PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 735 
southeastern slope of Georges Bank, obliterating the fresher pool that had occupied 
that situation in March. 
On the other hand the water more saline than 34 per mille that had occupied the 
eastern side of the Eastern Channel in March had sunk deeper than 100 meters by 
mid-April, with a corresponding decrease in temperature (p. 553). 
This general and rather complex seasonal alteration is illustrated more graphi- 
cally in profile by the flooding of the entire basin with water more saline than 34 
per mille, at depths greater than 140 to 160 meters, from March to April, on a line 
Fig. 113. — Vertical distribution of salinity in the center of the gulf near Cashes Ledge. A, March 2, 
1920 (station 20052) ; B, April 16, 1920 (station 20114); C, May 5, 1915 (station 10268); D, Septem- 
ber 1, 1915 (station 10308) 
running southward from Mount Desert (fig. 117). This was accompanied by a flat- 
tening out of the undulations that had marked the upper boundary of the bottom layer 
of high salinity in March (p. 717), the isohalines for 33 to 33.5 per mille sinking in the 
eastern side of the basin and rising in the western. 
However, the level where the salinity altered most rapidly with increasing depth 
remained approximately constant in the basin from March to April in 1920, center- 
ing at about 150 meters; the limits of salinity within which the gradient was most 
rapid (33 to 33.5 per mille) also remained constant, and the banking up of the saltesfc 
water of the basin (34.5 per mille) against the slope of German Bank persisted. 
