TRAWLING. 63 



moves forward, so that the fish can get no rest on any 

 part of it. Sooner or later the soles find their way into 

 the " cod," where still further disturbance is no doubt 

 cansed by the crowd of other fish. The endeavonrs 

 tliey all of course make to escape will bring them 

 sooner or later to one side or other of the cod, and by 

 following that part of the net backwards, and so getting 

 out of the crowd, they soon come to the mouth of the 

 pockets. Now the pressure of the water which enters 

 the mouth of the trawl expands the general body of the 

 net as it is being towed over the ground, tending to 

 keep open the passage between the pockets into the 

 cod, and which, as has been mentioned, is guarded by 

 a valve of netting to prevent the return of the fish. 

 But the pressure of this enclosed water would have no 

 such effect on the pockets, because they are virtually 

 outside the bag ; the boundaries of the actual cavity of 

 the net being at the inner margins of the pockets. The 

 backward pressure of the water on them is therefore 

 only on their outer surface, from their narrow closed 

 ends downwards, and tends to flatten them throughout 

 their entire length. Theoretically, then, the mouth of 

 the pockets should be closed with the rest, so far as 

 bringing the upper and under surfaces together would 

 do so ; and probably few fish would find their way 

 inside. But some of the soles, in their endeavours to 

 hide, and with their natural habit of running themselves, 

 if possible, below the surface, might even under these 

 conditions discover the entrance. The construction of 

 the net, however, is such that the mouths of the pockets 

 are always kept open ; for the cod of the net being 

 made with a small mesh offers great resistance to the 

 escape of the water flowing into it, and is accordingly 

 much expanded ; and the mouths of the pockets facing 



