or WHELK, a genus of shell-fish belonging to the order of vermes tellaceae. This animal is one of the snail kind. The shell is univalve, spiral, and gibbous. The aperture is oval, ending in a small strait canal. Linnaeus enumerates about 60 species, most of which are found in the southern seas. The six following are found in the British seas.
1. The pullus, or brown whelk, with five spires striated, waved, and tuberculated. Aperture wrinkled; upper part replicated. Length five eighths of an inch.
2. The undatum, or waved whelk, with seven spires, is spirally striated, and deeply and transversely undulated. Length three inches. Inhabits deep water.
3. The frutatum has eight spires, with elevated striae, undulated near the apex. Length near four inches.
4. The reticulatum, with spires scarcely raised, and strongly reticulated, is of a deep brown colour, and of an oblong form. The aperture white, glossy, and denticulated. Size of a hazel nut.
5. The minutum, or small whelk, with five spires, striated spirally, ribbed transversely. Size less than a pea. Found also in Norway.
6. The lappillus, or maffy whelk, with about five spires; side of the mouth slightly toothed: a very strong thick shell, of a whitish colour. A variety yellow, or fasciated with yellow, on a white ground; or fulcated spirally, and sometimes reticulated. Length near an inch and an half. Inhabits, in a vast abundance, rocks near low-water mark. This is one of the British shells that produce the purple dye analogous to the purpura of the ancients. See MUREX.
The process of obtaining the English purpura is well Phil. Trans. described by Mr William Cole of Bristol, in 1684, in abr. ii. 826. The following words: "The shells, being harder than most other kinds, are to be broken with a smart stroke of a hammer, on a plate of iron or firm piece of timber (with their mouths downwards) so as not to crush the body of the fish within; the broken pieces being picked off, there will appear a white vein lying transversely in a little furrow or cleft next to the head of the fish, which must be digged out with the stiff point of a horsehair pencil, being made short and tapering. The letters, figures, or what else shall be made on the linen, (and perhaps silk too), will presently appear of a pleasant light green colour; and if placed in the sun, will change into the following colours; (i.e. if in winter, about noon; if in summer, an hour or two after sunrise, and so much before setting; for in the heat of the day in summer, the colours will come on so fast, that the succession of each colour will scarcely be distinguished.) Next to the light green, it will appear of a deep green; and in a few minutes, change into a sea-green; after which, in a few minutes more, it will alter to a wotchet-blue; from that, in a little time more, it will be of a purple-red; after which (supposing the sun still shining), it will be of a very deep purple-red, beyond which the sun can do no more. But then, the last and most beautiful colour, after washing in scalding water and soap, will (the matter being again put into the wind or sun to dry) be of a fair bright crimson, or near to the prince's colour; which afterwards, notwithstanding there is no use of any dyptic to bind the colour, will continue the same if well ordered; as I have found in handkerchiefs, that have been washed more than 40 times; only it will be somewhat allayed from what it was after the first washing. While the cloth so writ upon lies in the sun, it will yield a very strong and fetid smell, as if garlic and asafoetida were mixed together."