﻿THE CURRENTS OF THE OCEAN. 147 



Here, again, the course of the tide-wave is favorable to an extreme accumulation. 

 There is a point of divergence between Santander and Bilboa, and the undulation which 

 passed on into the bottom of the bay must have been overtaken, and opposed on its 

 turning to the north, by the succeeding tide-wave, particularly in the early epoch of this 

 formation, before the bay was filled up as at present, and while the tide-wave would 

 occupy a longer time in its transit. At Santander and Bilboa, the average height of the 

 tide is nine or ten feet. I have no means of ascertaining what it is at the bottom of 

 the bay. 



The similarity in effect of the normal currents of the ocean, when they strike the 

 land, to the currents of the tides, is displayed in the general as well as the local deposits. 

 The deposit in the Mediterranean has been mentioned. 



Another striking example occurs in the Gulf of Mexico. There is a current which, 

 entering by Yucatan, makes a circuit of the coasts of Mexico, Texas, Louisiana, &c, 

 and finally becomes a tributary to the Gulf Stream. 



In the Bay of Campeachy there is a large bay deposit, and the shores of the Gulf 

 on the west and north (interrupted only by the deltas of the Mississippi) are altogether 

 alluvial, being composed of the same loose material as those of the Atlantic border of 

 the United States. M. Elie de Beaumont has dwelt with some particularity upon the 

 description of the Gulf coast. 



But the western coast of Peru affords, perhaps, the most interesting illustration of the 

 effect produced by the action of a constant ocean current. There is an antarctic cur- 

 rent which strikes the western coast of South America to the northward of the island of 

 Chiloe, and, pressing against the shores, follows their course up to the parallel of four 

 and a half degrees south, or the southern entrance of the estuary of Guayaquil, when it 

 turns off towards the Galapagos Islands. On the Peruvian coast there is a zone or belt 

 of sand, two thousand miles in length, and varying in breadth from seven to fifty miles. 

 The greater part of this sand is heaped up by gradual accumulation, according to the 

 law of constant transport from place to place, at the northern part of Peru, the terminus 

 of the connection between the current and the land. In this region it has created the 

 desert of Pachira. The rise of the tides in the River Guayaquil is six feet, which has 

 given birth to an estuary, the southern shore of which is sandy. This shore is the place 

 of meeting (against the land) of the ocean and tidal currents. 



As the form of the eastern coast of North America coincides with the general direc- 

 tion of the Gulf Stream, it may be suggested that we are to look to that as one of the 

 causes to which this form is due. The effect of the Gulf Stream as a normal current 

 of the ocean, where it actually impinges upon the extreme southern portion of the coast 



