148 



South Central Grand Bank. 



Evidently, from these data, there are sufficient intrusions of icy 

 water to maintain the bottom of the Bank in a more or less frigid 

 condition, even in August — this in the latitude of Paris and Boston. 



The mixing between the water masses of dissimilar physical 

 character over the Grand Bank is extremely active. It is necessar}' 

 to speak of this in order to show that the low bottom temperatures of 

 summer given in the table are not reminiscent of winter chilling, but 

 are maintained at these low levels by Arctic intrusions. In proof 

 of the activity of circulation over the Grand Bank, the following is 

 submitted: 



First: Wave action alone produces considerable mixing, the effects 

 of which extend downward to astonishing depths as pointed out by 

 several writers. Krummel (1911) states that waves have been 

 known to break in 25 fathoms (47 meters). Agassiz (1888) writes 

 that off the northeast coast of New England disturbances due to 

 wavesf and tide may extend to a depth of 300 fathoms (558 meters). 

 Bigelow (1905) attributes the spherical form of nullipore masses 

 which he dredged from Challenger Bank, off Bermuda, to the effects 

 of wave action. This bank has a depth of 30-40 fathoms (56-74 

 meters) and is exposed to oceanic influences, in which respects it 

 corresponds to the Grand Bank. 



Second: Tidal currents and oscillations have been recorded of a 

 velocity of 0.50 knot per hour by the Patrol in 1915 and 1921 on the 

 Grand Bank, which is bound to react in active mixings. Tide rips 

 have often been observed in calm weather clearly outlining the 



