by oxygen, after combining with metals,
so as to convert them into oxyds; What quantity is contained by
hydrogen, in its different states of existence; and to ascertain, with
more precision than is hitherto attained, how much caloric is disengaged
during the formation of water, as there still remain considerable doubts
with respect to our present determination of this point, which can only
be removed by farther experiments. We are at present occupied with this
inquiry; and, when once these several points are well ascertained, which
we hope they will soon be, we shall probably be under the necessity of
making considerable corrections upon most of the results of the
experiments and calculations in this Chapter. I did not, however,
consider this as a sufficient reason for withholding so much as is
already known from such as may be inclined to labour upon the same
subject. It is difficult, in our endeavours to discover the principles
of a new science, to avoid beginning by guess-work; and it is rarely
possible to arrive at perfection from the first setting out.

CHAP. X.

_Of the Combination of Combustible Substances with each other._

As combustible substances in general have a great affinity for oxygen,
they ought likewise to attract, or tend to combine with each other;
_quae sunt eadem uni tertio, sunt eadem inter se_; and the axiom is
found to be true. Almost all the metals, for instance, are capable of
uniting with each other, and forming what are called _alloys_[22], in
common language. Most of these, like all combinations, are susceptible
of several degrees of saturation; the greater number of these alloys are
more brittle than the pure metals of which they are composed, especially
when the metals alloyed together are considerably different in their
degrees of fusibility. To this difference in fusibility, part of the
phenomena attendant upon _alloyage_ are owing, particularly the property
of iron, called by workmen _hotshort_. This kind of iron must be
considered as an alloy, or mixture of pure iron, which is almost
infusible, with a small portion of some other metal which fuses in a
much lower degree of heat. So long as this alloy remains cold, and both
metals are in the solid state, the mixture is malleable; but, if heated
to a sufficient degree to liquify the more fusible metal, the particles
of the liquid metal, which are interposed between the particles of the
metal remaining solid, must destroy their