34 THE POPULAR SCIENCE MONTHLY. 



destruction of the mature oysters or the non-production of the young 

 is accomplished by means that are harmful only to those individuals 

 directly affected, a cause for the diminution is discovered in harmony 

 with the existing facts. 



Considering first the destruction of young, large numbers, immense 

 when compared with the production of the higher orders of animals, 

 are annually destroyed by the falling of the " spat " upon unfavorable 

 ground, the prevalence of heavy freshets which would drive the brood 

 into the bay and probably cause its loss, the ravages of various ene- 

 mies, and unusual changes of the temperature and density of the water. 

 But all these causes have been in operation continually since the first 

 discovery of the beds, and the animals have survived and increased 

 while contending with them. Therefore, some increase of power must 

 be assigned to one or all of these causes, in order to account for the 

 diminished number of oysters, and there is no reason to suppose that 

 there has been such increase. Thus, by reviewing all the natural causes 

 which affect the beds, we can assign to none of them the destruction 

 of either young or old oysters, or the extension of the beds which has 

 been coincident with the diminution of the number of animals. Remain- 

 ing, then, as the only other operating cause, is the agency of man. 



The oyster-fishery in these localities is carried on in two ways, 

 either by " tonging " or " dredging." The first method, being con- 

 fined to small areas and to a limited number of fishermen, and sus- 

 ceptible of use but in shoal water, need not be considered. The sec- 

 ond method of taking the oysters is as follows : the implement used is 

 called a dredge, or scrape, and resembles a large iron claw, the nails 

 representing the teeth of the dredge. To the back of this claw, or the 

 dredge, is fastened a bag of iron mesh-work, large enough to hold two 

 or three bushels. When the dredge is dragged along the bottom the 

 teeth or claws dig up the oysters and shells, which pass between them 

 and into the network behind. The action is somewhat like that of a 

 harrow. The dredges vary greatly in size, being from two to five feet 

 across the mouth, and of greater or less weight, according to the depth 

 of water in which it is intended to use them. The dredging-vessels 

 vary in size from five to thirty tons, and all use two dredges. When 

 on the oyster-ground the dredges are dropped one from each side, and 

 a sufficient amount of line paid out to insure the " taking " of the 

 teeth ; the vessel is then kept under easy sail and at a moderate speed 

 until the dredges are full, that being indicated by the strain on the 

 dredging-line and by other signs known to the fishermen. The in- 

 strument is then hauled in by means of a small winch, the contents 

 emptied on the deck, and the dredge put over again. This is continued 

 until the vessel is near the edge of the bed, when the "dredges are 

 recovered, the vessel put about, and the dredging resumed in an oppo- 

 site course. While the dredges are in the water, the mud, sand, sponge, 

 grass, or other debris brought up arc separated from the oysters, and, 



