40 University of California Publications in Zoology [ Vou. 14 
Golden Gate. While the water at the station nearest the latter (No. 
4967) has actually become slightly cooler, that at the northern end 
of the series (No. 4975) has risen 1°89 C, while that at the southern 
end (No. 5001) has risen 2°15 C. 
In the third period (July 22 to 31) the local differentiation has 
greatly increased, the total temperature range throughout the bay 
being over 5° C. As before. the coldest water lies in the vicinity of 
the Golden Gate, although this has risen nearly 2° C sinee the last 
observations. From the Golden Gate the temperature rises fairly 
uniformly toward the upper and lower ends of the bay, where approxi- 
mately the same temperatures are found. 
In the fourth period (October 7 to 12) a general fall of temper- 
ature has become evident, though the ends of the bay have cooled 
more rapidly than the central region near the Golden Gate. The 
latter waters remain, however, cooler than those farther removed from 
the ocean, the greatest difference now amounting to 3°8 C. 
In the fifth period (November 25 to December 5) we have for the 
second time a high degree of uniformity throughout the waters of the 
bay, the greatest difference recorded being 1°18 C. 
Finally, in the sixth period of our observations (January 13 to 28, 
1913), we behold an inversion of the summer temperature conditions. 
The highest temperatures are found in the central region of the bay, 
adjacent to the ocean, a downward gradient being manifest toward 
either end. The differences are not as great, however, as at the warm- 
est period of the year, the extremes being 6°04 and 9208 C. It is to 
be noted, also, that the water is decidedly colder in the northern than 
in the southern end of the bay. This is doubtless due to the lower 
temperature of the water from the rivers, coming as it does from 
regions where colder winter conditions prevail than in the coastal belt. 
It has thus been found that, while the various parts of the bay 
differ but slightly in their mean annual temperatures, they may differ 
very considerably in the total range of temperature which they under- 
go in the course of the annual cycle. The annual range for each 
station of our series is depicted in figure C. The ordinates in this 
chart represent not absolute figures, but the difference between the 
lowest and highest annual temperature for each station. The tem- 
peratures here considered are not the individual thermometer read- 
ings, but the means of the four readings recorded for each period, 
ie., those represented in the columns headed “‘mean of surface and 
bottom’’ in Tables 3 to 8. 
