HEAT. 4:3 



ually entered into common usage as to be unavoidable, but I 

 venture to think that additions to such cases should as far 

 as possible be avoided, as injurious to that precision of lan 

 guage which is one of the safest guards to knowledge, and 

 from the absence of which physical science has materially 

 suffered. 



Let us now shortly examine the question of latent heat, 

 and sec whether the phenomena cannot be as well, if not 

 more satisfactorily, explained without the hypothesis of la 

 tent matter, an idea presenting many similar difficulties to 

 that of invisible light, though more sanctioned by usage. 

 Latent heat is supposed to be the matter of heat, associated, 

 in a masked or dormant state, with ordinary matter, not ca 

 pable of being detected by any test so long as the matter with 

 which it is associated remains in the same physical state, but 

 communicated to or absorbed from other bodies, when the 

 matter with which it is associated changes its state. To 

 take a common example : a pound or given weight of water 

 at 172, mixed with an equal weight of water at 32, will 

 acquire a mean temperature, or 102 ; while water at 172, 

 mixed with an equal weight of ice at 32, will be reduced to 

 32. By the theory of latent heat this phenomenon is thus 

 explained : In the first case, that of the mixture of water 

 with water, both the bodies being in the same physical state, 

 no latent heat is rendered sensible, or sensible heat latent ; 

 but in the second, the ice changing its condition from the solid 

 to the liquid state abstracts from the liquid as much heat as 

 it requires to maintain it in the liquid state, which it renders 

 latent, or retains associated with itself, so long as it remains 

 liquid, but of which heat no evidence can be afforded by any 

 thermoscopic test. 



I believe this and similar phenomena, where heat is con 

 nected with a change of state, may be explained and dis 

 tinctly comprehended without recourse to the conception of 

 latent heat, though it requires some effort of the mind to di- 



