VI. The quality which Aristotle attributes to the air, is cold somewhat
under the highest degree, or nearly approaching to the highest degree.
Other philosophers, with more foundation of reason, esteem it indifferent
to heat and cold; and I, without setting about to combat this second
opinion, say it is more reasonable to suppose it cold than hot. Which
I shall attempt to demonstrate in the following manner: in order to
make a judgement of the qualities appertaining to a particular thing,
we should consider it in a state, where it is divested of the influence
of any extrinsic agent, by the operations of which it may be affected;
the air then so circumstanced, will always be found to be cold; and
from thence it should be inferred, that it naturally is cold. The minor
of this proposition is proved, by the air being only warm while it is
affected by the rays of the sun, and by its being found, that whenever
that influence is withdrawn, it becomes cold again, and that it is by so
much the more cold, in proportion to the absence of that influence. From
whence it is observable, that in the temperate zones, the air is coldest
when the nights are long; and that in the sub-polar, and circum-polar
ones, it is extremely cold, on account of the influence of the sun being
withdrawn from them for the space of six months together; and that when
it returns to enlighten them, because of the obliquity of its rays, it
still continues cold, far beyond the degree of mediocrity.
VII. Nor is saying that in the absence of the sun, the earth is the agent
that cools the air any reply to this; for if this was so, the lower
region of the air would be colder than the middle one, as being nearer to
the infrigidating cause; but this is contradicted by our experience; for
we very commonly see, that the water does not freeze in the lower region,
when in the middle one it is frozen into hail in the clouds; and very
often also, that which was frozen above, thaws suddenly upon its falling
down.
VIII. If it should be objected to this, that Aristotle and the
Peripatetics, when they say the air is warm, speak of the elemental air,
and not of the air of the atmosphere which is mixed with an infinite
number of heterogenous corpuscles, by some of which it may be made cold,
and especially by the many nitrous ones with which it is impregnated. To
this I answer first, that in the country where I am now writing, there is
not the least appearance of the air being nitrous, for that there is not
a grain of nitre to be found in the whole country, notwithstanding which,
the cold in winter is sometimes pretty sharp. I answer secondly, that
we can only talk of the pure elemental air by conjecture, for no mortal
has yet ever breathed any of it, nor is it possible that any one ever
should, on account of this element being an open expanse, exposed to the
inroads of the effluvias of all other bodies; and we should reason upon
sensible qualities, by pursuing the thread of palpable experiments; and
not by pursuing that of ideal proportions, as Aristotle did in making
the division of his elemental qualities; for the Author of nature is not
confined to pursuing only such proportions as fall within the compass
of our comprehension. This is the false principle, upon which all the
Pythagorean and Aristotelic philosophy has proceeded, and with respect
to the doctrine of the four elements, that seems to be tainted with the
same vice, as I shall shew more fully in another place. All that I shall
say at present is, that Aristotle dealt out, and distributed the four
qualities among the four elements, as if he had been the absolute master
of them all, and could dispose of and arrange them agreeable to his will
and pleasure.