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 fire. Hot
substances again are solidified by cold, and, when they consist
chiefly of earth, the process of solidification is rapid, and the
resulting substance is insoluble; but, when their main constituent
is water, the solid matter is again soluble. What kinds of substances,
however, admit of being solidified, and what are the causes of
solidification, are questions that have already been dealt with more
precisely in another treatise.
In conclusion, then, seeing that the terms hot and hotter are used
in many different senses, and that no one substance can be hotter than
others in all these senses, we must, when we attribute this
character to an object, add such further statements as that this
substance is hotter per se, though that other is often hotter per
accidens; or again, that this substance is potentially hot, that other
actually so; or again, that this substance is hotter in the sense of
causing a greater feeling of heat when touched, while that other is
hotter in the sense of producing flame and burning.
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