730 



BULLETIN OF THE BUREAU OF FISHERIES 



on the deeper strata as water moves over the bottom from greater depths farther out 

 at sea. Observations taken off the Isles of Shoals on April 16 and 22, 1913, illustrate 

 this by an increase in the salinity of the whole column. 



Any April profile running out from the northern or western shore of the gulf 

 will show the effect of the vernal runoff of land water by a band of low surface 

 salinity at the inshore end, broader or narrower and with actual values higher or lower, 

 according to the exact locality. Profiles from Massachusetts Bay (fig. 110) show it 

 as a wedge less saline than 32 per mille based against the western slope of the gulf. 

 Profiles normal to the coast anywhere between Portland and Penobscot Bay, for 

 this same month, would have cut across still lower salinities next the land. Its 

 direct result is the development of a stratum less saline than 32.5 per mille, 50 to 

 60 meters thick, by April, blanketing the surface from the western shores right 



Meter 



Fig. 107.— Vertical distribution of salinity a few miles off Mount Desert Island in various months. A, 

 March 3, 1920 (station 20056); B.April 12,1920 (station 20099); C.July 19, 1915 (station 10302); D, 

 August 18, 1915 (station 10305); E, October 9. 1915 (station 1032S) 



out to the central part of the basin, where only a superficial layer, 10 meters or so 

 thick, has so low a salinity in March. 



Observations taken in the eastern side of the gulf at any time during the few 

 weeks when the Nova Scotian current is bringing a large volume of comparatively 

 fresh water past Cape Sable would show a similiar wedge of low salinity, basing on 

 German Bank and extending out over the eastern side of the basin. This state is 

 illustrated on the profile for 1919 (fig. 103). In 1920, however, neither of our 

 spring cruises coincided with this event, so that the isohalines projected in east-west 

 profile inclose homogeneous water over German Bank (fig. 110), just as they do at 

 other times of year. 



Along the western coast of Nova Scotia (figs. 109 and 110) the tides stir the 

 water so thoroughly that vernal alteration at first proceeds at a nearly uniform rate, 



