I 



Report of the Board of Shell Fish Commissioners 33 



basis however for ascertaining even approximately the quan- 

 tity of oysters on a given bottom. From the vibrations on the 

 wire of the chain apparatus,* it is known that solid objects of 

 some kind are on the bottom and, being above ground where 

 oystering is or has been profitably carried on, the inference is 

 that the objects causing the wire to vibrate are oysters. No 

 one can be sure, however, that the vibrations on the wire are 

 caused by oysters for the same resuK would be brought about 

 if the chain were being dragged over coarse gravel, brickbats 

 or shells. On more than one occasion during the survey an 

 examination of a bottom by an oysterman showed that what 

 had been recorded on the survey boat as a dense growth of 

 oysters was in reality -stones. To decide that all bottoms, on 

 which the presence of oysters might be inferred from the chain 

 and sounding records, . are natural bars, would be to decide a 

 most important matter on incomplete and doubtful evidence. 

 Knowing that the data secured by the survey boat are insuffi- 

 cient for its guidance in ascertaining the status of the grounds 

 surveyed, the Commission set about to develop a system of 

 examinations whereby reliable data could be secured regard- 

 ing the actual condition of the oyster grounds, and it is 

 believed that the facts secured by the method adopted, when 

 added to those secured by the survey boats, place the Com- 

 mission in a position in which its action concerning an oyster 

 ground of disputed status can be satisfactorily explained and 

 defended. 



i 



EXAMINATIONS WITH DREDGE. 



Lient. Francis Winslow, in the survey made by him in 1878 

 of the oyster bars of Tangier and Pocomoke Sounds, calculated 

 the number of oysters per square yeard on the grounds sur- 

 veyed from data secured by dragging a dredge of known width 

 for a definite distance and time, over them. 4 



*See page 114. 



^"Report on the Oyster Beds of the James River, Va., and of Tangier 

 and Pocomoke Sounds, Md. and Va. y " page 7, Report for 1881. Appendix 

 No. 11, United States Coast and Geodetic Survey. 



