ement of these means. If, for example, a military commander
intended effectually to bombard a city;--such being the object proposed,
he would immediately proceed to estimate, admeasure, or calculate his
means to produce the effect, and his success would depend on the
knowledge he possessed of the nature and properties of the materials
employed: he must calculate the distance, elevation, proportionate
quantity of powder, and the time the fuzee should burn previously to the
explosion of the shell; with various other necessary circumstances. This
is an example of a very pure process of reasoning as applied to things,
and accords with the definition that has been attempted. If it were
necessary to multiply instances of the reasoning on things, perhaps the
construction of a thermometer would be a well-adapted illustration; and
it would likewise exhibit that which I am very anxious to impress,
namely, the very gradual manner in which knowledge, by the operation of
reasoning has been applied to the purposes of utility. That many
substances, and particularly metallic bodies, augmented in magnitude by
being heated, or, as we now term it, expanded by heat, was known many
centuries ago, and was a fact of hourly occurrence to the artificers in
metals. A similar increment of bulk was also observed in fluids; and it
was likewise known, that their dimensions contracted as they cooled.
This fact appeared to obtain so generally, that it became an aphorism,
that bodies expanded by heat and contracted by cold. Of the precise
gradations of heat they were, however, ignorant. Most of the senses
became tests, although they were inaccurate criteria. The sight conveyed
some distinctive marks; so that when some metallic bodies were heated
to a high degree, they were observed to become red, and as the heat was
increased, they were rendered white. By the touch, a variety of
discriminations of temperature was obtained, to which appropriate terms
were annexed, explanatory of its effects, or according with the
feelings; as burning, scorching, scalding, blistering hot;--descending
to blood, loo, gently, or agreeably warm. The ear was not exempted from
its share of information, by detecting the boiling of water, or by
discovering when a heated metal was immersed in that fluid, that it was
hissing-hot: even the smell detected some obscure traces, sufficient to
discourage or invite an approach. These tests, although they might serve
for ordinary purposes,