This discovery of the nature of nitric acid seems to have been about the
last work of importance that Cavendish did in the field of chemistry,
although almost to the hour of his death he was constantly occupied with
scientific observations. Even in the last moments of his life this habit
asserted itself, according to Lord Brougham. "He died on March 10, 1810,
after a short illness, probably the first, as well as the last, which he
ever suffered. His habit of curious observation continued to the end.
He was desirous of marking the progress of the disease and the gradual
extinction of the vital powers. With these ends in view, that he might
not be disturbed, he desired to be left alone. His servant, returning
sooner than he had wished, was ordered again to leave the chamber of
death, and when he came back a second time he found his master had
expired."(3)

JOSEPH PRIESTLEY

While the opulent but diffident Cavendish was making his important
discoveries, another Englishman, a poor country preacher named Joseph
Priestley (1733-1804) was not only rivalling him, but, if anything,
outstripping him in the pursuit of chemical discoveries. In 1761 this
young minister was given a position as tutor in a nonconformist academy
at Warrington, and here, for six years, he was able to pursue his
studies in chemistry and electricity. In 1766, while on a visit to
London, he met Benjamin Franklin, at whose suggestion he published his
History of Electricity. From this time on he made steady progress in
scientific investigations, keeping up his ecclesiastical duties at the
same time. In 1780 he removed to Birmingham, having there for associates
such scientists as James Watt, Boulton, and Erasmus Darwin.

Eleven years later, on the anniversary of the fall of the Bastile in
Paris, a fanatical mob, knowing Priestley's sympathies with the
French revolutionists, attacked his house and chapel, burning both and
destroying a great number of valuable papers and scientific instruments.
Priestley and his family escaped violence by flight, but his most
cherished possessions were destroyed; and three years later he quitted
England forever, removing to the United States, whose struggle for
liberty he had championed. The last ten years of his life were spent
at Northumberland, Pennsylvania, where he continued his scientific
researches.

Early in his scientific career Priestley began investigations upon the
"fixed air" of Dr. Black, and, oddly enough,