258 DILATATION OF THE CASKS. 



which arc folublc in water, and he found in each a particula 



dilatation differing from thofe of the other gafes. In this re- 



fpecl my experiment differ much from his. 

 Apparatus of The apparatus of Cit. Charles confifted of a barometer 

 A barometer' wllole chamber or upper fpace was of great extent, The gas 

 with a large va- on which the experiment was to be performed was cnclofcd 

 cuum, and a re- j n lne refervoir, or lower fpace of the barometer, at the tem- 

 forthegasto perature 0°, and under the preflure of 28 inches of mercury, 

 prefs on the When the barometer was plunged in boiling water, the mer- 

 mercury. c ^ ^^ ^ ^ tube, and the excefs of the whole column 



above 28 inches indicates tlie elailicity acquired by the gas ; 

 This was in?.c- but Cit. Charles having had the politenefs to fhew me his ap- 



^rrTfeonhe 6 P aratus > l favv that the tube of the barometer was too large in 



mercury gave proportion to the capacity of the refervoir; fo that the eleva- 



room for ex- t ; on f tne mercury above 28 inches did not indicate all the 

 paniion. . * 



fpring the gas had acquired, becaule in that cafe its volume in 



the refervoir ought to have remained conftant. It appears then 



to me, that the real dilatation of the gafes cannot be decided 



from his experiments. 



Art. III. Description of Apparatus. 

 Apparatus for A receiver B (Fig. 1. PI. IX.) has a cock of iron R, to 



'lobfwkh an which ma y be ad J ulted a bended tube I, D, (Fig. 2). The 

 iron cock ; filled key of the cock carries a lever L L bored at its two extremi- 

 st ufual, and ties m or der to receive two cords, by means of which the 

 water to be cock ma y be opened and fliut under the water. In order to 

 heated. The introduce the gas into the receiver I ufe a bell glafs M, (Fig. 1 .) 

 expanded pafs to wn ich are adapted a cock and bended tube T, plunged in 

 out, and the a veiTel Q, S. When water is poured into the veiTel, and the 

 fured! 10n mCa " coc k °P ened > tne gas compreiTed in the bell efcapes through 

 the tube and fills the receiver B, reverfed on a bath P, O, of 

 mercury. The receiver B being full I fhut the cock : I adjufl 

 the tube I, D, (Fig. 2.) to it, and I fix it in a cylindrical 

 cage of iron E, F, G, H, which I then carry to a copper vcf- 

 fel A, D, filled with water. In order that there might be no 

 communication between the exterior air and the gas inclofed 

 in the receiver, when the cock is opened I caufe the extre- 

 mities of the tube I, D, of one or two millimetres (thirtieths 

 of an inch) to be plunged in a fmall bath K, X, of mercury. 

 This done I heat the bath, and from 10° to 10° for example, 

 I open the cock and (hut it immediately. The gas dilated by 



the 



