3l6' On the The.ori) of Mtxed O'asei. 



unless it is heated to ^12'degrees of Farenhelt's 

 thermometer; were i"t then practicable to' mix * 

 vapour of a less heat with atmospherical ^aiftlie 

 spring, of the gases would reduce it in an in-' 

 stant to the state of a liquid ; so that" the d^fffi- 

 culty, which renders l)e Luc's theory olSjectidii- 

 able in its origmal form, is not removed irr 

 reaTity by tile present modiftca^ion of itl 



The theory of inixed gases has been fouml.to^ 

 be indefensible on tlie principles of therrie-, 

 chanical philosophy ; and I suspect that part of 

 it which relates to the separate existence of 

 vapour in the atmosphere, will prove equally 

 unfortunate when brought to the test of expe- 

 riment. Mr. DaltoUj in all probability, sup- 

 posedheha.d done allthatthe confirmation of this 

 theory required, by inventing the doctrine of 

 separate equilibria ; for nothing more has beeiv 

 offered in support, of his opinions,, particularly 

 of that relating to the existence of uncombined 

 vapour pervading the atmosphere, unless the 

 statement of the following experiment with his- 

 explanation of it may be referred to this head. . 

 If two parcels of dry air, which are equal' la 

 bulk, density and temperature,- be confined^by 

 equal columns of mercury, in two tubes of 

 equal bores, one of which is wet and the other 

 dry; the air, which is thus exposed to w^ater, 

 will expand more than thafHvhich is ^ept dry,, 



3 



