340 GENERAL OBSERVATIONS. 
three to five hundred yards, throughout that extent, and 
in most parts bristled with rocks. ‘The banks, between 
which the water is thus hemmed in, are, for the whole of 
this distance, every where precipitous, and composed en- 
tirely of masses of slate ; which, in several places, run in 
ledges across from one bank to the other, forming rapids 
or cataracts, which the natives distinguish by the name of 
Yellala. The lowest and the most formidable of these 
barriers was found to be a descending bed of mica slate, 
whose fall was about thirty feet perpendicular in a slope 
of 300 yards. ‘Though in this low state of the river it was 
scarcely deserving the name of a cataract, it was stated 
by the natives to make a tremendous noise in the rainy 
season, and to throw into the air large volumes of white 
foam. Even now the foam and spray at the bottom are 
said to have mounted eighteen or twenty feet into the air. 
On visiting this Yellala, Capt.'Tuckey, Professor Smith, 
and Mr. Fitzmaurice were not a little surprised to observe, 
how small a quantity of water passed over this contracted 
part of the river, compared with the immense volume 
which rolled into the ocean through the deep  funnel- 
shaped mouth; the more so, as they had previously as- 
certained, in their progress upwards, that not a single tri- 
butary stream of water, sufficient to turn a mill, fell into 
the river on either side, between the mouth and the ca- 
taract; and they concluded, that the only satisfactory 
explanation of this remarkable difference in the quantity, 
was the supposition that a very considerable mass of water 
must find its way through subterraneous passages, under 
