PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 
793 
isohalines show a sudden transition from the one to the other (most abrupt at this 
shoaler levels) and parallel to the edge of the continent. It is especially suggestive 
that while considerable overflows of water more saline than 33 per mille appear on 
the profiles in two regions — one from the Eastern Channel across Browns Bank, as 
just described (p. 788), and the other in the offing of Nantucket Shoals — neither 
profile (nor the chart for 200 meters, fig. 150) suggests any tendency for this most 
saline water to enter the Eastern Channel. On the contrary, the isohalines for 
the highest values at each level cross the latter, leaving the oceanic triangle occupied 
by the intermediate salinities of the slope water (33 to 35 per mille) . 
As to the date when bottom water of high salinity may be expected to drift in 
over the edge of the continent toward Nantucket Shoals, I can only point out that 
in 1913 water of 33 to 33.5 per mille and upwards in salinity was encountered at 40 
meters over the outer edge of that sector of the shelf as early as July 10 (stations 
10060 to 10062). In 1914 water of this high salinity had encroached on the south- 
western part of Georges Bank by July 19 and had reached the 40-meter contour off 
Nantucket Shoals some time prior to the last week in August (fig. 145) ; but in 1916, 
a backward year (p. 772), the bottom water over this part of the shelf was only 
32.5 to 33 per mille on July 19 to 25 (stations 10354 to 10355, fig. 159) — i. e., 
about 1 per mille less saline than at about the same season of 1913 or of 1914, cor- 
responding almost exactly to the readings obtained there in May, 1920. 
Water more saline than 35 per mille may be expected to wash the slope 
at the 100-meter level right across the mouth of the gulf at some time during the 
summer, and perhaps continuously throughout the summer during some years, for 
the Canadian Fisheries Expedition had 35.35 per mille at 100 meters on the slope 
of the La Have Bank in July, 1915 (Bjerkan, 1919; Acadia station 41), where the 
100-meter salinity on July 28, 1914, was only 34.16 per mille (station 10233; both 
readings taken over the 450-meter contour line) . 
Only on one occasion have our lines reached water of full oceanic salinity (36 
per mille) — namely, abreast the western end of Georges Bank on July 21, 1914 
(p. 780, figs. 145 and 156). Failure to find water as saline as this at our outermost 
stations anywhere else between the offings of Chesapeake Bay and Cape Sable on 
any other cruise, or off Nova Scotia, suggests that this pure “Gulf Stream water” 
may be expected to approach the edge of the continent more closely thereabouts, 
as it moves northward in summer, than either to the west or to the east. 
We have yet to learn whether oceanic water approaches so close to the edge of 
the continent every summer as it did in 1914. In 1913 and 1916 (the one an early 
and the other a late season in the sea) it certainly did not do so until well into the 
summer, if at all. We may assume, therefore, that the situation pictured on the July 
profile for 1914 (fig. 156) is most likely to be reproduced in August, taking one sum- 
mer with another. 
Although this highly saline water probably approaches within a few miles of 
the 200-meter contour at about this longitude (68° to 70°) by the end of every 
August, it has never been found actually encroaching on the continental shelf abreast 
of the Gulf of Maine or anywhere else along the North American littoral north of 
Chesapeake Bay at any season. Bjerkan’s (1919) record of 35.9 per mille at 50 
meters at the Acadia station 44 miles off La Have Bank on July 22, 1915, combines 
