92 University of California Publications in Zoology. [Vol. 6 



PUGET SOUND SAMPLE (ELLIOT BAY'). 

 1. July 3 ? ? 1.01365 



i JD15.56 ~ density reduced to standard temperature. 

 2 4 Dt = density at observed temperature. 



This table shows that the temperature of the locality farthest 

 from the mouth of the bay was on the dates (near midsummer) 

 approximately 6° C. higher during the entire flow of a tide than 

 that of the locality nearer the mouth. This is a difference of 

 about 30 per cent. It also shows that while the observed density 

 of the lower station water is a little higher than that of the 

 upper, the density of the upper station water considered in rela- 

 tion to tht diffi mice in temperature is greater by a value clearly 

 recognizable in the third decimal place. 



This comparison of temperatures and densities is of course 

 far from complete. It should at least be extended to a mid- 

 winter period. Almost certainly, should this be done, the upper 

 station water will be found to be then colder instead of warmer 

 than the lower station water. It is quite certain, too, that de- 

 terminations made at the seasons when evaporation and precip- 

 itation are at their maxima, say in late August or early Septem- 

 ber for evaporation, and February or March for precipitation, 

 the density differences of the two localities will be found still 

 greater. There can, therefore, be no doubt that these two local- 

 ities constitute two environments with rather large and readily- 

 measurable differences. Are there corresponding differences in 



