97 
‘ 
1914] Sumner, et al.: Physical Conditions in San Francisco Bay 3 
Herewith are the averages for surface and bottom considered sep- 
arately for each phase of the tide: 
Flood Ebb 
Surface Bottom Surface 3ottom 
‘ or ~\ = =) ia : ~ 
Fahr. Cent. Fahr. Cent. Fahr. Cent. Fahr, Cent. 
55.974 13.819 55.477 13.048 55.112 12.840 54.574 12.541 
The various local and seasonal differences in these tables have been 
represented graphically in a series of charts (pl. 3 and text figs. A-K) 
which will next be considered. 
In plate 3 the mean annual temperature, based upon the six periods 
of observation, is indicated for each station. Since the surface and 
bottom temperatures were taken in each ease, and the stations were 
visited both at flood and ebb tide, each station mean is normally based 
upon twenty-four observations. 
It will be seen that the highest mean temperatures for the year 
were found at the southernmost group of stations, the next highest 
temperatures being in San Pablo Bay. The lowest mean temperatures 
for the year are in the vicinity of the Golden Gate. 
In figure A, the same data are represented in the form of a curve. 
The stations are arranged along the horizontal axis, at distances pro- 
portionate to their relative positions in the bay, while the temperatures 
are indicated on the vertical axis. 
The differences shown by the last two charts are obviously not 
creat, all of the figures lying between 1220 and 13°28 C (53°6 and 
5629 F). From the biological standpoint, moreover, it is likely that 
these annual temperature averages have little significance. Important 
differences in the temperature conditions of different parts of the 
bay are largely effaced in the process of averaging, as will appear 
from a glance at the next chart (fig. B) showing a separate curve for 
each of the bimonthly periods. 
In the curve for the first period of our observations (February 
13 to 27, 1912) it will be seen that the bay was at a strikingly uniform 
temperature level throughout its entire length. The extremes are 
11°76 C off San Francisco and 12°56 C off Angel Island, the total 
range being only 0°8 C. 
Passing to the next period (April 23 to May 6), local temperature 
differences begin to manifest themselves. At each end of the bay the 
water is now appreciably warmer than in the neighborhood of the 
