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O1 
1914] Sumner, et al.: Physical Conditions in San Francisco Bay 
lower (southern) third of the bay. At each point the observations 
extended through a considerable number of years (six to fourteen), 
the latest being made in 1890. We have employed only surface 
figures in the construction of the curve here presented. At no point, 
however, was the difference between the surface and bottom readings 
worth considering. 
The mean latitude of these points in Chesapeake Bay is very 
nearly the same as that of San Francisco Bay. The mean annual 
water temperature for the former bay, computed from the records 
referred to, is 14°38 C (57°89 F), that for the latter bay being 
12°91 C (55°23 F). The chief difference between the temperature 
conditions of these two bodies of water lies, however, in their respective 
annual ranges. In Chesapeake Bay this amounts to 22°12 C (39°82 F), 
while in San Francisco Bay it is not much more than a third (thirty- 
eight per cent) as great, being 8°35 C (15°03 F).° Thus the equable 
climate for which the California coast is famous is reflected in (we 
should rather say, is largely due to) the equable temperature of its 
coastal waters'®, though the direction of the prevailing winds is hke- 
wise an important factor. 
The resemblance between the Chesapeake Bay curve and that for 
Woods Hole is sufficiently striking. The latter is based upon the 
monthly means for a period of six years, as recorded at the Woods 
Hole station of the Bureau of Fisheries (see Sumner, Osburn, Cole, 
and Davis, 1913, p. 47). The vertical distance between the Woods 
Hole and Chesapeake Bay curves remains surprisingly constant 
throughout the year, representing, on the average, 3°82 C. The 
mean annual temperature of the surface water in Woods Hole Harbor 
is 10956 C (51°01 F), or more than 2° C lower than that of San 
Francisco Bay. The annual range, computed as for the other points, 
is 21°50 C (38°74 F).”” 
In some loealities of the California coastal region we behold the 
anomaly of familiar garden fruits and vegetables failing to ripen 
15 These figures are based in each case upon the difference between the 
highest and lowest monthly mean for the year. The actual range for any single 
year, i.e., the difference between the lowest and highest temperature reached, 
would, of course, be much greater than this. 
16Of course, the annual range of the water temperature, outside of San 
Francisco Bay, is even less, being only 3°3 C. But it would not be fair to 
compare this with inclosed bodies of water, such as Chesapeake Bay and Vine- 
yard Sound. 
17 Rathbun (1890, p. 458 and pl. LXX) has made a similar comparison be- 
tween water temperatures recorded at the Vineyard Sound Lightship and some 
which were recorded along the San Francisco water front. The relations be- 
tween the two sets of figures are in general harmony with those which we have 
indicated. 
