NATURE OF RIVER DEPOSITS. 265 



currents, and finally sink down, and form 

 layers of mud in the profound depths of the 

 ocean. Rivers, however, convey not only the in- 

 organic materials of the countries through which 

 they flow, but also the leaves, branches, and trunks 

 of trees, and other vegetable remains, and the car- 

 cases of land animals that fall into the streams, 

 and terrestrial, lacustrine, and fluviatile shells. 

 The remains of man and works of art are also 

 occasionally transported to the delta, and en- 

 gulphed in the mud, silt, and sand ; and relics 

 of this kind are sometimes drifted out to sea, and 

 deposited in the bed of the ocean. 



In the rivers of India and of America these 

 operations are in daily progress on an immense 

 scale. In the Mississippi rafts formed of prostrate 

 forests are transported to the delta of that mighty 

 stream, and become buried in the freshwater 

 deposits which are there rapidly accumulating. 

 In these sediments the remains of the animals 

 as well as plants of the new world, are en- 

 gulphed. 



It is evident that should deposits of this nature 

 become dry land, the naturalist, by an examination 

 of the imbedded organic remains, may with cer- 

 tainty determine the characters of the fauna and 

 flora of the country whence these fluviatile sediments 



