RESEARCH IN BRITISH WEST AFRICA. 193 
The most noteworthy feature in these tables is the enormous variation in the 
different years, e.g. 29°42 inches in 1902 as compared with 66°07 inches in 1905. 
In 1908, 24°67 inches, or more than half the amount for the year, fell during the 
month of August. The rainfall at MacCarthy Island is never so great as that 
at Bathurst. 
The dry season, from November to May, is the season of excessive heat and 
cold; the highest maximum recorded for Bathurst was 104° in May 1904 and 
1906, while the lowest minimum was 46° in December 1900. The Harmattan, a 
north-east wind blowing from the Sahara, cold at night, and extremely hot and 
dry by day, blows intermittently from December to April. The range of 
temperature within 24 hours during this season is enormous, amounting sometimes 
to 30° at Bathurst and 59° up-country, but, in the latter district, 40° is not un- 
common. The excessive dryness of the air during the dry season may be gauged 
by the fact that at Bathurst there is sometimes a difference of 22° between the 
wet- and dry-bulb thermometers, while up-country it is often greater. The mean 
temperature for the year at Bathurst is, however, not exceedingly high, ranging 
between 75° and 85°, owing to the cool sea-breeze from the Atlantic, but up- 
country, beyond reach of the sea-breeze, it is usually about 20° higher than at 
Bathurst. 
IV. THe TRIBES INHABITING THE COLONY AND PROTECTORATE. 
According to the Census of 1901, the total population of the Colony and 
Protectorate was slightly over 90,000, but it is more than probable that this 
figure was considerably under the actual population. The details of the 
Census of 1911 are not yet available. 
The natives of the Gambia belong to four distinct tribes: Mandingoes, Foulahs, 
Joloffs and Jolahs. Although there are a few professional fishermen at Bathurst 
and a certain amount of desultory fishing is carried on up-river, no tribe is to any 
extent dependent on the river for food. The country is-essentially suitable for 
farming and cattle-rearing, and all four tribes carry on both these industries, 
though in varying degrees. Permanency of occupation of villages and the degree 
of segregation varies with the different tribes. The principal agricultural export 
from the Gambia is ground nuts or monkey nuts (Arachis hypogaea), and of 
these some 35,000 to 40,000 tons are exported annually. Guinea corn, maize, 
millet, rice, cassava, etc., are extensively grown for local consumption. The 
villages are situated generally in the centre of the area being farmed, and this 
always ensures an extensive clearing surrounding them. As the nature of the 
vegetation fringing the banks of the river precludes the possibility of any large 
settlement being established in the vicinity of the river itself, habitations are not 
found actually on the river banks, except in a few isolated instances, where there 
are wharves or ferries. The importance of this is obvious, inasmuch as where 
there are extensive clearings there are few or no tsetse, and the chances of infec- 
tion by trypanosomiasis are accordingly diminished. 
The Mandingoes are by far the most numerous tribe and are to be found 
scattered over the whole Colony and Protectorate. They are an agricultural 
people and live in large, well-built and cleanly-kept villages. There are 
generally a few large trees in each village, but in very few cases does one see 
