740 



BULLETIN OF THE BUREAU OF FISHERIES 



ANNUAL VARIATION IN THE SALINITY OF THE BOTTOM WATER IN 



APRIL 



The station data for 1920 picture salinity in the deep trough of the Gulf of 

 Maine during a spring when a very considerable volume of water enters via the 

 bottom of the Eastern Channel. Probably the deep water was equally saline in April, 

 1913, if not more so, when thesurface of the southwestern part of the gulf and the whole 

 column of water on Georges Bank were considerable salter than at the corresponding 



Portland 



Fig. 118.— Depth below the surface of the isobalobath of 34 per mille, April 6 to 18, 1920 



date in 1920 (p. 725). In 1919, however, no salinities higher than 33 per mille were 

 recorded in the bottom of the basin either in March or in April (fig. 103; ice patrol 

 stations 1 to 3 and 19 to 22). This difference is partly to be explained on the assump- 

 tion that the indraft into the bottom of the gulf ceases during the period (later or 

 earlier in the spring in different years) when the Nova Scotian current is flooding 

 into the upper strata of the gulf from the east.- In part, too, the difference between 

 lower salinities in the deeps of the gulf in 1919, than in 1920, can be explained by 

 the fact that the one was an early and the other a tardy season. However, so wide 



