ON THE MATERIALITY OF CALORIC. 201 



panfion is wholly arbitrary, commencing far from the abfolute 

 privation of heat, and falling far fhort of its maximum. 3dly, 

 The caloric, latent in bodies, or chemically combined with 

 them, has no effect on the thermometer. \thly> The experi- and the laws de- 

 ments of Dr. Crawford, though fufficient to fhew that the ™ l0 P e . J \* , 



° . Crawtord apply 



expanfion of the mercury of the thermometer bears a ratio to onlj ro a (mall 



the aclual increments of heat, in any temperature between the P a "ofthisfcale. 

 boiling and freezing points of water, by no means prove that 

 this proportion holds univerfally. 



Equal weights of heterogeneous bodies, it is prefumed, 

 contain unequal quantities of caloric ; and the ratio of thefe 

 quantities is approximated in the following manner. 



. Equal weights of the fame body, at different temperatures, Common me- 

 give, on admixture, the arithmetical mean : but equal weights *£ r ^ r , ^'J"^ 

 of different bodies, at different temperatures, afford a tempe-lmc b> the cam- 

 rature which varies considerably from the mean. Thus a pound ™ n tc ^T e " turo 

 of water at J 00 degrees, and a pound at 200», give the tern- the mean, 

 perature of 150° ; but a pound of water at 200*, and a pound 

 of mercury at 100°, afford, not the mean, but a temperature 

 confiderably higher. Hence it follows that a pound of mer- 

 cury has not the power of fixing and retaining fo much caloric 

 as a pound of water : and the fixation of more heat, by the 

 water than by the mercury, is afcribed to the fuperior energy 

 of a power inherent in both, and termed capacity for caloric. 

 . From an extenfive feries of experiments Dr. Crawford in- Capacities per- 

 fers, that the capacities of bodies are permanent, fo long as ^ ane " t ^ 

 they retain their form. Thus, the capacity of water has to pothe/is, 

 that of mercury the ratio of 28 to 1, at any temperature be- 

 tween 32° and 212°. The difference of capacities of bod'es, 

 it is inferred, therefore would continue the fame, down to the 

 abfolute privation of temperature. Imagine, then, two bo- 

 dies at this point of privation : they may ftill contain unequal 

 quantities of combined caloric; for, when chemically com- 

 bined, caloric does not produce temperature. On Dr. Craw- not applicable at 



ford's hypothefis, thefe comparative quantities of combined ™ motc and un - 

 i • • iu / j- u i jv , r • l know n tempera- 



caloric, in the two bodies, may be learned by oblerving the tures, 



ratio of temperature, produced, by the addition to each, of 



fimilar quantities of heat. This fuppofition, however, is ma- 



nifeftly gratuitous; and the contrary might be maintained 



with equal or greater probability : for it may be fuppofed that, 



at this attuned negation of temperature, one body renders 



latent 



