DILATATION OF THE CASE!?. *£07 



Motion is an attribute of matter, independently of which Heat can pafs 

 it cannot pOffibly fubfift. If therefore, the phenomena of heat cu ^ . but mo- 

 can be (hewn to take place, where matter is notprefent, wetion ft rely can- 

 mall derive, from the fact, a conclufive argument againft that ™* tt * d ^ere 

 theory of heat, which affigns motion as its caufe. Now, in there is no mat- 



the experiment of Count Rumford, before alluded to, heatj"* Hencethe 



» t ... neat is matter. 



patted through a torricellian vacuum, in which, it need hardly 



be obferved, nothing could be prefent to tranfport or propa- 

 gate motion This experiment, in my opinion, decidedly 

 proves, that heat can fubfift independently of other matter, 

 and confequently of motion — in other words that heat is a dif~ 



Unci and peculiar body. 



xiii. 



Enquiries' concerning the Dilatation of the Gafcs and Vapors. 

 Read to the National rnftitute of France. By Cit. Gay 

 ■Lussac*. 



ils.J • 



A jit. I. The Objttl of this Memoir. 



iNATURAL philofophers have been long engaged in re- The refearches 

 fearches on the dilatation of the gafes ; but their labours pre- ? n the § a f es are 

 fent fucii variations in their remits, that fo far from having 

 fixed the general opinion, they have on the contrary left us 

 great reafon to wifh for more accurate invefiigations. 



The attention of philofophers has not been equally directed The expanfkms 

 to the dilatation of vapors. ' Though the prodigious effe&s ofj^'gJJ,^^ 

 the vapor of water has long been known and applied with the mined, 

 happieft eiTecl:, Ziegler and Bettancourt are the only perfons 

 who within my knowledge have attempted to meafure them. 

 Their experiments however are not adequate to (hew the true 

 dilatation of the vapor; for as there was always. w r ater in their 

 apparatus, every, new degree^ of heat not only produced a 

 dilatation of the vapor formed' by the preceding degrees, but 

 alio increalcd the volume by the formation of new vapors ; 

 twt) caufes which evidently tend to raife the mercury in thfcir 



* From the Annales de Cm'rtnV, XLlil. 187. 

 + IMfe apparatus of Bettancourt confifts in a boiler of copper 

 cloied by a cover of the fame metal, through which pafs three tubes. 



The 



