On the Tliedrx/ of Mixed Gases, 311 



• 



provided the' fcoitesponding 2ltigTr>onrati(irt!^ -df 

 their tempei-aiures be equ^J-; wWch' phi^fid- 

 mcnon is thus explained on the ^rincipk^' of 

 the theon'. The vapour that arises froin'th(* 

 sides of the vt-et tube, possesses a spring- ©f its 

 ©wn; therefore it takes off part of thfe' weighr> 

 of the mercury from the air, and thereby leavesi 

 it to expand Itself, so as to re-adjust thdequi'-^ 

 Librium. According to this explanationy iP 

 / and or represent the lengths of the columns 6l? 

 dry and moist air at any temperature ; and if-c] 

 denote the length of a column of mfertitiiY,^ 

 equalin weight to the pressut^ that confines 

 the contents of the tubes-; arid if/beputfof 

 ihe spring of vapour of the same temperature' 

 measured' by a column of mercury, wc have' 



^^^w-y^ from which we also get r=~-^ ^ 



the last expression affords us an opportunitv' 

 of comparing the preceding explanation, and' 

 therefore the theory itself with facts ; for, ac- 

 cording to ^'the experiments of Mr. Schmidt^ 

 lOOiD "parts of dry air at 32 degrees ot 

 Farcnheit, will expand to 1087, M parts, by 

 being raised to 5i> degrees, in contact with 

 water; call' this number^; according to the 

 same authoi^, 1000 parts of dry air at 32 de- 

 grees will expand to- 10>3,61 parts, by- being 



