454 



FORMATION OF LAKES IN LOUISIANA: 



[Ch. XIX. 



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of the half-drained locli, a new island or ' mud-lump ' was 

 seen, which had begun to rise slowly in 1837, and had at- 

 tained before 1840 a height of several yards, with a length 

 of about 100 feet, and a width of 25 feet. It was still strewed 



over with dead freshwater mussels 



shells, but 



many land plants had already sprung up, so that its surface 



was green. 



I have described elsewhere a similar upheaval, but on a 



much 



fc> 



at Boston, Massachusetts, in the year 1852,* where the 

 weight of stone and sand artificially superimposed on pliant 

 strata, far exceeded that of the Scotch railway mound just 

 alluded to. 



if 



Miss 



— Another striking* feature 



in progress, is the formation by natural causes of great lakes, 

 and the drainage of others. These are especially frequent in 

 the basin of the Red River in Louisiana, where the largest of 

 them, called the Bistineau, is more than thirty miles long, and 

 has a medium depth of from fifteen to twenty feet. In the 

 deepest parts are seen numerous cypress trees, of all sizes, 

 now dead, and most of them with their tops broken by the wind, 

 yet standing erect under water. This tree resists the action 

 of air and water longer than any other, and, if not submerged 

 throughout the whole year, will retain life for an extraordi- 

 nary period. Lake Bistineau, as well as Black Lake, Cado 

 Lake, Spanish Lake, Natchitoches Lake, and many others, 

 have been formed, according to Darby, by the gradual eleva- 

 tion of the bed of the Red River, in which the alluvial accu- 

 mulations have been so great as to raise its channel, and cause 

 its waters, during the flood season, to flow up the mouths 

 of many tributaries, and to convert parts of their courses 

 into lakes. In the autumn, when the level of Red River is 

 again depressed, the waters rush back, and some lakes become 

 grassy meadows, with streams meandering through them.t 

 Thus, there is a periodical flux and reflux between Red River 

 and some of these basins, which are merely reservoirs, alter- 



* See Elements of Geology, 6th ed. 



p. 157. 



f Darby's Louisiana, p. 33. 



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