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V. Remarh on the prefent State of Aerojlatton. By 

 Mr. G. J. Wright. 



[Concluded from p. 346 of our laft Volume.] 



1 HE machine being conflrufted, it only remains to fill 

 it with inflammable air (hydrogen gas). The ufual method 

 of procuring inflanmiable air is by the folution of iron in ful- 

 phuric acid or common oil of vitriol : for this purpofe a 

 number * of air-tight cafks are difpofed in circles of ten or 

 twelve in each circle. The cafks compofing one circle com- 

 municate, by their individual tubes, to one centre calk con- 

 taining water, whofe height mud be fuch as that the orifice 

 of each tin tube fliould be fome inches under the fluid f. The 

 centre cafks (or coolers, as they are technically termed) are 

 the only ones immediately conne6led with the balloon, and 

 that by varnifhed filken tubes proceeding from their fum- 

 mits : there muft: alfo be a fecond orifice in the head of each 

 cafk compofing the circles ; each fuch orifice being for the 

 purpofe of introducing the ingredients, and provided alfo with 

 an air-tight plug. The iron (of which the turnings from the 

 boring of cannon are reckoned the bed) being placed in the 

 caflcs, the diluted acid % (having been previoufly well mixed 

 in a ieparate veflcl purpofely provided) is to be poured upon 

 it, flopping up the orifice with the plug as foon as the fvnell 

 of the gas is perceived: the quantity of acid firft put into 

 each calk mult be half the requifite proportion for the weight 

 of iron therein contained ; and this rule muft be obferved 

 throughout the whole number of calks, fo that on the fecond 

 fubfequent addition the aggregate quantity of gas Ihall be 

 produced §. 



The 



* This was the method adopted by Mr. Garnerin ; but its complexity 

 renders it verv exceptionable, as in otlier expert nents two or three csfks 

 have been made to anlV.tr all that he cfrt:£t> with thirty, and in much kfs 

 time. 



t Without this precaution the inflammable aT is liable to carry along 

 \vith it fome of the acid in a vaporous iVate, which in one inftance became 

 gradually condenfed in the balloon when arrived to a colder region, de- 

 luging the aeronaut with fome quarts of this acidulous liquor. 



X It is ntctlTary to dilute the acid in a Ieparate velTcl, .lOt merely on 

 account of the great difference in the relpiftlve griivities <>f the acid and 

 water, which renders lliriing ntceffary, but alfo on aciovint of the grt- ( 

 quantity of heat liber.nted, which is fufHciciit to occalion ebullition in lomc 

 inftances, and might derange the apparatus. 



§ This is the method adopted by fon;e experimenters; but a more ex- 

 pedient on'.- dcfervcb to lupcrlede it; cipecial'y as by nearly the like Hnd 

 tmdcrmentioircd procef's MellVs. Baldwin, Sadkr, and Lunardi, fuccefs- 

 f'jlly inflated their machiut in two hours. 



C» The 



