116 Report of the Board of Shell Fish Commissioners 



When the drag is passing over barren bottoms the chains tow 

 smoothly and evenly and no vibrations are transmitted to the 

 wire, but when shells or oysters are struck by the chains the 

 wire is made to jerk and vibrate. If the vibrations are infre- 

 quent the inference is that shells or oysters are very scattering 

 and when the vibrations become more frequent or constant a 

 scattering, medium or dense growth of oysters is inferred. 



A small boat containing small buoys with 10-pound dumb- 

 bells for sinkers is towed behind the launch at a distance such 

 that it remains above the chain drag. At one or more points 

 on each line of soundings small buoys are cast over to mark 

 stations to be occupied and examined by the "INVESTIGA- 

 TOK" which, with an expert tongman, follows the survey 

 launch (see page 37). The position of each buoy on the line of 

 soundings and the number of each is recorded in both the angle 

 record and sounding record books. Their positions are also 

 plotted '6n the boat sheets, being indicated by small flags (see 

 frontispiece) . 



Between consecutive plotted positions of the launch in a 

 line of soundings, shown in .figure 8 by the numerals above 

 the lines (32-41), seven observations of the depth of water, 

 character of the bottom and condition of the oyster ground 

 have been made. The positions of these observation stations 

 are plotted on the lines of soundings by dividing the part of the 

 plotted line between consecutive positions of the launch into 

 eight equal spaces, the points separating these spaces indi- 

 cating the positions of the sounding stations. The findings of 

 the local assistant with the chain apparatus at these stations 

 are indicated by writing the symbols B, S, M or D below the 

 lines, as shown in figure 8. 



The results of the use of the chain apparatus having been 

 thus plotted on the lines of soundings, the limits of the oyster 

 or shell covered bottom are then shown upon the boat sheet by 

 drawing a line (X-Y and M-N in figure 8) across the ends of 

 the lines of soundings through the spaces which separate the 

 soundings, indicating barren bottom, from those indicating the 

 presence of shell or oysters. 



