18 DISCOVERY REPORTS 



The N 70 H net is the same as the N 70 V except that it has no weight or supporting 

 wires and its bucket is of a simple light pattern. A different closing mechanism was 

 used with the horizontal nets to that used for vertical nets: see Kemp and Hardy (1929). 



The N 100 H, designed for the capture of macroplankton, particularly Euphausians 

 and Amphipods, is also made of two grades of netting: 4 mm. mesh (knot to knot) in 

 front and 15 meshes to the inch behind. The galvanized iron ring has a diameter of 

 100 cm. and is towed by three wire bridles. From the ring extends a cylinder of coarse 

 mesh netting, 3 1 ft. long, followed by a band of canvas, 6 in. wide, fitted with rings to 

 take the closing rope. Joined to this is the catching part of the net, io| ft. long; it tapers 

 from 100 cm. diameter (11 ft. in circumference) to join a canvas cylinder, 1 ft. 8 in. in 

 circumference and 1 ft. long, for attachment to the bucket. The two sections of netting 

 are 3^ ft. and 7 ft. long, of the coarser and the finer grade mesh respectively. Three 

 supporting ropes run down the net to be fastened to the bucket. A closing rope passes 

 through the rings on the canvas band. 



A comparison of the composition of the respective catches of the three nets N 70 V, 

 N 70 H and N 100 H is made in the zooplankton section on p. 92. 



The stations worked by each of the two ships may be termed either full routine 

 stations or horizontal routine stations. 



At a full routine station the following procedure was carried out. The N 50 V net was 

 lowered to a depth of 100 m. and then hauled open to the surface at a rate of 1 m. per 

 second. 1 This gave a sample of the phytoplankton which is usually limited almost 

 entirely to the upper 100 m. of water, although some interesting exceptions, of diatoms 

 extending to much deeper layers, will be recorded. At the same time as the N 50 V was 

 being used, or (if another winch was not available) immediately after it, a series of samples 

 was taken with the N 70 V in the following order as deep as the sounding would allow : 

 50 m. to the surface, 100-50 m., 250-100 m., 500-250 m., 750-500 m., and 1000- 

 750 m. In addition, at some stations hauls were made from 2000-1000 m. In each 

 instance the net was hauled at a uniform speed of 1 m. per second 1 and closed by a 

 releasing mechanism and throttling rope as the upper limit of the haul was reached. 

 Whilst these samples were being taken with the nets, a vertical series of hydrological 

 samples and observations was also being taken. 



As soon as this vertical work was finished the ship steamed forward at a speed of 

 2 knots (approximately: 1 m. per second) and a series of three N 100 H nets was towed 

 simultaneously on the same wire for a distance of 1 mile. The three nets were fastened 

 to the wire, the deeper two by release mechanisms, at such distances apart as would 

 allow the top net to fish just below the surface (0-5 m.), the middle net at a depth of 

 about 50 m. and the bottom net at about 100 m. The maximum depth reached by the 

 bottom net was recorded by the use of a Kelvin sounding tube attached to the towing 

 rope just below the bottom net. At the end of the towing rope below the Kelvin tube 

 was slung a stream-line lead of 56 lb. weight. At the end of the 1 mile tow, immediately 

 before the nets were hauled in, the lower two nets were closed by sending a messenger 



1 For methods of winding and counteracting the rolling of the ship, see Kemp and Hardy, 1929, p. 199. 



