4 NATURAL OYSTER BEDS OF DELAWARE. 



METHODS OF THE SURVEY. 



The methods employed were those pursued in former surveys of 

 like character, and are explained in detail in a description of the beds 

 of the James River, 1 from which some of the following is repeated: 



A "boat sheet" was prepared, on which were accurately platted 

 the positions, as determined by triangulation, of lighthouses and the 

 towers erected as shore signals. These data were furnished by the 

 State and were based on a development of the triangulation employed 

 in the survey of the planted or leased beds. 



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

 but principally by means of a length of chain dragged over the bot- 

 tom 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 

 minutes — 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 

 boat sheet. At regular intervals of twenty seconds, as measured 

 by a clock under the observation of the recorder, the leadsman made a 

 sounding and reported to the recorder the depth of water and the 

 character of the bottom, immediately after which the man at the wire 

 reported the character of the chain indications since the last sound- 

 ing — that is, whether they showed barren bottom or dense, scat- 

 tering, or very scattering growths of oysters. 



With the boat running at 3 miles per hour the soundings were 

 between 80 and 90 feet apart, and, as the speed of the boat was 

 uniform, the location of each was determinable within a yard or two 

 by dividing the platted distance between the positions determined 

 by the sextant by the number of soundings. The chain, of course, 

 gave a continuous indication of the character of the bottom, but the 

 record was made at the regular twenty-second intervals observed 

 in sounding. 



The chain, while indicating the absence or the relative abundance 

 of objects on the bottom, gives no information as to whether they 

 are shells or oysters, nor, if the latter, their size and condition. To 

 obtain these data it was necessary to supplement the observations 



i Moore, H. F. : Condition and extent of the oyster beds of James River, Virginia. Bureau of Fisheries 

 Document No. 729. 



