1042 OYSTERS, AND ALL ABOUT THEM. 



provided with four or five dredges, each resembling in 

 shape a common clasp purse. 



These dredsres are formed of network, with a strong 



cj 7 O 



iron frame, which serves the double purpose of acting as a 

 scraper and keeping the mouth open, while giving it a 

 proper pressure as it travels over the oyster-beds. 



Different descriptions of dredges are used, according 

 to the depth of water and character of the bottom. Dredges 

 are made on nearly the same plan on all parts of the coast ; 

 the only difference being in their breadth and consequent 

 weight, and in the character of the body of the dredge. 



Deep-sea dredges for rough bottoms have the under 

 part of the bag made of iron rings, from two to three inches 

 in diameter ; the upper part is made of strong netting, as it 

 is not exposed to the wear and tear of being dragged over 

 the ground. 



Deep-sea dredges for muddy bottoms have the bag 

 made of stout canvas, with numerous small eyelet-holes 

 in it. 



Where it is desired to bring up brood uninjured, a hide 

 net is substituted for the iron rings ; in the Blackwater they 

 use " half skin-backed " dredges, the other half of the lower 

 side being made of wire network. 



The largest deep-sea dredges are used in St. George's 

 Channel; they are frequently 12 to 15 feet broad. They 

 are towed astern of the boats, and are left overboard for a 

 much longer time, as they have a large carrying capacity. 



Dredges that are worked on the side of boats vary 

 between 16 and lylbs. as used on the Whitstable grounds, 

 to the yolbs. deep-sea dredges. Whatever their weight, 

 their framework is constructed in the same manner ; the 

 lower part of the frame is flattened and turned forwards at 

 such an angle as to enable it to scrape the surface ; this 



