THREE MILES OF ROPE. 



731 



let many small things through, the bottom of the bag, to the 

 height of about nine inches, is lined with a light open kind of 

 canvas, called by the sailors "bread-bag." Eaw hides have' 

 been used for making the dredge bag, but, though very strong, 

 they are apt to become too much so to another sense than 

 tou'-h. It is bad economy to use too light a rope in such ope- 

 rations, and best to fasten it to only one arm of the dredge, the 

 eyes of the two arms being tied together with a thinner cord, 

 In case, then, the dredge becomes entangled at the bottom, this 

 cord will break first, and thus releasing one of the arms of the 

 dredge, may so change the direction of the strain upon the rope 

 as to free the dredsre itself. 



Dredging in deep water, that is, at depths beyond 200 

 fathoms, is -a matter of some difficulty, and can hardly be done 

 with the ordinary machinery at the disposal of amateurs. The 

 description of the apparatus used in the Porcupine, in 1S69 and 

 '70, on her dredging cruise in the Bay of Biscay, will show 

 what is necessary. These arrangements are also shown in the 

 cut. This vessel, a gun-boat of the English navy, of 382 tons, 

 was fitted out specially for this work. Amidships she was 

 furnished with a double cylinder donkey-engine, of about twelve- 

 horse power, with drums of various sizes, large and small. 

 The large drum was generally used, except when the cord was 

 too heavy, and brought up the rope at a uniform rate of more 

 than a foot a second. A powerful derrick projected over the 

 port bow, and another, not so strong, over the stern. Either 

 of these was used, for dredging, but the one at the stern was 

 generally used for soundings. The arrangement for stowing 

 away the dredge rope was such as made its manipulation sin- 

 gularly easy, notwithstanding its great weight, about 5,500 

 pounds. A row of some twenty large pins of iron, about two 

 feet and a half long, projected over one side of the quarter- 

 deck, rising obliquely from the top of the bulwark. Each of 

 these held a coil of from two to three hundred fathoms, and 



