112 DISCOVERY REPORTS 



a drop of at least 30 feet, and probably more, would be required. This was felt to be an 

 undesirably long drop, the shock of which sooner or later might result in the collapse of 

 the heavy frame, if not in the loss of the entire apparatus. With a view therefore to 

 keeping the drop within reasonable limits it was eventually decided to throttle the 

 net in the region of the narrow cod-end, at a point only 15 ft. away from the bucket. 

 By closing at this point the backward fall of the net could be reduced to as little 

 as 12 ft. There was another and equally important reason for choosing such an 

 unusual closing position. With such an arrangement a large part of the net, the part 

 forward of the closing point, must obviously continue to fish after throttling had taken 

 place, and it was hoped that the steadying influence thereby exerted on the bucket 

 behind would contribute materially towards preserving the catch from damage. 



To allow such a large apparatus to fall back open and then to arrest it, still fishing, 

 in its backward path, would it was realized tax the gear severely ; by the sudden jerk 

 bridles and stray line in particular would be put to an unusually severe test, while the 

 unwieldy ring might well be strained to the point of collapse. To provide against mishap 

 the heavy ring, which if suspended in air from a single point is inclined to buckle under 

 its own weight, was specially stiff^ened by the introduction of a system of four thin steel 

 wires stretched taut across the mouth of the frame, radiating in the form of a cross from 

 a small steel ring in the centre which was to act as a fair-lead for the closing rope (Fig. 2, c, 

 and Plate II). For the cross-wires the ordinary 4 mm. diameter plankton wire was used. 

 It is of exceptional strength but small enough not to cause any serious obstruction in 

 the mouth of the net. Further protection against buckling was provided by employing 

 six bridles of 6 mm. diameter wire instead of the usual four. Obstruction in the mouth 

 of a tow-net, especially that caused by bridles, should of course be reduced wherever 

 possible, and in this respect the efficiency of the N 450 would doubtless be increased by 

 the introduction of a heavier frame than that at present in use ; with a sufliiciently rigid 

 frame there would be no need for so many bridles — three would be enough — and at the 

 same time it would be possible to dispense altogether with the stiffening cross-wires. 

 For the stray line, on the strength of which so much would depend, i J in. circumference 

 wire was used, and a special preventer was provided, connecting the eye of the bridles 

 with the after end of the stray line, in case the towing shackle, which is of rather light 

 construction, should carry away when the whole weight of the fishing apparatus fell 

 suddenly on to it. 



These arrangements, although not altogether satisfactory at first, with gradual 

 modification eventually achieved their purpose. With the throttling rope rigged to 

 operate internally and so near the bucket, the fore part of the net, as anticipated, con- 

 tinued to fish after the narrow cod-end had been throttled. The net in consequence 

 became a double-acting one, traversing in its path two distinct horizons — a lower prior 

 to closing and an upper during its ascent to the surface — and yielding therefrom a 

 catch in the bucket and another in the bag formed by the constriction of the net 1 5 ft. 

 above. The condition of the material in the bucket, the major concern of the experi- 

 ment, was excellent, there being no sign of the buffeting to which it had previously 



