970 BULLETIN OF THE BUREAU OF FISHERIES 



to the right of the surface current, the water at 20 to 30 meters 72° and 108° to 

 the right of it, respectively. 



This calculation shows that even in winter wind currents are virtually negligible 

 in the Gulf of Maine at depths greater than, say, 20 meters, and so weak at 10 to 

 15 meters that they can oppose but little resistance to hydrostatic forces or to tidal 

 oscillations (as deflected by the earth's rotation) , which may tend to drive the water 

 in the opposite direction. 



The general effect of the wind on the circulation of the gulf may be summarized 

 as follows: In summer the prevailing southerly-southwesterly winds tend to main- 

 tain the anticlockwise circulation of the surface water, so far as they are effective at 

 all in producing a constant circulation. It is probable, also, that the easterly set 

 caused by the wind is chiefly responsible for the accumulation of the surface pool of 

 high temperature, though low salinity, in the ofRng of Massachusetts Bay, which is 

 characteristic of July and August. The outflow that takes place southward past 

 Cape Cod and over the eastern end of Georges Bank, however, is against the prevail- 

 ing wind. In winter the prevalent northwesterly winds assist the southerly drift in 

 the western side of the gulf and are the chief cause for the wider dispersal of water 

 of low salinity off its northern shore than off the western, but the general movement 

 of water inward (northward) along the eastern branch of the basin is contrary to 

 the wind. 



Winter as well as summer wind currents are conflned to the upper 10 to 20 

 meters. Consequently the dominant circulation of the deeper strata does not receive 

 its motive power from this source. 



HORIZONTAL TIDAL OSCILLATIONS AS DEFLECTED BY THE EARTH'S 



ROTATION 



Huntsman (1923, 1923a, and 1924) recently has suggested that the tidal oscilla- 

 tions deflected by the effect of the earth's rotation are the chief motive force for the 

 great eddies, anticlockwise and clockwise, that occupy the basins and circle about 

 the islands and submarine banks in high latitudes. In his own words (Huntsman, 

 1924, p. 278), " the rotation of the earth " acts " as an imperfect valve in diverting the 

 ebb and flood toward opposite sides of the channels and basins," thus causing a bal- 

 ance of inflow on the one side, of outflow on the other. 



That the earth's rotation must exert a deflective effect on the tidal currents is 

 beyond dispute. It is equally clear that if the oscillatory (back and forth) move- 

 ment of the tides of any partially inclosed basin be altered by any agency into a 

 progressive forward movement, the current, lilie any other, will be held against the 

 right-hand bank in the northern hemisphere by the deflective force of the earth's 

 rotation, and thus circulate anticlockwise, as Huntsman states. Fiu-thermore, the 

 deflective effect of the earth's rotation as it affects the tidal oscillation, if effective 

 at all in this respect, must be most definitely so in regions where tidal currents attain 

 considerable velocities at the strength of flood and ebb, as they do in the Gulf of 

 Maine. 



Beyond stating this proposition and certain applications of it to definite regions, 

 Huntsman has not yet published any discussion of the dynamic principles involved, 

 nor am I able to give it the physical analysis necessary for its proof or disproof. 



