THE SOURCES OF GREAT RIVERS. 483 



is a remarkable fact, common to almost the whole of 

 them, and one which shows perhaps better than any- 

 thing else how large a portion of the earth's surface 

 is even yet occupied by the wilderness. It would be 

 too long to go over them all in detail ; but the obser- 

 vation may be said to apply to the sources of nearly 

 all the great rivers of Asia, Africa, South America, 

 and Australia; and even in North America it is only 

 of quite recent years, that the restless spirit of adventure 

 which characterizes the American people has succeeded 

 in fixing the approximate sources of the Mississippi, 

 the Missouri, the Columbia, the St. Lawrence (the head 

 waters thereof, beyond the lakes, that is), and those of 

 others of the principal streams of North America. Some 

 of these are even now very imperfectly known, and 

 their position, as marked upon the. maps, must still be 

 regarded merely as approximately correct. 



The explanation of these curious facts is not far to 

 seek; the habitations of man, or of civilized man at 

 all events, are almost invariably for commercial con- 

 venience located at first near the margins of the seas ; 

 and as the country adjacent to the coasts becomes 

 occupied, the human tide rolls onwards towards the 

 highlands of the interior, where all great rivers take 

 their rise, often amid inaccessible mountains, or among 

 dense primeval forests or morasses. Most of the North 

 American and the Asiatic rivers are examples of the 

 former; and those of South America and Africa of 

 the latter class of streams; and it is from the summit 

 of its principal divide, or watershed, that the great rivers 

 of continents mostly take their rise; first as rivulets, tur- 

 bulent and noisy, in their infantile gambols; but eventu- 

 ally issuing to the ocean as swelling tides, bearing the 



