192 Report of the Board of Shell Fish Commissioners 

 Velocity of Currents. 



The observed maximum velocities of the currents are also 

 given in the general description of the oyster grounds. These 

 observations were begun after the survey had been in progress 

 for some time and are not as complete therefore as desired. 



The apparatus for measuring the velocity of the currents con- 

 sists of a cylinder of light wood, six feet in length, so weighted 

 with lead at one end that, when placed in the water, it sinks to 

 a depth of 5% feet. A light line, graduated at 25, 50 and 100 

 foot intervals, is fastened to a staple, near the end of the pole 

 projecting from the water. When the examination boat is 

 anchored and has swung with the current, the pole is placed in 

 the water and, as it is carried with the current, note is made of 

 the time required for it to travel 50 or 100 feet. From this 

 record the velocity of the current in distance per hour is cal- 

 culated. 



Density of the Water. 



The density or salinity of the water over each of the oyster 

 grounds surveyed has been tested on as many occasions and 

 under conditions as different as was possible during the survey. 

 The results are published with those relating to currents and 

 bottoms. 



The density of sea water indicates the amount of salts con- 

 tained. Fresh water contains no salts and is taken as the 

 standard for all density (specific gravity) measurements. The 

 apparatus used to determine the density of salt water consists 

 of a series of three sealed glass bulbs, each weighted at the bot- 

 tom and ending above in a slender, hollow stem containing a 

 graduated scale. The scale in the stem of bulb No. 1 reads down- 

 ward from 1.000 (the density of fresh water) to 1.011; No. 2 

 from 1.010-1.021, and No. 3 from 1.020-1.031. The weight of 

 No. 1 is just sufficient to cause it to sink in fresh water until 

 figure 1.000, on the scale, stands at the level of the surface of 

 the water. The more salt the water contains the higher the 

 bulb floats, the density being indicated by the figure appearing 



