42 



DEPTHS OF THE OCEAN 



was much line out and the weight was 



speed when there 

 considerable. 



Trawling. For trawHng, former expeditions employed the model designed 



by Sigsbee, lo feet in breadth. This appliance, notwithstanding 

 all its good points, is too small for catching large animals. 

 Modern fishing steamers, which are quite small compared with 

 the expedition ships of former days, mostly operate trawls 120 

 feet in length, having a span of about 60 to 80 feet, with a 

 height at the entrance many times greater than that of the 

 trawls employed for scientific purposes. Seeing then that a 

 great many trials have been made in all oceans with the dredge 

 and with Sigsbee's trawl, it was advisable to try whether a 

 larger appliance would not yield different species and bigger 

 catches, and it was natural to select as a model the appliance 

 supposed to be best adapted for catching fish, namely, the 



Otter trawl. Otter trawl in use among fishermen. 



Fig. 24.— The Otter Board. 



The difference between the otter trawl (Fig. 23) and the 

 beam trawl (see the "Challenger" trawl, Fig. 11) is that in the 

 case of the former the appliance is kept distended by means of 

 otter boards, working on the principle of an otter for trout 

 fishing or a kite in the air. The otter boards (Fig. 24) are 

 attached to the line by bridles, and thus have a tendency to 

 spread when towed along through the water. The regular 

 trawlers use two steel lines of colossal dimensions, up to 3 

 inches in circumference and with a breaking strain of 20 tons ; 

 these are wound round two large drums that are keyed on to 

 the slow axle of the trawl-winch (see Fig. 25), from which each 

 line passes to its gallows and then astern, being carefully 

 fastened with chains during the time that the vessel goes ahead 

 towing the trawl after it. Sigsbee, it will be remembered, went 

 astern when trawling, and he had one winch for winding the 

 wire round the drum and another for the actual hauling in. 



It is quite evident that the system adopted by the regular 

 trawlers economises labour, for it is simple, and space is saved 

 by using only one winch. The otter trawl, again, has to be 



