100 PROCEEDINGS OF THE AMERICAN ACADEMY 



Lieutenant C. H. Davis, U. S. N., presented a paper upon 

 the " Geological Action of the Tidal and other Currents of 

 the Ocean." 



" The object of this memoir," he said, " is to present the subject 

 of the tides and currents of the ocean as a geological problem. The 

 tides have heretofore been regarded only as an astronomical problem. 

 It is the prevailing opinion among geologists, at present, that the actual 

 condition of the earth and the changes of former periods are to be as- 

 cribed to causes now in operation. Among the present active causes 

 of change, the ocean holds a prominent place. But it has been sup- 

 posed to operate principally by means of the agitations of its surface, 

 or by violent and tumultuous disturbances. The tides and currents 

 of the sea have been treated in a general way only. This memoir 

 announces the discovery of a permanent, systematic, and uniform re- 

 lation between the tidal currents and those shores which are now, or 

 have been at any earlier period, subjected to their action. The cur- 

 rents created by the tides are to be counted among the most effective 

 agents employed throughout all periods in giving their present form 

 and body to the great continents, and in preparing a suitable home for 

 that marine animal life of which there is such an enormous display in 

 the fossils of earlier strata, and which constitutes at present an impor- 

 tant part of the sustenance of man. 



" If this agency be established, the whole economy of the eai;"lh's 

 condition will appear to be connected with the normal and regular 

 movements of the ocean, rather than with its violent and irregular ac- 

 tion. The title of the Geological Action of the Tides does not exclude 

 the consideration of those currents of the ocean produced by other 

 causes, which exert an influence by coming in contact with the land. 

 But these currents hold a subordinate place to the tides. They owe 

 their existence and direction, in part, to the continents, and move al- 

 ways in the same course. But the tides have contributed largely in 

 giving their present forms to the continents, and are themselves con- 

 stantly undergoing alternate changes of rest and motion, flux and re- 

 flux, by which they are peculiarly qualified for their oflice of distribu- 

 tion and construction. The view now presented will account for the 

 alluvial deposits on this coast, and for similar sandy formations else- 

 where, as in Holland, the Landes of France, Northern Peru, &c. It 

 will explain the geological peculiarities of the great plains of North 



