R.R.S. 'DISCOVERY': SCIENTIFIC EQUIPMENT 



167 



subsidiary sheaves, so arranged that the wire is sHghtly deflected in its passage aft. This 

 system has worked extremely well, but has the disadvantage that it will not permit the 

 passage of shackles and swivels. When, as in trawling, it is required to wind the bridles 

 on to the drum of the winch it is necessary to "hang off" the wire with chain strops. 

 This could be obviated by mounting the counter on one of the pedestal fair-leads, 

 though the accuracy would not be so great, owing to the smaller diameter and the 

 tendency to wear. 



The recording sheaves used with light wire on the plankton and hydrographic 

 machines were slung sheaves of a coinparatively cheap type ; they were found to require 

 continual attention, one of the principal difficulties being that the toothed wheel con- 

 veying the movement from the axle was insecurely attached to its shaft. The reverse 

 direction of movement in alternate dials is also an inconvenience and the more expen- 

 sive types in which this defect is overcome are to be preferred. 



The Wire Ropes used are all of galvanized steel. The two light ropes were made by 

 Bullivant and Co., Ltd., and the heavy warps by Thos. and Wm. Smith, Ltd. All have 

 proved very satisfactory. The specifications of the ropes are as follows : 



The long length of tapered rope is made in three sections, the reduction in diameter 

 being effected by dropping wires at varying points spread over a long distance. In 

 deep-water work, wire ropes are subject to stresses which approach the breaking strain 

 more nearly than in any ordinary commercial use, and since a considerable part of 

 the available strength is absorbed by the mere weight of wire outboard, the advantages 

 of a tapered rope are manifest. The short lengths, 6 mm. in diameter, have an eye 

 spliced at each end and can be connected by shackles. They are used for fish traps, 

 the rope being unshackled and attached to the buoy when a sufficient length has been 

 paid out. 



For greasing wire ropes a mixture of 50 per cent tallow and 50 per cent castor oil 

 was applied hot, forming a durable coating which partially filled up the lay. In cold 

 weather it was liable to become too hard and to fall off as a powder, but this can be 

 prevented by increasing the proportion of castor oil. This method gave excellent results, 



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