THE OCEAN. 



669 



J. D. Hague states, that at Baker Island (of coral), in the Pacific (0° 15' N., 17G° 22' 

 W.), this fact is well exhibited. In Fig. 1098. I I I is the southwest point of the 

 island, and RRR, the outline of the coral-reef platform, mostly a little above low- 

 tide level; its width, c d, 100 j'ards. In the summer season, when the wind is from 

 the southeast, the beach has the outline s, s, s; during the winter months, when the 

 wind is northeast, the material is transferred around the point, and has the position 

 w, w, w, having a width at a b of 200 feet. A vessel wrecked in summer, and 

 stranded at V, was transferred to V in the course of the month of November. 



Fig. 1099. 



(8.) The combination of wave-action and marine currents tvith the 

 currents of rivers produces results analogous to those proceeding from 

 marine currents and waves alone, but with greater complication, and, 

 in the present age, of far greater extent, because rivers add so vastly 

 to the material of deposits by their detritus. 



The flow of rivers and the movements of the ocean are, in general, 

 in direct opposition. The in-flowing tide sets back the rivers, quiets 

 the waters, and floods the adjoin- 

 ing tidal flats ; and, consequently, a 

 deposition of detritus takes place 

 over the flats,' and especially about 

 the mouth of the stream. The turn 

 of the tide sets the river again in 

 full movement; and it takes up 

 the detritus deposited ove,r its bed 

 (but only little of what fell over 

 the flats), and bears it to the ocean. 

 Here, the current loses much of its 

 velocity, in the face of the waves, 

 And with the spreading of the wa- 

 ters ; and hence a deposition of de- 

 tritus goes on in the shallow sea,ofF 

 the mouth of the stream ; and this 

 continues until the next tidal flow 

 dams up the fresh-water stream 

 anew. Between the tidal currents, 

 especially the in-flowing, and the 

 river, there is a region of com- 

 parative equilibrium in the two 

 movements ; and there the accu- 

 mulation^ of sand or detritus take 

 place, forming sand-bars. 



Fluvio-marino formation along the coast of 

 North Carolina. 



Humphreys and Abbot observe, in speaking of the Mississippi delta, that, as the river- 

 water rises above the saltwater, from its low density, there is a dead angle between the 

 two. The current out of the Passes pushes sand and earth before it, until, reaching, it 



