1920] Allen: Plankton of the San Joaquin River 21 



water and reading while in that position. Temperature was forgotten 

 once during the year and on a few occasions it was taken at some 

 distance from the point of collection. This was usually when there 

 was a- high wind that made any appreciable variation improbable. 



The condition of the tide was recorded when it could be detected. 

 Dixon Brothers' Tide Record is of some value for comparison, but it is 

 so fragmentary that it cannot be depended upon. Corrections for this 

 locality from the United States Tide Tables are of some value. 



Records were kept of cloudiness, rain, fog, wind, roughness of the 

 water, etc., at the time collections were being taken. 



The hour and minute of collection was regularly recorded, usually 

 at beginning and end. 



Preservation of Materials 

 The collections were preserved in formalin in four-ounce, cork- 

 stoppered bottles of the so-called vaselinetype. The formalin was not 

 measured accurately, but it was intended to be from 6 to 10 per cent. 

 The stronger solutions were used for the heavier collections. The 

 formalin for one collection was forgotten until two days after it was 

 taken, but so far as known that is the only serious error. The total 

 number of collections during 1913 is 242. The year 1913 was very dry 

 with very little flood water at any station. On the contrary, the 

 water was unusually low much of the time. For this reason it would 

 not show the local plankton range and distribution most typically. 

 But there were some features strikingly similar to river conditions in 

 other parts of the world, and it will make a good basis of comparison 

 with 1914 which was a wet year. 



Tests of Salinity 



In spite of the low water it is not at all probable that sea water 

 ever had any influence here except in causing tides. Surface samples 

 of San Joaquin River water were taken at Station II at about the 

 twentieth of each month. These samples were titrated for chlorine 

 content by the scientific staff of the U. S. S. "Albatross" and their 

 report is presented herewith. It is given in parts of chlorine per 1000. 



Jan. 19 0.0280 July 19 0.0800 



Feb. 19 0.0745 Aug. 21 0.0964 



Mar. 29 0.1025 Sept. 21 0.1764 



Apr. 26 0.1680 Oct. 19 0.2352 



May 24 0.0032 Nov. 22 0.6600 



June 21 0.0072 Dec. 20 0.1404 



