Page:Natural History, Mollusca.djvu/50

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composed of the black liquor of some species of Cuttle; and an ink is prepared in Italy from this liquor, which, according to Cuvier, differs from the genuine China ink only in being a little less black. Among the ancients this secretion was certainly the basis of the ordinary writing ink, and the soft blackish-brown colour, known as sepia, is at this day manufactured from it.

The Tyrian purple, the most celebrated manufacture of that famous crowning city whose merchants were princes, was the juice of a shell-fish. Several species were employed to communicate various tints, but the principal was the Murex trunculus, one of the commonest shells of the Mediterranean, which may be compared for size and general appearance to our familiar Whelk.
But there is a shell occurring by myriads on our own rocky shores, which has a like property; it is the Purpura lapillus, a small white univalve, surrounded by one or more bands of brown more or less distinct. I have myself been entertained with making experiments on the purple dye of this shell-fish, which, perhaps, some of my readers may like to imitate. In order to this, having collected a few of the animals, which adhere to the rocks between tide-marks, break the shells with the blow of a hammer, taking care not to crush the animals: throw them then into a basin of fresh water, in which they will die in a few minutes. Examining them now, you will find, just behind the head, under the overlapping edge of the