﻿THE CURRENTS OF THE OCEAN. 149 



But the causes of the tides, and therefore the tides themselves, have always existed. 

 We may ascend to an ancient geological period, when the regular progress of the tidal 

 undulations was much less interrupted than now ; still we must admit the existence of 

 tidal currents so long as we conceive the interposition of shoals, islands, or continents in 

 the path of those undulations. Theoretically speaking, then, we should expect to find a 

 certain conformity between the oceanic deposits of all ages and the currents of the epochs 

 in which they were made, which conformity should be the more apparent the nearer 

 we come to the actual epoch. It has been pointed out that there exists a fixed relation 

 on the part of the tidal currents to the alluvial deposits, in their structure, position, and 

 amount; or, as the tidal currents depend on the form of the land, it may be said that on 

 the south coast of New England this relation is maintained between the present deposits 

 and the shores of the post-pliocene period. So distinct is this relation, that the character 

 of the alluvial deposit on the borders and in the depths of the sea is readily determined 

 when the direction and other circumstances of the local currents are known. This sug- 

 gests a principle of conformation by means of which the geologists will be able to reason 

 back from the forms of the earlier deposits to the currents of their respective periods. 



It is the prevalent opinion among geologists that the most important and durable 

 changes in the surface of the globe have been ushered in by epochs of convulsive dis- 

 turbance. This is not the place to discuss the limits of these changes. It may be pre- 

 sumed that during these convulsions the operation of the tidal laws was overruled, or 

 controlled. But since these laws are active and unchangeable, they must have struggled 

 to regain their natural ascendency, to which they will have been restored in periods of 

 quiet action. Accordingly the currents created by the tides are to be counted among the 

 most effective of the natural agents at work throughout all periods of quiet action in 

 giving their present form to the great continents; and thus the whole economy of the 

 earth's condition appears to be as intimately connected with the regular movements of 

 the ocean, depending upon astronomical influences, as with its occasional and tumult- 

 uous disturbances. This action of the tides, or, in other words, the influence in this 

 manner of the moon upon the earth's surface, is a new application of the law of gravi- 

 tation, which has been employed by the Author of the universe, not only in holding 

 together the bodies of the system, but also in distributing the materials of which they 

 are composed according to His plan of creation. 



The tidal theory now introduced into geology does not assume the discovery of a new 

 law, but indicates a new mode of operation of an established law. It conforms to that 

 view to which all improvements in science seem to tend, — a simplification of the laws 

 of creation. 



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