322 
WHITE AND BLACK WATERS. 
appear brown like coffee, or of a greenish black. These 
waters, notwithstanding, are most beautiful, clear, and 
agreeable to the taste. I have observed above, that the 
crocodiles, and, if not the zaneudos, at least the mos- 
quitos, generally shun the black waters. The people 
assert too, that these waters do not colour the rocks' ; and 
that the white rivers have black borders, while the black 
rivers have white. In fact, the shores of the Guainia, known 
to Europeans by the name of the Bio Negro, frequently 
exhibit masses of quartz issuing from granite, and of a 
dazzling whiteness. The waters of the Mataveni, when 
examined in a glass, are pretty white ; those of the Atabapo 
retain a slight tinge of yellowish-brown. When the least 
breath of wind agitates the surface of these ‘black rivers 
they appear of a fine grass-green, like the lakes of Switzer- 
land. In the shade, the Zama, the Atabapo, and the 
Guainia, are as dark as coffee-grounds. These phenomena 
are so striking, that the Indians everywhere distinguish the 
waters by the terms black and white. The former have 
often served me for an artificial horizon; they reflect the 
image of the stars with admirable clearness. 
The colour of the waters of springs, rivers, and lakes, 
ranks among those physical problems which it is difficult, 1 
not impossible, to solve by direct experiments. The tints of 
reflected light are generally very different from the tints o 
transmitted light ; particularly when the transmission takes 
place through a great portion of fluid. If there were no 
absorption of rays, the transmitted light would be of a colour 
corresponding with that of the reflected light ; and in genei- 1 
we judge imperfectly of transmitted light, by filling with water 
a shallow glass with a narrow aperture. In a river, tb e 
colour of the reflected light comes to us always fromth e 
interior strata of the fluid, and not from the upper stratum- 
Some celebrated naturalists, who have examined the purest 
waters of the glaciers, and those which flow from mountain® 
covered with perpetual snow, where the earth is destitute o 
the relics of vegetation, have thought that the proper colon r 
of water might be blue, or green. Nothing, in fact, proved 
that water is by nature white; and wo must always adm 
the presence of a colouring principle, when water viewed tb 
reflection is coloured. In the rivers that contain a colouring 
