first came up to the confluence
of the Leeba and Leeambye.

A species of the silver-tree of the Cape ('Leucodendron argenteum') is
found in abundance in the parts through which we have traveled since
leaving Samoana's. As it grows at a height of between two and three
thousand feet above the level of the sea, on the Cape Table Mountain,
and again on the northern 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 approximation to the altitude. The rapid flow of the Leeambye,
which once seemed to me evidence of much elevation of the country
from which it comes, I now found, by the boiling point of water, was
fallacious.*

* 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.

The forests became more dense as we went north. We traveled 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