That these extensive plains are covered with grasses only, and the little islands with but scraggy trees, may be accounted for by the fact, observable every where in this country, that, where water stands for any length of time, trees can not live. The want of speedy drainage destroys them, and injures the growth of those that are planted on the islands, for they have no depth of earth not subjected to the souring influence of the stagnant water. The plains of Lobale, to the west of these, are said to be much more extensive than any we saw, and their vegetation possesses similar peculiarities. When the stagnant rain-water has all soaked in, as must happen during the months in which there is no rain, travelers are even put to straits for want of water. This is stated on native testimony; but I can very well believe that level plains, in which neither wells nor gullies are met with, may, after the dry season, present the opposite extreme to what we witnessed. Water, however, could always be got by digging, a proof of which we had on our return when brought to a stand on this very plain by severe fever: about twelve miles from the Kasai my men dug down a few feet, and found an abundant supply; and we saw on one of the islands the garden of a man who, in the dry season, had drunk water from a well in like manner. Plains like these can not be inhabited while the present system of cultivation lasts. The population is not yet so very large as to need them. They find garden-ground enough on the gentle slopes at the sides of the rivulets, and possess no cattle to eat off the millions of acres of fine hay we were now wading through. Any one who has visited the Cape Colony will understand me when I say that these immense crops resemble sown grasses more than the tufty vegetation of the south. I would here request the particular attention of the reader to the phenomena these periodically deluged plains present, because they have a most important bearing on the physical geography of a very large portion of this country. The plains of Lobale, to the west of this, give rise to a great many streams, which unite, and form the deep, never-failing Chobe. Similar extensive flats give birth to the Loeti and Kasai, and, as we shall see further on, all the rivers of an extensive region owe their origin to oozing bogs, and not to fountains.