In order to explain wherein resides the quality of cork, it is
necessary to refer to a chemical analysis of it. In cork bark there is
70 per cent. of suberine, which is soluble in alcohol and ether, and
is plastic, ductile, and malleable under the action of humid heat.
Mixed with suberine, cerine and resin give cork its insolubility and
inalterability. These substances are soluble in alcohol and ether, but
insoluble in water.

According to the origin of cork, the wax and resin exist in it in very
variable proportion. The more resinous kinds resist the dissolving
action of wine better than those that are but slightly resinous. The
latter soon become corroded and spoiled by wine. An attempt has often
been made, but without success, to improve poor corks by impregnating
them with the resinous principle that they lack.

Various other processes have been tried without success, and so it
finally became necessary simply to separate the good from the bad
corks by a practical and rapid operation. A simple examination does
not suffice. Mr. Bouché has found that corks immersed in water finally
became covered with brown spots, and, by analogy, in order to test
corks, he immersed them in water for a fortnight or a month. All those
that came out spotted were rejected. Under the prolonged action of
moisture, the suberine becomes soft, and, if it is not resinous
enough, the cells of the external layer of the cork burst, the water
enters, and the cork becomes spotted.

It was left to Mr. Salleron to render the method of testing practical.
He compresses the cork in a very strong reservoir filled with water
under a pressure of from four to five atmospheres. By this means, the
but slightly resinous cork is quickly dissolved, so that, after a few