a tea-kettle, for the residue left was obviously an earthy
substance, whereas the steam driven off was supposed to be air. The
fact that pure water leaves no residue was not demonstrated until
after alchemy had practically ceased to exist. It was possible also to
demonstrate that water could be turned into fire by thrusting a red-hot
poker under a bellglass containing a dish of water. Not only did the
quantity of water diminish, but, if a lighted candle was thrust under
the glass, the contents ignited and burned, proving, apparently, that
water had been converted into fire. These, and scores of other similar
experiments, seemed so easily explained, and to accord so well with the
"four elements" theory, that they were seldom questioned until a later
age of inductive science.

But there was one experiment to which the alchemist pinned his faith in
showing that metals could be "killed" and "revived," when proper means
were employed. It had been known for many centuries that if any metal,
other than gold or silver, were calcined in an open crucible, it turned,
after a time, into a peculiar kind of ash. This ash was thought by the
alchemist to represent the death of the metal. But if to this same ash
a few grains of wheat were added and heat again applied to the crucible,
the metal was seen to "rise from its ashes" and resume its original
form--a well-known phenomenon of reducing metals from oxides by the
use of carbon, in the form of wheat, or, for that matter, any other
carbonaceous substance. Wheat was, therefore, made the symbol of the
resurrection of the life eternal. Oats, corn, or a piece of charcoal
would have "revived" the metals from the ashes equally well, but the
mediaeval alchemist seems not to have known this. However, in this
experiment the metal seemed actually to be destroyed and revivified,
and, as science had not as yet explained this striking phenomenon, it is
little wonder that it deceived the alchemist.

Since the alchemists pursued their search of the magic stone in such
a methodical way, it would seem that they must have some idea of
the appearance of the substance they sought. Probably they did, each
according to his own mental bias; but, if so, they seldom committed
themselves to writing, confining their discourses largely to
speculations as to the properties of this illusive substance.
Furthermore, the desire for secrecy would prevent them from expressing
so important a piece of information. But