refpeclhig Heat and Caloric* 75 



Jamaica, the quantity in the whole is latent, and in each 

 fpecific and latent : the fame holds with regard to a fyftem 

 of fubftances in England in the month of January. The 

 heat in both cafes is latent. If the one fyftem of bodies 

 could be tranfported to the other in a moment, and placed 

 in contact with it, a portion of that heat which was latent 

 in Jamaica, would be counted fenjible heat in London ! 

 This is exactly where the docti ine lands us when viewed gene- 

 rally ; and yet we are to confider heat as having two diftinct 

 modes of exiftence ! But let us take a clofer view of it : 



When by the pa fling of a folid body into a fluid form 

 the unrounding atmofphere is found to have loft heat, this 

 heat, they fay, has not been merely abforbed by the fub- 

 ftance that has become fluid, but has become latent in it. 

 When a liquid panes into the aeriform Mate, the fame phe- 

 nomenon accompanies the change, and alfo the fame af- 

 fertion ; and the doctrine is meant to convey the idea that 

 heat has not only been changing its place, but has itfelf 

 undergone a change as to its ftate, its properties, and mode 

 of action. 



It is a generally received axiom, that no more caufes 

 fhould be admitted in phyfics than what are true and fuffi- 

 cient to account for the phenomena. Let us inquire whe- 

 ther this axiom be not violated in the cafes ftated, when re- 

 courfe is had to the doctrine of latent, as diftinguifhed from 

 free, heat, to affift in explaining the phenomena. 



The dimenfions of bodies are enlarged when heat is 

 poured into them (D) . The primitive hioleculae (indepen- 

 dent of the heat) of which the bodies are formed, are forced 

 farther from each other by the interpofed matter of heat. 

 Continue the action of the fame caufe, their cohefion will 

 be deftrnyed entirely (C), and they will be diffufed throuph 

 the predominating fubftance (heat), as the particles of fa- 

 line fubftances diffufe themfelves through water when dif- 

 folved in that liquid. In the cafe juft put for illuftration, who 

 ever fuppofes the water to have undergone any change as to 

 its effence or properties, whether directly poured upon the 

 faline fubftance or furnifhed to it by the atmofphere. 



In chemical combinations it is admitted that we cannot, 

 La. ti priori. 



