772 
BULLETIN OP THE BUREAU OF FISHERIES 
the same dates in 1912 or in 1915.' Probably the correct explanation is that 1916 
was a tardy spring, when the effect of vernal freshening from the land continued 
evident until later in the season than usual, and when the approach of water of 
high salinity to the continental shelf was delayed until later in the season. As a 
result of this retardation of the vernal cycle — associated, no doubt, with the severity 
of the preceding winter and the lateness of the spring — the salinity of the surface 
was very nearly uniform on July 24, 1916, right across the whole breadth of the 
western end of Georges Bank, where a considerable north-south gradation is to be 
expected at that season in more normal years (fig. 136). 
Contrasting with 1916 and with 1914, the summers of 1912 and 1913 may be 
characterized as “salt” in the western side of the gulf, with surface values averaging 
about 0.1 to 1 per mille higher at corresponding localities and dates than in 1914 — 
August as well as in July — but with very little difference from summer to summer 
in the eastern side. The surface values for 1915 paralleled those for 1914 except for 
the closer approach of oceanic water to the continental shelf off Nova Scotia, men- 
tioned above (p. 771). 
No wide annual fluctations in salinity have been recorded for any part of the 
gulf at a given season, or are such to be expected. 
VERTICAL DISTRIBUTION 
The salinity of the deep strata of the gulf, like that of the surface, remains 
more nearly constant during July and August than over any period of equal duration 
earlier in the summer or in the spring. Two stations in the basin off Cape Cod, 
four weeks apart in 1914 (stations 10214 and 10254, July 19 and August 22), exem- 
plify this for the western side of the gulf, the values, depth for depth, being nearly 
alike in spite of the time interval separating them, with the one station slightly the 
more saline at some levels, the other at other levels. 
The graph (fig. 138) illustrates how little variation in salinity has been recorded 
for the deeper levels in the western side of the basin at different dates in August of 
different years, individual stations seldom differing by more than 0.2 to 0.4 per 
mille in either direction from the mean values of 32.6 per mille at 50 meters, 33 per 
mille at 100 meters, 33.4 per mille at 150 meters, 33.9 per mille at 200 meters, and 
about 34.1 per mille at 250 meters. 
Except in localities where the tide runs strong enough to keep the whole column 
of water thoroughly mixed from top to bottom, the salinity of the gulf is invariably 
lower at the surface in summer than on the bottom, as already stated for the spring 
months. I should emphasize, also, that the increase in salinity with depth is con- 
tinuous, or at most is interrupted by homogeneous strata; we have never found 
fresher water underlying salter in the gulf. Thus, the intermediate layer of low 
temperature, characteristic of certain summers (p. 602), is not reproduced by the 
salinity; but the vertical distribution varies widely from place to place in the gulf, 
a convenient division in this respect being (1) into the coastal zone, (2) into the 
basin, and (3) into the offshore rim. 
In the western section of the coastal zone, out to the 100-meter contour, the 
vertical increase of salinity, with increasing depth, averages much more rapid in 
