194 DISCOVERY REPORTS 



Closing Mechanism for Small Horizontal Nets. The apparatus shown in Fig. i8 is 

 used for closing i m. and 70 cm. nets towed horizontally. In attaching nets to the wire 

 for horizontal work it is essential, as Hjort has pointed out, that the net should be free 

 to revolve on the wire rope ; for the rope is continually twisting, and the net, if clamped 

 to it, will become wound round and will not tow properly. The closing mechanism i^ 

 consequently made to swivel freely on the wire rope, and is supported by a brass screw 

 stop a similar to those used by Hjort. The mode of action of the mechanism is evident 

 from the figure. It is attached to the wire rope at the points marked b by two screw bolts. 

 The messenger depresses the striking piece c, and the link which carries the bridles 

 of the net is slipped from d. The throttling rope, by which the net is hauled to the 

 surface, is attached at e. It will be noticed that a ring for the release of a messenger to 

 a lower net can be passed through a slot/ in the base plate and secured by a pin on the 

 moving portion. The second messenger is thus released simultaneously with the closure 

 of the net. In Fig. 18 h the apparatus is shown assembled on the wire rope, with a 

 messenger for the release of a lower net. 



This type of release gear has proved very satisfactory, but the heavy messengers 

 that were used tend to bend or break the cast brass fork of the moving portion. Repairs 

 were easily effected, but it would perhaps be better if this movable part were made of 

 steel. The messengers (g) were of a very simple type, stream-line in form, 3 lb. in weight, 

 and made in two halves seized together with a piece of twine. A still heavier messenger, 

 that shown in Fig. 19 w, was also sometimes used with this apparatus. Both messengers 

 took approximately half a minute to travel 100 m., the time varying somewhat with 

 the angle of the warp. In serial work it was found best to attach the messenger for the 

 lower net to the release of the upper by means of a length of stiff galvanized wire, rather 

 than by cod-line and a ring : by this method all chance of the line fouling the stop was 

 prevented. 



Opening and Closing Mechanism for Large Horizontal Nets. The apparatus used 

 with large nets is more elaborate and is shown in Figs. 19 and 20. Like the smaller 

 mechanism described above, it is designed to swivel on the warp, to which it is 

 attached by means of the two sliding clamps a and b. The primary release is at c and 

 is opened by a small messenger striking the forked lever d. At the same time another 

 small messenger for despatch to a lower net can be released from the catch e. The 

 secondary release is at/. This link takes the whole towing weight of the net, and since 

 it was anticipated that if the messenger acted directly (as with the primary release) the 

 friction would be so great as to prevent movement, a double action was fitted by 

 inserting the tumbler block g, the whole being arranged to give a leverage greatly in 

 favour of the messenger. The rods effecting this release are attached above to the semi- 

 circular striking piece Ji, which must of course be large and wide enough to permit free 

 passage to the primary messenger; at the lower end they actuate another catch, by which 

 the secondary messenger can be slipped to a net attached lower down the warp. We 

 found in practice that with a net towing from the link / the apparatus was canted out 



