was necessary. Civilization must accompany
Christianization; and commerce was essential to civilization; for
commerce, more speedily than any thing else, would break down the
isolation of the tribes, by making them mutually dependent upon and
serviceable to each other.

It was well known that northward, beyond the desert, lay a great lake,
in the midst of a country rich in ivory and other articles of commerce.
In former years, when rains had been more abundant, the natives had
frequently crossed this desert; and somewhere near the lake dwelt a
famous chief, named Sebituane, who had once lived on friendly terms
in the neighborhood of Sechele, who was anxious to renew the old
acquaintance. Mr. Livingstone determined to open intercourse with this
region, in spite of the threats and opposition of the Boers.

So the missionary became a traveler and explorer. While laying his plans
and gathering information, the opportune arrival of Messrs. Oswell and
Murray, two wealthy Englishmen who had become enamored with African
hunting, enabled him to undertake the proposed expedition, Mr. Oswell
agreeing to pay the guides, who were furnished by Sechele.

This expedition, which resulted in the discovery of Lake Ngami, set out
from the missionary station at Kolobeng on the 1st of June, 1849.
The way lay across the great Kalahari desert, seven hundred miles in
breadth. This is a singular region. Though it has no running streams,
and few and scanty wells, it abounds in animal and vegetable life. Men,
animals, and plants accommodate themselves singularly to the scarcity of
water. Grass is abundant, growing in tufts; bulbous plants abound, among
which are the 'leroshua', which sends up a slender stalk not larger than
a crow quill, with a tuber, a foot or more below the surface, as large
as a child's head, consisting of a mass of cellular tissue filled with
a cool and refreshing fluid; and the 'mokuri', which deposits under
ground, within a circle of a yard from its stem, a mass of tubers of
the size of a man's head. During years when the rains are unusually
abundant, the Kalahari is covered with the 'kengwe', a species of
water-melon. Animals and men rejoice in the rich supply; antelopes,
lions, hyenas, jackals, mice, and men devour it with equal avidity.

The people of the desert conceal their wells with jealous care. They
fill them with sand, and place their dwellings at a distance, that their
proximity may not betray the precious sec