778 



BULLETIN OF THE BXJEEAU OP FISHERIES 



Channel as the normal seasonal sequence to the late June state of 1915, a type of 

 circulation also suggested by a corresponding rise in bottom temperature on Browns 

 Bank (p. 619). 



Much lower salinities, however, on the neighboring parts of Georges Bank at 

 this same date ^^ are equally clear evidence that no drift had taken place westward 

 from the channel; nor have we ever found any indication of an overflow in that 

 direction. 



It is probable that offshore water encroaches over the outer edge of Georges 

 Bank to some extent during most summers, at deeper levels as well as at the surface 

 (p. 771) , an event made evident in 1914 by the very high salinity of the bottom water 

 (34.9 per mille) on its southwest part on July 20 (fig. 142, station 10216). The 

 effect of this highly saline water, however, was so closely confined to the southern 

 side of the bank at the time, that a station on its northern part, only 42 nules away 

 (station 10215) showed no evidence of it, the salinity not only being much lower 

 (32.09 to 32.9 per mille) but the whole column much more nearly homogeneous 



.6 ,8 35 



Fig. 142.— Vertical distribution of salinity on the oashore banks in July, 1914. A, Browns Bank, 

 July 24 (station 10228); B, northeast part of Georges Bank, July 24 (station 10226); 0, eastern 

 part of Georges Bank, July 23 (station 10223); and D, southwestern part of Georges Bank, July 

 20 (station 10216) 



surface to bottom. Nor did any overflow from offshore take place farther east on 

 Georges Bank in 1914 up to the last week of July (if it ever does), although water 

 of 34 to 35 per mille then washed the bottom below the 100-meter contour all along 

 the outer edge of the bank (stations 10217, 10219, 10221, and 10222). 



In summers when the seasonal cycle is more backward (1914 seems to have 

 been rather a forward year in this respect) oceanic water may not encroach on the 

 bottom on any part of Georges Bank before August and perhaps not then. In 1916, 

 for example, two stations on the western and southwestern parts of the bank (10347 

 and 10348) gave no evidence of any such event on July 23, the salinity being nearly 

 uniform vertically at both, its value (32.4 to 32.6 per mille) no higher than the mean 

 for the whole column on the northern parts of the bank at about that same date 

 in 1914. 



Wide regional variations in salinity are to be expected over the broken bottom 

 of Nantucket Shoals, depending on the strength and on the mixmg effects of the tidal 



« station 10223 and 10224, 32. 6 to 33. 03 per mille in 56 to 76 meters; fig. 142. 



