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45 2 MODERN TIMES.
not certainly justify deductions of such magnitude as those
which were sometimes advanced; but these clothed themselves
in the unassuming garb of hypothesis and did not
ask that people should accept them unconditionally, but
rather that they should criticize them freely.
Religion will never have anything to fear at the hands of
science if she ceases to be hostile to freedom of inquiry
and recognizes her true calling to lie in the ethical education
of the human race and in the perfecting of the
spiritual life.
PHYSICS AND CHEMISTRY IN THE LAST
HUNDRED YEARS.
WHILE mineralogy, botany, and zoology were changing
from sciences merely descriptive of objects to sciences
involving explanations of processes, physics and chemistry
also were assuming a new form in consequence of improvement
in the methods of investigation and the number
of new discoveries.
This period in chemistry was inaugurated by the discovery
of oxygen and the abolition of the theory of
phlogiston, and was characterized by the introduction of
the method of quantitative analysis.
In 1774, JOSEPH PRIESTLEY discovered oxygen by heating
red oxide of mercury. At the same time he observed
that the gas so obtained supported breathing and combustion
better than ordinary air; but he was unable to draw
the conclusions which the facts offered. He was a highlygifted
amateur who prosecuted science extensively rather
than deeply. He enriched chemistry with a multitude of
discoveries, and, as KOPP says, did more than professional
men of science to improve our knowledge of the gases*
LAVOISIER was the first to recognize the full significance
of the discovery of oxygen. Two years anterior to it he
* KOPP op. cit. i, 239.