THE SECRETS OF THE SEA 319 



rear edges and to these a heavy knit sack is lashed 

 which drags behind and catches whatever is 

 loosened from the bottom. This sack is protected 

 by stout canvas lest it be torn as it drags over 

 the rocks. The dredge is drawn by two pairs of 

 round iron arms, the after ends of each being 

 turned around the standards at each end of the 

 dredge frame and they may be folded down over 

 its mouth when it is not in use. The forward end 

 of each pair of arms is bent into an eye and the 

 dredge rope is securely fastened to one of these. The 

 eye of the other pair is lashed to the rope with spun 

 yarn which will break under a severe strain, usually 

 allowing the whole to swing around and pull loose. 

 The line used in dredging is % inch, of ' ' plow " steel, 

 and of special make for flexibility and strength. 



If the dredge be hauled too rapidly over the 

 bottom it will skip most of the material or per- 

 haps bury itself in some muddy place and in case 

 of meeting with rocks it will be badly damaged, 

 if not carried away and lost. The work requires 

 the greatest care and constant attention, especially 

 on the plateau where the powerful Gulf Stream 

 current and the waves of the open sea must be 

 reckoned with. 



