,illustration3 ,pl4 #a4 ,published by ,bumpus ,griffin ,london1 #ahca4 ,,the ,,art ,,of ,,glass-,,blowing1 ,,or ,,plain ,,instructions ,,for ,,making ,,the ,,chemical ,,and ,,philosophical ,,instruments ,,which ,,are ,,formed ,,of ,,glass2 ,,such ,,as ,,barometers1 ,,thermometers1 ,,hydrometers1 ,hour-,glasses1 ,funnels1 ,syphons1 ,,tube ,,vessels ,,for ,,chemical ,,experiments1 ,,toys ,,for ,,recreative ,,philosophy1 c4 ,,by ,a ,,french ,,artist4 ,,illustrated ,,by ,,engravings4 ,,london3 ,,published ,,by ,,bumpus ,,and ,,griffin1 #c1 ,,skinner-,,street2 ,,and ,,richard ,,griffin ,,and ,,co4 ,,glasgow3 ,,sold ,,also ,,by ,,stillies1 ,,brothers1 ,,edinburgh4 #ahca4 ,w4 ,,wilson1 ,,printer1 #eg1 ,,skinner-,,street1 ,,london4 ,,the ,,polytechnic ,,library4 ,the design of the ,publishers of the ,,polytechnic ,,library is to produce a ,series of highly-instructive ,works1 which the ,public may be tempted to buy1 because they will be cheap1--be induced to read1 because they will be brief1--be competent to understand1 because they will be clearly written1--and be able to profit by1 because they will be ,,works ,,of ,,practical ,,utility4 ,every volume1 therefore1 will contain a complete ,treatise relating to one of the useful arts or sciences1 or the chemical or mechanical trades4 ,,just ,,published1 ,,price ,,half-,a-,,crown1 ,,vol4 ,i4 ,,of ,,the ,,polytechnic ,,library1 ,neatly printed in #ahmo4 and bound in ,cloth1 containing ,,the ,,art ,,of ,,glass-,,blowing1 ,or ,plain ,instructions for ,making the ,,chemical ,,philosophical ,,instruments ,,which ,,are ,,formed ,,of ,,glass2 ,such as ,,barometers1 ,,thermometers1 ,,hydrometers1 ,hour-,glasses1 ,funnels1 ,syphons1 ,,tube-,,vessels ,,for ,,chemical ,,experiments1 ,,toys ,,for ,,recreative ,,philosophy1 c4 ,,by ,a ,,french ,,artist4 ,,illustrated ,,by ,,upwards ,,of ,,one ,,hundred ,,figures1 ,elegantly engraved on ,copper plates4 ,artists and ,students of the ,experimental ,sciences will find this work adapted to aid them effectually in the economical preparation of their ,apparatus2 and persons who would willingly occupy their leisure hours in practising the charming art of working ,glass and ,enamels with the ,blowpipe1 but who have hitherto been deterred by the anticipated expense of the instruments1 and the imaginary difficulties of the undertaking1 are taught herein the simplest1 most expeditious1 least expensive1 and most effectual methods of working ,glass into every variety of useful or fanciful device4 ,,published ,,by ,,bumpus ,,griffin1 ,,skinner-,,street1 ,,london2 ,r4 ,,griffin ,,and ,,co4 ,,glasgow2 ,,and ,,stillies1 ,,brothers1 ,,edinburgh4 ,,the ,,following ,,works1 ,,intended ,,to ,,form ,,part ,,of ,,the ,,polytechnic ,,library1 ,are nearly ready for ,publication4 ,,the ,,domestic ,,chemist2 ,comprising ,instructions for ,,the ,,detection ,,of ,,adulterations ,in numerous ,articles employed in ,,domestic ,,economy ,,the ,,arts4 ,to which is prefixed1 ,,the ,,art ,,of ,,detecting ,,poisons ,,in ,,food ,,and ,,organic ,,mixtures4 ,contents4 ,,part ,i4--,,instructions ,,for ,,the ,,detection ,,of ,,mineral ,,poisons ,,in ,,vegetable ,,or ,,animal ,,mixtures4--,copper1 ,lead1 ,antimony1 ,arsenic1 ,mercury1 ,iron1 ,barytes1 ,lime1 ,alumina1 ,potash1 ,soda1 ,sulphuric ,acid1 ,nitric ,acid1 ,muriatic ,acid4 ,,part ,,ii4--,,instructions ,,for ,,the ,,examination ,,of ,,articles ,,supposed ,,to ,,be ,,adulterated4--,alcohol1 ,ale1 ,anchovy ,sauce1 ,arrow-,root1 ,beer1 ,brandy1 ,bread1 ,calomel1 ,carmine1 ,cayenne ,pepper1 ,cheese1 ,chocolate1 ,chrome ,yellow1 ,cinnamon1 ,cloves1 ,cochineal1 ,coffee1 ,confectionery1 ,crabs' ,eyes1 ,cream1 ,cream of ,tartar1 ,epsom ,salts1 ,flour1 ,gin1 ,gum ,arabic1 ,spirits of ,hartshorn1 ,honey1 ,hops1 ,ipecacuanha1 ,isinglass1 ,ketchup1 ,lakes1 ,leeches1 ,lemon ,acid1 ,litharge1 ,magnesia1 ,milk1 ,mushrooms1 ,mustard1 ,olive ,oil1 ,parsley1 ,pepper1 ,peruvian ,bark1 ,pickles1 ,porter1 ,red ,oxide of ,mercury1 ,rhubarb1 ,sal ,ammoniac1 ,salt1 ,saltpetre1 ,soap1 ,soluble ,tartar1 ,spanish ,liquorice1 ,spirits1 ,sugar1 ,sulphur1 ,tamarinds1 ,tapioca1 ,tartaric ,acid1 ,tartar ,emetic1 ,tea1 ,ultramarine1 ,verdigris1 ,vermilion1 ,vinegar1 ,volatile ,oils1 ,wax1 ,white ,lead1 ,wine1 ,water17including directions for testing the purity of all descriptions of ,rain1 ,river1 or ,spring ,water47 ,,part ,,iii4--,,instructions ,,for ,,the ,,preparation ,,of ,,the ,,tests ,,employed ,,in ,,domestic ,,chemistry ,,and ,,for ,,the ,,performance ,,of ,,various ,,chemical ,,operations2 ,,with ,,description ,,of ,,the ,,glasses ,,and ,,apparatus ,,proper ,,to ,,be ,,employed4 ,the work is written in a popular manner1 and intended for the use of ,families1 ,publicans1 ,wine and ,spirit ,merchants1 ,oilmen1 ,manufacturers1 ,apothecaries1 ,physicians1 ,coroners1 and ,jurymen4--,price ,three ,shillings4 ,,the ,,perfumer',s ,,oracle4 ,the object of this work is to present a comprehensive and practical account of the ,preparation of ,,perfumes and ,,cosmetics1 according to the newest1 most successful1 and most economical processes4 ,it will be adapted either for ,professional ,persons1 or for ,ladies who may wish to amuse themselves with this elegant branch of experimental science4--,price ,three ,shillings4 ,illustration3 ,pl4 #b4 ,published by ,bumpus ,griffin ,london1 #ahca4 ,illustration3 ,pl4 #c4 ,published by ,bumpus ,griffin ,london1 #ahca4 ,illustration3 ,pl4 #d4 ,published by ,bumpus ,griffin ,london1 #ahca4 ,,translator',s ,,preface4 ,the scientific instruments prepared by the glass-blower are numerous and highly useful3 barometers1 thermometers1 syphons1 and many other vessels constructed of tubes1 are indispensable to the student of physics or chemistry4 ,some of these instruments are high in price1 and liable to frequent destruction2 and those by whom they are much employed are subject to considerable expense in procuring or replacing them4 ,it is therefore advisable that he who desires to occupy himself in the pursuit of experimental science1 should know how to prepare such instruments himself2 that1 in short1 he should become his own glass-blower4 8,the attainment of a ready practice in the blowing and bending of glass10 says ,mr4 ,faraday1 8is one of those experimental acquirements which render the chemist most independent of large towns and of instrument-makers40 ,unquestionably the best method of learning to work glass is to obtain personal instructions from one who is conversant with the art3 but such instructions are not easily obtained4 ,the best operators are not always the best teachers2 and to find a person equally qualified and willing to teach the art1 is a matter of considerable difficulty4 ,in large towns1 workmen are too much engaged with their ordinary business to step aside for such a purpose2 and in small towns glass-blowers are seldom to be found4 ,in most cases1 also1 they are too jealous of their supposed secrets to be willing to communicate their methods of operating to strangers1 even when paid to do so4 ,the following ,treatise is a free translation of ,l',art du ,souffleur la ,lampe1 par ,t4 ,p4 ,,danger4 ,the author is employed1 in ,paris1 in preparing glass instruments for sale1 and in teaching others the art of preparing them4 ,he has presented in this work the most minute instructions for the working of glass which have ever been offered to the public4 ,the general processes of the art are so fully explained1 and the experimental illustrations are so numerous1 that nothing remains except the reducing of these instructions to practice to enable the student to become an adept in the blowing of glass4 ,i trust that1 in publishing this work in an ,english dress1 ,i may be considered as aiding in some degree the progress of physical science4 ,this work contains a description of a cheap blowpipe and a very convenient lamp2 both of them the invention of the author3 but any other kind of lamp or blowpipe may be employed instead of these4 ,the reader who wishes for a description of the blowpipes generally employed in ,england1 may consult ,mr4 ,,griffin',s ,practical ,treatise on the ,use of the ,blowpipe in ,chemical and ,mineral ,analysis4 ,london1 ,september #ahca4 ,,author',s ,,preface4 ,the flame of a lamp1 or candle1 condensed and directed by a current of air1 is exceedingly useful in a great number of arts4 ,the instrument which is employed to modify flame is the ,,blowpipe4 ,this is an indispensable agent for jewellers1 watch-makers1 enamellers1 glass-blowers1 natural philosophers1 chemists1 mineralogists1 and1 indeed1 for all persons who are occupied with the sciences1 or their application to the arts4 ,its employment offers immense advantages in a multitude of circumstances2 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 it4 ,students1 especially those who desire to exercise themselves in chemical manipulation1 must feel the want of a simple and economical process1 by means of which they could give to glass tubes1 of which they make great use1 the various forms that are necessary for particular operations4 ,how much reason have they to complain of the high price of the instruments of which they make continual use6 ,the studies of a great number are shackled from want of opportunity to exercise themselves in manipulation2 and many1 not daring to be at the expense of a machine of which they doubt their ability to make an advantageous use1 figure to themselves the employment of the glass-blower's apparatus as being beset with difficulties1 and so rest without having even an idea of the numberless instruments which can be made by its means4 ,many persons would very willingly occupy their leisure time in practising the charming art of working glass and enamels with the blowpipe2 but the anticipated expense of the apparatus1 and the difficulties which they imagine to foresee in the execution of work of this kind1 always repels them4 ,the new species of blowpipe which we have offered to the public1 and which has received the approbation of the ,society for the ,encouragement of ,arts1 obviates all these inconveniences3 its moderate price1 its portability1 and the facility with which it can be used1 adapt it to general employment4 ,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 houses1 at little cost1 and with the greatest facility1 the experiments which are necessary to familiarise them with the sciences4 ,it is with such a view that we present to them this little ,treatise1 which is destined to teach them the simplest1 the most expeditious1 the least expensive1 and the most effectual methods of constructing themselves the various instruments which they require in the prosecution of their studies4 ,the word glass-blower1 generally speaking1 signifies a workman who occupies himself in making of glass and enamel1 the instruments1 vessels1 and ornaments1 which are fabricated on a larger scale in the glass-houses3 but the domain of the sciences having laid the art of glass-blowing under contribution1 the artists of the lamp have divided the labours thereof4 ,some apply themselves particularly to the construction of philosophical and chemical instruments2 others occupy themselves with little ornamental objects1 such as flowers1 c42 and1 among the latter1 some manufacture nothing but pearls1 and others only artificial eyes4 ,finally1 a few artists confine themselves to drawing and painting on enamel1 which substance is previously applied to metallic surfaces by means of the fire of a muffle4 ,as we intend to treat separately of these different branches of the art1 we commence with that of which the manipulation is the simplest4 ,paris1 #ahbi4 ,,contents4 ,page ,i4--,instruments employed in ,glass-,blowing #a ,the ,blowpipe #a ,the ,glass-,blower's ,table #c ,the ,eolipyle #e ,blowpipe with ,continued ,current #e ,the ,lamp #h ,the ,candlestick #i ,combustibles #i ,oil1 ,tallow1 c4 #i ,the ,wicks #aj ,relation between the ,diameter of the ,beaks of the ,blowpipe and the ,wicks of the ,lamp #ab ,,ii4 ,preliminary ,notions of the ,art of ,glass-,blowing #af ,the ,flame #af ,places fit to work in #ai ,means of obtaining a ,good ,fire #ai ,choice and ,preservation of ,glass #bb ,preparation of ,glass ,tubes before heating them #be ,method of presenting ,tubes to the ,fire1 and of working them therein #bf ,,iii4 ,fundamental ,operations in ,glass-,blowing #cj #a4 ,cutting #ca #b4 ,bordering #cd #c4 ,widening #cf #d4 ,drawing-out #cf #e4 ,choking #cg #f4 ,sealing #ch #g4 ,blowing #ci #h4 ,piercing #df #i4 ,bending #dh #aj4 ,soldering #di ,,iv4 ,construction of ,chemical and ,philosophical ,instruments #ed ,adapters #ee ,apparatus for various ,instruments #ee ,archimedes's ,screw #eg ,areometers #ga ,barker's ,mill #eg ,barometers #eh ,cistern ,barometer #eh ,dial ,barometer #eh ,syphon ,barometer #ei ,stop-cock ,barometer #ei ,compound ,barometers #ei ,gay-,lussac's ,barometer #fj ,bunten's ,barometer #fa ,barometer pierced laterally for ,demonstrations #fa ,bell ,glasses for ,experiments #fa ,blowpipe #fb ,capsules #fc ,cartesian ,devils #fd ,communicating ,vases #fe ,cryophorus #ee ,dropping ,tubes #fe ,fountains #ff ,fountain of ,circulation #ff ,fountain of ,compression #fg ,intermitting ,fountain #fh ,hero's ,fountain #fh ,funnels #fh ,hour ,glasses #gj ,hydraulic ,ram #gj ,hydrometers #ga ,baum's ,hydrometer #ga ,nicholson's ,hydrometer #gc ,hydrometers with two1 three1 or four branches #gd ,manometers #gd ,mariotte's ,tube #ge ,phosphoric ,fire-bottle #ge ,pulsometer #ge ,pump #gf ,retorts for ,chemical ,experiments #gf ,rumford's ,thermoscope #gg ,syphons #gh ,spoons #hj ,spirit ,level #hj ,test ,glass with a foot #hj ,thermometers #ha ,ordinary ,thermometer #ha ,dial ,thermometer #hc ,chemical ,thermometer #hd ,spiral ,thermometer #he ,pocket ,thermometer #hf ,maximum ,thermometer #hf ,minimum ,thermometer #hf ,bellani's ,maximum ,thermometer #hg ,differential ,thermometer #hg ,thermoscope #gg ,tubes bent for various purposes #hh ,vial of the four ,elements #ij ,water ,hammer #ia ,welter's ,safety ,tubes #ib ,v4 ,graduation of ,chemical and ,philosophical ,instruments #ic ,of the substances employed in the preparation of these instruments #ic ,of ,graduation in general #id ,examination of the ,bore of ,tubes #ie ,division of ,capillary ,tubes into parts of equal ,capacity #ie ,graduation of ,gas ,jars1 ,test ,tubes1 c4 #ig ,graduation of ,hydrometers #ii ,graduation of ,barometers #ajc ,graduation of the ,manometer #aje ,graduation of ,thermometers #aje ,graduation of ,rumford's ,thermoscope #aab ,graduation of ,mariotte's ,tube #aab ,,the ,,art ,,of ,,glass-,,blowing4 ,i4--,instruments employed in ,glass-,blowing4 ,on seeing1 for the first time1 a glass-blower at work1 we are astonished at the multitude and the variety of the modifications to which he can make the glass submit4 ,the small number and the simplicity of the instruments he employs1 is also surprising4 ,the blowpipe1 or1 in its place1 the glass-blower's bellows and a lamp1 are indeed all that are indispensable4 ,,the ,,blowpipe4 ,originally1 the blowpipe was only a simple1 conical tube1 more or less curved towards its point1 and terminated by a very small circular opening4 ,by means of this1 a current of air was carried against the flame of a candle1 and the inflamed matter was directed upon small objects1 of which it was desirable to elevate the temperature4 ,workers in metal still derive immense advantages from the use of this little instrument3 they employ it in the soldering of very small articles1 as well as for heating the extremities of delicate tools1 in order to temper them4 ,but since the blowpipe has passed into the hands of mineralogical chemists1 its form has been subjected to a series of very curious and important modifications4 ,in spite1 however1 of these ameliorations1 which rendered the instrument better adapted for the uses to which it was successively applied1 we are far from having drawn from it all the advantages to which we might attain1 were its employment not as fatiguing as it is difficult4 ,we require no other proof of this than the small number of those who know well how to make use of the blowpipe4 ,the most economical blowpipe is a tube of glass1 bent near one end1 and pointed at its extremity4 ,a bulb is blown near that part of the tube which corresponds with the curvature 7pl4 #c1 fig4 #g47 ,this bulb serves as a reservoir for moisture deposited by the air blown into the tube from the mouth4 ,if you employ a tube without a bulb1 the moisture is projected in drops into the flame1 and upon the objects heated by it--an effect which is very inconvenient in practice4 ,to put this instrument into action1 accustom yourself to hold the mouth full of air1 and to keep the cheeks well inflated1 during a pretty long series of alternate inspirations and expirations2 then1 seizing lightly with the lips the mouth of the blowpipe1 suffer the air compressed by the muscles of the cheeks1 which act the part of a bellows1 to escape by the beak of the blowpipe1 which you will be able to do without being put to the least inconvenience with regard to respiration4 ,when the air contained in the mouth is pretty nearly expended1 you must take advantage of an inspiration1 to inflate the lungs afresh2 and thus the operation is continued4 ,you must never blow through the tube by means of the lungs2 first1 because air which has been in the lungs is less proper for combustion than that which has merely passed through the nose and mouth2 secondly1 because the effort which it would be necessary to make1 to sustain the blast for only a short time1 would by its frequent repetition become very injurious to your health4 ,the jet of flame produced by the mouth-blowpipe can only be used to heat small objects3 when instruments of a considerable bulk have to be worked1 it is customary to employ the lamp1 or glass-blower's table4 ,,the ,,glass-,,blower',s ,,table4 ,artists give this name to an apparatus which consists of the following articles3-- #a4 ,a ,table1 below which is disposed a double bellows1 capable of being put in motion by means of a pedal4 ,this bellows furnishes a continued current of air1 which can be directed at pleasure by making it pass through a tube terminating above the table in a sharp beak4 ,the bellows with which the glass-blower's tables are commonly furnished have very great defects4 ,the irregular form which is given to the pannels diminishes the capacity of the instruments1 without augmenting their advantages4 ,if we reflect an instant on the angle1 more or less open1 which these pannels form when in motion1 we instantly perceive that the weight with which the upper surface of a bellows is charged1 and which always affords a vertical pressure1 acts very unequally on the arm of a lever which is continually changing its position4 ,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 flame4 ,all these inconveniences would disappear1 were the upper pannel1 like that in the middle1 disposed in such a manner as to be always horizontal4 ,it ought to be elevated and depressed1 in its whole extent1 in the same manner2 so that1 when charged with a weight1 the pressure should be constantly the same1 and the current of air uniform4 #b4 ,a lamp1 of copper or tin plate4--,the construction of this article1 sufficiently imperfect until the present time1 has varied according to the taste of those who have made use of it4 ,we shall give1 farther on1 the description of a lamp altogether novel in its construction4 #c4 ,the glass-blower's table is generally furnished with little drawers for holding the tools employed in modelling the softened glass4 ,careful artists have the surface of their table coated with sheet iron1 in order that it may not be burned by the hot substances that fall1 or are laid upon it4 ,as glass-blowers have frequent occasion to take measures1 it is convenient to have the front edge of the table divided into a certain number of equal parts1 marked with copper nails4 ,this enables the workman to take1 at a glance of the eye1 the half1 third1 or fourth of a tube1 or to give the same length to articles of the same kind1 without having perpetual recourse to the rule and compasses4 ,but when it is desirable to have the tubes1 or the work1 measured with greater exactness than it can be measured by this method1 the rule and the compasses can be applied to4 ,,the ,,eolipyle4 ,we shall merely make mention of this instrument4 ,it is a globular vessel1 commonly formed of brass4 ,if filled with a very combustible liquor1 such as alcohol1 and strongly heated1 it affords a rapid current of vapour1 which1 if directed by means of a fine beak into the middle of a flame1 produces the same effect as the air which issues from a blowpipe4 ,the eolipyle is a pretty toy1 but not a good instrument for a workman1 its action being too irregular4 ,,blowpipe ,,with ,,continued ,,current4 ,it is after having1 during a long period1 made use of the instruments of which we have spoken1 and fully experienced their inconveniences1 that1 aware of the indispensable necessity for such instruments in the arts and sciences1 we have thought it our duty to make known to the public a ,new ,apparatus1 which is1 not only calculated to fulfil the same purposes1 but presents advantages which it is easy to appreciate4 ,the price of it is only the sixth part of that of the glass-blower's table#a4 ,it is very portable1 and capable of being attached to any table whatever4 ,it unites the advantages of not fatiguing the workman1 of leaving his hands free1 and of rendering him absolute master of the current of air1 which he can direct on the flame either of the lamp or the candle1--advantages which are not offered in the same degree even by the table of the glass-blower4 #a ,in ,paris1 the blowpipe which is here described is sold for six francs 7five shillings ,english72 or1 with the improved lamp and candlestick1 twelve francs4 ,the instrument which we have presented is1 properly speaking1 nothing but a simple blowpipe1 ,c1 7pl4 #a1 fig4 #ai7 communicating with a bladder1 or leather bag1 fixed on ,e1 which is kept full of air by means of a bent tube1 ,d1 through which the operator blows occasionally with the mouth4 ,this tube is closed at its inferior extremity1 ,f1 by a valve1 which permits the passage of air into the reservoir1 but not of its return1 so that the air can only escape by the beak of the blowpipe4 ,the valve at ,f is constructed in the following manner3--,at about two inches from the end of the tube a contraction is made1 as represented at a1 pl4 #a1 fig4 #bd4 ,this reduces the internal diameter of the tube about one-third4 ,a small conical piece of cork or wood is now introduced into the tube in the manner represented by c4 ,the base of the cone must be large enough to close the tube at the point where it is contracted2 it must1 however1 not be so large as to close the tube at the wide part4 ,a brass pin is inserted in the point of the cone1 as is shewn in the figure4 ,between the cone and the end of the tube1 the piece of wood1 b1 is fixed2 the shape of this piece of wood is best shewn by figure #be1 on the same plate4 ,there is a hole in the centre1 in which the pin of the cork cone can move easily4 ,the cone or valve is therefore at liberty to move between the contraction a1 and the fixture b4 ,consequently1 when air is blown into the tube at e1 the valve is forced from the contraction1 falls into the position indicated by the dotted lines d1 and allows the air to pass by its sides4 ,when1 on the contrary1 the operator ceases to blow1 the valve is acted upon by the air in the bladder1 which1 pressing back at f1 drives the valve close against the contraction1 and effectually closes the aperture4 ,a slight hissing is heard1 but when the contraction is well made1 and the cork is good1 an extremely small quantity of air escapes4 ,the workman1 seated before the table where he has fixed his instrument1 blows from time to time1 to feed the reservoir or bladder1 which1 being pressed by a system of strings stretched by a weight1 produces an uniform current of air4 ,the force of this current of air can be modified at pleasure1 by pressing the reservoir more or less between the knees4 7,fig4 #bb represents a blowpipe complete1 formed not of glass1 but of brass tubes4 ,fig4 #bb1 bis1 represents the bladder or reservoir appertaining to this blowpipe47 ,m4 ,,gaultier ,,de ,,claubry1 who was charged by the ,committee of ,chemical ,arts of the ,society of ,encouragement 7of ,paris7 to make a report on this instrument1 was astonished at the facility with which the author1 in his presence1 reduced the oxide of cobalt to the metallic state1 and fused the metal to a globule2 an experiment which even ,m4 ,berzelius could not perform with the simple blowpipe1 since he expressly says1 in his work on that instrument1 that oxide of cobalt suffers no change when heated before the blowpipe4 ,the results obtained with cast iron1 oxide of tin1 c4--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 contrived4 ,a detailed account of the glass tubes belonging to this improved blowpipe will be found in the fourth part of this work1 at the article ,blowpipe4 ,,the ,,lamp4 ,while occupied in rendering popular1 if we may so speak1 the use of the blowpipe--an instrument which is so advantageous in a great number of circumstances--we have also endeavoured to improve the lamp1 which has1 until the present time1 been used by all those who employ the glass-blower's table4 ,the lamp which we recommend 7pl4 #a1 fig4 #bc7 is of a very simple construction4 ,it possesses the advantages of giving much less smoke than the old lamp1 and of being cleaned with the greatest facility4 ,it also gives sensibly more heat2 because the portion of flame which1 in the common lamps1 rises perpendicularly1 and is not used1 is1 in this case1 beaten down by a cap or hood1 and made to contribute to the force of the jet4 ,this cap also keeps the flame from injuring the eyes of the operator1 and destroys the smoke to such an extent1 that the large hoods with which glass-blowers commonly garnish their work table1 to carry off the smoke1 become unnecessary4 ,this is a peculiar advantage in the chamber of a student1 where a large hood or chimney can seldom be conveniently prepared4 ,,the ,,candlestick4 ,for mineralogical researches1 chemical assays1 and the soldering of small objects1 as in jewellery1 we recommend the use of a little candlestick1 which1 by means of a spring fixed to the bottom1 maintains the candle always at the same height4 ,a reservoir1 or shallow cup1 formed at the top of the candlestick1 to hinder the running away of the tallow or wax1 allows the operator to consume the fragments of tallow or grease which are ordinarily lost in domestic economy4 ,there is a little hole in the centre of the cup or upper part of the candlestick1 through which the wick of the candle passes4 o1 pl4 #a1 fig4 #bb1 is a representation of this candlestick4 ,,combustibles4 ,oil1 ,tallow1 c4--,among the substances which have been employed to feed the fire of the glass-blower's lamp1 those to which the preference is to be given are wax1 olive oil1 rape oil1 poppy oil1 and tallow4 ,animal oils1 such as bone oil and fish oil1 are much esteemed by some glass-blowers1 who pretend that with these substances they obtain better results than with other combustibles4 ,nevertheless1 animal oils1 generally speaking1 do not give so much heat as purified rape oil1 while they exhale an odour which is extremely disagreeable4 ,as to alcohol1 which is sometimes used with the eolipyle1 its combustion furnishes so feeble a degree of heat that its employment cannot be recommended4 ,purified rape oil is that of which the use is the most general4 ,next to olive oil and wax1 it affords the greatest heat1 and the least smoke4 ,but1 in a word1 as in the working of glass1 the operator has more need of a bright flame without smoke1 than of a high temperature1 any combustible may be employed which is capable of furnishing a flame possessing these two qualities4 ,the vegetable oils thicken1 and suffer alterations more or less sensible1 when they are long exposed to the action of the air4 ,they should be chosen very limpid1 and they may be preserved in that state by being enclosed in bottles1 which should be kept quite full and well corked4 ,the ,wicks4--,there has never been any substance so generally used for wicks as cotton2 some glass-blowers1 indeed1 have employed wicks of asbestus1 but without deriving from them the advantages which might have been expected2 the greater number1 therefore1 keep to cotton4 ,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 it4 ,the alteration of the cotton is probably brought about by the dust and water which the air always holds in suspension4 ,such cotton burns badly1 forms a bulky coal1 and permits with much difficulty the capillary ascension of the liquid which serves to support the flame2 so that it is impossible to obtain a good fire1 and necessary to be incessantly occupied in snuffing the wick4 ,cotton is equally subject to alteration when lying in the lamp1 even though impregnated with oil4 ,you should avoid making use of wicks that are too old4 ,when you foresee that you will remain a long time without having occasion to employ the lamp1 pour the oil into a bottle1 which can be corked up1 and let the wick be destroyed1 previously squeezing from it the oil which it contains4 ,it is indispensable to make use of none but new and good cotton2 it should be clean1 soft1 fine1 and not twisted4 ,it is best to preserve it in boxes1 after having folded it in many double papers1 to exclude dust and moisture4 ,when you wish to make wicks1 take a skein of cotton and cut it into four or six pieces1 dispose them side by side in such a manner as to make a bundle1 more or less thick1 and eight or ten inches in length2 pass a large comb lightly through the bundle1 to lay the threads even1 and tie it gently at each end1 to keep the threads from getting entangled4 ,relation between the diameters of the beaks of the blowpipe1 and the wicks of the lamp4--,we believe that we cannot place better than here a few observations respecting the size of the opening in the beak of the blowpipe1 considered in relation to the size of the wick of the lamp4 ,these observations will probably be superfluous to those who are already conversant with the use of the blowpipe2 but as every thing is interesting to beginners1 who are frequently stopped in their progress by very slight difficulties1 and as this ,treatise is particularly designed for beginners1 we do not hesitate to enter into the minutest details on subjects which we deem interesting4 ,the point of your blowpipe should be formed in such a manner1 that you can fix upon it various little beaks or caps1 the orifices in which1 always perfectly round1 ought to vary in size according to the bulk of the flame upon which you desire to act4 ,you cannot1 without this precaution1 obtain the maximum of heat which the combustion of the oil is capable of affording4 ,this employment of little moveable caps offers the facility of establishing a current of air1 greater or smaller1 according to the object you wish to effect2 above all1 it allows you to clean with ease the cavity or orifice of the beak1 as often as it may be necessary4 ,these caps can be made of different materials4 ,it is most advisable to have them made of copper or brass2 those which are formed of tin plate 7white iron71 and which are commonly used in chemical laboratories1 are the worst kind of all4 ,they soon become covered with grease or soot1 which either completely closes up the orifices1 or1 at least1 very soon alters the circular form which is necessary to the production of a good fire4 ,glass caps are less liable to get dirty1 and are much cheaper than the above2 but1 on the other hand1 they have the disadvantage of being easily melted4 ,this can to a certain extent be remedied by making the points of very thick glass1 and by always keeping them at some distance from the flame4 ,moreover1 as you can make them yourself when you are at leisure1 their use is very commodious4 ,if they are to be used with the blowpipe described in this work1 they must be fixed in the cork that closes the passage through which the current of air arrives4 ,c c and ,c c 7pl4 #a1 fig4 #ai7 are two glass beaks1 c c are the corks1 which can indifferently be adapted to c1 in the wooden vice1 by which the various parts of the blowpipe are connected when it is in action4 ,of whatever material the beak may be made1 its orifice must be perfectly round1 and the size of the orifice1 as we have before observed1 must have a relation to the size of the wick which is to be used with it4 ,you can ascertain the diameters of the orifices by inserting into them a little plate of brass1 having the form of a long isoceles triangle1 such as is represented by pl4 #a1 fig4 #b4 ,it should be an inch long1 the twelfth of an inch wide at one end1 and diminish to nothing at the other4 ,when divided into eight equal parts1 it will give1 at the divisions1 the respective proportions of #a1 #b1 #c1 #d1 #e1 #f1 #g eighths of the diameter at the wide end1 as is exemplified by the figure above referred to4 ,we have stated in the following table the relative diameters which long experience has recommended to us1 as being adapted to produce the greatest effect2 yet it is not to be imagined that these proportions are mathematically correct and indispensable for the obtaining of good results4 ,a sensible difference of effect would be perceived1 however1 were these proportions departed from in a notable manner4 ---------------------------------------- ---------------------- ,diameter of the ,diameter of the ,height of the wick wick1 orifice of the above the surface in inches4 beak1 of the oil1 in parts of an inch4 in inches4 ---------------------------------------- ---------------------- #ifth #dhth #a #bdth #a #afth #a #b #abth #a ---------------------------------------- ---------------------- ,it must be mentioned1 that this table has been formed from experiments made with a glass-blower's lamp of the ordinary construction2 so that1 with the new lamp with the hood1 described in this work1 it will not be necessary to employ wicks of so great a bulk1 nor yet to elevate them so much above the level of the oil1 in order to produce the same effect4 ,hence there will be a very considerable saving in oil4 ,the wicks of a quarter of an inch in diameter are only adapted for mineralogieal examinations1 for soldering very fine metallic substances1 and for working very small tubes4 ,when the objects are of considerable bulk1 it is in general necessary to have a flame sufficiently large to cover the whole instrument1 or at least all the portion of the instrument which is operated upon at once4 ,for working tubes1 of which the sides are not more than the twelfth of an inch in thickness1 you should have a wick at least as wide as the tube that is worked upon4 ,the diameter of the lamp-wick usually employed is one inch2 a wick of this size is sufficient for all the glass instruments which are in common use4 ,,the ,,art ,,of ,,glass-,,blowing4 ,,ii4--,preliminary ,notions of the ,art4 ,,the ,,flame4 ,it is only by long habitude1 and a species of routine1 that workmen come to know1 not only the kind of flame which is most proper for each object they wish to make1 but the exact point of the jet where they ought to expose their glass4 ,by analysing the flame1 upon the knowledge of which depends the success of the work1 we can immediately obtain results1 which1 without that1 could only be the fruit of long experience4 ,flame is a gaseous matter1 of which a portion is heated to the point of becoming luminous2 its form depends upon the mode of its disengagement1 and upon the force and direction of the current of air which either supports its combustion or acts upon it mechanically4 7,pl4 #a1 fig4 #a47 ,the flame of a candle1 burning freely in still air1 presents in general the form of a pyramid1 of which the base is supported on a hemisphere4 ,it consists of four distinct parts3 the immediate products of the decomposition of the combustible by the heat which is produced1 occupy the centre1 o1 where they exist in the state of an obscure gaseous matter1 circumscribed by a brilliant and very luminous envelope1 s2 the latter is nothing but the obscure matter itself1 in the circumstances where1 on coming into contact with the atmosphere1 it combines with the oxygen which exists therein1 and forms what is properly called flame4 ,the blueish light which characterises the inferior part of the flame1 s1 is produced by a current of cold air1 which1 passing from below upwards1 hinders the combustion from taking place at the bottom of the flame1 at the same temperature that exists in the parts of the flame not immediately subject to this influence4 ,finally1 on observing attentively1 we perceive a fourth part1 which is but slightly luminous1 and exists as an envelope of all the other parts of the flame4 ,the greatest thickness of this envelope corresponds with the summit of the flame4 ,from this point it gradually becomes thinner1 till it arrives at the lowest part of the blueish light1 where it altogether disappears4 ,it is in this last-described portion of the flame that the combustion of the gas is finished1 and there it is that we find the seat of the most intense heat which the flame of the candle affords4 ,if we compare the temperature of the different parts of the flame1 we find that the maximum of heat forms a ring corresponding to the zone of insertion1 ,a ,a2 a point which is the limit of the superior extremity of the blueish light4 ,when the flame is acted upon by the blowpipe1 it is subject to two principal modifications3-- #a4 ,if1 by means of a blowpipe with a very fine orifice1 you direct a current of air through the middle of the flame1 you project a portion of the flame in the direction of the blast4 ,the jet thus formed appears like a tongue of fire1 blueish1 cylindrical1 straight1 and very long2 the current of air occupies its interior4 ,this flame is enveloped on all sides by an almost invisible light1 which1 extending beyond the blue flame1 forms a jet1 ,a ,b1 very little luminous1 but possessing an extremely high temperature4 ,it is at the point ,a1 which corresponds with the extremity of the blue flame1 that the maximum of heat is found4 ,the extreme point of the jet ,b possesses a less degree of heat4 ,this flame is adapted for mineralogical assays1 for soldering1 for working enamels1 and in general for all small objects4 #b4 ,when the orifice of the blowpipe is somewhat large1 or when 7the orifice being capillary7 the current of air is very strong1 or the beak is somewhat removed from the flame1 the jet of fire1 instead of being prolonged into a pointed tongue1 is blown into a brush4 ,it makes then a roaring noise1 and spreads into an irregular figure1 wherein the different parts of the flame are confounded beyond the possibility of discrimination4 ,this flame is very proper for the working of glass1 and particularly of glass tubes2 it ought to be clear and very brilliant1 and above all should not deposit soot upon cold bodies suddenly plunged into it4 ,the maximum of temperature in this flame is not well marked2 we can say1 however1 that in general it will be found at about two-thirds of the whole length of the jet4 ,as this roaring flame contains a great quantity of carburetted hydrogen1 and even of vapour of oil1 escaped from combustion1 it possesses a disoxidizing or reducing property in a very high degree4 ,,places ,,fit ,,to ,,work ,,in4 ,every place is adapted for a workshop1 provided it is not too light and the air is tranquil4 ,the light of the lamp enables one to work with more safety than day-light1 which does not permit the dull-red colour of hot glass to be seen4 ,currents of cold air are to be avoided1 because they occasion the fracture of glass exposed to them on coming out of the flame4 ,,means ,,of ,,obtaining ,a ,,good ,,fire4 ,the lamp should be firmly seated upon a steady and perfectly horizontal table1 and should be kept continually full of oil4 ,the oil which escapes during the operation1 from the lamp into the tin-stand placed below it1 should be taken up with a glass tube having a large bulb1 and returned to the lamp4 ,when you set to work1 the first thing you have to do is to examine the orifice of the beak4 ,if it is closed1 or altered in form1 by adhering soot1 you must carefully clean it1 and open the canal by means of a needle or fine wire4 ,in the next place1 you freshen the wick by cutting it squarely1 and carrying off with the scissars the parts which are carbonised4 ,you then divide it into two principal bundles1 such as ,c1 ,k 7pl4 #a1 fig4 #ba71 which you separate sufficiently to permit a current of air1 directed between the two1 to touch their surfaces lightly1 without being interrupted in its progress4 ,by pushing the bundles more or less close to one another1 and by snuffing them1 you arrive at length at obtaining a convenient jet4 ,it is a good plan to allow1 between the two principal bundles and at their inferior part1 a little portion of the wick to remain3 you bend this down in the direction of the jet1 and make it lie immediately beneath the current of air4 ,the wick must be prevented from touching the rim of the lamp1 in order to avoid the running of the oil into the stand of the lamp4 ,this is easily managed by means of a bent iron-wire1 disposed as it is in the lamp described in this work2 see pl4 #a1 fig4 #bc1 where the wire is seen in an elevated position4 ,when the wick is in the lamp1 the wire is brought down round the wick and level with the surface of the lamp4 ,a few drops of oil of turpentine1 spread on the wick1 makes it take fire immediately1 over its whole extent1 on the approach of an inflamed substance4 ,to obtain a good fire1 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 flame4 ,the beak must not enter the flame1 as it can then throw into the jet only an inconsiderable portion of the ignited matter4 ,see pl4 #a1 fig4 #bj4 ,on the other hand1 if the lamp be too far away from the blowpipe1 the flame becomes trembling1 appears blueish1 and possesses a very low degree of heat4 ,for mineralogical experiments1 and for operations connected with watch-making and jewellery1 the current of air should project the flame horizontally4 ,for glass-blowing1 the flame should be projected in the direction intimated by the arrow in pl4 #a1 fig4 #bj--that is to say1 under an angle of twenty or twenty-five degrees4 ,the current of air ought to be constant1 uniform1 and sufficiently powerful to carry the flame in its direction4 ,when it is not strong enough to produce this effect1 it is necessary to add weights to the bellows or the bladder1 according as the glass-blowers' table or our lamp is employed4 ,the point to which you should apply1 in the use of these instruments1 is to enable yourself to produce a current of air so uniform in its course that the projected flame be without the least variation4 ,finally1 when you leave off working you should extinguish the flame1 by cutting off the inflamed portion of the wick with the scissars4 ,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 operation4 ,,choice ,,and ,,preservation ,,of ,,glass4 ,the only materials employed in the fabrication of the objects described in this ,treatise1 are tubes of common glass or of flint-glass4 ,they can be had of all diameters1 and of every variety of substance4 ,they are commonly about three feet long1 but some are found in commerce which are six feet in length4 ,you should choose tubes that are very uniform--that is to say1 straight and perfectly cylindrical1 both inside and outside4 ,a good tube should have the same diameter from one end to the other1 and the sides or substance of the glass should be of equal thickness in every part4 ,this is indispensable when the tubes are to have spherical bulbs blown upon them4 ,we shall describe1 in the article ,graduation1 the method of ascertaining whether or not a tube is uniform in the bore4 ,the substance of the glass should be perfectly clear1 without bulbs1 or specks1 or stripes4 ,the tubes are so much the more easy of use1 as the glass of which they are made is the more homogeneous4 ,under this point of view1 the white glass1 known in commerce by the name of crystal or flint-glass1 is preferable to common glass3 it is more fusible1 less fragile1 and less liable to break under the alternations of heat and cold2 but it is dearer and heavier1 and has the serious disadvantage of becoming permanently black when exposed to a certain part of the flame4 ,this is an effect1 the causes and consequences of which will be explained in a subsequent chapter4 ,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 hydrogen1 and the hydro-sulphurets2 for these compounds are capable of decomposing flint-glass1 in consequence of its containing oxide of lead4 ,in general1 hard common glass is preferable to flint-glass for all instruments which are to be employed in chemistry4 ,flint-glass should only be used for ornamental objects1 and for the barometers1 thermometers1 and other instruments employed in philosophical researches4 ,it sometimes happens that glass tubes lose their transparence and ductility1 and suddenly become almost infusible1 in the fire of the lamp3 this effect takes place when they have been kept for some time in a melted state4 ,it is then almost impossible to bring them back to their original condition2 it can only be done by exposing them for a long time to an exceedingly high temperature4 ,you can prevent this accident by working such kind of glass with considerable rapidity1 and in a pretty brisk fire4 ,there are tubes1 however1 which vitrify so promptly that it is only a person well versed in the art who can make good use of them4 ,it is best not to employ such glass4 ,but how can it be discriminated before-hand8 ,it is experience1 sooner than any characters capable of description1 that will teach you how to make choice of good glass2 nevertheless we have observed1 that1 among the glass tubes which occur in commerce1 those possessing a very white colour manifest this bad quality most particularly4 ,it may be observed1 that1 for tubes which are to have thin sides1 this vitrifiable sort of glass is better than any other4 ,for certain philosophical instruments it is necessary to employ flat tubes4 ,these are formed of flint-glass1 are very small1 and have a canal or bore1 which1 instead of being round1 as in common tubes1 has the form of a long and very flat oval4 ,this disposition has the advantage of rendering more perceptible the column of liquid that may be introduced1 and which in a round canal would scarcely be visible4 ,in choosing this sort of tubes1 carefully avoid those of which the canal is twisted1 and not found to be in the same plane1 in the whole length of the tube4 ,the tubes should be sorted1 according to their sizes and qualities1 and should be deposited in large drawers or on long shelves1 in such a manner as to be equally supported through their whole extent4 ,they should also be sheltered from dust and from moisture4 ,if you cannot conveniently warehouse them in this manner1 you should tie them up in parcels1 and support them in a perpendicular position4 ,it is a very bad plan to place them in an inclined direction1 or to support them by their extremities on wooden brackets1 as it is the fashion to do in chemical laboratories2 because1 as the tubes are then supported only at certain points1 they bend1 in course of time1 under the influence of their own weight1 and contract a curvature which is extremely prejudicial in certain instruments1 and which it is almost impossible to correct4 ,,preparation ,,of ,,tubes ,,before ,,heating ,,them4 ,before presenting a tube to the flame1 you should clean it well both within and without1 in order to remove all dust and humidity4 ,if you neglect to take this precaution1 you run the risk of cracking or staining the glass4 ,when the diameter of the tube is too small to permit of your passing a plug of cloth or paper to clean its interior1 you can accomplish the object by the introduction of water1 which must1 many times alternately1 be sucked in and blown out1 until the tube is deemed clean4 ,one end of it must then be closed at the lamp1 and it must be gradually exposed to a charcoal fire1 where1 by raising successively all parts of the tube to a sufficiently high temperature1 you endeavour to volatilize and expel all the water it contains4 ,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 tube1 which you keep in the interior of the tube to be dried during the time that it is being heated4 ,you can here advantageously substitute alcohol for water1 as being much more volatile1 and as dissolving greasy matters2 but these methods of cleansing should only be employed for valuable objects1 because it is extremely difficult fully to expel moisture from a tube wherein you have introduced water1 and because alcohol is too expensive to be employed where there is no particular necessity4 ,when the tubes no longer contain dust1 or moisture1 you measure them1 and mark the divisions according to the sort of work which you propose to execute4 ,,method ,,of ,,presenting ,,tubes ,,to ,,the ,,fire1 ,,and ,,of ,,working ,,them ,,therein4 ,the two arms are supported on the front edge of the table1 and the tube is held with the hands either above or below1 according as it may be necessary to employ more or less force1 more or less lightness4 ,you ought1 in general1 to hold the tube horizontally1 and in such a manner that its direction may be perpendicular to that of the flame4 ,yet1 when you wish to heat at once a large portion of the tube1 or to soften it so that it shall sink together in a particular manner1 as in the operation of sealing1 you will find it convenient to incline the tube1 the direction of which1 however1 must always be such as to turn the heated part continually towards you4 ,we are about to give a general rule1 upon the observance of which we cannot too strongly insist1 as the success of almost every operation entirely depends upon it4 ,the rule is1 never to present a tube to the flame without ,,continually ,,turning it2 and turning it1 too1 with such a degree of rapidity that every part of its circumference may be heated and softened to the same degree4 ,as melted glass necessarily tends to descend1 there is no method of preventing a heated tube from becoming deformed but that of continually turning it1 so as to bring the softened part very frequently uppermost4 ,when you heat a tube near the middle1 the movement of the two hands must be uniform and simultaneous1 or the tube will be twisted and spoiled4 ,when the tubes have thick sides1 they must not be plunged into the flame until they have previously been strongly heated4 ,you expose them at first to the current of hot air1 at some inches from the extremity of the jet2 you keep them there some time1 taking care to turn them continually1 and then you gradually bring them towards1 and finally into1 the flame4 ,the thicker the sides of the tubes are1 the greater precaution must be taken to elevate the temperature gradually3 this is the only means of avoiding the fractures which occur when the glass is too rapidly heated4 ,though it is necessary to take so much care with large and thick tubes1 there are1 on the contrary1 some tubes so small and so thin that the most sudden application of the fire is insufficient to break them4 ,practice soon teaches the rule which is to be followed with regard to tubes that come between these extremes4 ,common glass ought to be fused at the maximum point of heat2 but glass that contains oxides capable of being reduced at that temperature 7such as flint-glass7 require to be worked in that part of the flame which possesses the highest oxidating power4 ,if you operate without taking this precaution1 you run the risk of decomposing the glass4 ,thus1 for example1 in the case of flint-glass1 you may reduce the oxide of lead1 which is one of its constituents1 to the state of metallic lead4 ,the consequence of such a reduction is the production of a black and opaque stain upon the work1 which can only be removed by exposing the glass1 during a very long time1 to the extremity of the jet4 ,you must invariably take the greatest care to keep the flame from passing into the interior of the tube2 for when it gets there it deposits a greasy vapour1 which is the ordinary cause of the dirt which accumulates in instruments that have been constructed without sufficient precaution as to this matter4 ,in order that you may not blacken your work1 you should take care to snuff the wick of the lamp whenever you perceive the flame to deposit soot4 ,you can judge of the consistence of the tubes under operation as much by the feel as by the look of the glass4 ,the degree of heat necessary to be applied to particular tubes1 depends entirely upon the objects for which they are destined4 ,as soon as the glass begins to feel soft1 at a brownish-red heat1 for example1 you are at the temperature most favourable to good bending4 ,but is it intended to blow a bulb8 ,the glass must1 in this case1 be completely melted1 and subjected to a full reddish-white heat4 ,we shall take care1 when speaking hereafter of the different operations to be performed1 to mention the temperature at which each can be performed with most success4 ,when an instrument upon which you have been occupied is finished1 you should remove it from the flame gradually1 taking care to turn it continually1 until the glass has acquired sufficient consistence to support its own weight without becoming deformed4 ,every instrument formed thus of glass requires to undergo a species of annealing1 to enable it to be preserved and employed4 ,to give the instrument this annealing1 it is only necessary to remove it from the flame very gradually1 allowing it to repose some time in each cooler place to which you successively remove it4 ,the thicker or the more equal the sides of the glass1 the more carefully it requires to be annealed4 ,no instrument should be permitted to touch cold or wet bodies while it is warm4 ,,the ,,art ,,of ,,glass-,,blowing4 ,,iii4--,fundamental ,operations in ,glass-,blowing4 ,all the modifications of shape and size which can be given to tubes in the construction of various instruments1 are produced by a very small number of dissimilar operations4 ,we have thought it best to unite the description of these operations in one article1 both to avoid repetitions and to place those who are desirous to exercise this art in a state to proceed1 without embarrassment1 to the construction of any instrument of which they may be provided with a model or a drawing2 for those who attend properly to the instructions given here1 with respect to the fundamental operations of glass-blowing1 will need no other instructions to enable them to succeed in the construction of all kinds of instruments capable of being made of tubes4 ,these fundamental operations can be reduced to ten1 which may be named as follows3-- #a4 ,cutting4 #b4 ,bordering4 #c4 ,widening4 #d4 ,drawing out4 #e4 ,choking4 #f4 ,sealing4 #g4 ,blowing4 #h4 ,piercing4 #i4 ,bending4 #aj4 ,soldering4 ,we proceed to give a detailed account of these different operations4 #a4--;,,cutting4 ,the different methods of cutting of glass tubes which have been contrived1 are all founded on two principles2 one of these is the division of the surface of glass by cutting instruments1 the other the effecting of the same object by a sudden change of temperature2 and sometimes these two principles are combined in one process4 ,the first method consists in notching the tube1 at the point where it is to be divided1 with the edge of a file1 or of a thin plate of hard steel1 or with a diamond2 after which1 you press upon the two ends of the tube1 as if to enlarge the notch1 or1 what is better1 you give the tube a slight smart blow4 ,this method is sufficient for the breaking of small tubes4 ,many glass-blowers habitually employ an agate1 or a common flint1 which they hold in one hand1 while with the other they rub the tube over the sharp edge of the stone1 taking the precaution of securing the tube by the help of the thumb4 ,for tubes of a greater diameter1 you can employ a fine iron wire stretched in a bow1 or1 still better1 the glass-cutters' wheel2 with either of these1 assisted by a mixture of emery and water1 you can cut a circular trace round a large tube1 and then divide it with ease4 ,when the portion which is to be removed from a tube is so small that you cannot easily lay hold of it1 you cut a notch with a file1 and expose the notch to the point of the blowpipe flame3 the cut then flies round the tube4 ,this brings us to the second method of cutting tubes--a method which has been modified in a great variety of ways4 ,it is founded on the property possessed by vitrified matters1 of breaking when exposed to a sudden change of temperature4 ,acting upon this principle1 some artists apply to the tube1 at the point where they desire to cut it1 a band of fused glass4 ,if the tube does not immediately separate into two pieces1 they give it a slight smart blow on the extremity1 or they drop a little water on the heated ring4 ,other glass-blowers make use of a piece of iron heated to redness1 an angle or a corner of which they apply to the tube at the point where it is to be cut1 and then1 if the fracture is not at once effected by the action of the hot iron1 they plunge the tube suddenly into cold water4 ,the two methods here described can be combined4 ,after having made a notch with a file1 or the edge of a flint1 you introduce into it a little water1 and bring close upon it the point of a very little tube previously heated to the melting point4 ,this double application of heat and moisture obliges the notch to fly right round the tube4 ,when the object to be cut has a large diameter1 and very thin sides--when it is such a vessel as a drinking-glass1 a cup1 or a gas tube--you may divide it with much neatness by proceeding as follows4 ,after having well cleaned the vessel1 both within and without1 pour oil into it till it rises to the point1 or very nearly to the point1 where you desire to cut it4 ,place the vessel1 so prepared1 in an airy situation2 then take a rod of iron1 of about an inch in diameter1 make the extremity brightly red-hot1 and plunge it into the vessel until the extremity of the iron is half an inch below the surface of the oil3 there is immediately formed a great quantity of very hot oil1 which assembles in a thin stratum at the surface of the cold oil1 and forms a circular crack where it touches the sides of the glass4 ,if you take care to place the object in a horizontal position1 and to plunge the hot iron without communicating much agitation to the oil1 the parts so separated will be as neat and as uniform as you could desire them to be4 ,by means of this method we have always perfectly succeeded in cutting very regular zones from ordinary glass4 ,the method which is described in some works1 of cutting a tube by twisting round it a thread saturated with oil of turpentine1 and then inflaming the thread1 we have found to be unfit for objects which have thick sides4 ,some persons employ cotton wicks dipped in sulphur4 ,by the burning of these1 the glass is strongly heated in a given line1 or very narrow space1 which is instantly cooled by a wet feather or a wet stick4 ,so soon as a crack is produced1 it can be led in any required direction by a red-hot iron1 or an inflamed piece of charcoal4 ,finally1 you may cut small portions from glass tubes in a state of fusion1 by means of common scissars4 #b4--;,,bordering4 ,to whatever use you may destine the tubes which you cut1 they ought1 almost always1 to be bordered4 ,if you merely desire that the edges shall not be sharp1 you can smoothen them with the file1 or1 what is better1 you can expose them to the flame of the lamp until they are rounded4 ,if you fear the sinking in of the edges when they are in a softened state1 you can hinder this by working in the interior of the tube a round rod of iron1 such as pl4 #a1 fig4 #e4 ,the rod of iron should be one-sixth of an inch thick2 one end of it should be filed to a conical point1 and the other end be inserted into a thin1 round1 wooden handle4 ,you will find it convenient to have a similar rod with a slight bend in the middle4 ,when you desire to make the edges of the tube project1 bring the end to a soft state1 then insert in it a metallic rod1 and move it about in such a manner as to widen a little the opening4 ,while the end of the tube is still soft1 place it suddenly upon a horizontal surface1 or press it by means of a very flat metallic plate4 ,the object of this operation is to make the end of the tube flat and uniform4 ,the metallic rod which you employ may be the same as we have described in the preceding paragraph4 ,instead of agitating the rod in the tube1 you may hold it in a fixed oblique position1 and turn the tube round with the other hand1 taking care to press it continually and regularly against the rod4 ,see pl4 #a1 fig4 #f4 ,very small tubes can be bordered by approaching their extremities to a flame not acted upon by the blowpipe2 particularly the flame of a spirit-lamp4 ,when the edges of a tube are to be rendered capable of suffering considerable pressure1 you can very considerably augment their strength by soldering a rib or string of glass all round the end of the tube--see pl4 #a1 fig4 #ab4 ,holding the tube in the left hand1 and the string of glass in the right1 you expose them both at once to the flame4 ,when their extremities are sufficiently softened1 you attach the end of the rib of glass to the tube at a very short distance from its extremity2 you then continue gradually to turn the tube1 so as to cause the rib of glass to adhere to it1 in proportion as it becomes softened4 ,when the rib has made the entire circumference of the tube1 you separate the surplus by suddenly darting a strong jet of fire upon the point where it should be divided2 and you continue to expose the tube to the flame1 always turning it round1 until the ring of glass is fully incorporated with the glass it was applied to4 ,you then remove the instrument from the flame1 taking care to anneal it in so doing4 ,during this operation you must take care to prevent the sinking together of the sides of the tube1 by now and then turning the iron rod in its interior4 ,it is a red heat1 or a brownish red heat1 that is best adapted to this operation4 #c4--,,widening4 ,when you desire to enlarge the diameter of the end of a tube1 it is necessary1 after having brought it to a soft state1 to remove it from the flame1 and to press the sides of the glass outwards by means of a large rod of iron with a conical point4 ,the tube must be again heated1 and again pressed with the conical iron rod1 until the proper enlargement is effected4 ,this operation is much the same as that of bordering a tube with projecting edges4 #d4--;,,drawing ,,out4 ,you can draw out or contract a tube either in the middle or at the end4 ,let us in the first place consider that a tube is to be drawn out in the middle4 ,if the tube is long1 you support it with the right hand below1 and the left hand above1 by which means you secure the force that is necessary1 as well as the position which is commodious1 for turning it continually and uniformly in the flame4 ,it must be kept in the jet till it has acquired a cherry red heat4 ,you then remove it from the flame1 and always continuing gently to turn it1 you gradually separate the hands from each other1 and draw the tube in a straight line4 ,in this manner you produce a long thin tube in the centre of the original tube1 which ought to exhibit two uniform cones where it joins the thin tube1 and to have the points of these cones in the prolongation of the axis of the tube4 ,see pl4 #a1 fig4 #c4 ,to draw out a tube at its extremity1 you heat the extremity till it is in fusion1 and then remove it from the flame2 you immediately seize this extremity with the pliers1 and at the same time separate the two hands4 ,the more rapidly this operation is performed1 the glass being supposed to be well softened1 the more capillary will the drawn-out point of the tube be rendered4 ,instead of pinching the fused end with the pliers1 it is simpler to bring to it the end of a little auxiliary tube1 which should be previously heated1 to fuse the two together1 and then to draw out the end of the original tube by means of the auxiliary tube--see pl4 #a1 fig4 #d and #aa4 ,in all cases1 the smaller the portion of tube softened1 the more abrupt is the part drawn out4 ,when you desire to draw out a point from the side of a tube1 you must heat that portion alone1 by holding it fixedly at the extremity of the jet of flame4 ,when it is sufficiently softened1 solder to it the end of an auxiliary tube1 and then draw it out4 ,pl4 #a1 fig4 #ah1 exhibits an example of a tube drawn out laterally4 ,a red heat1 or a cherry red heat1 is best adapted to this operation4 #e4--;,,choking4 ,we do not mean by choking1 the closing or stopping of the tube1 but simply a diminution of the interior passage1 or bore4 ,it is a sort of contraction4 ,for examples1 see pl4 #b1 fig4 #ae1 #bj1 #bi4 ,you perform the operation by presenting to the flame a zone of the tube at the point where the contraction is to be effected4 ,when the glass is softened1 you draw out the tube1 or push it together1 according as you desire to produce a hollow in the surface of the tube1 or to have the surface even1 or to cause a ridge to rise above it4 ,a cherry red heat is the proper temperature to employ4 #f4--,,sealing4 ,if the sides of the tube to be sealed are thin1 and its diameter is small1 it is sufficient to expose the end that you wish to close to the flame of the lamp4 ,when the glass is softened it sinks of itself1 in consequence of the rotatory motion given to it1 towards the axis of the tube1 and becomes rounded4 ,the application of no instrument is necessary4 ,if the tube is of considerable diameter1 or if the sides are thick1 you must soften the end1 and then1 with a metallic rod or a flat pair of pliers1 mould the sides to a hemisphere1 by bringing the circumference towards the centre1 and continuing to turn the tube in the flame1 until the extremity is well sealed1 and perfectly round4 ,examples of the figure are to be seen in pl4 #b1 fig4 #c and #e4 ,instead of this method1 it is good1 when the extremity is sufficiently softened1 to employ an auxiliary tube1 with the help of which you can abruptly draw out the point of the original tube1 which becomes by that means cut and closed by the flame4 ,in order that this part may be well rounded1 you may1 as soon as the tube is sealed1 close the other extremity with a little wax1 and continue to expose the sealed part to the flame1 until it has assumed the form of a drop of tallow4 ,see pl4 #b1 fig4 #ae4 ,you can also seal in this fashion1 by blowing1 with precaution1 in the open end of the tube1 while the sealed end is in a softened state4 ,if you desire the sealed part to be flat1 like pl4 #c1 fig4 #cj1 you must press it1 while it is soft1 against a flat substance4 ,if you wish it to be concave1 like the bottom of a bottle1 or pl4 #c1 fig4 #b1 you must suck air from the tube with the mouth2 or1 instead of that1 force the softened end inwards with a metallic rod4 ,you may also draw out the end till it be conical1 as pl4 #b1 fig4 #d1 or terminate it with a little button1 as pl4 #b1 fig4 #f4 ,in some cases the sealed end is bent laterally2 in others it is twirled into a ring1 having previously been drawn out and stopped in the bore4 ,in short1 the form given to the sealed end of a tube can be modified in an infinity of ways1 according to the object for which the tube may be destined4 ,you should take care not to accumulate too much glass at the place of sealing4 ,if you allow it to be too thick there1 you run the risk of seeing it crack during the cooling4 ,some farther observations on sealing will be found at the article ,water ,hammer1 in a subsequent section4 ,the operation of sealing succeeds best at a cherry-red heat4 #g4--;,,blowing4 ,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 spherical4 ,this is one of the most difficult operations4 ,to blow a bulb at the extremity of a tube1 you commence by sealing it2 after which1 you collect at the sealed extremity more or less glass1 according to the size and the solidity which you desire to give to the bulb4 ,when the end of the tube is made thick1 completely sealed1 and well rounded1 you elevate the temperature to a reddish white heat1 taking care to turn the tube continually and rapidly between your fingers4 ,when the end is perfectly soft you remove it from the flame1 and1 holding the tube horizontally1 you blow quickly with the mouth into the open end1 without discontinuing for a single moment the movement of rotation4 ,if the bulb does not by this operation acquire the necessary size1 you soften it again in the flame1 while under the action of which you turn it very rapidly1 lest it should sink together at the sides1 and become deformed4 ,when it is sufficiently softened you introduce1 in the same manner as before1 a fresh quantity of air4 ,it is of importance to observe that1 if the tube be of a large diameter1 it is necessary to contract the end by which you are to blow1 in order that it may be turned round with facility while in the mouth4 ,when the bulb which you desire to make is to be somewhat large1 it is necessary1 after having sealed the tube1 to soften it for the space of about half an inch from its extremity1 and then1 with the aid of a flat piece of metal1 to press moderately and repeatedly on the softened portion1 until the sides of the tube which are thus pressed upon1 sink together1 and acquire a certain degree of thickness4 ,during this operation1 however1 you must take care to blow1 now and then1 into the tube1 in order to retain a hollow space in the midst of the little mass of glass1 and to hinder the bore of the tube from being closed up4 ,when you have thus1 at the expense of the length of the tube1 accumulated at its extremity a quantity of glass sufficient to produce a bulb1 you have nothing more to do than to heat the matter till it is raised to a temperature marked by a reddish-white colour1 and then to expand it by blowing4 ,instead of accumulating the glass thus1 it is more expedient to blow on the tube a series of little bulbs close to one another 7see pl4 #a1 fig4 #h71 and then1 by heating the intervals1 and blowing1 to unite these little bulbs into a large one of convenient dimensions4 ,we have already observed1 and we repeat here1 that it is indispensably necessary to hold the glass out of the flame during the act of blowing4 ,this is the only means of maintaining uniformity of temperature in the whole softened parts of the tube1 without which it is impossible to produce bulbs with sides of equal thickness in all their extent4 ,when you desire to form a bulb at the extremity of a capillary tube1 that is to say1 of a tube which has a bore of very small diameter1 such as the tubes which are commonly employed to form thermometers1 it would be improper to blow it with the mouth2 were you to do so1 the vapour which would be introduced1 having a great affinity for the glass1 would soon obstruct the little canal1 and present to the passage of the air a resistance1 which1 with the tubes of smallest interior diameter1 would often be insurmountable4 ,but1 even when the tubes you employ have not so very small an internal diameter1 you should still take care to avoid blowing with the mouth2 because the introduction of moisture always injures fine instruments1 and it is impossible to dry the interior of a capillary tube when once it has become wet4 ,it is better to make use of a bottle of ,indian rubber1 which can be fixed on the open end of the tube by means of a cork with a hole bored through it4 ,you press the bottle in the hand1 taking care to hold the tube vertically1 with the hot part upwards2 if you were not to take this precaution1 the bulb would be turned on one side1 or would exhibit the form of a pear1 because it is impossible1 in this case1 to give to the mass in fusion that rotatory motion which is necessary1 when the tube is held horizontally1 to the production of a globe perfectly spherical in its form1 and with sides of equal thickness4 ,whenever you blow into a tube you should keep the eye fixed on the dilating bulb1 in order to be able to arrest the passage of air at the proper moment4 ,if you were not to attend to this1 you would run the risk of giving to the bulb too great an extension1 by which the sides would be rendered so thin that it would be liable to be broken by the touch of the lightest bodies4 ,this is the reason that1 when you desire to obtain a large bulb1 it is necessary to thicken the extremity of the tube1 or to combine many small bulbs in one1 that it may possess more solidity4 ,in general1 when you blow a bulb with the mouth1 it is better to introduce the air a little at a time1 forcing in the small portions very rapidly one after the other2 rather than to attempt to produce the whole expansion of the bulb at once3 you are then more certain of being able to arrest the blowing at the proper time4 ,when you desire to produce a moderate expansion1 either at the extremity or in any other part of a tube1 you are enabled easily to effect it by the following process1 which is founded on the property possessed by all bodies1 and especially by fluids1 of expanding when heated2 a property which characterises air in a very high degree4 ,after having sealed one end of the tube and drawn out the other1 allow it to become cold1 in order that it may be quite filled with air2 close the end which has been drawn out1 and prevent the air within the tube from communicating with that at its exterior2 then gradually heat the part which you desire to have expanded1 by turning it gently in the flame of a lamp4 ,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 tube2 the glass expands1 and produces a bulb or swelling more or less extensive1 according as you expose the glass to a greater or lesser degree of heat4 ,to blow a bulb in the middle of a tube1 it is sufficient to seal it at one of its extremities1 to heat the part that you wish to inflate1 and1 when it is at a cherry-red heat1 to blow in the tube1 which must be held horizontally and turned with both hands1 of which1 for the sake of greater facility1 the left may be held above and the right below4 ,if the bulb is to be large1 the matter must previously be thickened or accumulated1 or1 instead of that1 a series of small bulbs first produced1 and these subsequently blown into a single larger bulb1 as we have already mentioned4 ,see pl4 #a1 fig4 #h4 ,for some instruments1 the tubes of which must be capillary1 it is necessary to blow the bulbs separately1 and then to solder them to the requisite adjuncts4 ,the reason of this is1 that it would be too difficult to produce1 from a very fine tube1 a bulb of sufficient size and solidity to answer the intended purpose4 ,you make choice of a tube which is not capillary1 but of a sufficient diameter1 very cylindrical1 with equal sides1 and tolerably substantial3 it may generally be from the twentieth to the twelfth of an inch thick in the glass4 ,you soften two zones in this tube1 more or less near to each other1 according to the bulk you desire to give to the bulb1 and you draw out the melted part in points4 ,the talent consists in well-centering--that is to say1 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 them4 ,this operation is technically termed drawing a cylinder between two points4 ,the tube so drawn out is exhibited by pl4 #a1 fig4 #d4 ,you cut these points at some distance from the central or thick part1 and seal one end2 you next completely soften the little thick tube and expand it into a bulb1 by blowing with the precautions which have already been described4 ,you must keep the glass in continual motion1 if you desire to be successful in this experiment4 ,much rapidity of movement1 and at the same time lightness of touch1 are requisite in the operation here described4 ,it is termed blowing a bulb between two points4 ,pl4 #a1 fig4 #aj1 exhibits a bulb blown between two points4 ,to obtain a round bulb1 you should hold the tube horizontally2 to obtain a flattened bulb1 you should hold it perpendicularly1 with the fused extremity turned above2 to obtain a pear-shaped bulb1 you should hold the fused extremity downwards4 ,when you are working upon a bulb between two points1 or in the middle of a tube1 you should hold the tube horizontally1 in the ordinary manner2 but you are to push the softened portion together1 or to draw it out1 according as you desire to produce a ridge or a prolongation4 ,when you are at liberty to choose the point from which you are to blow1 you should prefer1 #ast1 that where the moisture of the breath can be the least prejudicial to the instrument which is to be made2 #b;dly1 that which brings the part which is to be expanded nearest to your eye2 #c;dly1 that which presents the fewest difficulties in the execution4 ,when bulbs are to be formed in complicated apparatus1 it is good to reflect a little on the best means of effecting the object4 ,it is easy to understand that contrivances which may appear very simple on paper1 present difficulties in the practical execution which often call for considerable management4 #h4--,,piercing4 ,you first seal the tube at one extremity1 and then direct the point of the flame on the part which you desire to pierce4 ,when the tube has acquired a reddish-white heat1 you suddenly remove it from the flame1 and forcibly blow into it4 ,the softened portion of the tube gives way before the pressure of the air1 and bursts into a hole4 ,you expose the tube again to the flame1 and border the edges of the hole4 ,it is scarcely necessary to observe1 that1 if it be a sealed extremity which you desire to pierce1 it is necessary to turn the tube between the fingers while in the fire2 but if1 on the contrary1 you desire to pierce a hole in the side of a tube1 you should keep the glass in a fixed position1 and direct the jet upon a single point4 ,if the side of the tube is thin1 you may dispense with blowing4 ,the tube is sealed and allowed to cool2 then1 accurately closing the open extremity with the finger1 or a little wax1 you expose to the jet the part which you desire to have pierced4 ,when the glass is sufficiently softened1 the air enclosed in the tube being expanded by the heat1 and not finding at the softened part a sufficient resistance1 bursts through the tube1 and thus pierces a hole4 ,you may generally dispense with the sealing of the tube1 by closing the ends with wax1 or with the fingers4 ,there is still another method of performing this operation1 which is very expeditious1 and constantly succeeds with objects which have thin sides4 ,you raise to a reddish white heat a little cylinder of glass1 of the diameter of the hole that you desire to make1 and you instantly apply it to the tube or globe1 to which it will strongly adhere4 ,you allow the whole to cool1 and then give the auxiliary cylinder a sharp slight knock2 the little cylinder drops off1 and carries with it the portion of the tube to which it had adhered4 ,on presenting the hole to a slight degree of heat1 you remove the sharpness of its edges4 ,when you purpose to pierce a tube laterally1 for the purpose of joining to it another tube1 it is always best to pierce it by blowing many times1 and only a little at a time1 and with that view1 to soften the glass but moderately4 ,by this means the tube preserves more thickness1 and is in a better state to support the subsequent operation of soldering4 ,there are circumstances in which you can pierce tubes by forcibly sucking the air out of them2 and this method sometimes presents advantages that can be turned to good account4 ,finally1 the orifices which are produced by cutting off the lateral point of a tube drawn out at the side1 may also be reckoned as an operation belonging to this article4 #i4--;,,bending4 ,if the tube is narrow1 and the sides are pretty thick1 this operation presents no difficulty4 ,you heat the tube1 but not too much1 lest it become deformed2 a reddish-brown heat is sufficient1 for at that temperature it gives way to the slightest effort you make to bend it4 ,you should1 as much as possible1 avoid making the bend too abrupt4 ,for this purpose1 you heat a zone of one or two inches in extent at once1 by moving the tube backwards and forwards in the flame1 and you take care to bend it very gradually4 ,but if the tube is large1 or its sides are thin1 and you bend it without proper precautions1 the force you employ entirely destroys its cylindrical form1 and the bent part exhibits nothing but a double flattening1--a canal1 more or less compressed4 ,to avoid this deformity it is necessary1 first1 to seal the tube at one extremity1 and then1 while giving it a certain curvature1 to blow cautiously by the other extremity1 which for convenience sake should previously be drawn out4 ,when tubes have been deformed by bad bending1 as above described1 you may1 by following this method1 correct the fault2 that is to say1 upon sealing one extremity of the deformed tube1 heating the flattened part1 and blowing into the other extremity1 you can with care reproduce the round form4 ,in general1 that a curvature may be well-made1 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 operation1 while the other side be only softened to such a degree as to enable it to give way under the force applied to bend it4 ,on this account1 after having softened in a cherry-red heat one side of the tube1 you should turn the other side1 which is to form the exterior of the curvature1 towards you1 and then1 exposing it to the point of the jet1 you should bend the tube immediately upon its beginning to sink under the heat4 ,when you desire to bend the extremity of a tube into a ring you must employ a metallic rod1 with which1 by pressing on the tube1 you separate with a curve1 ,c1 7see pl4 #a1 fig4 #ad7 all the portion ,a ,c which is necessary to produce the desired curl4 ,you then successively soften all parts of this curve1 and gradually twist it in the direction indicated by the arrow1 pressing the iron rod constantly upon the extremity of the curve4 ,when the end ,a comes into contact with bend ,c you solder them together at this point1 and thus complete the ring4 ,pl4 #b1 fig4 #bg1 and pl4 #c1 fig4 #bg1 exhibit examples of rings formed by this process4 #aj4--,,soldering4 ,if the tubes which you propose to solder are of a small diameter1 pretty equal in size1 and have thick sides1 it is sufficient1 before joining them together1 to widen them equally at their extremities1 by agitating a metallic rod within them4 7,pl4 #a1 fig4 #ag47 ,but if they have thin sides1 or are of a large diameter1 the bringing of their sides into juxta-position is very difficult1 and the method of soldering just indicated becomes insufficient4 ,in this case you are obliged to seal1 and subsequently to pierce1 the two ends which you desire to join4 ,the disposition which this operation gives to their sides very much facilitates the soldering4 ,finally1 when the tubes are of a very different diameter1 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 to4 ,pl4 #a1 fig4 #i and #ae1 exhibit examples of this mode of adapting tubes to one another4 ,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 completely4 ,see pl4 #a1 fig4 #g4 ,when the holes are well prepared1 you heat at the same time the two parts that are to be soldered together1 and join them at the moment when they enter into fusion4 ,you must push them slightly together1 and continue to heat successively all their points of contact2 whereupon the two tubes soon unite perfectly4 ,as it is almost always necessary1 when you desire the soldering to be neatly done1 or the joint to be imperceptible1 to terminate the operation by blowing1 it is proper to prepare the extreme ends of the tubes before-hand4 ,that end of the tube by which you intend to blow should be carefully drawn out1 provided it be so large as to render drawing out necessary2 and the other end of the tube1 if large1 should be closed with wax1 as in pl4 #a1 fig4 #i1 or if small1 should be sealed at the lamp 7pl4 #a1 fig4 #ae74 ,when the points of junction are perfectly softened1 and completely incorporated with each other1 you introduce a little air into the tube1 which produces a swelling at the joint4 ,as soon as this has taken place1 you must gently pull the two ends of the joined tube in different directions1 by which means the swelled portion at the joint is brought down to the size of the other parts of the tube1 so that the whole surface becomes continuous4 ,the soldering is then finished4 ,to solder a bulb or a cylinder between two points1 to the extremity of a capillary tube1 you cut and seal one of the points at a short distance from the bulb 7pl4 #a1 fig4 #af71 and at the moment when this extremity is in fusion you pierce it by blowing strongly at the other extremity4 ,by this means the opening of the reservoir is terminated by edges very much widened1 which facilitates considerably its being brought into juxta-position with the little tube4 ,in order that the ends of the two tubes may be well incorporated the one with the other1 you should keep the soldered joint for some time in the flame1 and ought to blow in the tube1 push the ends together and draw them asunder1 until the protuberance is no longer perceptible4 ,if1 after having joined two tubes1 it should be found that there still exists an opening too considerable to be closed by simply pushing the two tubes upon one another1 you can close such an opening by means of a morsel of glass1 applied by presenting the fused end of an auxiliary tube4 ,you should avoid soldering together two different species of glass--for example1 a tube of ordinary glass with a tube of flint-glass2 because these two species of glass experience a different degree of contraction upon cooling1 and1 if joined together while in a fused state1 are so violently pulled from one another as they become cool1 that the cohesion of the point of soldering is infallibly overcome1 and the tube breaks4 ,you ought also1 for a similar reason1 to take care not to accumulate a greater mass of glass in one place than in another4 ,if the first operation has not been sufficient to complete the soldering1 the tube must be again presented to the flame1 and again pushed together at the joint1 or drawn asunder1 or blown into1 according as it may appear to be necessary4 ,in all cases the soldering is not truly solid1 but inasmuch as the two masses of glass are well incorporated together1 and present a surface continuous in all points4 ,the mineralogical flame 7pl4 #a1 fig4 #a1 ,a ,b7 is that which is to be employed in preference to the larger flame1 when you desire to effect a good joining3 it is sufficient to proportion the size of the flame to the object you wish to execute4 ,,the ,,art ,,of ,,glass-,,blowing4 ,,iv4--,construction of ,chemical and ,philosophical ,instruments4 ,when a person is well acquainted with the fundamental operations which we have just described1 the preparation of the instruments of which we are about to speak can present scarcely any difficulty4 ,indeed1 some of them are so extremely simple1 and are so easy of execution1 that it is sufficient to cast a glance upon the figures which represent them1 to seize at once the method which must be followed in their construction4 ,of such instruments we shall not stop to give a detailed description1 but shall content ourselves with presenting the design4 ,on the other hand1 it is of importance to observe that a certain number of instruments are graduated or furnished with pieces1 or mountings1 of which it is not the object of our art to teach the construction1 and which demand a more or less extensive knowledge of the sciences4 ,we shall treat of these mountings but summarily1 referring the student1 for more detailed instructions1 to the works on natural philosophy and chemistry1 in which these instruments are especially treated of4 ,our reason for this is1 that we do not wish to abandon the plan we had adopted of describing simply the art of glass-blowing4 ,to describe the use and application of philosophical instruments1 or to explain the principles on which they act1 would be passing quite out of our province4 ,,adapters4--,these are tubes of glass of various forms1 employed in chemistry to connect together the different pieces constituting an apparatus--as1 for example1 to join a retort to a receiver during the operation of distillation4 ,you should take care to border the extremities of an adapter2 or you may widen them into the form of the mouth of a bottle1 when they are to be closed air-tight by corks4 ,besides this1 there is nothing particular to be observed in the preparation of adapters4 99 99 99 99 99 ,,apparatus ,,for ,,boiling ,,in ,,vacuo4--,represented by pl4 #c1 fig4 #ai4 ,employ a tube about a quarter of an inch in diameter4 ,blow two bulbs2 give the tube the necessary curvature2 fill one of the bulbs with nitric ether2 boil the ether to expel the atmospheric air from the apparatus1 then seal the opening in the other bulb4 99 99 99 99 99 ,,apparatus ,,for ,,freezing ,,in ,,vacuo4 ,the ,cryophorus4--,take a tube one-third of an inch or rather more in diameter1 and pretty thick in the sides4 ,blow a bulb at each end2 the first at the sealed part of the tube1 the other at the open point2 then give to the tube the curvature represented by pl4 #c1 fig4 #cb4 ,introduce as much water as will half fill one of the bulbs2 make the water boil1 and draw off the point and seal the apparatus during the ebullition4 99 99 99 99 99 ,,apparatus ,,for ,,conducting ,,water ,,in ,,bent ,,tubes4--,solder a funnel 7see ,,funnels7 to the end of a tube2 pierce two holes in this tube in the same line1 and solder to each a little addition proper to receive a cork4 ,finish the instrument by bending it in the manner indicated by pl4 #d1 fig4 #ah4 99 99 99 99 99 ,,apparatus ,,for ,,experiments ,,on ,,running ,,liquids4--,a tube bent once at a right angle1 mounted with a funnel1 pierced laterally1 and soldered at the same point to a smaller tube4 ,see pl4 #c1 fig4 #ag4 99 99 99 99 99 ,,apparatus ,,for ,,exhibiting ,,the ,,phenomena ,,of ,,capillary ,,tubes4--,this apparatus consists of a capillary tube soldered to another tube of a more considerable diameter4 ,sometimes it is bent like the letter ,u4 ,pl4 #c1 fig4 #ae4 99 99 99 99 99 ,,apparatus ,,for ,,the ,,preparation ,,of ,,phosphuret ,,of ,,lime4--,an apparatus that can be employed for the preparation of phosphuret of lime1 as well as in a variety of other chemical experiments1 consists of a tube sealed at one extremity1 slightly bent and choked at two inches and a half from the sealed part1 and drawn out 7after the introduction of the substances to be operated upon7 at the other extremity4 ,this little distillatory apparatus is represented by pl4 #c1 fig4 #bi4 99 99 99 99 99 ,,archimedes',s ,,screw4--,there is no particular process for the making of this instrument4 ,it is1 however1 necessary for one who would succeed in making it1 to exercise himself in the art of well bending a tube4 ,after a few attempts1 you may finish by producing a pretty-regular spiral4 ,the tube chosen for this instrument should be six or seven feet long1 and about one-third of an inch in diameter4 ,you commence by making a bend1 nearly at a right angle1 about four inches from one of its extremities4 ,this bent portion serves afterwards as a handle1 and very much facilitates the operation2 it represents the prolongation of the rational axis which may be conceived to pass through the centre of the spiral4 ,see pl4 #d1 fig4 #aj4 99 99 99 99 99 ,,barker',s ,,mill4--,apparatus for exhibiting the rotatory motion produced by the running of liquids4--,contract a tube at its two extremities1 pierce it laterally about the middle of its length1 and solder to the hole an additional tube1 terminated by a funnel4 ,soften the principal tube at the side opposite to the part that was pierced1 and form there a conical cavity by pressing the softened glass inward with the aid of a metallic rod4 ,this cavity must be so carefully made that the whole apparatus can be supported on a pivot4 ,bend the contracted ends of the tube horizontally1 and in different directions1 cut off their extremities at a proper length1 and slightly border the edges of the orifices4 ,see pl4 #c1 fig4 #cc4 ,you may produce this apparatus under a different form1 as may be seen at pl4 #c1 fig4 #e4 99 99 99 99 99 ,,barometers4--,barometers serve to measure the pressure of the atmosphere4 ,the following are the varieties most in use4 99 99 99 99 99 ,,cistern ,,barometer4--,take a tube about thirty-two inches long1 and at least one-third of an inch in diameter1 internally2 seal one of its extremities1 free it with most particular care from moisture1 fill it with mercury1 and make the mercury boil in the tube1 by heat1 in order to drive out every particle of air which might be present4 ,when the tube is full of mercury1 and the boiling has taken place1 turn it upside down1 and plunge the open end into a cistern also filled with mercury which has been boiled4 ,see pl4 #b1 fig4 #d4 99 99 99 99 99 ,,dial 7or ,,wheel7 ,,barometer4--,the tube intended for this barometer should be very regular in the bore4 ,it should be thirty-nine inches long4 ,close it at one end1 and bend it like the letter ,u at about thirty-two inches from the sealed extremity4 ,see pl4 #b1 fig4 #e1 and ,graduation of the ,dial ,barometer4 ,,syphon ,,barometer4--,make use of such a tube as might be employed for a ,cistern ,barometer2 solder to its open end a cylindrical or spherical reservoir1 and bend the tube close to the point of junction in such a manner as to bring the cylinder parallel with the tube4 ,if the reservoir is to be closed with a cover of leather1 cut off the remaining point of the cylinder1 slightly widen the orifice1 and then border it4 ,if no leather is to be applied1 but the point of the cylinder left open1 it is necessary1 after the introduction of the mercury1 to draw off the point abruptly1 and to leave an opening so small that mercury cannot pass by it4 ,pl4 #b1 fig4 #f4 99 99 99 99 99 ,,stop-,,cock ,,barometer4--,this differs from the preceding barometer only by having a stop-cock mounted in iron between the reservoir and the tube4 99 99 99 99 99 ,,compound ,,barometers4--,blow a bulb at each end of a barometer tube of about thirty-three inches in length4 ,solder a small and almost capillary tube to the point which terminates one of the bulbs1 and bend the great tube very near this bulb4 ,this must be done in such a manner that the centre of one bulb shall be thirty inches from the centre of the other bulb4 ,introduce a quantity of mercury sufficient to fill the great tube and half the two bulbs2 fill the remaining space in the last bulb with alcohol4 ,you may give a different disposition to this instrument4 ,divide a barometer tube into two1 three1 or four pieces1 and reunite the pieces by intermediate capillary tubes1 so as to form a series of large and small tubes1 soldered alternately the one at the end of the other4 ,then communicate to this compound tube the form exhibited by pl4 #c1 fig4 #be1 and join1 at each superior bend1 a little tube1 for the convenience of easily filling the instrument with mercury3 seal these tubes as soon as the mercury is introduced4 ,the graduation of compound barometers is made by bringing them into comparison with a good standard barometer4 ,after taking two or three fixed points1 it is easy to continue the scale4 99 99 99 99 99 ,,gay ,,lussac',s ,,barometer4--,take a tube which is very regular in the bore1 four-tenths of an inch in diameter1 and thirty-five inches and a half in length4 ,seal one of its extremities and draw out the other2 then cut the tube at about two-thirds of its whole length from the sealed end1 and reunite the two pieces by means of a capillary tube soldered between them1 the whole being kept in a line4 ,see pl4 #b1 fig4 #a4 ,pierce laterally the part of the tube which is drawn out1 at some inches from the base of the point1 and force the margin of the hole into the interior of the tube1 by means of a conical point of metal1 in such a manner as to form a little sunk funnel1 of which the orifice must be very small4 ,after having introduced the proper quantity of mercury into the instrument1 boil it1 and assist the disengagement of the bubbles of air by agitating a fine iron wire within the tube4 ,then remove the part of the tube which was drawn out1 by sealing the end of the wide part4 ,give to the whole instrument the curvature indicated by pl4 #b1 fig4 #c4 99 99 99 99 99 ,,bunten',s ,,barometer4--,this instrument differs from the preceding but in one point1 namely1 that the capillary tube is formed of two soldered pieces1 of which the one1 passing into the other1 is terminated by a capillary point4 ,this arrangement is exhibited by pl4 #b1 fig4 #b4 99 99 99 99 99 ,,barometer ,,pierced ,,laterally ,,for ,,demonstrations4--,take a tube thirty-nine inches long1 with thick sides1 and two-tenths of an inch internal diameter4 ,seal it at one end1 and choke it at the distance of eight inches therefrom4 ,pierce a hole in the tube about twelve or sixteen inches from the choked part1 and solder to the hole an additional piece1 which can be closed by a cork or covered by a piece of bladder4 ,the instrument is represented by pl4 #b1 fig4 #ae4 99 99 99 99 99 ,,bell-,,glasses ,,for ,,experiments4--,these are pieces of tube sealed at one end1 and widened or bordered at the other4 ,they are extremely useful1 and much employed in chemical experiments4 ,they also supply the place of bottles for preserving small quantities of substances4 ,sometimes they are required to be straight1 as pl4 #c1 fig4 #ab4 ,sometimes they need to be curved1 as pl4 #c1 fig4 #bi4 ,this is particularly the case when they are to be employed as retorts1 for which purpose the sealed part should be made thin4 ,pl4 #c1 fig4 #f1 exhibits a retort with a tubulure4 99 99 99 99 99 ,,blowpipe4--,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 work4 ,see pl4 #a1 fig4 #ai4 ,the beak ,c1 which is employed with the candlestick1 is merely a bent tube1 at the extremity of which a bulb is blown4 ,the bulb is terminated by a point1 the thickness of the sides of which is augmented by turning it for a long time in the flame4 ,as for the beak used with the lamp1 it is simply a bent tube ,c1 of which the orifice has been diminished by turning it round in the flame4 ,the point of this beak is not drawn out like that of the beak described in the preceding paragraph1 but is allowed to be thick1 that it may not melt in the flame of the lamp4 ,the tube ,d ,f has four-tenths of an inch internal diameter1 and is pretty thick in the sides4 ,you must commence by bordering and slightly widening one of its extremities1 and then proceed to choke it at about two inches from its other extremity1 taking care to give to the choked part a figure as perfectly conical as possible1 in order that the valve may act well4 ,we have described the valve at length at p4 #f4 ,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 latter4 ,its use is to lengthen or shorten the tube for the convenience of the blower4 ,the lower end is wound round with waxed thread1 to make it fit air-tight4 ,the mouth-piece is executed by widening the end of the tube1 and then1 while the widened part is still soft1 by pressing the two sides obliquely1 one against the other4 ,by this means you give to the mouth-piece a flattened form1 which adapts it better to the lips4 ,the tube is finished by slightly bending this extremity4 ,in order that the bladder1 or air reservoir1 may be conveniently and securely attached to the tube ,e1 you must take care to widen the end of this tube1 and to turn up the edges strongly1 by pressing the soft end against a flat metallic surface4 99 99 99 99 99 ,,capsules4--,these are very small mercury funnels1 of which the opening or neck has been closed4 ,to transform these funnels into capsules1 you must cut the neck as close as possible1 and then soften1 close1 and flatten the opening4 ,in performing this operation1 hold the capsule by the edge with your pincers1 and employ a piece of metal to press the glass together and make it close the hole and form the flat bottom of the capsule4 ,see pl4 #b1 fig4 #bc4 ,another ,method4--,after having blown a bulb at the end of a point1 soften a narrow zone of the bulb1 and then blow suddenly and strongly into it2 by which means you separate the bulb into two capsules1 which only need to be bordered4 ,if you find any difficulty in presenting to the flame the capsule which forms the part of the bulb opposed to the point1 you can attach to it a little rod of glass1 which you can afterwards easily separate by a slight smart blow4 ,occasionally you will have to make capsules with double sides1 which will be described at the article ,nicholson's ,hydrometer4 99 99 99 99 99 ,,cartesian ,,devils4--,blow a bulb at the extremity of a very small tube1 and heat a portion of the bulb1 for the purpose of prolonging it into a beak4 ,this can be effected with the aid of an auxiliary tube1 which1 on being joined to the heated part of the bulb1 carries away with it the portion of glass which adheres4 ,this portion of the bulb becomes thus prolonged into a little point1 which must be cut at its extremity1 so as to leave a small opening4 ,the principal tube must be cut at the distance of half an inch from the bulb1 and the ends of it must be drawn out and twisted into a ring4 ,instead of forming laterally a little beak to the bulb1 you may pierce the tail1 after twisting it into the form of a ring1 or you may manage in such a manner as not to obliterate the canal of the twisted part4 ,in general1 little enamel figures are suspended to the ring of these globes1 as is represented by pl4 #b1 fig4 #bb4 ,a simple bulb1 blown at the extremity of a small portion of tube1 can supply the place of the ,ludion or ,cartesian devil4 ,see pl4 #b1 fig4 #h4 99 99 99 99 99 ,,communicating ,,vases4--,employ a tube of a large diameter2 terminate one of its extremities with a funnel1 fashion the other like the neck of a bottle2 and bend the tube into the shape shewn by pl4 #d1 fig4 #aa4 ,then twist some other tubes into various forms1 according to the end you propose to attain1 and adjust these tubes to the neck of the large tube by means of corks1 which have holes bored through them4 ,in this manner an exchange of tubes is provided for various experiments4 99 99 99 99 99 ,,dropping ,,tubes4--,the name dropping tube is given to an instrument of glass which is very much employed in chemistry1 for the purpose of transferring small quantities of liquor from one vessel into another1 without disturbing either of the vessels4 ,dropping tubes are made of a great variety of forms and sizes1 according to the purposes to which they are intended to be applied4 ,blow a bulb between two points1 and then1 before the glass has regained its consistence1 lengthen the bulb into an oval form4 ,cut and border the two points4 ,if the bulb1 or reservoir1 is to be so large that it cannot be formed at the expense of the thickness of the tube1 and yet be sufficiently strong1 it must be blown separately from a larger tube1 and then soldered to two smaller tubes1 one of which should have a certain curvature given to it4 ,see pl4 #b1 fig4 #bj4 ,sometimes a dropping tube is employed to measure small quantities of liquid4 ,in this case the point should be drawn off abruptly1 and the scale should be marked on the shank or tube with spots of black enamel4 ,pl4 #b1 fig4 #ba1 represents a peculiar variety of dropping tube employed in some experiments4 ,it is made in the same manner as the common dropping tubes1 excepting that1 when the tail is formed1 it is sealed at the extremity1 bent there into a ring1 and then pierced at ,a4 ,pl4 #c1 fig4 #bf1 represents another variety of dropping tube1 a description of which is unnecessary4 99 99 99 99 99 ,,fountains4--,it will readily be understood by those acquainted with the construction of hydraulic apparatus1 that1 by means of a judicious arrangement of glass tubes1 a great variety of fountains may be produced4 ,the following are given as examples4 99 99 99 99 99 ,,fountain ,,of ,,circulation4--,take a tube1 twenty-four or thirty inches long1 nearly half an inch in diameter1 and with pretty thick sides2 blow a bulb at one of its extremities1 and bend the other into a ,u1 after having drawn it out as indicated by pl4 #c1 fig4 #d4 ,pierce the tube at ,b1 and join there a short piece adapted to receive a cork4 ,then prepare a bulb of the same size as the first bulb1 and solder it to the extremity of a very long and almost capillary tube1 which you must bend in zig-zag1 in such a manner as to make it represent a ,maltese cross1 a star1 a rose1 or any other figure that may be suggested4 ,the side of the bulb opposite to that which is attached to this twisted tube1 ought to be formed like the neck of a bottle1 in order that it may receive the drawn-out part of the larger tube1 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 bulb4 ,this disposition is shewn in the figure4 ,seal now the other end of the little tube to the bulb of the large tube2 then1 with a little cement or sealing-wax1 close the space between the bulb of the little tube and the point of the large tube4 ,the instrument being thus prepared1 as much alcohol1 previously coloured red1 must be inserted by the neck b as is sufficient to fill one of the bulbs4 ,the neck is then closed with a cork1 and a little cement or sealing-wax4 ,or1 instead of forming this neck to the instrument1 the additional piece may be drawn out to a point1 which permits it to be sealed hermetically4 99 99 99 99 99 ,,fountain ,,of ,,compression4--,introduce into a tube of large diameter a piece of capillary tube with thick sides4 ,this must pass a little beyond the extremity of the large tube1 which is to be softened and soldered to the other1 so that it shall be fixed concentrically4 ,the common point is then to be drawn out4 ,when the tube is quite cold1 and the small tube properly fixed in the centre of the large one1 cut the latter at a proper distance1 border it1 and choke it near the end1 which must be fashioned in such a manner as to be capable of being completely closed by a cork4 ,see pl4 #b1 fig4 #bi4 99 99 99 99 99 ,,intermitting ,,fountain4--,this apparatus is represented by pl4 #c1 fig4 #af4 ,solder a cylindrical reservoir to the extremity of a capillary tube1 pierced at a1 and sealed at its extremity4 ,draw out abruptly the point of the reservoir1 and give it a very small orifice2 then give to the capillary tube the form indicated by the figure4 ,prepare next a funnel resembling a mercury-funnel1 but much larger2 choke the neck of this funnel1 and bend the tube into the form of a syphon4 99 99 99 99 99 ,,hero',s ,,fountain4--,solder a bulb to the extremity of a tube1 and transform the bulb into a funnel4 ,close the funnel with a cork1 and solder to the other end of the tube a bulb similar to the first4 ,next1 solder a third bulb between two tubes1 of which one must be twice as long the other2 solder the longer of these tubes to the bulb of the first tube1 and draw out the point of the shorter tube4 ,you have now a long tube1 with a funnel at one end1 a contracted point at the other1 and two bulbs in its length4 ,give to the whole apparatus the form indicated by pl4 #c1 fig4 #ba4 99 99 99 99 99 ,,funnels4--,it will be seen1 upon looking over the engravings1 that funnels require to be made for a great variety of instruments2 you ought therefore to acquire as soon as possible the art of making them well4 ,the following are those most frequently required4 99 99 99 99 99 ,,retort ,,funnel4--,blow a bulb at the extremity of a tube2 present the superior hemisphere of the bulb to the flame1 and when it is sufficiently softened1 blow strongly into the other end of the tube4 ,the air will force its way through the bulb1 making a hole which will be larger or smaller according to the extent of surface which may have been softened4 ,the opening of the funnel being made thus1 there is nothing more to do than to adjust the edges1 which1 in the present state1 are both fragile and irregular4 ,this it is very easy to do4 ,the edges are softened1 the most prominent parts are cut off with the scissars1 and the parts which are thin are bent back on themselves1 that they may become thicker4 ,upon turning the funnel round in the flame1 the smaller irregularities give way1 and the edges become rounded4 ,see pl4 #b1 fig4 #bd4 ,when the funnel is desired to be very large in proportion to the size of the tube1 a bulb is made from a larger tube1 and afterwards soldered to the small tube1 and transformed into a funnel in the manner above described4 99 99 99 99 99 ,,funnel ,,for ,,introducing ,,mercury ,,into ,,narrow ,,tubes4--,the mercury-funnel is represented by pl4 #b1 fig4 #be4 ,blow a bulb between two points2 cut off one of the points1 and open the bulb at that place1 in the manner described in the preceding article4 99 99 99 99 99 ,,hydrostatic ,,funnel4--,this is represented by pl4 #c1 fig4 #ca4 ,it is an instrument of constant use in chemical experiments4 ,form a funnel at the extremity of a tube in the manner described above1 having previously blown a bulb near the middle of the tube4 ,when this has been done1 bend the tube into the form shown by the figure4 99 99 99 99 99 ,,hour-,,glasses4--,blow four bulbs on a tube close to each other2 open the two end bulbs like funnels1 and then form them into flat supports or pedestals1 according to the method described at the article ,test-glass with a foot4 ,obstruct entirely the canal which separates one of these feet2 choke to a certain extent the passage between the two remaining bulbs2 and close the canal between the other foot and the bulbs1 after introducing the quantity of sand which you have found to be necessary4 ,see pl4 #c1 fig4 #ac4 99 99 99 99 99 ,,hydraulic ,,ram4--,this instrument is represented by pl4 #d1 fig4 #ae4 ,employ a tube about six feet long1 with thick sides and of large diameter4 ,seal it at one extremity1 k1 and border it at the other2 solder at p an additional piece1 choked so as to receive a valve4 ,pierce the tube at l2 draw it out1 and fix a funnel there2 then twist the tube into a spiral4 ,form1 on the other hand1 a fountain of compression1 o1 and a funnel1 m2 and fix both of these pieces by means of sealing-wax1 as soon as the two valves p and l have been put into their places4 99 99 99 99 99 ,,hydrometers4--,hydrometers are instruments which1 on being plunged into liquids1 indicate immediately their density or specific gravity4 ,areometers differ from hydrometers sometimes in graduation1 sometimes merely in name4 ,the following are examples of hydrometers1 of which a great many varieties are in use4 99 99 99 99 99 ,,baum',s ,,hydrometer4--,make a cylinder between two points1 and solder it to the extremity of a tube with thin sides1 and which must be very regular on the outside4 ,close the open part which is to form the stalk of the hydrometer with a little wax4 ,see pl4 #a1 fig4 #i and #ae4 ,when the soldering1 which must be well done1 is complete1 and the stalk well centered1 choke the reservoir at a little distance from the base of the point1 by drawing it out in such a manner as considerably to diminish the canal in this part4 ,remove then the ball of wax which closed the tube1 draw off the point of the cylinder1 and make the part which was pulled away from the cylinder by the choking1 into a bulb1 by blowing with precaution into the tube4 ,if the reservoir is required to be spherical instead of cylindrical1 it must be softened and expanded by blowing4 ,when it is intended to ballast the instrument with mercury1 the canal must be completely stopped at the point where it is choked4 ,in this case1 the part drawn away from the cylinder is expanded into a bulb by blowing through the extreme point1 which is to be cut off after the instrument is completed4 ,in the first case1 you ballast the instrument with lead shot1 which you fix in the lower bulb by means of a little wax1 which closes the canal at the choked part4 ,in the second case1 after having proved the ballast by putting it first into the large reservoir1 it is removed into the little bulb1 and the latter is immediately sealed4 ,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 water4 ,if1 therefore1 on proving the ballast1 you perceive the stalk to rest obliquely1 you must take care1 on retiring it from the water1 to wipe it dry1 and to present the choked part between the cylinder and the little bulb to the flame2 when it is softened1 it is easy1 by giving it a slight bend in the direction where the stalk of the hydrometer passes from the vertical1 to rectify the defect4 ,finally1 when the instrument is ballasted1 you must seal the stalk1 after having fixed in its interior the strip of paper which bears the graduated division4 ,this method of operation serves equally for all the areometers known under the names of areometer of ,baum1 pse-sels1 pse-liqueurs1 pse-acides1 and hydrometers1 which differ only in the scheme of their graduation4 ,as to the size and the length of the stalks1 they depend upon the dimensions you desire to give to the degrees of the scale1 and upon the use to which the instruments are destined4 ,for the areometer of ,baum1 and for the pse-sels1 the stalks are generally thicker and shorter than for hydrometers4 ,pl4 #d1 fig4 #ai1 #bj1 and #ba1 represent different hydrometers4 99 99 99 99 99 ,,nicholson',s ,,hydrometer4--,solder a bulb to the extremity of a capillary tube2 open it so as to form a very wide funnel1 or rather capsule2 border the edges1 and melt the point of junction with the tube so as to close the opening of the latter4 ,solder the other extremity of the tube to a cylindrical reservoir4 ,soften the point at the lower extremity of the cylinder1 and obstruct the canal so as to convert the point into a glass rod2 bend this rod into a hook4 ,now blow a bulb at the end of a point1 as if to make a mercury funnel2 but1 after having softened the hemisphere of the bulb opposite to the point1 and placed the latter in the mouth1 instead of blowing into the bulb so as to make a funnel1 strongly suck air from the bulb3 by this means the softened part of the glass is drawn inwards1 and you obtain a capsule with double sides1 as exhibited by pl4 #b1 fig4 #ag4 ,this capsule must have a small handle fastened across it1 by which it may be hung to the hook formed at the bottom of the cylinder described above4 ,this hydrometer being always brought to the same level1 the point to which it must be sunk in the liquid experimented with1 is marked on the stalk by applying a little spot of black enamel4 ,the instrument is represented by pl4 #d1 fig4 #bc4 ,a variation in form is shewn by pl4 #d1 fig4 #bb4 99 99 99 99 99 ,,hydrometer ,,with ,,two ,,branches4--,to measure the relative density of two liquids which have no action on each other1 you employ a simple tube1 bent in the middle and widened at its two extremities4 ,see pl4 #b1 fig4 #aa4 99 99 99 99 99 ,,hydrometer ,,with ,,three ,,branches4--,this consists of a tube bent in such a manner that the two branches become parallel4 ,to this tube another is soldered at the point of curvature1 and is bent in the direction exhibited by pl4 #b1 fig4 #ab4 ,when the two branches are put into different liquids1 and the operator sucks air from the third branch1 the two liquids rise in their respective tubes to heights which are in the inverse ratio of their specific gravities4 99 99 99 99 99 ,,hydrometer ,,with ,,four ,,branches4--,this is merely a tube bent three times1 and widened at its extremities4 ,pl4 #b1 fig4 #ac4 ,to graduate hydrometers with two1 three1 and four branches1 you have to divide their tubes into a certain number of equal parts4 99 99 99 99 99 ,,manometers4--,make choice of a tube nearly capillary1 very regular in the bore1 and with sides more or less thick1 according to the degree of pressure which it is to support4 ,seal this tube at one end1 blow a bulb with thick sides near the middle1 and curl it in ,s1 just as is represented by pl4 #b1 fig4 #i4 ,for manometers which serve to measure the elasticity of the air under the receiver of the air-pump1 what is generally employed is a tube closed at one end and bent into a ,u4 ,pl4 #b1 fig4 #aj4 ,you should take care to contract these at some distance from the sealed part1 in order to avoid the breaking of the instrument on the sudden admission of air4 ,manometers are graduated1 as will be explained in the sequel4 99 99 99 99 99 ,,mariotte',s ,,tube4--,this is represented by pl4 #b1 fig4 #g4 ,it consists of a tube thirty-nine inches long1 closed at one end1 bordered and widened at the other1 and bent into a ,u at the distance of eight inches from its sealed end4 ,the graduation of this instrument will be described hereafter4 99 99 99 99 99 ,,phosphoric ,,fire-,,bottle4--,this is a short piece of tube closed at one end1 and widened and bordered at the other1 in such a manner as to receive a cork4 ,pl4 #c1 fig4 #cd4 ,it is in this little vessel that the phosphorus is enclosed4 ,glasses of this form can be employed in a great variety of chemical experiments4 99 99 99 99 99 ,,pulsometer4--,this instrument consists of a tube1 of which each extremity is terminated by a bulb2 it is partly filled with nitric ether1 and sealed at the moment when the ebullition of the ether has chased the atmospheric air wholly from the interior of the vessel4 ,pl4 #b1 fig4 #af4 99 99 99 99 99 ,,pump4--,solder a cylinder1 ,b 7pl4 #d1 fig4 #ab71 to the extremity of a small tube1 ,c1 and form their point of coincidence into a funnel1 to which you will adapt a valve4 ,pierce the wide tube or body of the pump at ,d1 and solder there a piece of tube bent into an elbow and widened at the other end into a funnel1 which is to be furnished with a second valve1 as is represented in the figure4 ,prepare then the fountain of compression ,e1 and1 by means of a cork and a little sealing-wax1 fix it upon the branch ,d4 ,to prepare the piston1 ,a1 blow a bulb at the end of a tube1 flatten the end of the bulb1 and choke it across the middle1 in order to form a place round which tow can be twisted1 to make it fit the tube air-tight4 ,finish the piston by twisting the other end of the tube into a ring1 as at ,a4 ,the valves are formed of small cones of cork1 or wood1 having in the centre an iron wire of sufficient size and weight to enable them to play well4 99 99 99 99 99 ,,retort ,,for ,,chemical ,,experiments4--,plate #c1 fig4 #i1 represents a combination of a large and a small tube1 forming a retort1 which can be employed with much advantage in many chemical experiments4 ,when a gas is to be distilled by means of such a vessel1 the ingredients are put into the wide tube1 which is previously closed at one end1 and then the other end of the tube is either drawn out or soldered to a narrow tube4 ,pl4 #c1 fig4 #h and #bi1 represent such vessels under different forms4 ,very often a sort of retort can be formed by joining a wide tube to a long bent narrow tube1 by means of a cork4 99 99 99 99 99 ,,tubulated ,,retort4--,this is represented by pl4 #c1 fig4 #f4 ,prepare a retort1 such as is described in the preceding article1 but one which is bent near the closed end2 pierce it at ,a 7fig4 #f71 and solder there a little piece of tube previously drawn out and sealed1 such as is represented by pl4 #a1 fig4 #aa4 ,when the soldering is finished1 soften the end of the little tube1 pierce it1 and fashion it into a bottle neck1 so that it can be closed by a cork4 ,finish the instrument by forming the open end according to the purpose to which it may be destined4 ,in the figure1 the end is represented as drawn out for the convenience of blowing into the retort to pierce the tubulure4 99 99 99 99 99 ,,rumford',s ,,thermoscope4--,this instrument is represented by pl4 #c1 fig4 #ce4 ,it is necessary to take a tube almost capillary1 to solder a bulb at each extremity1 to pierce it laterally at b1 and to solder there a piece of tube previously drawn out1 but of which you open the point for the purpose of finishing the sealing of the bulb ,a4 ,after doing this1 you bend the two branches1 as shewn in the figure4 ,when the liquid has been introduced into the instrument1 you must seal the little piece of tube which serves as a reservoir4 ,this instrument can be made in another manner4 ,take two pieces of tube1 one of them twice as long as the other2 solder a bulb at one end of each of these tubes1 and at about the third part of the length of the long tube1 parting from the bulb1 bend it at a right angle2 pierce the little tube at a corresponding distance1 and solder to the hole the end of the long tube4 ,the soldering being finished1 and the whole system having the form indicated by pl4 #c1 fig4 #ce1 introduce1 by the open end of the short tube1 a small quantity of coloured acid1 and then seal the end of the short tube1 which serves as a reservoir4 ,the interior diameter of the tubes which are generally employed as thermoscopes1 is one-eighth or one-twelfth of an inch4 ,the mode of graduation is described in a subsequent chapter4 99 99 99 99 99 ,,syphons4--,the simple syphon is a glass tube bent1 at a little distance from the middle1 into a form which is intermediate between those of and 1 the legs being stretched apart like those of the latter1 but the bend being rounded like that of the former4 ,the tube is bent near the middle1 and not exactly at the middle1 in order that the legs may be of unequal lengths2 an arrangement which is indispensable4 ,syphons are made of different lengths and diameters1 for various purposes4 ,they can be made of tubes so capillary that it is sufficient to put them into water to make them act3 the liquid rises in them by capillary attraction1 and does not require to be sucked through the tube1 as it does when large syphons are employed4 99 99 99 99 99 ,,wirtemberg ,,syphon4--,this syphon is the same as the simple syphon1 excepting that the two branches are of equal length1 and are bent in ,u at both extremities4 ,pl4 #c1 fig4 #bb4 99 99 99 99 99 ,,syphon ,,with ,,three ,,branches4--,this instrument is represented by pl4 #b1 fig4 #ai4 ,close a tube at one end and draw it out at the other2 pierce it at some inches from the contracted extremity1 and solder to the hole a little tube of which the other end has been closed with wax4 ,give the tube the bend necessary to constitute a syphon1 and open the two branches4 ,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 tube4 ,when the syphon is desired to be well finished1 the mouth-piece of the little tube must be bordered and widened1 and a bulb must be blown near the mouth-piece4 99 99 99 99 99 ,,syphon ,,with ,,jet ,,of ,,water4--,this instrument is represented by pl4 #c1 fig4 #a4 ,take a tube of a large diameter1 close it at one end1 and draw it out at the other4 ,cut the contracted part in such a manner as to be able to introduce1 through the orifice1 the extremity1 also drawn out1 of another tube1 which should be almost capillary4 ,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 reservoir4 ,pierce again the latter1 at ,b1 and solder there another branch of the same diameter as the former2 but fix it in such a manner that its side shall be contiguous to the side of the reservoir4 ,finally1 give to the branches the bend represented by the figure4 99 99 99 99 99 ,,spoons4--,solder a bulb to the extremity of a capillary tube2 open the bulb as for a funnel1 but make the opening laterally4 ,cut with scissars the edges of the part blown open1 and in such a manner as to form a spoon or a ladle1 according as the bulb had the form of a sphere or an olive4 ,this instrument is useful for taking small quantities of acids4 ,pl4 #c1 fig4 #aa4 99 99 99 99 99 ,,spirit ,,level4--,the spirit level is represented by pl4 #b1 fig4 #bh4 ,choose a piece of tube very straight1 and with sides precisely of the same thickness in all parts4 ,seal it at one end1 and draw it out abruptly at the other4 ,fill it almost entirely with alcohol1 and seal the point by the jet of a candle4 99 99 99 99 99 ,,test ,,glass ,,with ,a ,,foot4--,take a tube drawn out at one end2 choke it at an inch from the base1 in such a manner as to obstruct the canal almost entirely4 ,pl4 #a1 fig4 #ab4 ,cut off the point1 close the opening1 and soften the whole end completely2 then blow it into a bulb and burst it into a funnel4 ,now present the contracted part to the fire1 so as totally to close the passage4 ,border and soften the funnel1 and by pressing it against a flat plate of metal give it the form of a foot1 or pedestal4 ,cut the tube at the length which you desire the test-glass to have1 and border the edges of the opening4 ,this is a very useful little chemical instrument4 ,it is represented by pl4 #c1 fig4 #aj4 99 99 99 99 99 ,,thermometers4--,thermometers are instruments employed for appreciating changes of temperature1 either in the atmosphere or in substances which we have occasion to examine4 ,the following are the principal varieties now employed4 99 99 99 99 99 ,,ordinary ,,thermometer4--,if you desire to make standard thermometers1 you must have capillary tubes of perfect accuracy in the bore4 ,you are assured of regularity in the diameter of a tube when a drop of mercury1 made to pass along the canal by means of a gentle inclination1 or by air blown from an ,indian-rubber bottle1 gives everywhere a metallic column of the same length4 ,for ordinary thermometers this precaution is superfluous4 ,in all cases you employ a tube more or less capillary1 at one of the extremities of which you blow or solder a spherical or cylindrical reservoir4 ,see pl4 #d1 fig4 #a and #b4 ,you fill the instrument with well-purified mercury1 or alcohol1 which you boil in the tube1 in order to chase the air from it4 ,as it is necessary to heat the instrument throughout its whole length1 you must place it on a railing of iron wire1 inclined in the manner represented by pl4 #d1 fig4 #ad1 and covered with burning charcoal1 or red-hot wood ashes4 ,it is better1 however1 to employ a kind of muff1 formed of two concentric wire grates1 between which you put burning charcoal1 and reserve the centre for the instrument4 ,the tube is thus kept in a vertical position1 which allows the bubbles of air to escape with more facility4 ,an iron wire is made use of to fasten the tube precisely in the centre of the column of fire4 ,the operation is considerably promoted by soldering a little funnel to the upper extremity of the thermometer tube2 and1 in order to avoid the interruption of the column of liquid by bubbles of air1 it is better to give to the superior part of the reservoir the form of a cone 7pl4 #d1 fig4 #c71 rather than to preserve the completely spherical form indicated by pl4 #d1 fig4 #b4 ,when the ebullition has expelled all the air which was contained in the mercury1 or alcohol1 you immediately plunge the open extremity of the instrument into a vessel filled with one or the other of these liquids2 or1 instead of this1 you pour the liquid into the funnel1 in order that the instrument may be quite filled at the common temperature4 ,you then cut off the funnel1 if one has been used1 and1 by properly elevating the temperature of the reservoir1 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 temperature3 this operation is termed regulating the course of the thermometer4 ,there are two methods of closing thermometers3 you may either produce a vacuum above the column of mercury1 or you may allow air to remain there4 ,in the first case1 after having drawn out the end of the tube1 you heat the liquid until a single drop passes out of the opening2 you then instantly bring the point into the jet1 and seal it4 ,in the second case1 you seal the instrument at the ordinary temperature1 and having previously raised to a reddish-white heat the button of glass which is formed by the sealing1 you suddenly elevate the temperature of the mercury4 ,the liquid1 on rising1 compresses the enclosed air1 which dilates the red-hot button at the summit of the tube1 and produces a species of reservoir4 ,this reservoir is indispensably necessary when you leave air above the column of liquid1 in order to provide against the bursting of the instrument on those occasions when the temperature of the mercury comes to be considerably elevated4 ,see pl4 #d1 fig4 #ac4 99 99 99 99 99 ,,dial ,,thermometer4--,terminate a piece of tube1 of six-tenths of an inch in diameter1 with two points1 and solder to one of these points a tube one-eighth of an inch in diameter and six inches long2 close the end of this small tube1 and1 heating a zone of the reservoir1 near the base of the other point1 blow a bulb there4 ,cut off the point by which you have blown1 at a little distance from the bulb2 open and border the end of the narrow tube1 and bend it into a ,u4 ,see pl4 #d1 fig4 #af4 ,fill the bulb and the reservoir with alcohol1 and add a drop of mercury which fills a certain space in the narrow tube4 ,this mercury bears on its surface a little iron weight1 to which a thread is fastened2 the other end of this thread passes over a pulley1 whose axis turns a needle4 ,the expansion or contraction of the alcohol causes the mercury to rise and fall1 and consequently produces a movement of the needle or index of the dial4 ,this thermometer is graduated like the others1 by being brought into comparison with a standard thermometer4 99 99 99 99 99 ,,chemical ,,thermometer4--,this instrument is merely a common thermometer1 the divisions of which1 graduated on paper1 are enclosed in a very thin glass tube1 to hinder them from being altered or destroyed when the instrument is plunged into liquids4 ,pl4 #d1 fig4 #d1 #e1 #f1 and #g1 represent chemical thermometers of various kinds4 ,the case of the thermometer can be made in two different ways4 ,according to the first1 you take a tube of a pretty large diameter1 and with very thin sides2 you draw out one end and obliterate the point1 which you bend into a ring1 in a direction perpendicular to that of the case2 you pass through this ring the stalk of the thermometer1 which is thus placed parallel to the large tube4 ,after having fixed the graduated scale in the interior of the case1 by means of a small drop of sealing-wax1 which has been dropped on the slip of paper1 and which1 being supported against the side of the case1 needs only to be warmed to adhere there and fix the scale securely to its envelope1 you close the upper extremity of the case by drawing it out1 obliterating the canal and soldering it to the thermometer tube which has been introduced into the ring at the lower end of the case4 ,you heat the connecting piece till it is soft1 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 case4 ,see pl4 #d1 fig4 #f and #g4 ,the second method of making the case is as follows3--,you take a tube with thin sides1 and sufficiently large to contain the entire thermometer2 you draw out the tube at one end1 and choke it at some distance from the point of the contracted part4 ,this you must do in such a manner as to form a little bulb1 which is to be ballasted in the manner described at the article ,hydrometers4 ,after having introduced into the case a little ball of cotton1 you place therein the thermometer1 furnished with its scale1 and in such a manner that the reservoir rests on the cotton4 ,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 cord4 ,see pl4 #d1 fig4 #d and #e4 99 99 99 99 99 ,,spiral ,,thermometer4--,take a tube which is not capillary1 but which has thin sides2 close one of its ends1 and bend it round by pressing it with a metallic rod2 continue to bend it round till it has made several turns1 all in the same plane4 ,see pl4 #a1 fig4 #ac4 ,the latter turns may be managed with the fingers instead of the metallic rod4 ,when the reservoir so formed is sufficiently large1 solder to the end of it a capillary tube1 which you point in a direction perpendicular to that of the axis of the spiral4 ,the instrument is represented by pl4 #d1 fig4 #h4 99 99 99 99 99 ,,pocket ,,thermometer4--,the pocket thermometer differs in nothing from the thermometer just described1 except that the capillary tube1 instead of passing away from the spiral in a straight line1 is turned round1 so as to form a continuation of the spiral4 ,see pl4 #d1 fig4 #ag4 99 99 99 99 99 ,,maximum ,,thermometer4--,this instrument consists of an ordinary mercurial thermometer1 bent at a right angle near the origin of the reservoir1 and in the horizontal column of which a little steel or iron rod has been introduced3 this rod1 by gliding in the tube1 where it experiences very little friction1 serves as an index4 ,since this index does not permit the instrument to be sealed with the vacuum above the mercury1 you must terminate the sealing by a little reservoir1 as we have described at the article on the second method of closing thermometers4 ,the instrument is represented by pl4 #d1 fig4 #bd4 99 99 99 99 99 ,,minimum ,,thermometer4--,this instrument is constructed pretty nearly in the same manner as the preceding4 ,the liquid1 however1 must be alcohol1 and the index a little rod of enamel1 which ought not to be quite so large as the bore of the thermometer tube4 ,you seal the tube by making a vacuum above the column4 99 99 99 99 99 ,,bellani',s ,,maximum ,,thermometer4--,this thermometer is represented by pl4 #d1 fig4 #i4 ,take a tube which is very regular1 and about one-eighth or one-twelfth of an inch diameter in the bore2 solder a reservoir at each end1 one of them much larger than the other2 make a bend near the large reservoir1 and then fill the instrument with alcohol to ,a4 ,above that1 place the first index1 which consists of a very small piece of tube closed at one end and cut off square at the other4 ,in the interior of this tube the two ends of a hair are fixed1 by means of a little rod of iron1 which is pushed into the tube4 ,introduce a quantity of mercury above this index1 make the bend ,b1 add again mercury as far as ,c1 then another index similar to the first4 ,finally1 fill the rest of the tube and the half the little reservoir with alcohol1 and seal the point4 99 99 99 99 99 ,,differential ,,thermometer4--,this instrument is represented by pl4 #c1 fig4 #ad4 ,take a tube ten or twelve inches long1 and one-eighth or one-twelfth of an inch internal diameter2 blow a bulb at one end1 and bend the tube at a right angle towards the fourth part of its length4 ,prepare a second tube in the same manner1 and solder the bent ends together1 so as to form a single tube with a bulb at each end1 having previously poured into one of the bulbs a small quantity of sulphuric acid tinged red4 ,instead of following the above method1 you may take a single tube of twenty or twenty-four inches in length1 and of the above-mentioned diameter2 you solder a bulb at each end1 bend the tube twice till it represents the figure1 pour in the acid1 and then seal the open points4 ,the graduation of the differential thermometer1 as well as of all the other thermometers1 is described in a subsequent section4 99 99 99 99 99 ,,tube ,,for ,,crystallizing ,,spermaceti4--,take a little capillary tube2 curl one of its ends into a ring1 and solder the other to a cylindrical reservoir1 two-thirds of the capacity of which you fill with very pure spermaceti dissolved in sulphuric ether2 you then seal the point of the reservoir4 ,see pl4 #c1 fig4 #bg4 99 99 99 99 99 ,,tube ,,for ,,demonstrating ,,the ,,non-,,conductability ,,of ,,heat ,,by ,,liquids4--,this is represented by pl4 #b1 fig4 #bf4 ,it is a tube sealed at one end1 bordered at the other1 and bent in such a manner as conveniently to permit the upper part of a column of liquid to be exposed to heat4 99 99 99 99 99 ,,tube ,,for ,,estimating ,,the ,,density ,,of ,,vapours4--,represented by pl4 #b1 fig4 #ad4 ,it is merely a tube sealed at one end1 bordered at the other1 and bent as shewn by the figure4 99 99 99 99 99 ,,tubes ,,for ,,exposing ,,substances ,,to ,,heat ,,and ,,gases4--,this instrument consists of a tube bent in the middle into a ,u4 ,pl4 #c1 fig4 #c4 ,it is much employed in chemistry1 for containing substances which we wish at the same time to expose to an elevated temperature and to the action of certain gases4 ,this tube can also be employed for cooling gases1 or liquids1 in distillation2 the bent part being1 in this case1 dipped into water or a freezing mixture1 or enveloped in wet paper or cloth4 99 99 99 99 99 ,,tubes ,,for ,,the ,,preservation ,,of ,,objects ,,of ,,natural ,,history1 ,,or ,,of ,,chemical ,,preparations4--,take a tube of which the width and length corresponds with the object which is to be enclosed2 draw it out at one end1 and1 after having obstructed the point1 twist it into a ring4 ,introduce the object by the open extremity1 which you must afterwards draw out2 fill the tube with the liquid necessary to preserve the object1 and then seal the point4 ,see pl4 #b1 fig4 #bg4 ,if you desire to have the power of taking out the object at will--as1 for example1 when grain is preserved1 or when1 in chemistry1 the tube is employed to contain salts and other compounds1 of which small quantities are now and then required for use--you do not seal the end of the receiver1 but border it in such a manner that it can be closed by a cork4 ,in some cases a cork is not sufficient to secure the substance from the action of air3 it must then be assisted with a little cement4 ,by melting together two parts of yellow wax1 one part of turpentine1 and a small quantity of ,venetian red1 a very useful cement for such purposes is obtained4 ,it is sometimes necessary to suspend the objects enclosed within the tube3 you then introduce a little glass hook1 the tail of which you solder to the upper extremity of the tube2 managing this operation at the same time that you make the external ring for the support of the instrument4 ,by turning the hook round cautiously1 which is done when the end of the tube is in a soft state1 and by cooling the whole with care1 you may succeed in fixing the hook in the centre of the tube4 ,see pl4 #c1 fig4 #bj4 99 99 99 99 99 ,,tube ,,for ,,emptying ,,eggs4--,it is a simple tube1 drawn out to a capillary point at one end1 and bent there into a ,v4 ,see pl4 #c1 fig4 #bc4 ,the application which the author has made of this instrument1 and of the tube represented by pl4 #c1 fig4 #bf1 has been shewn in a memoir inserted in the ,annales des ,sciences ,naturelles1 ,tom4 ,,xv4 ,novembre #ahbh1 concerning a new method of preparing and rendering durable collections of eggs destined for cabinets of ,natural ,history4 99 99 99 99 99 ,,vial ,,of ,,the ,,four ,,elements4--,this instrument is represented by pl4 #b1 fig4 #bg4 ,take a tube drawn out at one end1 obstruct the canal two inches from the extremity1 and twist the contracted part into a ring4 ,draw out the other end of the tube1 introduce the proper liquids1 remove the point of the tube1 and seal it4 ,the liquids generally employed for filling the vial of the four elements are1 #a4 ,mercury2 #b4 ,a very concentrated solution of carbonate of potash2 #c4 ,oil of turpentine2 #d4 ,alcohol4 ,a portion of air is also allowed to remain in the tube4 99 99 99 99 99 ,,water ,,hammer4--,pl4 #b1 fig4 #ah1 is a representation of this instrument4 ,choose a tube of a good diameter1 and with thick sides2 seal it at one end and draw it out at the other4 ,blow a bulb at the base of the contracted part2 then1 having put a quantity of water in the tube1 let it boil therein1 to expel the atmospherical air4 ,when you imagine that all the air has been expelled1 and that nothing remains in the tube but steam and water1 seal the open point4 ,when you have to seal a tube in this manner1 you should be careful to draw out the extremity of the tube somewhat abruptly1 and leave a very small opening1 so that it shall be sufficient to expose the point to the jet of a candle blown by a mouth blowpipe1 to have the sealing completely and suddenly effected4 ,you can afterwards round this sealed part by turning it in the flame of the lamp1 provided1 however1 that you have preserved a sufficient thickness of glass at the sides of the point4 ,if you omit to take this precaution1 the pressure of the atmosphere1 acting with great force on the softened glass when it is unsupported by the partial vacuum within the tube1 is capable of producing such a flattening1 or even sinking in of the matter1 as could not subsequently be rectified2 except1 indeed1 by heating simultaneously the liquid contained in the tube and the glass to be mended1 which is an operation of a very delicate description4 99 99 99 99 99 ,,welter',s ,,safety ,,tubes4--,after having closed a tube at one end and drawn it out at the other1 give it the curvature exhibited by plate #c1 fig4 #ah4 ,pierce it then laterally1 in the middle of the part a b1 and solder there the extremity of a tube1 to the other end of which a funnel has been soldered3 it is necessary that the funnel be closed by a cork4 ,the soldering being terminated1 a bulb must be blown and the tube bent in ,s1 in the manner shewn by the figure4 ,then open the closed end1 and cut off the contracted point4 ,,the ,,art ,,of ,,glass-,,blowing4 ,v4--,graduation of ,chemical and ,philosophical ,instruments4 ,,of ,,the ,,substances ,,employed ,,in ,,the ,,preparation ,,of ,,these ,,instruments4 ,before proceeding to the subject of graduation1 it is necessary to say a few words respecting the substances which are generally employed to fill a variety of instruments1 particularly barometers and thermometers4 ,mercury4--,it ought to be completely purified from all foreign substances4 ,you can separate it from the dust it may contain by passing it through a piece of chamois leather2 you tie a very hard knot1 and by pressure oblige the mercury to pass out in a fine rain4 ,this process is sufficient for the purification of mercury which merely contains extraneous bodies in suspension2 but it is not sufficient when the mercury to be purified contains tin1 lead1 or other metals1 in solution4 ,it is then necessary to distil the mercury2 upon which the fixed metals remain behind4 ,the oxide of mercury produced by the distillation is removed by agitating the distilled metal with sulphuric acid1 and subsequently washing it with a large quantity of water1 till all the acid is removed2 it is then dried as completely as possible with blotting-paper1 and afterwards is moderately warmed4 ,alcohol ought to be very pure and well rectified4 ,it is necessary to colour it1 because1 being colourless of itself1 it could not be seen in capillary tubes4 ,to colour alcohol1 you infuse carmine in it1 and1 after some time1 decant or filter the clear solution4 ,the liquid should be perfectly transparent1 and free from all extraneous substances4 ,it is not proper to employ alcohol in the construction of standard thermometers2 mercury being much preferable4 ,sulphuric ,acid4--,it is made use of for the differential thermometer1 and the thermoscope of ,rumford4 ,it has the advantage of being lighter than mercury1 and very slightly volatile3 these two qualities1 joined to its tendency to absorb the vapour of water1 render it very proper to be employed for various instruments4 ,it must be very concentrated1 and tinged red by carmine4 ,ether4--,sulphuric and nitric ether1 with which some small instruments are filled1 are merely employed to shew with what facility these liquids are brought to their boiling point4 99 99 99 99 99 ,,of ,,graduation ,,in ,,general4--,graduation1 generally speaking1 consists in dividing lines1 surfaces1 and capacities1 into a certain number of equal or proportional parts4 ,it is not our intention to treat here of the methods furnished by practical geometry for effecting such divisions with mathematical accuracy2 these methods are known to every body4 ,we shall confine ourselves to describing the processes of graduation which are peculiar to the instruments constructed by the glass-blower4 99 99 99 99 99 ,,examination ,,of ,,the ,,bore ,,of ,,tubes4--,we have already observed1 that1 for standard thermometers and other instruments which require to be made very accurate1 it is necessary to employ tubes which are extremely regular in the bore4 ,when a drop of mercury1 passed successively along all parts of the tube1 forms everywhere a column of the same length1 the examiner is assured of the goodness of the tube4 ,that a tube may be regular in the bore1 it is not necessary that the bore be cylindrical2 it is sufficiently accurate when equal lengths correspond to equal capacities4 ,a tube with a flat canal1 for example1 can be perfectly accurate without at all approaching the cylindrical form4 ,it is only necessary that a drop of mercury occupy everywhere the same length4 ,we may observe1 by1the way1 that1 in flat canals1 the flattening should be always in the same plane4 99 99 99 99 99 ,,division ,,of ,,capillary ,,tubes ,,into ,,parts ,,of ,,equal ,,capacity4--,as it is very difficult to meet with capillary tubes which are exactly regular in the bore1 it happens that the tubes which glass-blowers are obliged to employ have different capacities in parts of equal length4 ,you commence the division of these tubes into parts of equal capacity by a process described by ,m4 ,gay-,lussac4 ,you introduce a quantity of mercury1 sufficient to fill rather more than half the tube1 and make a mark at the extremity of the column4 ,you then pass the mercury to the other end of the tube1 and again mark the extremity of the column4 ,if you so manage that the distance between the two marks is very small1 you may consider the enclosed space as concentric1 and a mark made in the middle of the division will divide the tube into two parts of evidently equal capacity4 ,you divide one of these parts1 by the same process1 into two equal capacities1 and each of these into two others2 and in this manner you continue to graduate the tube until you have pushed the division as far as you judge proper4 ,but it is still more simple to introduce a drop of mercury into the tube1 so as to form a little cylinder1 and then to mark the two extremities of the cylinder4 ,if it were possible to push the drop of mercury from one end of the tube to the other1 in such a manner as to make it coincide1 at every removal1 with the last mark1 it would be very easy to divide the tube accurately2 but as it is very difficult1 not to say impossible1 to attain this precision of result in moving the column of mercury1 you must endeavour to approach exactness as nigh as may be4 ,you measure1 every time you move the mercury1 the length of the cylinder it produces1 and carry this length to the last mark1 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 column4 ,you thus obtain a series of small and corresponding capacities4 99 99 99 99 99 ,,graduation ,,of ,,gas ,,jars1 ,,test ,,tubes1 ,c4--,if the tube is regular in the bore1 close one end1 either by sealing it at the lamp1 or by inserting a cork1 and pour into the interior two or three small and equal portions of mercury1 in order to have an opportunity of observing the irregularities produced by the sealed part4 ,take care to mark1 with a writing diamond1 the height of the mercury1 after the addition of each portion4 ,when equal portions of mercury are perceived to fill equal spaces1 take with the compass the length of the last portion1 and mark it successively along the side of the tube1 where you must previously trace a line parallel to its axis4 ,for tubes which are irregular in the bore1 and where equal lengths indicate unequal capacities1 it is necessary to continue the graduation in the same manner that you commenced it--that is to say1 to fill the tubes by adding successively many small and equal portions of mercury1 and marking the height of the metallic column after every addition4 ,these divisions will of course represent parts of an ounce or of a cubic inch according to the measure which you make use of4 ,when you have thus traced on the tube a certain number of equal parts1 you can1 by means of the compasses1 divide each of them into two other parts of equal length4 ,the first divisions being very close to one another1 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 extent4 ,when the tube which you desire to graduate is long and has thin sides1 it would be difficult to fill it with mercury without running the risk of seeing it break under the weight of the metal4 ,in this case1 you must use water instead of mercury4 ,bell-glasses of large dimensions are graduated by filling them with water1 placing them in an inverted position on a smooth and horizontal surface1 which is slightly covered with water1 and passing under them a series of equal measures of air4 ,but it is then necessary to operate constantly at the same temperature and under the same atmospheric pressure1 because air is very elastic and capable of being greatly expanded4 ,in all cases1 tubes1 bell-glasses1 c4 ought to be held in a position perfectly vertical4 ,the most convenient measure is a dropping-tube1 on the stalk of which a mark has been made1 or a small piece of tube1 sealed at one end1 and ground flat at the other2 the latter can be accurately closed by a plate of glass4 ,the marks which are traced on tubes being generally very close to one another1 you facilitate the reading of the scale by giving a greater length to those marks which represent every fifth division1 and by writing the figures merely to every tenth division4 ,see pl4 #d1 fig4 #h4 ,the number of divisions is somewhat arbitrary2 nevertheless1 #ajj1 #abj1 #cfj1 #ajjj1 are divisions which1 in practice1 offer most advantages4 99 99 99 99 99 ,,graduation ,,of ,,hydrometers4--,cut a band of paper on which the graduation of the instrument can be traced1 and let fall upon it a little drop of sealing-wax2 then roll the paper upon a little glass tube1 and introduce it into the stalk of the hydrometer4 ,the instrument is afterwards to be plunged into distilled water1 which is carefully kept at the temperature of #dj ,f4 above zero4 ,give the instrument sufficient ballast to make it sink till the point 7a1 pl4 #d1 fig4 #bj17 which you desire to make to represent the density of water1 touches the surface of the water4 ,mark this point with much precision2 it is the zero of the instrument4 ,the other degrees are taken by plunging the hydrometer into distilled water to which you have added #a1 #b1 #c1 #d1 #e1 c4 tenths1 or #a1 #b1 #c1 #d1 #e1 c4 hundredths1 of the substance for which you wish to construct the hydrometer1 according as you desire the scale to indicate tenths or hundredths4 ,when you have thus marked the degrees on the stalk of the instrument1 transfer them to the paper with the help of the compasses4 ,the scale being completed1 replace it in the tube of the hydrometer1 where it must be fixed2 in so doing1 take care to make the degrees on the scale coincide precisely with those marked on the stalk4 ,you can thus procure hydrometers for alcohol1 acids1 salts1 c4 which are instruments that indicate the proportion of alcohol1 acid1 salt1 c4 contained in a given mass of water4 ,but if it were necessary to plunge the hydrometer in a hundred different solutions in order to produce the scale1 it is easy to conceive that that would be extremely troublesome1 especially for hydrometers which are employed in commerce1 and which do not need to be so extremely accurate4 ,when the density of the mixtures or solutions is a mean between those of the substances which enter into them1 you may content yourself with marking the zero and one other fixed point1 7a and b1 pl4 #d1 fig4 #bj47 ,then1 as the stalk of the hydrometer is evidently of equal diameter in all its extent1 you can divide the space which separates the two fixed points into a certain number of equal parts4 ,one of these1 being taken for unity1 represents a particular quantity of the substance which you have added to a determined weight of distilled water4 ,by means of this unity you can carry the scale up and down the stalk of the instrument4 ,it is thus1 that1 to obtain a ,baum's hydrometer1 after having obtained the zero by immersion in distilled water1 you plunge the instrument into a solution containing a hundred parts of water and fifteen of common salt1 to have the #aeth degree1 or containing a hundred water and thirty salt1 to have the #cjth degree4 ,upon dividing the interval into fifteen or thirty equal parts1 according as you have employed one or the other solution1 you obtain the value of the degree1 which you can carry upwards or downwards as far as you wish4 ,among the substances for which hydrometers are required in commerce1 are some which it is impossible to obtain free from water--such are alcohol1 the acids1 c4 ,in this case it is necessary to employ the substances in their purest state1 and deprived of as much water as possible4 ,the employment of hydrometers is very extensive3 they are used to estimate the strength of lyes1 of soap solutions1 of wines1 milk1 c4 ,there is1 in short1 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 sold4 ,the employment of hydrometers would be still more general1 if they could be made to give immediately the absolute specific gravity of the liquids into which they might be plunged1 the specific gravity of water being considered as unity4 ,it is possible to graduate a thermometer of this description by proceeding as follows3-- ,make choice of a hydrometer of which the exterior part of the stalk is very regular4 ,introduce the band of paper on which the scale is to be written1 and then ballast the instrument4 ,make a mark where the surface of the distilled water touches the stalk4 ,remove the hydrometer from the water1 wipe it perfectly dry1 and weigh it very accurately with a sensible balance4 ,then pour into it a quantity of mercury equal to its own weight2 plunge it again into the water1 and again mark the point where the stalk touches the surface of the water4 ,pour the mercury out of the instrument1 transfer the two marks to the scale1 and divide this fixed distance into fifty equal parts4 ,having by this operation obtained the value of the degree1 you carry it upwards and downwards1 to augment the scale4 ,if you take the first point near the reservoir1 the hydrometer will be proper to indicate the density of liquids which are heavier than water2 if you take it towards the middle of the tube1 the contrary will be the case4 ,if you destine the hydrometer for liquids much heavier than water--such as acids1 for example--you might1 after having determined the first point1 add to the original ballast as much mercury as is equal to the weight of the whole instrument2 then the point where the stalk would touch the surface of the water1 and which would be represented by #ajj1 would be very high1 and the second point1 which would be found below1 would be represented by #bjj4 ,on dividing the space into a hundred equal parts1 you would have the value of the degree1 which could be carried up and down for the extension of the scale4 ,the specific gravities being in the inverse ratio of the volumes plunged into the liquid1 the numbers of the scale which mark the specific gravities diminish from below2 so that1 on marking the lowest point #ajj1 you have1 on proceeding upwards1 the successive degrees #jii1 #jih1 #jig1 #jif1 c4 ,the hydrometers with two1 three1 and four branches1 are graduated by having their tubes divided into a hundred or a thousand equal parts4 ,the divisions on each branch must correspond with those on the other branches4 99 99 99 99 99 ,,graduation ,,of ,,barometers4--,the graduation of this instrument consists in dividing a piece of metal1 wood1 or ivory1 into inches and parts of inches4 ,the divided rod is then employed to measure the height of the mercury in the tube4 ,as the rule is moveable1 the operation presents no sort of difficulty3 all that is necessary is to make the zero of the scale coincide with the inferior level of the mercury2 the point which corresponds with the superior level of the mercury1 seen in the tube1 indicates the height of the barometric column4 ,it is in this manner that the cistern barometer is graduated4 ,but if the barometer is one of those in which the surface of the mercury is variable1 such as the barometer of ,gay-,lussac1 it is necessary to have recourse to a different process of graduation4 ,if the two branches of the instrument are very regular1 and of equal diameter1 you first measure with precision the height of the column of mercury1 then divide it in the middle1 and fix the scale1 which must be graduated in such a manner that the mark of fifteen inches corresponds exactly with the middle point4 ,this mode of graduation serves to indicate merely the apparent height of the barometric column4 ,if you desire that the scale should immediately indicate the real height1 you must fix the zero at the middle of the column1 and then double the figure which marks each degree4 ,when you do not wish to write the real height1 you make two divisions1 of which one proceeds upwards1 the other downwards4 ,you do not1 in this case1 double the value of each division1 but in observations made with such a barometer scale you add the degree marked by the two surfaces1 in order to find the real height4 ,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-pump4 ,you take the height of the mercury in the gauge1 and fix at the middle of the column the zero of a double scale1 of which one division proceeds upwards1 the other downwards2 or1 instead of this1 if you choose to have only one scale1 and that an ascending scale1 you double the value of every degree4 ,the zero of the barometric scale can be fixed below the inferior surface of the mercury2 but then1 to have the real height1 it is necessary to measure precisely the height of the mercury in the two branches of the instrument1 and to deduct the smaller from the larger4 ,dial 7or ,wheel7 ,barometer4--,the disposition which should be given to this instrument is precisely the same as that of the ,dial ,thermometer1 described in a preceding section4 ,you make a small iron weight float on the inferior surface of the mercury1 and fix to this weight a silk thread1 which is stretched by a counterpoise1 and rolls over a very moveable pulley4 ,the axis of this pulley carries a needle1 which turns backwards or forwards according as the column of mercury augments or diminishes4 ,you arrange the whole in such a manner that the extreme variations of this column cannot make the needle describe more than one circumference2 with this view you give the pulley a diameter of nearly an inch4 ,the dial barometer being rather an object of luxury than an instrument of precision1 you graduate it by inscribing the following words1 at full length1 on the scale4 ,in pl4 #d1 fig4 #af1 for example1 you write1 ,at the point a ,tempest4 444 b ,much rain4 444 c ,rain or ,wind4 444 d ,temperate4 444 e ,fine ,weather4 444 f ,fixed ,fair4 444 g ,very ,dry4 ,you write nothing at the inferior division4 99 99 99 99 99 ,,graduation ,,of ,,the ,,manometer4--,the graduation of this instrument consists in dividing the tube where the air is to be compressed1 into a given number of parts of equal capacity2 but as1 in general1 such tubes are employed as are nearly capillary and very regular1 the operation is reduced to a linear division1 where every degree occupies an equal space4 99 99 99 99 99 ,,graduation ,,of ,,thermometers4 ,construction of ,standard ,thermometers4--,having constructed your instrument with a very regular tube1 or one which has been divided into parts of equal capacity1 and having filled it with the proper liquid1 according to the instructions given in a preceding section1 the graduation is to be effected as follows4 ,procure very pure ice1 break it into small pieces1 and fill a vessel with it4 ,when the ice begins to melt1 plunge the thermometer into the middle of it1 in such a manner that1 without touching the sides of the vessel1 the whole thermometer1 or at least that part of it which contains the liquid1 may be covered with ice4 ,allow the instrument to remain in this state until1 in spite of the gradual melting of the ice1 the surface of the column of liquid remains at a fixed point1 and neither falls nor rises4 ,mark this point very carefully on the stalk of the thermometer1 either with a thread or a little drop of sealing-wax1 or with the trace of a diamond or a flint4 ,this is the freezing point1 the zero of the centigrade scale1 the thirty-second degree of ,fahrenheit's scale4 ,as for the second fixed point1 it is marked during an experiment with boiling water1 performed as follows3--,you employ a vessel of tin plate sufficiently high to enclose the whole thermometer2 you pour into this vessel distilled water1 till it is about an inch deep1 and then you heat it4 ,the vessel is surmounted by a cover pierced with two holes1 one of which is intended to receive the stalk of the thermometer1 the other to allow the steam to escape4 ,when1 on continuing the ebullition1 you observe that the mercury ceases to rise in the tube1 you mark the point at which it has stopped1 just as you marked the first point4 ,the last mark indicates the boiling point2 the one hundredth degree of the centigrade scale1 the two hundred and twelfth degree of ,fahrenheit's scale4 ,you transfer to paper the distance which is found between the first point and the second point determined1 and you divide this distance into one hundred equal parts1 or degrees1 for the centigrade thermometer1 into eighty parts for the thermometer of ,raumur1 and into one hundred and eighty for that of ,fahrenheit4 ,if the tube of the instrument is very regular in the bore1 the degrees should be equal in length2 if1 on the contrary1 you have been obliged to divide it into parts of equal capacity1 you find how many of these parts or little spaces it is necessary to take to constitute one of the above degrees4 ,you find this by dividing their whole number by #ajj1 or #hj1 or #ahj1 according to the degrees of the scale which you intend to make use of4 ,thus1 if you find between the two points fixed by melting ice and boiling water1 three hundred divisions of equal capacity1 it is necessary to include three of these divisions in every degree of the centigrade scale4 ,the vessel employed to take the boiling point must be of metal1 and its surface should be perfectly clean and well polished1 and have no rough points4 ,if sand1 or other matters1 were permitted to repose on the vessel1 and to form asperities1 the water would enter into ebullition at an inferior temperature4 ,this operation should1 moreover1 be performed under an atmospherical pressure1 which is indicated by the barometer when the mercury stands at twenty-nine inches and a half4 ,but as this pressure is different according to the elevation of the place of operation1 and1 indeed1 suffers continual variations even in the same place1 it follows that the temperature of boiling water is subject to continual changes1 and that1 in the graduation of the thermometer1 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 upon4 ,you succeed in making the necessary corrections by the help of the following table1 which is founded on the experiments of ,sir ,g4 ,shuckburg and of the ,committee of the ,royal ,society4 ,see the ,table on the opposite page4 ,common ,thermometers4--,having1 by the method which we have just described1 obtained a ,standard ,thermometer1 you may procure with facility as many ordinary thermometers as you desire4 ,it is proper to employ the most regular tubes which you can obtain1 and when the instruments are ready to be graduated1 you must bring them into comparison with your standard thermometer4 ,you place them together into a liquid of which you gradually raise the temperature1 and you mark several points on the scale of the new thermometer1 the intervals between which are subsequently divided into as many degrees as are marked on the scale of the standard thermometer4 ,thus1 for example1 you mark the #aj and #ae1 and afterwards divide the interval into five equal parts4 ,this gives you the length of a degree on the stalk of the new instrument4 ,the more you multiply these fixed points1 the more you insure the precision of the thermometer4 ,when you have taken a certain number of points1 you measure the remainder with the compasses4 99 99 99 99 99 ---------------------------------------- ------------------- ,height of the ,barometer in ,inches4 ---------------------------------- ,correction in ,when the boiling ,when the boiling #ajjjths of the point is found point is found interval between by immersing by immersing the freezing the ,instrument the ,instrument and boiling points in ,steam4 in ,water4 of ,water4 ---------------------------------------- ------------------ 444 #cj4fj #aj 444 #cj4ej #i #cj4ga #cj4da #h #cj4ej #cj4bi #g #cj4dh #cj4ah #f #cj4cg #cj4jg #e ,lower4 #cj4be #cj4ie #d #cj4ad #cj4hd #c #cj4jc #cj4gc #b #bi4ia #cj4fa #a #bi4hj #cj4ej #j #bi4fi #bi4ci #a #bi4eh #bi4bh #b #bi4dg #bi4ag #c #bi4cf #bi4jf #d #bi4be #bh4ie #e ,higher4 #bi4ad #bh4hd #f #bi4jc #bh4gc #g #bh4ib #bh4fb #h #bh4ha #bh4ea #i #bh4gj #aj ,the boiling point to be marked so much higher or lower than the stand of the mercury during the experiment4 ---------------------------------------- ------------------ ,the zero1 #j1 of the thermometer of ,fahrenheit1 is taken by means of a mixture of snow and common salt1 and its maximum point is1 like that of the preceding thermometer1 taken by means of boiling water2 but this interval is divided into #bab degrees2 so that the scale marks #cb where the centigrade and ,raumur's scales mark #j4 ,the thermometer of ,delisle has but one fixed point1 which is the heat of boiling water2 this is the zero of the instrument4 ,the inferior degrees are #j1jjja 7one ten-thousandth part7 of the capacity of the bulb and stalk of the thermometer4 ,it marks #aej at #j of the centigrade1 or #cb of ,fahrenheit's thermometer4 ,the dial1 the maximum and the minimum thermometers1 are graduated according to the same principles as the common thermometers4 ,you can1 with a mercurial thermometer1 make the centigrade scale rise to #cjj or #djj degrees above zero2 but with an alcohol thermometer1 you must never go beyond the heat of boiling water4 ,on the contrary1 the inferior degrees of the alcohol thermometer can be carried to the very lowest point1 while those of the mercurial thermometer should be stopped at thirty or thirty-five degrees below the zero of the centigrade scale1 as the mercury then approaches very near the point of its congelation4 ,in all cases1 the degrees of thermometer scales are indicated by the sign - when they are below zero1 and by the sign when they are above it2 the -is always marked1 but the generally omitted4 ,see pl4 #d1 fig4 #f4 ,we may observe here that it is proper from time to time to plunge the standard thermometer into melting ice1 for the purpose of verifying its exactness4 ,it has been found that thermometers constructed with a vacuum above the column of mercury gradually become inaccurate1 the #j ascending1 until it corresponds with #a or #b4 ,this singular effect is attributable to the constant pressure of the atmosphere1 which1 being supported merely by the resistance of the very thin sides of the thermometer1 finally presses them together1 and diminishes the capacity of the reservoir4 ,it is partly for the sake of avoiding this inconvenience that we consider it good not to make an entire vacuum above the mercury1 but to leave a portion of air in the tube1 and at the same time to form a little reservoir at the summit of the instrument4 ,differential ,thermometer4--,to graduate this instrument1 you first maintain the two bulbs at an equal temperature1 by which you determine the first fixed point1 which is zero4 ,then1 enveloping one of the two bulbs with melting snow1 and elevating the other by means of a vessel with warm water1 to a known temperature--to #bj ,centigrade1 for example--you fix a certain space1 which you afterwards divide into #bj equal parts or degrees4 ,the scale is continued by carrying successively to each side the known value of a degree4 99 99 99 99 99 ,,graduation ,,of ,,rumford',s ,,thermoscope4--,this instrument is graduated by dividing the tube which separates the two bulbs into equal parts1 the number of which is arbitrary1 though1 in general1 the thermoscope tube is divided into nine or eleven parts4 ,there is always an odd number of degrees1 and you manage so that the odd degree is found in the middle of the tube4 ,it carries the mark of zero at each end1 and the figures #a1 #b1 #c1 c4 proceed from each end of this middle degree1 and form two corresponding scales4 99 99 99 99 99 ,,graduation ,,of ,,mariotte',s ,,tube4--,you divide the little branch which is sealed at the end into a certain number of parts of equal capacity1 and the large branch into inches and parts of inches4 ,it is necessary to take care that the zero of the two ascending scales correspond1 and are situated above the inferior bend formed by the two branches of the instrument4 ,,the ,,end4 ,w4 ,,wilson1 ,,printer1 #eg1 ,,skinner-,,street1 ,,london4