26 ii. 2. 



a much greater intensity. Another distinction is this. In some 

 of the bodies which are called hot the heat is derived from 

 without, while in others it belongs to the bodies themselves ; 

 and it makes a most important difference, whether the heat has 

 the former or the latter origin. For to call that one of two 

 bodies the hotter, which is possessed of heat, we may almost say, 

 accidentally and not of its own essence, is very much the same 

 thing as if, finding that some man in a fever was a musician, 

 one were to say musicians are hotter than healthy men. Of that 

 which is hot per se and that which is hot per accidens, the former 

 is the slower to cool, while not rarely the latter is the hotter to 

 the touch. The former again is the more burning of the two — 

 flame for instance as compared with boiling water — while the 

 latter, as the boiling water, which is hot per accidens, is the more 

 heating to the touch. From all this it is clear that it is no 

 simple matter to decide which of two bodies is the hotter. For 

 the first may be the hotter in one sense, the second the hotter 

 in another. Indeed in some of these cases it is impossible to 

 say simply even whether a thing is hot or not. For the actual 

 substratum may not itself be hot, but may be receptive of heat 

 as an attribute ; as, supposing hot water or hot iron had single 

 names, would be the case with the substratum of the substances 

 denoted by such names. It is after this manner that blood is 

 hot.'* In such cases, in those, that is, in which the substratum 

 owes its heat to an external influence, it is plain that cold is 

 not a mere privation, but an actual existence.'^ 



There is no knowing but that even fire may be another of these 

 cases. For the substratum of fire may be smoke or charcoal, and, 

 though the former of these is always hot, smoke being an uprising 

 vapour, yet the latter becomes cold when its flame is extinguished, 

 as also would oil and pinewood under similar circumstances. But 

 even substances that have been burnt nearly all possess some heat, 

 cinders, for example, and ashes, the dejections also of animals, 

 and, among the excretions, bile ; because some residue of heat 

 has been left in them after their combustion. It is in another 

 sense that pinewood and fat substances are hot ; namely, because 

 they rapidly assume the actuality of fire. 



Heat appears to cause both coagulation and melting.'^ Now 

 such things as are formed merely of water are solidified by cold, 

 while such as are formed of nothing but earth are solidified by 

 649 a. 



