Report of the Board of Shell Fish Commissioners 193 



at the water's surface. In pure sea water the amount of salts 

 is sufficient to float bulb No. 3 at about 1.026. Bulb No. 1 is 

 used to determine the density of brackish water, while No. 2 

 serves to indicate the density of water between brackish and 

 salt. 



The density of water is, to a small degree, affected by_ tem- 

 perature, it being less when the water is warm. For all prac- 

 tical purposes, however, this error may be disregarded and, in 

 the density records published, no correction for temperature 

 has been made. The temperatures of all samples have been 

 recorded, however, and are on file. 



The Food of Oysters. 



Oysters from the natural bars and specimens of water from 

 near the bottoms, immediately above the bars, have been sys- 

 tematically collected and examined with reference to the organ- 

 isms constituting the food of the oyster and with reference to 

 the quantity of this food in the water. 



Minute organisms of numerous species literally fill the water 

 of the Chesapeake Bay and its tributaries, some of which are 

 of value to the oyster as food, others not. By opening oysters 

 from bars in various localities, removing the contents of their 

 stomachs, with a medicine dropper, and examining the contents 

 with a microscope, those organisms which constitute the food 

 of the oyster in each locality can be identified. Such material 

 has been collected and preserved from numerous localities in 

 Anne Arundel and Somerset Counties, and will be collected 

 from each locality as it is surveyed. 



Knowing which organisms, found in the water of a certain 

 locality, are valuable as food for oysters, all other kinds occur- 

 ring in the specimens are ignored in the examinations and 

 excluded from the estimates of the food value of the water. 



The method of collecting specimens of water and preparing 

 them for examination is as follows : The launch Investigator, 

 having been anchored at a flag buoy preparatory to making an 

 examination of an oyster bar, a water cup, holding a little more 

 than one quart, is lowered to the bottom and filled. The water 

 is emptied into a flask such a^ is shown in figure 11, and note is 



