244 WOODED SWAMPS. [CHAP. XXXIV. 



and its tributaries, and fine mud at more distant 

 points. The larger portion, however, of the whole 

 area consists of swamps, supporting a luxuriant 

 growth of timber, interspersed with lakes, most of 

 which are deserted river bends. These lakes are 

 slowly filling up, and every swamp is gradually 

 becoming shallower, the substances accumulated 

 in them being, for the most part, of vegetable 

 origin, unmixed with earthy matter. It is only on 

 their exterior margins (except after a sudden sub 

 sidence, during an earthquake like that of 181112,) 

 that the waters of the Mississippi throw down sedi 

 ment in the interior of any large swamp or lake, 

 for the reeds, canes, and brushwood, through which 

 the waters must first pass, cause them to flow slowly, 

 and to part with all the matter previously held in 

 mechanical suspension. Long before they reach the 

 central parts of a morass or lake, they are well 

 filtered, although still deeply stained by vegetable 

 matter in a state of decomposition. 



Over a large portion of the submerged areas of 

 the great plain, trees are seen growing everywhere 

 in the water. Into the deeper water, where no 

 forest can grow, the trunks of trees are floated, and 

 many of these sink, when water-logged, to the bottom, 

 which is also raised by an annual deposit of leaves, 

 and of peaty matter derived from decaying plants, 

 of which there is an exuberant growth round the 

 borders of every swamp. That the admixture of 

 inorganic matter is very small, has been shown by 

 the observations of Messrs. Dickeson and Brown, 

 who state, &quot; that when the woods are burning, 



