The “extraordinary quiet rise of the periodical flood,” proved by the first expedition, argues that the Congo “issues from the gradual overflowing of a lake or a chain of lakes.”  The increment in the lower bed, only eight to twelve feet where the Nile and the Ganges rise thirty and the Binuwe fifty, would also suggest that it is provided with many large reservoirs.  The Introduction to Tuckey’s “Narrative” (p. xviii.) assumes that the highest water is in March, but he entered the stream only on July 6, and the expedition ended in mid-October.  The best informants assured me that from March till June there are heavy freshets.  As in the Ogobe, the flood begins in early September, somewhat preceding that of the Lualaba, but, unlike the former stream, it attains its highest in November and December, and it gradually subsides from the end of June till August, about which time the water is lowest.

In the middle region of the Tanganyika, I found the rainy season lasting from September to May.  At Lake Liemba, the south-eastern projection of the Tanganyika, Dr. Livingstone in 1867 saw no rain from May 12 to September, and in Many-wema-land, west of the central Tanganyika, about south latitude 5deg., the wet season began in November, and continued till July with intervals, marking the passage of the belt of calms.  But, for the Congo to rise in September, we must assume the rains to have fallen in early August, allowing ten or fifteen days for the streams to descend, and the rest for the saturation of the land.  This postulates a supply from the Central African regions far north of the equator.  Even for the March-June freshets, we must also undoubtedly go north of the Line, yet Herr H. Kiepert[FN#24] places the northernmost influent of Congo some 150 miles south of the equator.  Under these limitations I agree with Dr. Behm:—­“Taking everything into consideration, in the present state of our knowledge, there is the strongest probability that the Lualaba is the head stream of the Congo, and the absolute certainty that it has no connection with the Nile or any other river (system) of the northern hemisphere.”  And again:  “As surely as the sun stands over the southern hemisphere in our winter and the northern in our summer, bringing the rains and the swellings of the tropical rivers when it is in the zenith with regard to them, so surely can it be predicated, from a comparison of the rainy seasons and times of rising, that the Lualaba belongs to no river of the northern hemisphere; in the southern hemisphere Africa possesses only one river, the Congo, which could take up the vast water supply of the Lualaba.”  The Brazil shows the curious feature of widely different and even opposite rainy seasons in the same parallel of latitude; but this is not the place to discuss the subject.