It is a trying ordeal for any man to be compared with Black and
Cavendish, and Priestley cannot be said to stand on their level.
Nevertheless his achievements are not only great in themselves, but
truly wonderful, if we consider the disadvantages under which he
laboured. Without the careful scientific training of Black, without the
leisure and appliances secured by the wealth of Cavendish, he scaled
the walls of science as so many Englishmen have done before and since
his day; and trusting to mother wit to supply the place of training,
and to ingenuity to create apparatus out of washing tubs, he discovered
more new gases than all his predecessors put together had done. He laid
the foundations of gas analysis; he discovered the complementary
actions of animal and vegetable life upon the constituents of the
atmosphere; and, finally, he crowned his work, this day one hundred
years ago, by the discovery of that "pure dephlogisticated air" to
which the French chemists subsequently gave the name of oxygen. Its
importance, as the constituent of the atmosphere which disappears in
the processes of respiration and combustion, and is restored by green
plants growing in sunshine, was proved somewhat later. For these
brilliant discoveries, the Royal Society elected Priestley a fellow and
gave him their medal, while the Academies of Paris and St. Petersburg
conferred their membership upon him. Edinburgh had made him an honorary
doctor of laws at an early period of his career; but, I need hardly
add, that a man of Priestley's opinions received no recognition from
the universities of his own country.

That Priestley's contributions to the knowledge of chemical fact were
of the greatest importance, and that they richly deserve all the praise
that has been awarded to them, is unquestionable; but it must, at the
same time, be admitted that he had no comprehension of the deeper
significance of his work; and, so far from contributing anything to the