138 Proceedings of the Royal Society 
coast the winds are again ruled by the African continent only, and 
the year is divided into a dry and wet season. From April till 
November the undeflected south-east trade wind blows upon this 
coast, and either from the lowness of the land or the shelter it 
obtains from the high island of Madagascar, this wind brings the 
dry season. From November to March the north-east monsoon, 
here at its furthest south limit, having passed over the warm 
Indian Ocean, brings the rainy season. 
On the plateau inland, the climate and seasons are different. 
The mean annual temperature of the table-land in the neighbour- 
hood of the Victoria Nyanza was found by Speke and Grant to be 
only about 68° Fahr., a temperature not greater than that of the 
south coasts of the Mediterranean, a climate not unsuitable to 
Europeans, since a hot summer in England is far more oppressive. 
The rainfall in this high region is also an exceptionally small 
one for a tropical country, having been found to be only about 49 
inches, or not so much as that of many parts of England, and this 
may partly be accounted for by the fact that this part of Africa is 
deprived of all rain from northerly winds, which come overland, and 
the prevailing east winds lose much of their moisture on the high 
eastern slopes of the plateau before reaching this region. 
The traveller Burton gives an account of the very different 
climate of the deeper valley of the Tanganyika Lake. Here the 
rains divide the year into two unequal portions of eight and four- 
months, — namely, the wet monsoon, which commences with violence 
in the end of August, and lasts till May, and the dry hot weather 
which completes the year. During the wet monsoon (1858) the 
prevalent winds were constantly changing. The most violent 
storms came up from the south-east or south-west of the plateau of 
Umyamwesi, to westward of the lake. Here he says that there are 
but two seasons, a summer and winter, and the rains begin in the 
middle of November. u The moisture bearing wind in this part of 
Africa is the fixed south-east trade, deflected into a periodical 
south-west monsoon.” Further south in the Cazembe’s country, 
the rainy season appears from Dr Livingstone’s letter to begin in 
September, and he says that the floods in the country west of Tan- 
ganyika last till May or June. In the northern part of the Zambezi 
valley the traveller Silva Porto found the rains set in on the 
