284 
DENSE FORESTS. 
Chap. XYI. 
slope of the Cashan Mountains, and here at considerably greater 
heights (four thousand feet), the difference of climate prevents 
the botanical range being considered as affording a good approxi¬ 
mation to the altitude. The rapid flow of the Leeambye, which 
once seemed to me evidence of much elevation of the country 
from wliich it comes, I now found, by the boiling point of water, 
was fallacious.* 
The forests became more dense as we went north. We tra¬ 
velled much more in the deep gloom of the forest than in open 
sunlight. No passage existed on either side of the narrow path 
made by the axe. Large climbing plants entwined themselves 
around the trunks and branches of gigantic trees like boa- 
constrictors, and they often do constrict the trees by which they 
rise, and, killing them, stand erect themselves. The bark of a 
fine tree found in abundance here, and called ‘‘ motuia,” is 
used by the Barotse for making fish lines and nets, and the 
‘‘molompi,” so well adapted for paddles by its lightness and 
flexibility, was abundant. There were other trees quite new to 
my companions; many of them ran up to a height of fifty feet of 
one thickness, and without branches. 
In these forests, we first encountered the artificial beehives 
so commonly met with all the way from this to Angola; they 
consist of about five feet of the bark of a tree fifteen or eighteen 
* On examining this subject when I returned to Linyanti, I found that, 
according to Dr. Arnott, a declivity of three inches per mile gives a velocity in 
a smooth straight channel of three miles an hour. The general velocity of the 
Zambesi is three miles and three quarters per hour, though in the rocky parts 
it is sometimes as much as four and a half. If, however, we make allowances 
for roughness of bottom, bendings of channel, and sudden descents at cataracts, 
and say the declivity is even seven inches per mile, those 800 miles between 
the east coast and the great falls would require less than 500 feet to give the 
observed velocity, and the additional distance to this point would require but 
150 feet of altitude more. If my observation of this altitude may be depended 
on, we have a steeper declivity for the Zambesi than for some other great rivers. 
The Ganges, for instance, is said to be at 1800 miles from its mouth only 800 
feet above the level of the sea, and water requires a month to come that distance. 
But there are so many modifying circumstances, it is difficult to draw any 
reliable conclusion from the currents. The Chobe is sometimes heard of as 
flooded, about 40 miles above Linyanti, a fortnight before the inundation reaches 
that point; but it is very tortuous. The great river Magdalena falls only 500 
feet in a thousand miles ; other rivers much more. 
