but his suggestions were of such
importance that the king directed that a gold medal be bestowed upon the
young author at the public sitting of the Academy in April, 1776. Two
years later, at the age of thirty-five, Lavoisier was admitted a member
of the Academy.

In this same year he began to devote himself almost exclusively to
chemical inquiries, and established a laboratory in his home, fitted
with all manner of costly apparatus and chemicals. Here he was in
constant communication with the great men of science of Paris, to all of
whom his doors were thrown open. One of his first undertakings in this
laboratory was to demonstrate that water could not be converted into
earth by repeated distillations, as was generally advocated; and to show
also that there was no foundation to the existing belief that it was
possible to convert water into a gas so "elastic" as to pass through
the pores of a vessel. He demonstrated the fallaciousness of both these
theories in 1768-1769 by elaborate experiments, a single investigation
of this series occupying one hundred and one days.

In 1771 he gave the first blow to the phlogiston theory by his
experiments on the calcination of metals. It will be recalled that one
basis for the belief in phlogiston was the fact that when a metal was
calcined it was converted into an ash, giving up its "phlogiston" in the
process. To restore the metal, it was necessary to add some substance
such as wheat or charcoal to the ash. Lavoisier, in examining this
process of restoration, found that there was always evolved a great
quantity of "air," which he supposed to be "fixed air" or carbonic
acid--the same that escapes in effervescence of alkalies and calcareous
earths, and in the fermentation of liquors. He then examined the process
of calcination, whereby the phlogiston of the metal was supposed to
have been drawn off. But far from finding that phlogiston or any other
substance had been driven off, he found that something had been taken
on: that the metal "absorbed air," and that the increased weight of the
metal corresponded to the amount of air "absorbed." Meanwhile he
was within grasp of two great discoveries, that of oxygen and of the
composition of the air, which Priestley made some two years later.

The next important inquiry of this great Frenchman was as to the
composition of diamonds. With the great lens of Tschirnhausen belonging
to the Academy he succeeded in burning up several diamonds,