Belgian Congo 13 RIVER SYSTEM ; CLIMATE main stream , finally joining it at Isangi ; the Ruki, which joins the Congo at Coquilhatville ; and the Kasai, whose basin has been described above (p. 10) , and which receives as its main affluents the Lulua, the Sankuru , and the Lukenie (Fini or Mfini) on the right bank, and the Kwango system (including the Kwilu and Kwengo) on the left.

In the upper part of the Congo and in the Kasai there are, as a result of the double rainy season, two annual floods and two periods of low water. The Sanga (whose course lies entirely in French territory) and the Ubanghi, which are the principal tributaries from the north , have floods of the Nilotic type with one period of low water in April and one of high water in October. These make their influence felt on the main river in the exaggeration of the November December flood as compared with that of May and June.

(3) CLIMATE The data available for a consideration of the climatic regime of the Belgian Congo are very scanty and im perfect, but they are sufficient to give an idea of its general character. At the Equator the temperature is high at all seasons of the year, and at Eala (0° 5'N. ) the annual mean is about 76 ° F. (24.5 C. ) , while the range between the warmest and coldest months is only about 2 ° F. (1 ° C. ) . Farther to the north the mean annual temperature is somewhat higher, and at Nouvelle Anvers ( 1 ° 36' N. ) it is 78° F. (25.5° C. ) . On the other hand the range between February, the warmest month , and August, the coldest, is about 3.5 ° F. (2° C. ) . No figures exist for places actually in the Belgian Congo north of Nouvelle Anvers, but there appears to be a further increase both in the mean annual tempera ture and in the mean annual range, as far north at least as the limits of the tropical forest .