OYSTER BEDS OF JAMES RIVER, VIRGINIA. 9 



METHODS OF THE PRESENT SURVEY. 



To furnish authoritative and definite information as to the actual 

 extent and condition of the natural rocks and the character of the 

 bottoms embraced within the boundaries of the public beds, it was 

 necessary to depart widely from the methods of the previous surveys. 



It was decided to confine the investigation wholly to the public 

 beds, passing their boundaries only far enough to give assurance 

 that the entire area had been covered. Nothing was to be gained 

 by an examination of the excluded areas, as it is now almost impos- 

 sible to determine whether natural rocks were omitted from the 

 grounds laid out in 1892, and it is too late to correct such omissions 

 if they could be determined. For legal purposes, all that is not 

 avowedly public ground is barren bottom, and if held under leasehold 

 from the State can not be alienated from the possession of the lessees 

 as long as the law has been complied with. 



The methods followed have been essentially those pursued in for- 

 mer surveys conducted by the Bureau of Fisheries, with the changes 

 and improvements dictated by recent experience and the local 

 conditions. 



The Coast and Geodetic Survey furnished projections on which 

 were platted the triangulation points used in former surveys by that 

 bureau. Several of these points, including the light-houses, were 

 " recovered," and from them the signals, usually tripods, erected where 

 necessary, were cut in and platted by means of the sextant and 

 3-arm protractor. This method, while lacking the great precision 

 attained by means of the best theodolites and the nice computations 

 employed by the Coast Survey in its work, insures an accuracy more 

 than sufficient for the purposes of an oyster survey. 



The oyster beds were discovered by soundings with a lead line, 

 but principally by means of a length of chain dragged over the bottom 

 at the end of a copper wire running from the sounding boat. The 

 wire was wound on a reel and its unwound length was adjusted to 

 the depth of water and the speed of the launch, so that the chain was 

 always on the bottom. Whenever the chain touched a shell or an 

 oyster the shock or vibration was transmitted up the wire to the hand 

 of a man whose sole duty it was to give heed to such signals and 

 report them to the recorder. 



The launches from which the soundings were made were run at a 

 speed of between 3 and 4 miles per hour, usually on ranges ashore 

 to insure the rectitude of the lines. At intervals of three min- 

 utes — in some cases two minutes — the position of the boat was 

 determined by two simultaneous sextant observations of the angles 

 between a set of three signals, the middle one of which was common 

 to the two angles, the position being immediately platted on the 

 bo^t sheet. At regular intervals of twenty seconds, as measured by 



