Science and Education | Page 7

of air besides this particular
modification of nitrous air, and I knew no nitrous acid was used in the
preparation of mercurius calcinatus, I was utterly at a loss how to
account for it.
"In this case also, though I did not give sufficient attention to the
circumstance at that time, the flame of the candle, besides being larger,
burned with more splendour and heat than in that species of nitrous air;
and a piece of red-hot wood sparkled in it, exactly like paper dipped in
a solution of nitre, and it consumed very fast--an experiment which I
had never thought of trying with nitrous air." [7]
Priestley obtained the same sort of air from red lead, but, as he says
himself, he remained in ignorance of the properties of this new kind of
air for seven months, or until March 1775, when he found that the new
air behaved with "nitrous gas" in the same way as the dephlogisticated
part of common air does; [8] but that, instead of being diminished to
four-fifths, it almost completely vanished, and, therefore, showed itself
to be "between five and six times as good as the best common air I
have ever met with." [9] As this new air thus appeared to be completely
free from phlogiston, Priestley called it "dephlogisticated air."
What was the nature of this air? Priestley found that the same kind of
air was to be obtained by moistening with the spirit of nitre (which he
terms nitrous acid) any kind of earth that is free from phlogiston, and
applying heat; and consequently he says: "There remained no doubt on
my mind but that the atmospherical air, or the thing that we breathe,
consists of the nitrous acid and earth, with so much phlogiston as is
necessary to its elasticity, and likewise so much more as is required to
bring it from its state of perfect purity to the mean condition in which
we find it." [10]
Priestley's view, in fact, is that atmospheric air is a kind of saltpetre, in
which the potash is replaced by some unknown earth. And in

speculating on the manner in which saltpetre is formed, he enunciates
the hypothesis, "that nitre is, formed by a real decomposition of the air
itself, the bases that are presented to it having, in such circumstances, a
nearer affinity with the spirit of nitre than that kind of earth with which
it is united in the atmosphere." [11]
It would have been hard for the most ingenious person to have
wandered farther from the truth than Priestley does in this hypothesis;
and, though Lavoisier undoubtedly treated Priestley very ill, and
pretended to have discovered dephlogisticated air, or oxygen, as he
called it, independently, we can almost forgive him when we reflect
how different were the ideas which the great French chemist attached to
the body which Priestley discovered.
They are like two navigators of whom the first sees a new country, but
takes clouds for mountains and mirage for lowlands; while the second
determines its length and breadth, and lays down on a chart its exact
place, so that, thenceforth, it serves as a guide to his successors, and
becomes a secure outpost whence new explorations may be pushed.
Nevertheless, as Priestley himself somewhere remarks, the first object
of physical science is to ascertain facts, and the service which he
rendered to chemistry by the definite establishment of a large number
of new and fundamentally important facts, is such as to entitle him to a
very high place among the fathers of chemical science.
It is difficult to say whether Priestley's philosophical, political, or
theological views were most responsible for the bitter hatred which was
borne to him by a large body of his country-men, [12] and which found
its expression in the malignant insinuations in which Burke, to his
everlasting shame, indulged in the House of Commons.
Without containing much that will be new to the readers of Hobbs,
Spinoza, Collins, Hume, and Hartley, and, indeed, while making no
pretensions to originality, Priestley's "Disquisitions relating to Matter
and Spirit," and his "Doctrine of Philosophical Necessity Illustrated,"
are among the most powerful, clear, and unflinching expositions of
materialism and necessarianism which exist in the English language,
and are still well worth reading.
Priestley denied the freedom of the will in the sense of its
self-determination; he denied the existence of a soul distinct from the
body; and as a natural consequence, he denied the natural immortality

of man.
In relation to these matters English opinion, a century ago, was very
much what it is now.
A man may be a necessarian without incurring graver reproach than
that implied in being called a gloomy fanatic, necessarianism, though
very shocking, having a note of Calvanistic orthodoxy; but, if a man is