ON COLLECTING SHELLS. 429 



The whelk and oyster-dredgers employ a decked sailing-vessel, and work 

 several dredges simultaneously, each requiring a person to manage it. The 

 dredges are put overboard on the weather-side, and the ropes made fast to a 

 bulwark or thwart ; each dredger holds the rope in his hand, after giving it 

 a single turn round a thwart or " belaying-pin," to regulate the strain by 

 means of the spare line. "When a sufficient distance has been traversed, or 

 the ropes strain with the weight of mud and stones, the vessel is brought to, 

 and the dredges hauled up and emptied.* 



The length of line required is about double the depth of the water. If 

 the line is too short the di-edge will only skim the bottom ; if too long it will 

 be in danger of getting fast. \Yhen the bottom is loose sand or soft mud, the 

 line must be shortened, or the vessel have more way, or else the dredge will 

 be apt to get buried. 



The strength of the line ought to be sufficient to anchor the vessel in 

 smooth water, — though not, of course, when there is much w-ay on her, — so 

 that if the dredge gets foul it is necessary to let out the spare line and relieve 

 the strain, while the vessel is brought round. The dredge will then usually 

 capsize, and may be hauled up. 



If the bottom is at all rocky, a small strong dredge is best. The line 

 must be shortened, and some additional precautions may be taken, such as 

 fastening the rope to one ring of the dredge, and tieiug the other with spun 

 yarn, which will break under a sudden and dangerous strain, and release one 

 end of the dredge. 



In dredging on Coral-ground, Mr. Cuming employed a 3 inch hawser, 

 and had a patent buoy attached to the dredge by a I5 inch rope. More 

 than once the hawser parted, and the dredge was left down all night, but 

 recovered the next day. 



Mr. Mc Andrew's researches on the coast of Norway, were conducted in 

 the " Naiad," a Yacht of 70 tons, and extended from the shore to 250 fathom 

 water. The dredge employed was at least twice as strong and heavy as the 

 one we have represented, and all forged in one piece, instead of folding up. 

 The bag was fastened on the frame with thongs cut from the hide. Before 

 using, it requires to be towed astern for a couple of hours to soften it. In three 

 months work, only two cow-hides were used, and one of tho-e was torn by 

 accident on sharp rocks, Several spare dredges were on board (in case of 

 emergency ), but not used. 



Dredging in deep water (50 — 300 fms.) can only be done in calm 



II, a.m., to 4 or .5, p.m. Dredging can be carried on in Weymouth in almost any 

 weather, the bay is so protected.' {R. Damon.) 



* The collector may go out with the fishermen, and superintend his own dredge, 

 almost any time of the year, although oyster catching is illegal in the summer. The 

 scallop- hanks off Brighton are in 15 fms. water, and nearly out of sight of land. It 

 is not always possible to work over them and return the same night. 



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