PHYSICAL OCEANOGRAPHY OF THE GULF OF MAINE 971 



However, there are certain grounds for concluding that Huntsman's theorem is prob- 

 ably effective in basins sufficiently inclosed, and that if so, the tides and earth rota- 

 tion combined must have an unceasing pumping effect, working season in and season 

 out on the following principle : 



In the open sea, with no barrier to the free movement of the water, the rotation 

 of the earth will merely change the track of ebb and flood (if flowing back and forth . 

 with equal velocity) from a right line to a closed ellipse; but in an inclosed basin, 

 open to the tides only at one side, the case becomes altered by the fact that when 

 the tide is flowing in the water is confined and prevented by the right-hand shore 

 from eddying to the right. Consequently, the band of water closest the land on that 

 side must either flow farther in, parallel to the coast, than it would if unconfined, or 

 it must rise higher against the bank. No doubt both results actually follow. When 

 the water next the land is so diverted from its normal path water farther out toward 

 the center of the basin is correspondingly prevented from eddying to the right. 

 Consequently, the effect of the shore line, in turning the flood tide to the left from 

 the track it would follow if free to flow in any direction, extends far out to sea from 

 the confining bank against which it presses. Under such circumstances the deflec- 

 tive effect of the earth's rotation tends to transform what is fundamentally an 

 inshore current into a drift flowing into the basin in question, paralleling the 

 shore line. 



In the opposite side of the basin, which lies to the left of the flood tide, setting 

 inward, this deflective force tends to turn the inflowing current away from the shore; 

 consequently, it is reasonable to assume that the flood will not .flow as far inward as 

 it would otherwise. When the tide begins to ebb out of the basin conditions nat- 

 urally are reversed, the ebb being driven against the coast, which is to the right of 

 it (but to the left for the flood), and so carried farther out, but turned away from 

 the side against which the flood was pressed as it flowed in. 



. The mobility of the water makes the picture exceedingly difficult to visualize or 

 to represent by any diagram, and very hkely complicated by vertical movements 

 screwing forward, which I can not attempt to reconstruct ; but as a net result it is 

 reasonable to expect the flood to flow in farther than the ebb makes out in that side 

 of the basin which is to the right of an inflowing current, and for the ebb to flow 

 out farther than the flood makes in, in the opposite side. With a differential of this 

 sort established an eddying movement would necessarily follow, forced to assume 

 anticlockwise form by the confining shore line, in place of the clockwise character 

 which the rotation of the earth would give it if not so opposed by the coast line or 

 by the contour of the bottom. Translated into terms of the Gulf of Maine this 

 would call for a dominance of flood over ebb (hence a northerly component) in the 

 eastern side and a dominance of ebb over flood (i. e., a southerly component) in the 

 western, such as has actually been demonstrated by drift bottles and by measure- 

 ments with current meters. 



Tidal currents in the gulf of Maine, the reader will recall, run nearly as strong 

 right down to the bottom of the trough as they do at the surface. Consequently, 

 Georges Bank, confining the basin on the south, should act as a coast line toward 

 the deep tidal circulation, producing a west-east drift paralleling its northern slopes, 

 if the foregoing analysis be correct. Here, again, the theoretic expectation is actually 



