754 
BULLETIN OF THE BUREAU OF FISHERIES 
for the northern side during the first half of May, 1915 — i. e., less than half the 
regional variation recorded there for March and April of 1920 (32.91 to 34.1 per 
mille) . 
The locations of the isohalines for 33 per mille from month to month on the 100- 
meter charts for March (fig. 94), April (fig. 116), and May (fig. 127) illustrate the 
expansion of water of comparatively high salinity westward across the basin 
during a strong pulse in the inflowing bottom current, and the recession to be 
expected when the indraft is weak. Some change of this sort is consistent with the 
general progress of the vernal cycle. Salinity averaging about 0.6 per mille lower 
over the basin of the gulf at 175 to 200 meters in May, 1915, than in April, 1920, is 
probably to be explained on this same basis; but the observations taken by the Ice 
Patrol cutter in 1919, when the salinity of the east-central part of the basin 
increased through May, proves that the indraft continues active right through 
the month in some years. 
The differences that may be expected in this respect from one May to the next 
are more graphically illustrated by the west-east profiles of the gulf for that month 
of 1915 (fig. 126) and 1919 (fig. 121). Note especially the thick band of 34 per 
mille water on bottom in the latter year in the eastern side of the gulf, where the 
value was only slightly more saline than 33.5 per mille in 1915. The fact that this 
is the only month when we have found the salinity of the basin lowest, as a whole, 
in the eastern side, not in the western, deserves emphasis. 
The decrease in salinity that took place from February, 1920, to May over the 
continental slope to the southwest of Georges Bank has already been mentioned 
(p. 750). At 100 meters the May value (station 20129, ±34 per mille) was the lower 
by 1.3 per mille. 
Unfortunately no water samples have been collected in May along the 400-mile 
sector of the continental edge from the offing of Nantucket eastward to the offing of 
Sable Island, where 100-meter values varying from 33.4 to 34.8 per mille have been 
reported by the Canadian Fisheries Expedition (Bjerkan, 1919; Acadia stations 9 
and 10) and by the Ice Patrol 94 in the years 1914, 1915, and 1922, evidence of con- 
siderable fluctuations in the physical state of the slope water. 
With the low values just stated, and values even lower at the same relative 
location off the eastern slope of Georges Bank in March and April, 1920 (32.8 to 33.46 
per mille at 100 meters, stations 20068 and 20109), off Shelburne, Nova Scotia, on 
March 19 of that year (33.78 per mille at 100 meters, station 20077), it is evident 
that water of 35 per mille is usually separated from the slope by lower salinities east- 
ward from Georges Bank to the tail of the Grand Banks during the third month of 
the spring. 
Additional information as to the salinity along the seaward slope of the Scotian 
Banks in May is much to be desired. 
SALINITY IN JUNE 
A tendency toward progressive equalization is recorded from May to June as 
the overflow of the Nova Scotian current past Cape Sable and the outpourings of river 
waters are gradually incorporated into the gulf. 
•* Ice patrol station 29, May 17, 1914, 34.05 per mille at 200 meters; station 24, May 19, 1915, 33.66 per mille at about 100 
meters; station 213, May 28, 1922, 34.79 per mille at 100 meters; see 17. S. Coast Guard (1916) and Fries (1923). 
