as their smallest tributary, being entirely unnavigable
at all times of the year. Raging floods in the wet season, and mere
driblets in the dry, they are at present denied to the most powerful
or shallowest of river steamboats. The prospects of the Orange river
as a potential waterway are in any case practically destroyed by a
great bar which blocks approach to the estuary from the sea.

[Sidenote: Military character of streams of S.A.]

The streams of the South African plateau, whether river, spruit,
sluit, or donga, have, in addition to their extreme variability,
another marked and almost universal peculiarity. Running in deep beds,
of which the banks are usually level with the surrounding country, and
the sides terraced from the highest to the lowest water-mark, they
constitute natural entrenchments which are generally invisible, except
where rarely defined by a line of bushes, and, owing to the dead
uniformity of the surrounding country, are almost impossible to
reconnoitre. Nor, in 1899, were their defensive capabilities lessened
by the dearth of bridges, by the dangers of the drifts, and by the
absence of defined approaches to all crossing-places away from the
main roads. The "drifts," or fords, especially rendered the laying out
of a line of operations in South Africa a complex problem. Their depth
varied with the weather of the day; they were known by many names even
to local residents, and were of many types; but all alike were so
liable to sudden change or even destruction, that any information
concerning them, except the most recent, was practically useless.

[Sidenote: Effect of winds on climate.]

[Sidenote: The velds.]

To comprehend broadly the salient physiological features of a region
so enormous as South Africa, the causes of the climatic influences
which affect them must be understood. These causes on are simplicity
itself. The warm winds blow from the east, and the cold from the west;
the former, from the warm Mozambique current, skirting the eastern
seaboard, the latter, from the frigid Antarctic stream, setting from
south to north, and striking the western coast about Cape St. Martin.
It follows, therefore, that the climate and country become more genial
and fertile the further they are removed from the desiccating
influence emanating from the western seaboard. The dreariness of the
solitudes between Little Namaqualand and Griqualand West, the latter
slightly more smiling than the former, att