Science and Education | Page 5

he may have burned his
fingers a little, very few who have tried that operation have burned their
fingers so little. He made admirable discoveries in science; his
philosophical treatises are still well worth reading; his political works
are full of insight and replete with the spirit of freedom; and while all
these sparks flew off from his anvil, the controversial hammer rained a
hail of blows on orthodox priest and bishop. While thus engaged, the
kindly, cheerful doctor felt no more wrath or uncharitableness towards
his opponents than a smith does towards his iron. But if the iron could
only speak!--and the priests and bishops took the point of view of the
iron.
No doubt what Priestley's friends repeatedly urged upon him--that he
would have escaped the heavier trials of his life and done more for the
advancement of knowledge, if he had confined himself to his scientific
pursuits and let his fellow-men go their way--was true. But it seems to
have been Priestley's feeling that he was a man and a citizen before he
was a philosopher, and that the duties of the two former positions are at
least as imperative as those of the latter. Moreover, there are men (and I
think Priestley was one of them) to whom the satisfaction of throwing
down a triumphant fallacy is as great as that which attends the
discovery of a new truth; who feel better satisfied with the government
of the world, when they have been helping Providence by knocking an
imposture on the head; and who care even more for freedom of thought
than for mere advance of knowledge. These men are the Carnots who
organise victory for truth, and they are, at least, as important as the

generals who visibly fight her battles in the field.
Priestley's reputation as a man of science rests upon his numerous and
important contributions to the chemistry of gaseous bodies; and to form
a just estimate of the value of his work--of the extent to which it
advanced the knowledge of fact and the development of sound
theoretical views--we must reflect what chemistry was in the first half
of the eighteenth century.
The vast science which now passes under that name had no existence.
Air, water, and fire were still counted among the elemental bodies; and
though Van Helmont, a century before, had distinguished different
kinds of air as gas ventosum and gas sylvestre, and Boyle and Hales
had experimentally defined the physical properties of air, and
discriminated some of the various kinds of aëriform bodies, no one
suspected the existence of the numerous totally distinct gaseous
elements which are now known, or dreamed that the air we breathe and
the water we drink are compounds of gaseous elements.
But, in 1754, a young Scotch physician, Dr. Black, made the first
clearing in this tangled backwood of knowledge. And it gives one a
wonderful impression of the juvenility of scientific chemistry to think
that Lord Brougham, whom so many of us recollect, attended Black's
lectures when he was a student in Edinburgh. Black's researches gave
the world the novel and startling conception of a gas that was a
permanently elastic fluid like air, but that differed from common air in
being much heavier, very poisonous, and in having the properties of an
acid, capable of neutralising the strongest alkalies; and it took the world
some time to become accustomed to the notion.
A dozen years later, one of the most sagacious and accurate
investigators who has adorned this, or any other, country, Henry
Cavendish, published a memoir in the "Philosophical Transactions," in
which he deals not only with the "fixed air" (now called carbonic acid
or carbonic anhydride) of Black, but with "inflammable air," or what
we now term hydrogen.
By the rigorous application of weight and measure to all his processes,
Cavendish implied the belief subsequently formulated by Lavoisier,
that, in chemical processes, matter is neither created nor destroyed, and
indicated the path along which all future explorers must travel. Nor did
he himself halt until this path led him, in 1784, to the brilliant and

fundamental discovery that water is composed of two gases united in
fixed and constant proportions.
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