44 NATURAL AND CIVIL 



immense tract of countr}'-, it is always adding 

 beautjT^ and grandeur to the prospect. 



To this account of our rivers, some observa- 

 tions may be added respecting tlieir operations 

 and effects. ---Their first operation seems to 

 have been, to form themselves a channel. The 

 highest waters descend along the mountains, un- 

 til they meet with some obstacle to obstruct 

 their motion. Whatever this obstacle may be, 

 it operates as a dam, and serves to collect the 

 waters into a small pond or lake. Two causes 

 are constantly raising the waters, in such col- 

 lections : The earth is perpetually brought dowii 

 by the waters, to the bottom of such ponds ; 

 and the water is constantly rising by its own 

 accumulation. When it is raised above the 

 banks, the waters find their passage in the low- 

 est part, and begin to form a channel there ; and 

 a channel thus formed, will constantly be made 

 more and more deep, by the perpetual running 

 of the water. A similar operation must take! 

 place through the \\hole course of the river, 

 from its first rise and source, to its final dis- 

 charge into the waters of the ocean. Their 

 channels must at first have been formed by 

 their waters ; which, constantly accumulating, 

 and struggling for a passage, approach, or dis- 

 charge themselves into the neafest situation they 

 cotiki take to the centre of the earth. 



In this descent and passage to the ocean, all 

 the large rivers in this part of America, have 

 also formed large tracts of intervale lands. By 

 intervales we mean those low lands, which are 

 adjacent to the rivers, and are frequently over- 

 flowed by them in the spring and fall, or whenev- 



