752 



BULLETIN OF THE BUEEAU OF FISHERIES 



gulf would hardly have been as abrupt as we actually found it (figs. 125 and 126). 

 Therefore, the salinities prevailing at the time were not reminiscent of some preceding 

 event (as is too often the case), but evidence of a present state of circulation. 



The isohaline for 32 per mille reached the eastern side of the basin at the time 

 (fig. 126); and as the Grampus sailed eastward from this station (10270) on May 6 

 she did actually stem a current flowing westward with considerable velocity, as de- 

 scribed in a later chapter (p. 917) . In fact, it is unusual for the distribution of salinity 

 to accord as closely with direct navigational observation of a surface current as hap- 

 pened on this occasion. The profiles for 1919 also show this Nova Scotian drift 

 (outlined in this case by the isohaline for 32 per mille) reaching the eastern side of 

 the basin, but no farther, at the beginning of May and again at the end of the month 

 (fig. 121), in each case wedge-shaped in longitudinal section and involving the whole 

 upper 100 meters on the slope of German Bank, but thinning out to nothing at its 

 western edge. 



Meter Oij^j^' 



Fio. 126.— Salinity profile running eastward from the mouth of Massachusetts Bay to Oerman Bank, May 4 to 7, 1915 



If the May charts for 1915 (figs. 125 and 127) represent the normal seasonal 

 succession to the April charts for 1920, as close correspondence in 1919 makes likely, 

 an increase of 0.5 per mille (more or less) may be expected in the western side of the 

 basin from the one month to the next at the 40-meter level, contrasting with the 

 decrease in salinity that involves the whole coastwise zone, and an increase of about 

 0.2 per mille at the 100-meter level, though the precise magnitude of this change no 

 doubt varies from year to year. This is reflected at the 40-meter level, just as at 

 the surface, by a shift of the most saline center across the basin of the gulf from east 

 to west (cf. fig. 115 with 125), as well as by the development of a mass of water of 

 high salinity in the upper 100 meters in the offing of Massachusetts Bay, illustrated 

 in profile (figs. 121 and 126). 



This slight increase in salinity in the western side of the basin, coupled with the 

 freshening of the eastern side for which the Nova Scotian current is responsible, 



