i62 DISCOVERY REPORTS 



lively little deep-water work was undertaken, it was found that the wire had cut deeply 

 into them and spares made of manganese steel were substituted. 



It will be seen that the arrangement of fair-leads allows the longer wire to be used 

 on either side of the ship and it was hoped that two flights of nets, one deep and one 

 shallow, could be towed at the same time.^ In the 'Discovery' this was found im- 

 practicable in routine work, and though the young-fish trawl was often used with one 

 wire, while a flight of shallow horizontal nets was towed with the other, it was not 

 possible to work two sets of large nets simultaneously. It was found, moreover, that 

 to shoot deep-water nets on the starboard side was likely to cause serious damage to 

 the wire. After several long hauls had been made on this side of the ship it was dis- 

 covered that the wire was rapidly becoming unlaid and it would no doubt have been 

 ruined if this practice had been continued. This action, which was quite unexpected, 

 is due no doubt to the two turns round the fair-leads, these turns being right-handed 

 when facing the bow of the vessel. Hauling under a heavy strain on the starboard side 

 tends to take out the lay ; to work properly a wire laid up left-handed would be required, 

 and this of course would prove equally ineflicient on the port side. With the winch in 

 a better position and straighter leads, trouble of this nature is not likely to occur. 



The port and starboard stern Fair-leads are mounted in the rail, which is cut away 

 for the purpose. They consist of four rollers, mounted in a heavy frame, with a snatch 

 above: the vertical rollers are hourglass-shaped and all are brass bushed. The outboard 

 horizontal roller was originally 3I in. in diameter, but was found to give too sharp a 

 nip, flattening the wire unduly under heavy strains. A 5 in. roller was substituted and 

 the diameter might be increased even further with advantage. The fair-leads gave a 

 certain amount of trouble, for with heavy work it was found that the frames became 

 strained and continual attention was needed to see that the rollers revolved freely. It 

 is important that the frame should be of ver}' solid construction and that all the rollers 

 should be fitted with ball or roller bearings. The snatch at the top should be so made 

 that, when it is open, the whole space between the vertical rollers is clear; if it overlaps 

 the rollers, shackles and the screw stops used in plankton work are liable to jam when 

 being hauled through the fair-lead. 



Heavy Accumulators. The large compression springs shown in Plate IX (47) are 

 for use as accumulators. By means of the nipper referred to on p. 207 the strain on the 

 warp can be taken on this spring, which will thus compensate for sudden jars caused 

 by the pitching of the ship and save the gear from damage. Full compression is reached 

 with a strain of 6 tons. It was found in practice that the springs were too strong; they 

 would need to be weaker and much longer in order to give sufficient play. Experience 

 tends to show that heavy accumulators for deep-water work are not necessary. For 

 plankton work at shallow depths a light accumulator giving plenty of play is an un- 

 doubted advantage, but with deep nets sufficient compensation is afforded by the spring 

 of the wire rope and by the fact that under varying strains its curvature will alter. 



1 See Hjort, in Murray and Hjort, Depths of the Ocean, p. 49, fig. 32, London, 1912. 



