PLANKTON NET SPECIFICATIONS 



187 



four in number, are attached to shackles at the junctions of the four sections. The frames 

 for both these and the N 200 nets were made and galvanized by Messrs F. Braby of 

 Ida Works, Deptford, London. 



The four bridles are of galvan- 

 ized wire rope 6 mm. in diameter, 

 each 20 ft. long. Section A is of 

 netting^ with i| in. mesh (knot to 

 knot), 15I ft. long. The tarpaulin 

 canvas band D is 6 in. wide, but 

 should have been considerably 

 wider; it has fifteen 3 in. galvan- 

 ized iron rings sewn on at equal 

 intervals. The catching part of the 

 net, BC, is 45 ft. long, tapering 

 from a circumference of 50 ft. 

 (4I m. diameter) to one of 3 ft. at 

 the cod-end, where it joins the 

 canvas cylinder, 3 ft. long, for 

 attachment to the bucket. The 

 netting in section B is ^ in. mesh 

 (knot to knot),^ and that in C of 

 7 mm. (knot to knot) mesh.'- It 

 was found an improvement to line 

 the "cod-end" of the net with 

 finer 4 mm. material. The longi- 

 tudinal ropes, four in number, and 

 two transverse ropes were, like 

 those of the N 200, originally made 

 of stout log line, but later were 

 replaced by a soft 2 in. circum- 

 ference rope of tarred hemp, 

 known in Admiralty dockyards as 

 "Rumbo". Experience showed, 

 however, that any kind of twisted 

 rope is liable to twist still further 



Fig. 12. Section and sketch of part of the stream-Hne frame 

 for the N 450 net, showing the junction of two quadrants, a 

 towing shackle, rings for the attachment of the net, and the 

 fair-lead for the closing rope. 



in use, thus rolling the net up and decreasing its circumference. In consequence all 

 the ropes had to be removed and sewn on again after the turns had been taken out. 

 For roping large plankton nets a flat braided sennet would perhaps be suitable, if log 

 line of sufficient strength cannot be obtained. 

 The specifications of the five types of tow- net are summarised in the table on p. 188. 



^ Made by Messrs Stuart and Jacks of Lowestoft. 

 ^ Made by L. de Sereville, see footnote to page 186. 



