940 



BULLETIN OF THE BUREAU OF FISHERIES 



with general report. On the other hand, the westerly counterdrift set in motion 

 along the inshore side of the dynamic depression (or cabeUing zone) loses in velocity 

 and hugs the bank more closely from east to west. 



From the general oceanographic standpoint this demonstration that this sector 

 of the " Gulf Stream " receives a propulsive impulse from the local hydrostatic 

 forces (i.e., is strictly a dynamic drift) is one of the most interesting results of our 

 explorations. 



The upper 50 meters or so of the gulf being close to quiescent, dynamically, 

 during February and March, the chart for the surface (fig. 188) will as well represent 

 the gradient currents down to as deep as 100 meters or so for that season, leading 

 to the interesting result that the whole column down to this depth tended to drift 

 inward along the eastern side of the Eastern Channel at the time, outward along its 



Meter 



260 



Fig. 189.— Distribution of density on a profile ranning from tlie eastern end of Georges Bank across 

 the Eastern Channel, Browns Bank, and the Northern Channel, to the vicinity of Cape Sable, 

 March 13 to 23, 1920. Corrected for compression. 



western side, which is also evident in the profile (fig. 189). However, if we descend 

 to as great a depth as 150 meters a rather different dynamic distribution appears, 

 with the center of anticlockwise revolution located as a low close to the northern 

 slope of Georges Bank, with a weak but definite tendency toward a gradient drift 

 crossing the basin from northeast to southwest, shown better graphically by the 

 dynamic contours (fig. 190) than verbally. This drift was then bounded on the west 

 by a considerable dead area covering the whole west-central part of the basin (except 

 as interrupted by a subsidiary high marking a clockwise whirl in the offing of 

 Penobscot Bay), with a very weak southerly tendency along the western slope in 

 the offing of Massachusetts Bay. 



In the eastern side of the area tliis deep projection points to a slow creep inward 

 through the Eastern Channel; but with only one statipn in the latter it is impossible 



