10 OYSTER BEDS OF JAMES RIVER, . VIRGINIA. 



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 

 sounding — that is, whether they showed barren bottom or dense, 

 scattering, 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 uni- 

 form, 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 this data it was necessary to supplement the observations 

 already described by others more definite in respect to the desired 

 particulars. Whenever in the opinion of the officer in charge of the 

 sounding boat such information was required, a numbered buoy was 

 dropped, the time and number being entered in the sounding book. 

 Another launch, following the sounding boat, anchored alongside 

 the buoy, and a quantity of the oysters and shells were tonged up, 

 separated by sizes, and counted. 



In former surveys made by the writer, in order to arrive at an 

 estimate of the density of the oyster growth a definite area, usually 

 5 yards, was staked off by means of steel-shod pikes and everything was 

 removed from the bottom and counted. This method is accurate, 

 but slow and difficult in deep water, and, as it was desirable to make 

 a large number of observations, the system developed in the Maryland 

 survey was adopted. This consists essentially in making a known 

 number of " grabs" with the oyster tongs, exercising care to clean 

 the bottom of oysters as thoroughly as possible at each grab. In a 

 given depth of water and using the same boat and tongs an oysterman 

 will cover practically the same area of the bottom at each grab, but, 

 other factors remaining the same, the area of the grab will decrease 

 with an increase in the depth. 



Careful measurements were made and tabulated showing the area 

 per grab covered by the tonger employed on the work at each foot of 

 depth of water and for each pair of tongs and boat used. With this 

 data, and knowing the number of " grabs," the number of oysters 

 of each size per square yard of bottom was readily obtainable by 

 simple calculation. The following example will illustrate the data 

 obtained and the form of the record: 



