■:S^ NATUR/iL HISTORY 



in the water, and carried off by the current of the tides. 

 Nothing can be more certain, than that all up the river, and in 

 all the creeks which difcharge themfelves into it, the colour of 

 the water is conftantly clear or blackifh, even in the rainy fea- 

 fon, when it is fwollen. On confidering thefe circumftances, 

 I have been led to this general conclufion, which is fubmitted 

 to the proof of obfervation in different parts of the world. 

 The reddifl^ brown colour, fo common in frefhes of rivers, in 

 Europe, and we may add every where, is almoft entirely the 

 effedl of cultivation ; and the natural colour of rivers, even in 

 the highefl and longefl continued floods, where all the country 

 is flill in woods or paftures, is ever that of a very dark brown, 

 or blackifli, pretty much like that of the ftreams which rife 

 among peat-mofTes, but rather more diluted. It is compara- 

 tively very clear, and depofits but a trifling fediment. The 

 other is thick and opaque, and its fediment copious. Thus is 

 inan, in his Httle workings, made, in a fmall degree, one of the 

 engineers of nature. We cannot doubt, that entire ftrata will 

 owe to him their exiftence, accumulated in a feries of ages at 

 the bottom of the fea, and deftined, in future revolutions, to 

 adl a more diftinguilhed part. It may be curious too to con- 

 fider the differences that may be expeded betwixt the fl:rata 

 formed by thefe different depofitions, which may be fuppofed 

 between them to have been the origin of moft of the clays 

 upon our globe. Clay, earth or loam, ftirred up by the la- 

 bourer, gives rife to the one ; minutely decayed parts of ve- 

 getables form the body of the other. 



It mud alfo be obferved, that clearing the ground along 

 the coaft, by cutting down the trees, and opening ditches for 

 the difcharge of water, has expofed the land very much to the 

 wa filing of the fea. The roots of the mangroves formed a 

 plexus able to refill its force ; and the former equal, and very 

 flow deepening of the water, prevented its making a flrong 



impreffion 



