Page:Lake Ngami.djvu/434

426 and here and there an occasional baobob, which raises its enormous head high above the highest giant of the forest. The southern coast of the Lake is considerably elevated, and the water is so closely fringed by extensive belts of reeds and rushes that it is only accessible in a few places, or where the native cattle have broken through these natural defenses. The west shore of the Lake is also somewhat raised, though the water is very shallow; but it deepens considerably toward its eastern extremity.

The Ngami must have undergone very considerable changes at different periods. The natives have frequently pointed out to me places, now covered with vegetation, where they used to spear the hippopotamus. Again, there are unmistakable proofs of its having been at one time of smaller dimensions than at present, for submerged stumps of trees are constantly met with. This is not, I believe, to be attributed to the upheaving or to the sinking of the land, but that, in all probability, the Lake was originally of its present size, or nearly so, when a sudden and unusually large flood poured into it from the interior, which, on account of the flatness of the country, could not be drained off as quickly as it flowed in, but caused the water to rise above its usual height, which, remaining in that state some time, soon destroyed the vegetation.

Before the Lake was known, and when only rumors had reached us of its existence, the natives spoke of its waters as retiring daily to "feed." But I am rather inclined to think they pointed to a singular phenomenon that I observed when navigating its broad waters, which I then attributed to the wind, though, on consideration, I suspect it was more likely to have arisen from the effects of the moon's attraction.

When navigating the Lake, we were in the habit of landing every night to bivouac, always taking the precaution to unload the most important articles of our baggage. The canoes were then pushed in shore as far as the shallowness