16 University of California Publications in Zoology [Vol.22 



canal from the outskirts of the city. There was also a small slough 

 about one hundred yards from the place of collecting. The general 

 similarity to river conditions was well marked. 



Station IV was not used in this series. 



Stockton Channel and Smith Canal are more subject to disturb- 

 ance by prevailing winds than is the river. Smith Canal being shal- 

 lowest, Station III was probably most affected. 



Stockton Channel was .vastly more disturbed by river traffic than 

 either of the other stations. Smith Canal was rarely affected in this 

 way. Station II, in the river, was probably not stirred up one-tenth 

 as much as Station I. 



The turbidity of the water was least at Station III during 1913, 

 and greatest at Station II. But Station III was never clear and the 

 turbidity was not much less than at Station I. 



Since the times of taking the temperatures at the various stations 

 varied by an hour or more, an accurate comparison is impossible. The 

 observer, however, always expected to find the highest temperatures 

 at Station I, and the lowest at Station II and something between these 

 at Station III. 



There was no vegetation of consequence near Station I, but the 

 levees were heavily covered at both the others. No aquatic vegetation 

 occurs at any of the stations. 



River Currents and Depths 



Tidal currents were sometimes very noticeable at all the stations, 

 but strong currents of any sort were very rare except at Station II, 

 where they were noticeable for several months during the spring and 

 early summer. The highest estimate placed on the rate of the river 

 current in 1913 was four miles per hour. River transportation men, 

 notably Captain Curry of the Island Transportation Company, say 

 that five miles per hour is often reached during the heavier floods. 



The least depth of water noted at the stations at low tide was about 

 one and one-half meters at Station I, two and one-half meters at Sta- 

 tion II and one meter at Station III. 



Comparison of Stations 



The general form of the three channels is somewhat different. The 

 bed in all cases seems to be a clay with variable superimposed ooze. 

 Stockton Channel is a straight canal ending blindly at the steamer 

 landing, two and one-fourth miles from the river. It is nearly the 

 same width throughout, probably two hundred feet on the average. 



