30 THREE CRUISES OF THE " BLAKE." 



di'edge or trawl to drag too long on the bottom we obviated 

 the great loss of time due to fouling, reversing, or any other 

 accident out of sight. In the " Challenger " the best part of 

 the day was generally consumed in making a haul at a depth 

 of fifteen hundred fathoms. We experienced no inconvenience 

 from the kinking of the rope, if it was kept well stretched, 

 and not allowed to lie slack on the bottom. The uniform suc- 

 cess attending the use of this rope during our dredging seasons 

 enables me to recommend it to any future deep-sea dredging 

 expedition, as insuring an economy of space, time, and money ; 

 for the rope occupied about one ninth of the sjDace required 

 by a hemp roj^e, and was, at the end of the cruise, as good as 

 when we first left Key West. 



Not the least superiority of the steel rope over the hemp 

 rope is its power of telephoning, as it were, from the bottom. 

 By keeping hold of the wire rope on deck, the least movement 

 of the dredge or trawl on the bottom is transmitted with ab- 

 solute certainty, and it soon becomes an easy matter for the 

 officer in charge of the dredging not only to tell whether the 

 trawl is dragging well, but also the kind of bottom over which 

 it is passing. The vibrations of the rope when the trawl passes 

 over a gravelly, or a sandy, or a smooth, muddy bottom are all 

 characteristic and in sti-ong contrast with those produced by the 

 quick jumps of the trawl over a rough and sHghtly rocky bot- 

 tom. The movements of the dredge are repeated by the vibra- 

 tions of the steel rope so promptly that the moment it pulls or 

 passes over rough bottom the speed of the vessel can at once 

 be checked, or its dii-ection altered, before the tension is great 

 enough to affect the accumulator. 



Hea-v^ strains on the line can be detected in the same man- 

 ner, and for greater safety an accumulator is connected with 

 the pulley over which the wii-e rope leads to the bow of the 

 vessel at the end of the dredging-boom. This accumulator (Fig. 

 28) is made up of a series of india-rubber car-springs, suspended 

 along the foremast and kept in place by iron guides. These 

 are compressed by a strain, and expand again into their natural 

 position when the pressure is taken off. The amount of com- 

 pression indicates the care to be taken in handling the trawl 



