28 



THREE CRUISES OF THE "BLAKE. 



better than a trawl, which, when moved rapidly over the ground, 

 at the rate sometimes of two to two and a half miles an hour, 

 invariably brought up a fine harvest of fishes and Crustacea, in 

 addition to the usual contents of the sedentary and more slug- 

 gish forms. Although the deep-sea tow-net was used several 

 times, we never brought up any of the so-called deep-sea sipho- 

 nophores of Studer, even in localities where they came up on 

 the wire rope. 



All dredging expeditions previous to the first cruise of the 

 " Blake " had used best selected hemp rope for dredging.* 

 The objections, already mentioned, to the use of hemp rope, 

 speaking of sounding, apply with even greater force to its use 

 in dredging. The necessity of loading down the trawl with 

 weights, or of making the trawl itself enormously heavy, in 



Fig. 27. — Comparative Size of Dredging-Ropes. (Sigsbee.) 



order to sink a heavy rope strong enough to bring back not 

 only its own weight, but that of the trawl and its contents and 

 of the weights usually sent down with the dredge, — all this 

 increased the danger that the rope might part at great depths. 

 The rope also, after short use in deep water, becomes very brit- 

 tle from the great pressure to which it has been subjected, and 

 unfit to bear any considerable strain. My familiarity with the 

 successful use of very long steel ropes for mining purposes nat- 

 urally suggested their adaptation to the new purpose of deep- 

 sea work. The results anticipated have been fully realized, 

 and the gains in space (Fig. 27), in tune,^ in safety and facility 



^ The rope used for deep dredging is 

 usually two and one half inches in cir- 

 cumference. It weighs two pounds to 

 the fathom, breaking strain about two 

 tons; so that the weight of rope, trawl, 

 and contents is often more than half the 

 breaking strain. 



2 A haul of the trawl was frequently 



made by the "Blake," in fifteen hun- 

 dred fathoms, in less than two hours 

 and three quarters, dragging on the bot- 

 tom twenty-five minutes. The trawl can 

 safely be lowered at the rate of one hun- 

 dred fathoms in four minutes, and be 

 reeled in at the same or even a more 

 rapid rate. 



