76 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
In the northerly end of the profile Station 1 is introduced, to show 
how the cold salt bottom water wells up close to the shore. However, 
7 . . . . . . . 
as*pointed out in the discussion of temperatures, this phenomenon 1s 
Fath 44 45 46 
35| 
45 
Fie. 33.— Salinity profile across Massachusetts Bay, August 13 (Stations 
44, 45, 46). 
sporadic, probably the result of offshore winds driving the surface 
water away from the coast, their place being taken by water from 
below. Conditions at Station 1 show that the effect may be felt to 
as great a depth as 20 fathoms. 
DENSITY. 
The three features of sea water most interesting to the oceanog- 
rapher are temperature, salinity, and density; the former because 
of its biological importance; the second because it is the only safe 
clue to the geographic origin of water-masses; and the third because 
of its importance as determining circulation, both vertical and hori- 
zontal. The last is a product of the first two and of a third factor, 
namely pressure. And we must never lose sight of the fact that as it 
is determined by temperature as well as by salinity, it is a temporary 
quality, changing as the water becomes colder or warmer. In the 
accompanying table (p. 141), the densities in situ are calculated from 
—_— 
