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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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