PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 



733 



about 0.4 per mille on March 24, 1920, to about 0.9 per mille on April 19 (fig. 106), and 

 to 0.6 per mille on April 6 off Boston Harbor, where the whole column of water had 

 been virtually uniform, surface to bottom, on March 5. However, the curves for the 

 several pairs of stations remained more nearly parallel from March to April in the 

 eastern side of the gulf, although the salinity had increased considerably in the mean- 

 time (figs. 108, 114). 



32.2 



Meter 



20 ■ 



30 ■ 



40 



50 



70 



90 



100 



Fig. 111.— Vertical distribution of salinity at the mouth of Massachusetts Bay, ofl Gloucester, during the 

 winter and spring of 1912-1913. A, November 20 (station 10047); B, December 23 (station 10049); C, 

 February 13 (station 10053); D, March 4 (station 10054); E, March 19 (W. W. Welsh station 1); F, 

 April 3 (station 10055) 



SALINITY IN HORIZONTAL PROJECTION BELOW THE SURFACE IN 



APRIL 



The deeper down in the gulf the salinity is charted in horizontal projection for 

 April, the more nearly does it parallel the winter state. Thus the band of low salin- 

 ity (31 per mille) so conspicuous along the northwestern margin of the gulf on the 

 surface chart for mid-April (fig. 101) is but faintly suggested at 40 meters (fig. 115), 

 where the recorded values were only slightly lower (32 to 32.3 per mille) than in the 

 center of the basin (32.4 to 32.5 per mille) and closely reproduced the March state 

 (fig. 93) . How little effect the vernal inrush of river water exerts on the deep strata 

 of the Massachusetts Bay region before the end of April appears from the deep 

 readings taken there in the third week of the month in 1925 (fig. 102). 

 37755—27 -15 



