The boiling-point of water showed a descent, from the edge of the plateau to our furthest point west, of 170 feet; but this can only be considered as an approximation, and no dependence could have been placed on it, had we not had the courses of the streams to confirm this rather rough mode of ascertaining altitudes. The slope, as shown by the watershed, was to the "Loangwa of the Maravi," and towards the Moitala, or south-west, west, and north-west. After we leave the feeders of Lake Nyassa, the water drains towards the centre of the continent. The course of the Kasai, a river seen during Dr. Livingstone's journey to the West Coast, and its feeders was to the north-east, or somewhat in the same direction. Whether the water thus drained off finds its way out by the Congo, or by the Nile, has not yet been ascertained. Some parts of the continent have been said to resemble an inverted dinner-plate. This portion seems more of the shape, if shape it has, of a wide-awake hat, with the crown a little depressed. The altitude of the brim in some parts is considerable; in others, as at Tette and the bottom of Murchison's Cataracts, it is so small that it could be ascertained only by eliminating the daily variations of the barometer, by simultaneous observations on the Coast, and at points some two or three hundred miles inland. So long as African rivers remain in what we may call the brim, they present no obstructions; but no sooner do they emerge from the higher lands than their utility is impaired by cataracts. The low lying belt is very irregular. At times sloping up in the manner of the rim of an inverted dinner-plate--while in other cases, a high ridge rises near the sea, to be succeeded by a lower district inland before we reach the central plateau. The breadth of the low lands is sometimes as much as three hundred miles, and that breadth determines the limits of navigation from the seaward. We made three long marches beyond Muazi's in a north-westerly direction; the people were civil enough, but refused to sell us any food. We were travelling too fast, they said; in fact, they were startled, and before they recovered their surprise, we were obliged to depart. We suspected that Muazi had sent them orders to refuse us food, that we might thus be prevented from going into the depopulated district; but this may have been mere suspicion, the result of our own uncharitable feelings.