THE SHIP AND ITS EQUIPMENT 31 



The wire rope consisted of six strands, each made up of 

 seven wires (like piano wires about 1 mm. in 

 diameter), or altogether forty-two wires, with 

 a tarred hemp line in the middle. The 

 breaking strain of the whole was about 4 

 tons. Its weight per fathom was 1.12 lbs. 



0000 



a h c d 



Fig. 8. 

 a, b, c, Circumference of hemp lines used for trawling on board 

 the "Challenger," and d, of wire rope used for trawling on board 

 the "Blake." (From Sigsbee. ) 



n 



in the air, and i lb. in the water. We thus 

 get a breaking strain of about 4000 kilos ; 

 weight in water of 5000 fathoms 2300 kilos ; 

 so that with 5000 fathoms out, there were 

 about 1 700 kilos over for resistance (friction) 

 in the water, and for strains due to heavy 

 seas or sticking fast on the bottom. The 

 great strength of this line made it less 

 necessary to use accumulators, and they 

 were only employed occasionally during the 

 " Blake " expedition. 



Fig. 9 shows how Sigsbee worked the Method of 

 wire rope on board the "Blake.;' It was ^Jf ""^ 

 wound round a big drum (i), driven by a 

 small steam-winch, and led from the drum 

 over blocks of considerable diameter (2) to 

 the large steam-winch (3), which had a large 

 end-drum 55 centimetres (22.6 inches) in 

 smallest diameter. From here the line went 

 to a big boom (4) on the foremast (5). 



When dredging or trawling the appliance 

 was first lowered to near the bottom, while 

 the ship was stationary, and afterwards the 

 _ vessel went astern during the process of 



Fig. 9.-d^ck Arrange- paying out and dredging. This manner of 

 MENT OF THE "Blake." working was so successful, and conduced to 



(From Sigsbee.) '^ 



