3 8 THE POPULAR SCIENCE MONTHLY. 



that has not ; and, if that number is very large, it shows that the 

 population of the bed has been destroyed. Upon an unworked bed 

 the number of old shells will show approximately the number of oys- 

 ters perishing from natural causes ; and, should the number on any 

 worked bed exceed this on the undredged one, it may be concluded 

 that Nature is being assisted in her work of destruction. 



The quantity of matter brought up in the dredge was measured in 

 all cases during the season of 1879, as was also the quantity of oysters 

 and of debris. On the unworked beds in the bay this debris was found 

 to equal thirty per cent, of the whole amount of matter brought up. 

 On nearly every bed in the sounds the percentage of debris was greater 

 than that on the unworked beds, and in Pocomoke Sound it was ex- 

 traordinarily large, amounting in some of the beds to as much as 

 ninety-seven per cent. ! 



During the season of 1878 a method was devised by which the 

 number of oysters to the square yard could be determined approxi- 

 mately ; and, though this number was not near the true one, yet, as the 

 measurements were always made in the same manner, it was useful as 

 affording a standard for comparing the results of subsequent seasons 

 or of different localities. 



The number of oysters to the square yard obtained by this method 

 depended mainly upon the number of oysters brought up by the 

 dredge ; and, as already explained, the difficulty of obtaining the ani- 

 mals was much greater on the new and unworked beds than upon 

 those which had been dredged for many years ; therefore, the number 

 to the square yard, other things being equal, should be much greater 

 on the old beds than upon those recently discovered. To make this 

 plainer, a very simple illustration will suffice : Any person knows that 

 the plowing or harrowing of a field frequently subjected to that proc- 

 ess is much easier than the breaking up of entirely new ground, and 

 the dredging of an oyster-bed is very similar to the harrowing of a 

 field. 



The number of oysters to the square yard, as shown by the method 

 used, should then be greater upon the old beds than upon the new, 

 and, comparing the results of successive seasons on the same bed, if it 

 is found that the number of oysters to the square yard is decreasing, 

 it may be concluded that too large a number of the animals is annually 

 removed. The investigation of the beds in 1879 showed that on sixty 

 per cent, of the beds in Tangier Sound there was a decrease in the 

 number of oysters during the season of 1878-'79, and that on sixty 

 per cent, of the beds the number of oysters to the square yard was 

 less than on the newly discovered beds in the bay, and in no case was 

 the number much greater. In Pocomoke Sound, on every bed the 

 number of oysters to the square yard was considerably less than in 

 1878, and also much below the number on the new beds in the bay. 



On several of the beds in the sounds the ratio of young growth to 



