From time immemorial Cornwall has had a leading part in the mineral industries of England. Mines of tin, copper, lead, and zinc abound, and have been the chief source of revenue to the county. They give abundant employment to the laboring class, and men, women, and even children are freely employed in various ways about the mines. Since 1870 the mining industries have declined; the mines have been less productive, and the great discoveries of ore in this and other countries have greatly reduced prices and scattered the Cornish miners over the world. The fisheries of Cornwall have been another very important industry, especially the mackerel and pilchard fishing. The pilchard is a very delicious fish, similar to a herring, and is found almost exclusively on the Cornish coast. Cornwall abounds in interesting antiquities, and many of these are claimed to be almost as old as the granite rocks and cliffs of which they are composed. They are relics of the early Britons,--remains of villages, various sorts of sepulchral and memorial stones, and also some that were associated with ancient religious rites. Some of these, such as the "holed stones," have given rise to many superstitions among the common folk, who have been in the habit of dragging invalids through the orifices in the hope of curing them. There are also "cliff castles," especially at Land's End and at other points on the coast,--retreats of the native tribes from enemies,--and also earth-work forts on elevated sites throughout the country. The early Christian antiquities include churches and priories and the oratories or small chapels, frequently associated with a Baptistery or holy well. Some of these are as early as the fifth century. There is also an unusual number of crosses. As to their uses an ancient manuscript says: "For this reason ben crosses by ye way, that when folk passynge see ye croysses they shoulde thynke on Hym that deyed on ye croysse, and worshyppe Hym above althyng." They were also sometimes erected to guide and guard the way to the church, and sometimes for the beautiful custom of leaving alms on the crosses for poor wayfarers. The crosses were formerly far more numerous than now, but recently some of them have been rescued from doing duty as gate-posts and the like, to be reerected in the churchyards. There are also inscribed stones, such as the Camborne altar-slab, and others.