 ground that the
phenomena of respiration are essentially similar to those of combustion
and calcination, that the only portion of the air which supports animal
life is the oxygen. The azote or nitrogen is inhaled along with the
oxygen, but is exhaled unaltered. The oxygen, however, is gradually
converted into carbonic acid; and when a certain amount, but by no
means the whole, has been thus changed, the air becomes unfit for
respiration. If the carbonic acid is withdrawn by means of lime-water
or caustic alkali, the residue is air poor in oxygen, and the azote is
the same as that left after the calcination of metals, or the burning
of a candle, in air.

At the time of his impeachment, Lavoisier was engaged in experiments
on perspiration, along with Séguin. He had nearly finished his
experimental work, but had drawn up no account of it. His request that
his life might be prolonged until he had compiled a statement of his
results was refused; but Séguin, who was fortunately spared, undertook
the task. The facts collected do not, however, bear directly on our
subject, and shall not be further alluded to here.

This account of Lavoisier’s researches would be incomplete without
a reference to his text-book of chemistry, _Traité élémentaire de
Chimie_, in which his views are stated in order, and with great
clearness. The nomenclature current at the time was so cumbrous, that
it was almost, if not quite, impossible for the supporters of the new
theory to express their meaning in an intelligible manner. De Morveau
had suggested a nomenclature for salts; Black, too, had invented one;
but neither of these systems was adapted to represent the new views.
It was partly with the object of avoiding such embarrassment that
Lavoisier wrote his _Treatise_.

He begins with a clear statement of what is generally termed “the
states of matter”--solid, liquid, and gaseous--and points out
that solids and liquids are almost all capable of change into the
aeriform state by the addition of “caloric.” Proceeding next to the
