It is a fact well attested by whalers and fishers in the northern seas; and one that almost every author who adverts to the northern fisheries confirms, that innumerable and almost incredible numbers of whales, mackerel, herring, and other migratory fish, annually come down in the spring season of the year, from the artic seas towards the equator. Some authors describe the shoals of herring alone, to be equal in surface to the island of Great Britain. Besides these, innumerable shoals of other fish also come down. These fish when they first come from the north in the spring, are in their best plight and fattest condition: but as the season advances, and they move on to the southward, they become poor; so much so, that by the time they get on the coast of France, or Spain, as fishermen say, they are scarce worth catching. The history of the migratory fish affords strong grounds to conclude, that the shoals which come from the north, are like swarms of bees from the mother hive, never to return; particularly the herring and other small fish. They are not known to return in shoals: and it is doubted by some writers on the subject whether any of them ever return north again, or whether they are not entirely consumed by men, and by other fish. Whalers and other fishermen who go to the north, generally prosecute their business in the seas between latitudes sixty and seventy degrees, where whales are most abundant. Pinkerton, in his voyages, states, that the Dutch, who at different periods got detained in the ice, and were compelled to winter in high northern latitudes, could find but few fish to subsist on during the winter: which proves that the migrating fish do not winter amongst, or on this side of the ice.――All these facts relative to fish, appear to be well authenticated. Now, were the earth a compact and solid spheroid, according to the old theory; and were the seas frozen nearly to the bottom at the poles, as we would be led to conclude, where could all those fish, that come down to us every spring, breed? or, if they even all returned in the autumn, and all the north were a sea that did not freeze even to the poles, it would require a great stretch of credulity to imagine where they could obtain food for the winter; or even if their source of food were inexhaustible, could the region of the pole afford space sufficient for their health, so as to migrate south in the spring? If the earth be not hollow, (or at least greatly concave about the poles) where could all those fish find room in winter? But on Symmes's plan, admitting the globe to be a hollow sphere, and the inner, or concave part, as habitable as without, (at least as habitable for fish) the whole matter is at once explained.