TRAWLS, DREDGES, ETC. 



205 



In the ' William Scoresby ' the trawl was towed from two wire ropes in the manner 

 usual in commercial vessels. In the ' Discovery', bridles, 25 fathoms in length, were used 

 in conjunction with a single wire rope ; in connecting them a ball-bearing swivel of the 

 pattern shown in Fig. 22 (p. 198) was always used. In the south, and especially in 

 the Palmer Archipelago, trawling is attended with some risk, for the bottom is 

 frequently strewn with large stones and boulders, presumably ice-borne, which are 

 very liable to damage the gear. 



UPPER 



ii'\% 



sop/ml 



LOWER 





*0 MISHU 



-§-- — 



Fig. 24. Plan of otter trawl used in the R.R.S. 'Discovery'. 



The trawls, which were made by the Gourock Ropework Company, proved very 

 satisfactory and their catching power was greatly augmented by the addition of fine- 

 meshed bags attached to the back. On several occasions when the cod-end of the trawl 

 was so badly torn that it retained practically nothing, quantities of valuable material 

 were taken in these fine nets and almost always they yielded large supplies of small 



Fig. 25. Diagram of trawl, showing positions of fine-meshed 

 nets: a, net of coarse silk; b, net of 4 mm. mesh; c, net 

 of 7 mm. mesh; d, head-rope; e, foot-rope;/, cod-end. 



organisms, particularly of Crustacea, which would inevitably have escaped through the 

 meshes of the main net. Three sizes of fine-meshed net were used on the trawl, one 

 made of coarse silk with 16 meshes to the inch, one of 4 mm. and one of 7 mm. mesh, 

 and these were stitched to the baitings and lower end in the positions shown in Fig. 25. 

 As the foot-rope passes over the bottom it disturbs small organisms, which are carried 

 by the swirl of the water through the meshes of the back. The smaller and lighter 



