by its own motion. But
that which is nourished and grows is influenced by a certain regular
and equable motion. And as long as this motion remains in us, so long
does sense and life remain; but the moment that it abates and is
extinguished, we ourselves decay and perish.

By arguments like these, Cleanthes shows how great is the power of heat
in all bodies. He observes that there is no food so gross as not to be
digested in a night and a day; and that even in the excrementitious
parts, which nature rejects, there remains a heat. The veins and
arteries seem, by their continual quivering, to resemble the agitation
of fire; and it has often been observed when the heart of an animal is
just plucked from the body that it palpitates with such visible motion
as to resemble the rapidity of fire. Everything, therefore, that has
life, whether it be animal or vegetable, owes that life to the heat
inherent in it; it is this nature of heat which contains in itself the
vital power which extends throughout the whole world. This will appear
more clearly on a more close explanation of this fiery quality, which
pervades all things.

Every division, then, of the world (and I shall touch upon the most
considerable) is sustained by heat; and first it may be observed in
earthly substances that fire is produced from stones by striking or
rubbing one against another; that "the warm earth smokes"[121] when
just turned up, and that water is drawn warm from well-springs; and
this is most especially the case in the winter season, because there is
a great quantity of heat contained in the caverns of the earth; and
this becomes more dense in the winter, and on that account confines
more closely the innate heat which is discoverable in the earth.

X. It would require a long dissertation, and many reasons would require
to be adduced, to show that all the seeds which the earth conceives,
and all those which it contains having been generated from itself, and
fixed in roots and trunks, derive all their origin and increase from
the temperature and regulation of heat. And that even every liquor has
a mixture of heat in it is plainly demonstrated by the effusion of
water; for it would not congeal by cold, nor become solid, as ice or
snow, and return again to its natural state, if it were not that, when
heat is applied to it, it again becomes liquefied and dissolved, and so
diffuses itself. Therefore, by northern and other cold winds it is
frozen and hard