of his former pupil, Henry Cavendish (1731-1810), whose discovery
of the composition of many substances, notably of nitric acid and
of water, was of great importance, adding another link to the
important chain of evidence against the phlogiston theory.
Cavendish is one of the most eccentric figures in the history of
science, being widely known in his own time for his immense
wealth and brilliant intellect, and also for his peculiarities
and his morbid sensibility, which made him dread society, and
probably did much in determining his career. Fortunately for him,
and incidentally for the cause of science, he was able to pursue
laboratory investigations without being obliged to mingle with
his dreaded fellow-mortals, his every want being provided for by
the immense fortune inherited from his father and an uncle.

When a young man, as a pupil of Dr. Black, he had become imbued
with the enthusiasm of his teacher, continuing Black's
investigations as to the properties of carbonic-acid gas when
free and in combination. One of his first investigations was
reported in 1766, when he communicated to the Royal Society his
experiments for ascertaining the properties of carbonic-acid and
hydrogen gas, in which he first showed the possibility of
weighing permanently elastic fluids, although Torricelli had
before this shown the relative weights of a column of air and a
column of mercury. Other important experiments were continued by
Cavendish, and in 1784 he announced his discovery of the
composition of water, thus robbing it of its time-honored
position as an "element." But his claim to priority in this
discovery was at once disputed by his fellow-countryman James
Watt and by the Frenchman Lavoisier. Lavoisier's claim was soon
disallowed even by his own countrymen, but for many years a