272 YACHT EQUIPMENT 



From the catalogues and samples of two reliable 

 makers we take the following specifications as a guide : 



Wires. 



Circumference. 



Weight per 

 100 Fathoms. 



Breaking- 

 Strain. 



Approximate 

 Price per 



i 100 Fathoms. 





inches. 



lb. 



tons. 



cwt. 



£ s. 



(a) 6 by 12 



1 



32 



I 







2 2 



(b) 6 „ 24 



I 



88 



3 







3 3 



{c) 6 „ 24 



I* 



131 



4 



10 



— 



[d] 6 „ 18 



I 



100 



3 



II 



4 4 



\e) 6 ,, 18 



ii 



158 



4 



14 



4 10 



if) 6 „ 18 



i* 



224 



8 







5 10 



The selection of a rope will, of course, depend largely 

 upon the depth to which it is proposed to work, the 

 probable character of the bottom, and the size of the 

 dredge or trawl. If it is proposed to work down to 

 but not over 1,000 fathoms, a single length of 

 1,500 fathoms of i-inch rope, with breaking-strain 

 about 3 tons,* would probably serve the turn. Taking 

 the second rope specified as an example, a factor of 

 safety of four allows 4 hundredweight for the trawl and 

 its contents. 



Work at anything over 1,000 fathoms implies an 



* It may be mentioned here that H.M.S. " Challenger," used 

 hemp ropes of 2 inches and 2 \ inches circumference, with 

 breaking-strains of 1 ton 12 hundredweight and 2 tons 6 hun- 

 dredweight respectively. For shallow- water work was em- 

 ployed a rope of 3 inches circumference, with breaking-strain 

 of 2 tons 1 1 hundredweight. But it must be remembered that 

 in water a hemp rope carries much more of its own weight 

 than a steel rope. Sir John Murray informs us that the rope 

 was hauled at the rate of 1,000 fathoms per hour, and that 

 during the three and a half years' cruise, when trawlings and 

 dredgings were made at 354 stations, there were only eleven 

 cases of parting of the rope. Wire ropes were first used for 

 such work by Agassiz in 1877. 



