260 APPARATUS FOR FISHING. 



return. On each side of, and just beyond, the flapper, 

 however, is the entrance to a pocket ; and the fish, being 

 unable to return through the passage closed by the flapper, 

 very commonly enter the pockets and press on till at last 

 the gradual narrowing of the space stops their further 

 progress in that direction. To understand clearly the 

 facilities offered to the fish to enter the pockets it is 

 necessary to remember that the trawl when at work is 

 towed along with just sufficient force to expand the net by 

 the resistance of the water. But this resistance acts 

 directly only on the interior of the body of the net between 

 the pockets, and then on the purse. When the trawl first 

 begins to move, the pressure of the water inside the net 

 does not distend the pockets, but rather tends to flatten 

 them, because they are virtually outside the cavity of the 

 net, and their openings are at the farther end of it and 

 facing the other way. The water, however, which has 

 expanded the body of the net, then makes its way under 

 the flapper and enters the purse, which, being made with a 

 much smaller mesh than the rest of the net, offers so much 

 resistance that it cannot so readily escape in that direction ; 

 return currents are consequently formed along the sides, 

 and these currents open the mouths of the pockets, which 

 face the purse or last part of the net ; and the fish in their 

 endeavours to escape, finding these openings, follow the 

 course of the pockets until they have no room to proceed 

 any further. The whole of the net becomes therefore fully 

 expanded, but it does so by the pressure of the water in one 

 direction through the middle, and in the opposite one 

 through the pockets at the sides. 



Such then is the beam-trawl an enormous bag-net, 

 frequently 50 feet wide at the mouth and upwards of 100 

 feet in length, which sweeps slowly and quietly over the 



