244 THE DEPTHS OF THE SEA. [CHAP. vi. 



far the most common error in amateur dredging, 

 from the low angle at which the line is lying in the 

 water the dredge has its hest chance of getting an 

 occasional scrape. It is bad economy to use too 

 light a rope. I'or a dredge such as that described, 

 and for work round the coasts of Europe at depths 

 attainable from a row-boat or yawl. I would recom- 

 mend bolt-rope of the best Russian hemp, not less 

 than one and a half inch in circumference, which 

 should contain from eighteen to twenty yarns 

 in three strands. Each yarn should bear nearly a 

 hundredweight, so that the breaking strain of such a 

 rope ought to be upwards of a ton. Of course it is 

 never voluntarily exposed to such a strain, but in 

 shallow water the dredge is often caught among 

 rocks or coral, and the rope ought to be strong 

 enough in such a case to bring up the boat, even if 

 there were some little way on. 



Dredging in sand or mud, the dredge-rope may 

 simply be passed through the double eye formed by 

 the extremities of the two arms of the dredge ; but in 

 rocky or unknown ground it is better to fasten the 

 rope to the eye of one of the arms only, and to tie the 

 two eyes together with about three or four turns of 

 rope yarn. This breaks much more readily than the 

 dredge rope, so that if the dredge get caught it is 

 the first thing to give way under a strain, and in 

 doing so it very often so alters the position and form 

 of the dredge as to allow of its extrication. 



The dredge is slipped gently over the side, either 

 from the bow or from the stern in a small boat 

 more usually the latter while there is a little way 

 on, and the direction which the rope takes indi- 



