THEORY DEDUCED FROM PHYSICAL LAWS. 29 



61. A similar effect will be observed, by examining the 

 result when the urn was carried from a warm to a cold 

 place. 



A much greater effect was produced in this latter case 

 than in the former, when moist air was used, which can, 

 only be accounted for, on supposition that there is a great 

 expansion of air containing vapor, when a portion of that 

 vapor is condensed into water. 



62. This point being now established, independently of 

 all previous experiments on the specific caloric of atmos- 

 phereic air and the caloric of elasticity in steam, it adds a 

 high degree of probability, a priori to the dynamic theory 

 of atmospheric depositions given above. 



63. I do not pretend to draw from these experiments, the 

 specific caloric of air, though I may perhaps attempt this 

 by a more careful set of similar experiments at some future 

 time. 



64. The minus pressures, or where the apparatus was 

 transferred from a warm to a cold medium, are very im- 

 portant, indeed quite decisive in a comparative point of 

 view. For if the instantaneous heating and cooling effect 

 of the vessel on the included air at the moment of opening 

 the cock should be so considerable as to hinder us from 

 drawing any certain conclusions as to the exact number of 

 degrees air is heated by a given condensation, or cooled by 

 a given expansion, still, as these experiments were per- 

 formed with the same instrument arid in the same manner, 

 the comparative results must be correctly obtained. 



It is proper to mention, that to insure saturation, a small 

 quantity of water was put into the urn, in the case of moist 

 air. 



