In some cases a new species of fish has been introduced into a particular fishing ground, with marked success. Thus the U.S.A. fisheries collected and hatched the eggs of the shad on the Atlantic coast and introduced the larvae into the Pacific, with the result that a profitable shad fishery has now been established on the Californian coast. The application of science to the fishing industry is not restricted to biological investigations of the food, habits and development of living fishes. It is developing new processes for the better preservation of edible fish for food purposes, so that the large quantities of fish caught periodically—for example, in the summer herring fishery—may be stored up for gradual consumption during the winter. It has shown that fish waste can be manufactured into glue, cattle food, and fertilizers. It has developed into a profitable industry the extraction of oils from both edible and inedible fish, and the conversion of these oils into hard fats, suitable for the manufacture of soap and margarine. It has demonstrated that the skins of certain fish, notably the shark, can be tanned to make excellent leather. With the exception of these pioneer experiments and investigations, however, the fishing industry of to-day is simply an organized art—the art of catching wild fish. The story of the industry is essentially a description of the methods that are used for capturing the various species of fish that are of commercial importance, and for handling, curing, and disposing of the catch. Great Britain is situated in the midst of the greatest fishing grounds of the world. The British fishing industry is the most efficient and the most highly developed of any. Consequently, since fishing methods are essentially the same everywhere, it will be sufficient for us to consider, with few exceptions, the methods and equipment that are used by our own fishermen around our own shores. There is direct evidence that, as early as the third century, A.D., fish were caught in considerable quantities round the coast of Britain by the natives and used as food. Little is known about the early development of a fishing industry in this country. We know that in the fourteenth and fifteenth centuries, fish was in demand throughout the country, partly because of the religious observance of fast days, and partly, no doubt, because it afforded a welcome change in the regular winter diet of salted meat. In those days there was no winter root crop, so that cattle were killed in autumn and salted down for consumption during the winter.