THE SURFACE OF THE EARTH. 



141. Source of Mississippi. Ascending the main stream from 

 its point of confluence with the Missouri, after passing several 

 tributaries of less importance, we arrive at the falls of St. Anthony, 

 which constitute the limit of its navigable course. Above these 

 we find its source in% sheet of water, called Lake Istaca, situate 

 near the northern limit of the territory of the United States, 

 and at a short distance west of Lake Superior. 



142. Missouri and its tributaries Returning to the con- 

 fluence of the Mississippi with the Missouri, and ascending the 

 latter stream, we find innumerable tributaries, variously denomi- 

 nated Smoky-hill-fork, Republican-fork, Platt-river, White- 

 river, Yellow-stone-river, &c., until the stream, reduced to a 

 number of diverging threads, loses itself in the flanks of the 

 Rocky Mountains. 



Such is a brief and rapid view of this prodigious vein of inland 

 navigation. As shown in our general plan of the rivers, the total 

 length of the Mississippi and its chief tributary is estimated at 

 4500 miles. 



143. The Amazons. Among the rivers of Southern America, 

 which flow from the western declivities of the chain of the Andes, 

 by far the most important is the Amazons, which, considered 

 merely in its geographical character, ranks as the greatest of 

 rivers. The total length from the mouth to the source of any one 

 of its thousand tributaries, is less than the length of the 

 Mississippi similarly measured, but numerous and large as the 

 tributaries of the latter are, those of the Amazons are still 

 greater in number, width, and depth. 



This immense stream, and its countless affluents, drain a 

 vast plain lying between the tableland of Brazil, on the south, 

 and the chain of mountains rising from a similar tableland of 

 less extent, on the north* called the tableland of Paramo. It 

 receives tributaries accordingly from an extensive series of 

 declivities completely surrounding it, from those of Brazil on the 

 south, from the Andes of Peru on the south-west, from the Andes 

 of Quito on the north-west, and from those of the mountain- 

 chains of Paramo on the north. 



The plain and surrounding declivities drained by this immense 

 river system, is little less in extent than 3,000000 of square 

 miles, being ten times the magnitude of the French empire. Its 

 largest branch, considered as the commencement of the main 

 stream, is called the Maranon, a name which is sometimes applied 

 to the entire river. The main river and its tributaries are 

 navigable at distances of nearly 2500 miles from its mouth, and 

 its width, near its mouth, being nearly 100 miles, it resembles an 

 arm of the sea more than a river. 

 162 



