Proceedmgs of the American Philosophical Society. 47 



vapor at the existing temperature, so as to cause the water to boil, as in 

 the Cryophorus, or Leslie's experiment, still the entrance of -xryoi; of the 

 quantity requisite to fill the receiver caused the thermometer to rise a 

 tenth of a degree. An alternate motion of the key of the cock, through 

 one fourth of a circle within one third of a second of time, was adequate 

 to produce the change last mentioned. 



Dr. Hare considered the fact, that heat is produced, when to air, rare- 

 fied to one fourth of the atmospheric density, another fourth is added, 

 irreconcilable with the idea that this result arises from the compression 

 of the portion of air previously occupying the cavity, since the entering 

 air must be as much expanded as the residual portion is condensed. 



As, agreeably to Dalton, a cavity occupied by a vapor acts as a vacuum 

 to any air which may be introduced. Dr. Hare argued, that when a re- 

 ceiver, after being supplied with ether or water, is exhausted so as to re- 

 move all the air and leave nothing besides aqueous or ethereal vapor, the 

 heat, acquired by air admitted, cannot be ascribed, consistently, to the 

 condensation of the vapor. 



The facts above stated, he added, are not reconcilable with the idea 

 of De la Rive and Marcet, that the first portion of the entering air is 

 productive of cold, although a subsequent condensation is productive of 

 an opposite change. The effect upon the thermometer was too rapid, 

 and the quantity of the entering air too minute, to allow it to be refrige- 

 rated by rarefaction in the first place, and yet afterwards to be so much 

 condensed as to become warm by the evolution of caloric. 



Notwithstanding the experiments of Gay Lussac and of those of De la 

 Rive and Marcet, there appeared to Dr. Hare to be evidence in favor of 

 the heat being due to the space rather than to the air which it contained. 



With respect to Gay Lussac's celebrated experiment with the Torricel- 

 lian vacuum, supposing such a vacuum to be a pre-eminently good libera- 

 tor of heat, as it ought in reason to be, the caloric would be absorbed by 

 the mercury as rapidly as this metal could be made to encroach upon the 

 space occupied by the calorific particles. 



Admitting, that for equal weights, the specific heat of air is seven times 

 as great as that of mercury, there could not have been a capacity greater 

 than that of about 200 grains of the metal, whereas a very small stratum 

 of this metal, equal to one fourth of an inch, would, in the apparatus 

 employed, amount to more than a pound. 



The rapidity with which a mercurial thermometer is affected by the 

 changes of temperature in experiments like those which he had been de- 

 scribing, showed, in Dr. Hare's opinion, that there was something not 

 yet understood respecting the transfer of heat in such cases. It was 

 hardly reconcilable with the process of conduction or circulation, as ordi- 

 narily understood. 



