[Illustration: Delabole Slate Quarries] The important slate-quarries of the Duchy, of which the Delabole quarry is the most renowned, have already been mentioned. At Calstock and Gunnislake a few years ago there were numerous miners engaged in the manufacture of arsenic from the waste product of the abandoned copper mines. But now this has become an extinct industry. [Illustration: Shipping Slate, Port Gavin] Wulfram or tungsten, a metal used as an alloy for hardening steel, was also a waste product from the tin mines, but it is now utilised. At St Ives, pitchblende is now being worked for radium. =17. Fisheries.= If mining be a decayed industry in Cornwall, that of fishing shows no diminution. In an old book of natural history published in 1776, the principal fishery of pilchards is described. "Pilchards appear in vast shoals off the Cornish coasts about the middle of July, and disappear at the beginning of winter; though a few of them sometimes return again after Christmas. The fishing employs a great many men on the sea, and men, women, and children on land, in salting, pressing, washing, and cleaning; in making boats, nets, ropes, casks; and all the tradesmen depending on their construction and sale. The usual quantities exported each year, for ten years, from 1746 to 1756 inclusive, on the average is as follows: Fowey has exported 1732 hogsheads annually; Falmouth 14,631; Penzance and Mounts Bay 12,149; St Ives 1282; in all amounting to 29,795 hogsheads." And the same writer thus describes the fish. "The pilchard greatly resembles the herring, but differs from it in some particulars; it is a third less, and the body is proportionably broader: it has a black spot near the upper corner of the gills, and the belly is not so sharp. It has no teeth, either in the jaws, the tongue, or the palate." It is now held that the pilchard is identical with the sardine, but in a different stage of growth. The pilchards are taken generally from the middle of August to the middle of September, when large "schools" are seen coming up the Channel. Each fishing station generally has two or more companies or clubs of twenty or thirty men; each company owning various boats and generally two of the gigantic seines employed, which cost £250 or more. These nets are about 250 fathoms or more long and about 15 fathoms deep, and three boats go to each seine. The first boat, which is also the largest, is called the seine-boat, as it carries the net and seven men in it; the next is termed the "vollier," or "cock-boat," and carries another seine, called the tuck-seine, which is 100 fathoms long and 18 deep, this boat also carries seven men; the third boat is called the "lurker," and contains three or four men, and in this boat is the master. [Illustration: Pilchard Boats, Mevagissey]