On the Natural Hijiory of Guiana. 349 



The mouth of the Eflequebo, from the fand-hills and rocks being very near It, is exceed- 

 ingly different. Three large iflands prefent themfelves in a breaft, and divide its entrance 

 into four channels. The length of thefe iflands is, with the current, fouth and north ; and 

 from the tail or north end of each of them, as alfo from the banks of the main, or either 

 fide, run out fand- banks to a gbod diftance. They are perfe£lly firm, quick in very fe\T 

 fpots, and the body of them is above the level of low water. On the outfide of them, you 

 have the continuation of the mud-banks and fliallow water, as above, only that the en- 

 trance of thefe channels is dill (hallowcr than that of the Dcmerary. The dream of this 

 river runs very brown and muddy, and the fea is ftained with it for fome leagues off. A 

 granger naturally imputes this to the wafhings of a large flat country, or the llirring up of 

 the muddy bottom by the tides. The latter may in part be a caufe, though 1 believe it con- 

 tributes to it but very little, and the former in a (late of uncultivatlon, none at all. On 

 afcending forty miles or fo, you find the water clear again, or rather of a darkifli hue ; and 

 fo it continues above that. I was at firft at a lofs how to account for this; but, from a 

 number of circumdances, was foon led to conclude that the thickncfs and light brown 

 colour of the water near the mouth of the river, and on the coad, were almod entirely the 

 effeft of cultivation. Numberleis ditches and canals have been opened by the inhabitants, 

 which are receiving or difcharging water every tide ; and each particular piece on a planta- 

 tion is every way interfered with open little drains, which communicate with thefe ditches. 

 In digging and hoeing this clayey foil, much of it is fufpended in the water, and carried off 

 by the current of the tides. Nothing can be more certain, than that all up the river, anJ 

 in all the creeks which difchargc themfelves into it, the colour of the water is condantly 

 clear or blackidi, even in the rainy feafons when it is fwollcn. On confidcring thefe cir- 

 cumdances, I have been led to this general conclufion, which is fubmitted to the proof of 

 obfervation in different parts of the world. The reddlfli brown colour fo common in 

 ireflies of rivers in Europe, and we may add every where, is almod entirely the effe£l of 

 cultivation ; and the natural colour of rivers, even in the highed and longed continued' 

 floods, where all the country is ftill in woods or padures, is ever that of a dark brown, or 

 blackifli, pretty much like that of the ftreams which rife among peat-moffes, but rather more 

 diluted. It is comparatively very clear, and depofits but a trifling fediment. The other 

 is thick and opaque, and its fediment copious. Thus is man, in his little workings, made in 

 a fmall degree one of the engineers of Nature. We cannot doubt that entire drata will 

 owe to him their exidence, accumulated in a feries of ages at the bottom of the fea, and 

 deftined in future revolutions to aft a more diftinguidied part. It may be curious, too, to 

 confider the differences that may be expe£led betwixt the drata formed by thefe different 

 depofitions, which may be fuppofed between them to have been the origin of mod of the 

 clays upon our globe. Clay, earth, or loam, dirred up by the labourer, gives rife to the 

 one : minutely decayed parts of vegetables form the body of the other. 



It mud alfo be obferved, that clearing the ground along the coad, by cutting down treci, 

 and opening ditches for the difcharge of water, has expofed the land very much to the 

 wafliing of the fea. The roots of the mangroves formed a plexus able to refid its force, 

 and the former equal and very flow deepening of the water prevented its making a ftrong 

 impreffion on any place. The difcharge from the ditches at low water cut out channel* 

 in the mud, and left the fides of thefe channels more expofed to the returning waves, which 



Vol. II.— Nov. 1798. Z z ^^^ 



