27 fi - <)N COLLECTINU SHELLS. 



by the scraper passing over the irregularities of the bottom. 

 The cine amonnt of rope is tlien paid ont, and the rope hitched 

 to a bench or pollock-pin. 



" When there is anything of a current, from whatever cause, 

 it is usually convenient to attach a weight varying from fourteen 

 pounds to half a hundred-weight, to the rope three or four 

 fathoms in front of the dredge; this prevents, in some degree, 

 the lifting of the mouth of the dredge. If the weight be attached 

 nearer the dredge, it is apt tO injure the delicate objects 

 passing in. 



" The boat should move very slowly, probably not faster than 

 a mile an hour. In still water, or with a very slight current, the 

 dredge of course anchors the boat, and oars or sails are necessary ; 

 but if the boat be moving at all it is all that is required. I like 

 best to dredge with a close-reefed sail before a light wind, with 

 weights, against a verj^ slight tide or current ; but these are 

 conditions which cannot always be commanded. The dredge 

 may remain down from a quarter of an hour to twenty minutes, 

 by which time, if all things go well, it ought to be fairly filled. 



" In dredging from a small boat the simplest plan is for two 

 or three men to haul in, hand over hand and coil in the bottom 

 of the boat. For a large yawl or yacht, and for depths beyond 

 fifty fathoms, a winch is a great assistance. The rope takes a 

 couple of turns round the winch, which is worked by two men, 

 while a third takes it from the winch and coils it. 



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

 fathoms — is a matter of some diflBctilty, and can scarcely be 

 compassed with the ordinary machinery at the disposal of 

 amateurs. Deep-sea dredging can no doubt be carried on from 

 a good-sized steam yacht, but the appliances are so numerous 

 and so bulky, and the work is so really hard, that it is scarcely 

 compatible with pleasure-seeking." — Wyville Thomson, " The 

 Depths of the Sea." 



In the valuable and interesting work above quoted (p. 246), 

 may be found a full description, with figures, of the apparatus 

 used in deep-sea dredging b}^ the Poi^cupine. That vessel, on 

 Jul^^ 20th, 1870, dredged no less than 186 species of mollusks at 

 a single haul, ofl" the coast of Portugal, and from the great 

 depth of 994 fathoms. Nearly forty per cent, of these were of 

 unclescribed species ! " This remarkable collection," says Wyville 

 Thomson, " of which not much more than one-half is known to 

 conchologists, notwithstanding their assiduous labors, teaches 

 us how much remains to be done before we can assume that the 

 record of marine zoology is complete. Let us compare the vast 

 expanse of the sea-bed in the North Atlantic with that small 

 fringe of the coast on both sides of it which has yet been partially 

 explored, and consider Avith reference to the dredging last- 



