combination. All at once we find that a
simple substance changes face, puts off its characteristic qualities and
resumes them at will;--not merely when we liquefy or vaporize a solid,
or reverse the process; but that a solid is literally transformed into
another solid under our own eyes. We thought we knew phosphorus. We warm
a portion of it sealed in an empty tube, for about a week. It has
become a brown infusible substance, which does not shine in the dark
nor oxidate in the air. We heat it to 500 F., and it becomes common
phosphorus again. We transmute sulphur in the same singular way. Nature,
you know, gives us carbon in the shape of coal and in that of the
diamond. It is easy to call these changes by the name allotropism, but
not the less do they confound our hasty generalizations.

These facts of allotropism have some corollaries connected with them
rather startling to us of the nineteenth century. There may be other
transmutations possible besides those of phosphorus and sulphur. When
Dr. Prout, in 1840, talked about azote and carbon being "formed" in the
living system, it was looked upon as one of those freaks of fancy to
which philosophers, like other men, are subject. But when Professor
Faraday, in 1851, says, at a meeting of the British Association, that
"his hopes are in the direction of proving that bodies called simple
were really compounds, and may be formed artificially as soon as we
are masters of the laws influencing their combinations,"--when he comes
forward and says that he has tried experiments at transmutation,
and means, if his life is spared, to try them again,--how can we
be surprised at the popular story of 1861, that Louis Napoleon has
established a gold-factory and is glutting the mints of Europe with
bullion of his own making?

And so with reference to the law of combinations. The old maxim was,
Corpora non agunt nisi soluta. If two substances, a and b, are inclosed
in a glass vessel, c, we do not expect the glass to change them, unless
a or b or the compound a b has the power of dissolving the glass. But
if for a I take oxygen, for b hydrogen, and for c a piece of spongy
platinum, I find the first two combine with the common signs of
combustion and form water, the third in the mean time undergoing no
perceptible change. It has played the part of the unwedded priest, who
marries a pair without taking a fee or having any further relation with
the parties. We call this catalysis, catalytic a