﻿148 GEOLOGICAL ACTION OF 



of the United States, has been considered. The power it may exert in carrying for- 

 ward the tidal undulation while it is passing through it, and thus in affecting the con- 

 dition of the coast, is worthy of inquiry. But in this memoir the forms, localities, 

 and amounts of the alluvial deposits have been attributed to the active influence of local 

 currents ; the same reasonings could not be applied to the Gulf Stream, which only 

 touches the land in the beginning of its course. So far as the general course of the 

 Gulf Stream is owing to the line of soundings on the coast, it must be regarded as a 

 consequence, and not a cause, of the form of the bank against which it presses. It is 

 well known, however, that farther north there is a counter current inside of the stream 

 running in the opposite direction, and its superficial character shows that, here at least, 

 its movement is independent of the form of the bottom. The direction of its current is 

 in fact that of an eddy on a gigantic scale, and is caused, not so much by the form of 

 the bottom at its origin, as by the constantly increasing resistance of water of a lower 

 temperature; and perhaps it is in part to this resistance that we are to look for the 

 origin of the inside counter currents at the north, which resemble those created by the 

 land in retarding the tidal currents. The waters of the Gulf Stream are, moreover, 

 too clear to admit the supposition, that they take any part in alluvial formations other 

 than that already stated. 



The question may also arise, whether the whole alluvial and subaqueous formations 

 of this eastern coast of North America may not have been at one period united, and 

 whether the channels that now separate them may not have been subsequently made by 

 the draining of the continent, or some convulsive action of the sea. But the considera- 

 tion of this view will be deferred until it is formally presented. 



Section IV. — Conclusion. 



Hitherto the tides have been regarded chiefly as an astronomical problem; but if the 

 views brought forward in the preceding sections of this memoir are correct, they must 

 hereafter be treated also as a strict geological problem, applicable to all ages of the 

 earth's history. 



It has been shown in the preceding pages that there are territories, more or less inhab- 

 ited, which have been formed in historical times by the gradual accumulation of matter 

 held in suspension, and carried by the waters of the sea ; that this matter has been de- 

 posited chiefly in conformity with the laws of the tides ; and therefore that the tides must 

 have remained the same during the whole period of the deposit, their present courses and 

 other conditions being due, in general, to the forms of the shores at the commencement 

 of the actual epoch. 



