Trawling is said to have been invented at the end of the seventeenth century by the Brixham fishermen. The first trawlers were quite small vessels, and were followed towards the end of the eighteenth century by the smack. The smack reached its maximum size and efficiency at about the middle of the nineteenth century. Some of the smacks that are still fishing from Brixham—durable, seaworthy, and with beautiful lines—are probably a hundred years old. In 1870, there were a thousand first-class smacks in the North Sea, three hundred in the English Channel, and over a hundred in the Irish Sea. The smacks were fitted with a tank in the well of the ship, in which the fish were kept in sea-water and brought in alive. In Denmark to-day, plaice are brought ashore and sold alive. The subsequent development of trawl fishing has been in the construction of larger nets, worked by more powerful trawling vessels driven by steam. The size of beam trawl that can be worked by a large sailing smack is limited by the trawling power of the vessel, and also by the difficulty of constructing and handling very long beams. The maximum length of beam in general use by sailing smacks is fifty feet. The length of the net, from its mouth to the narrow of “cod” end, rarely exceeds a hundred feet. To each end of the beam is attached a triangular trawl-head of iron, which moves along the ground and serves to keep the beam about three and a half feet above the ground. These trawl crossheads are attached to the ship by bridles and warp. The upper edge of the net is attached to the beam, the lower edge being attached to a stout rope—the foot-rope—the ends of which are made fast to the crossheads. This foot-rope, being considerably longer than the beam, sweeps along the ground abaft of the beam, to form a deep curve known as the “bosom” of the net. The result is that, when the foot-rope disturbs the fish so that they leap to avoid it, the beam has passed on overhead and they leap into the net. Pockets are formed in the sides of the net by lacing the top and bottom together for about two-thirds of the distance from the mouth of the net towards the cod end. The mouth of a pocket is at the cod end of the net, so that fish reaching the cod end and attempting to return to the mouth of the net, generally enter the pockets. A flap of netting suspended some distance inside the mouth of the net serves as a valve. It is easily lifted by the incoming fish, but tends to prevent their escape. The netting is of hemp, the mesh gradually increasing from one inch at the cod end to about two inches near the mouth, and is preserved with tar. When fishing, the vessel moves ahead at a steady, slow rate of from two to three miles per hour, dragging the trawl behind it. Smacks always trawl with the tide. If they trawl against the tide, the net is lifted from the ground.