometer of Fahrenheit, -is taken by means of a mixture of snow -and common salt, and its maximum point is, -like that of the preceding thermometer, taken -by means of boiling water; but this interval is -divided into 212 degrees; so that the scale -marks 32° where the centigrade and Réaumur’s -scales mark 0°.</p> - -<p>The thermometer of Delisle has but one -fixed point, which is the heat of boiling water; -this is the zero of the instrument. The inferior -degrees are 0,0001 (one ten-thousandth -part) of the capacity of the bulb and stalk of -the thermometer. It marks 150° at 0° of the -centigrade, or 32° of Fahrenheit’s thermometer.</p> - -<p>The dial, the maximum and the minimum -thermometers, are graduated according to the -same principles as the common thermometers.</p> - -<p>You can, with a mercurial thermometer, make -the centigrade scale rise to 300 or 400 degrees -above zero; but with an alcohol thermometer, -you must never go beyond the heat of boiling -water. On the contrary, the inferior degrees -of the alcohol thermometer can be carried to -the very lowest point, while those of the mercurial -thermometer should be stopped at thirty -or thirty-five degrees below the zero of the centigrade -scale, as the mercury then approaches very -near the point of its congelation. In all cases, -<span class="pagenum" id="Page_111">111</span> -the degrees of thermometer scales are indicated -by the sign - when they are below zero, and -by the sign + when they are above it; the - -is always marked, but the + generally omitted. -See <a href="#pl_4">pl. 4</a>, fig. 6.</p> - -<p>We may observe here that it is proper from -time to time to plunge the standard thermometer -into melting ice, for the purpose of verifying -its exactness. It has been found that -thermometers constructed with a vacuum above -the column of mercury gradually become inaccurate, -the 0° ascending, until it corresponds -with + 1° or + 2°. This singular effect is -attributable to the constant pressure of the atmosphere, -which, being supported merely by -the resistance of the very thin sides of the -thermometer, finally presses them together, and -diminishes the capacity of the reservoir. It is -partly for the sake of avoiding this inconvenience -that we consider it good not to make an -entire vacuum above the mercury, but to leave -a portion of air in the tube, and at the same -time to form a little reservoir at the summit of -the instrument.</p> - -<p><i>Differential Thermometer.</i>—To graduate -this instrument, you first maintain the two -bulbs at an equal temperature, by which you -determine the first fixed point, which is zero. -Then, enveloping one of the two bulbs with -melting snow, and elevating the other by -means of a vessel with warm water, to a known -temperature—to 20° Centigrade, for example—you -fix a certain space, which you afterwards -divide into 20 equal parts or degrees. The -<span class="pagenum" id="Page_112">112</span> -scale is continued by carrying successively to -each side the known value of a degree.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_RUMFORDS_THERMOSCOPE" class="smcap">Graduation of Rumford’s Thermoscope.</span>—This -instrument is graduated by dividing the -tube which separates the two bulbs into equal -parts, the number of which is arbitrary, though, -in general, the thermoscope tube is divided into -nine or eleven parts. There is always an odd -number of degrees, and you manage so that -the odd degree is found in the middle of the -tube. It carries the mark of zero at each end, -and the figures 1, 2, 3, &c. proceed from each -end of this middle degree, and form two corresponding -scales.</p> - -<hr class="tb" /> - -<p><span id="GRADUATION_OF_MARIOTTES_TUBE" class="smcap">Graduation of Mariotte’s Tube.</span>—You -divide the little branch which is sealed at the -end into a certain number of parts of equal -capacity, and the large branch into inches and -parts of inches. It is necessary to take care -that the zero of the two ascending scales correspond, -and are situated above the inferior -bend formed by the two branches of the instrument.</p> - -<h3>THE END.</h3> - -<p class="copy">W. WILSON, PRINTER, 57, SKINNER-STREET, LONDON.</p> - - - - - - - - -<pre> - - - - - -End of Project Gutenberg's The Art of Glass-Blowing, by T. P. 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