^54 On the P'rutpoTfiofi df 



different season^ (5<^ the y«ar, I have found, that' 

 if a glass A^ss^i' filled with 1^2,4-00 grains of 

 rain water be emptied in the open air, and 

 l^j^i^ins of strong lime water be poured in, 

 and 'the mouth tb^n dosed; by sufficient time 

 atid €lgitation, the;wbdle of th^ liine' water is 

 ju^t'^glturated by the acid gas it -finds in that 

 To9uiii€f= of air.' But 125 grains of tl>e lime 

 water used require 70 grain measures of car- 

 bohits ^cid gas to saturate it 5 therefore, th« 

 iO3,4t)0 grain medsureis: of comwioti adr contain 

 tO^f^tbonaoacid ; or -ttto of the whok.-^ 

 The- -Wight oi the carbonic acid- atmospher-e 

 th^S is to that of the whole compound as 1 : 

 1460 ; but the w^ighjt- of'Carfx>nic acid gas in 

 a given portion ttf air at rtl"^e earth *s surface, is 

 Bearlf -rts^Ts- of tiie whole \ because the speci* 

 fie gravity of the gas is 14- that of common air. 

 I have since found that the air in an assembly, 

 in w^hich two htandred people had breathed for 

 two hours, with the windows and doors shut, 

 contained little more than 1 per cent, of car* 

 booic acid ^ gas. 



:^ Having nt)W determined the force with 

 ifc-hich each atmosphere presses on the earth^i 

 ftuc&ce, or in otlier words, its weight ; it re* 

 maips next to enquire into their specific gra- 



