RESEARCH IN BRITISH WEST AFRICA. 189 
The River Gambia rises near the source of the River Senegal on the north- 
east slope of the Footah-Jallon Mountains, to the north of Sierra Leone, and 
little more than 200 miles from the sea-coast. It flows first in a northerly 
direction and then west, entering British territory in, roughly, 13° 46’ W. For 
a short distance it forms the boundary of the French and British spheres of 
influence, but after the village of Bananko both banks are in British territory. 
It enters the sea about 100 miles south of Cape Verde, the most westerly point 
of Africa. The river is an important water-way, but though navigable for 
ocean-going steamers for about 250 miles from the sea, does not lead beyond the 
coast region. 
At Barraconda, 257 miles from Bathurst, there are falls or rapids, which make 
navigation even in the wet season difficult for any but very small steamers. 
Ocean-going steamers can, however, reach MacCarthy Island, 153 miles from 
Bathurst, at all times of the year. This is very important, inasmuch as 
European crews spend considerable time alongside the various wharves, subjected 
to all the influences of a tropical climate, and more often than not, without the 
usual precautions, 
The river is 27 miles wide at its mouth, but opposite Bathurst, 18 miles up, it 
is only 2} miles wide; it then gradually narrows, until near MacCarthy Island 
it is less than half a mile in width. No tributaries of any size pour their waters 
into the Gambia in British territory, and although numerous creeks of various 
sizes penetrate inland, they may be considered more as backwaters and overflows 
than as actual tributaries ; they generally end in swamps, which are firm ground 
in the dry season, and which are used by the natives for rice farms. This must 
be borne in mind in connection with much of what follows and is of great 
importance in the question of tsetse distribution. The largest of these creeks is 
the Bintang Bolon (creek), which will be considered in greater detail later on. 
(See figs. 10 and 11.) The country through which the river flows is open, as 
compared with the forest belt of West Africa, which commences some 60 or 70 
miles further down the coast, and extends to Accra on the Gold Coast. The 
valley of the river from MacCarthy Island to the end of British territory is 
hemmed in by low rocky hills of volcanic formation from 50 to 100 feet high, 
while the character of the surrounding country is park-like. 
A study of the vegetation on the river banks necessarily involves a con- 
sideration of the nature of the water at various points, and this also in both the 
wet and the dry seasons. Towards the end of the wet season (7.e., October, 
November) the water is fresh down to the Suarra-Kunda creek, but in the dry 
season the fresh water recedes to a point a few miles east of Ballangar. From 
this point to Elephant Island the water is brackish, while below this the full 
influence of the sea is marked. The banks of the river, from its mouth to 
Ballangar, are fringed with mangrove swamp, behind which are plains densely 
covered with coarse grass, growing to a height of ten feet or over, and interspersed 
with thin bush and clumps of timber. The district between Ballangar and 
Barijali forms a transition stage in which there are mangroves in front, and 
trees, shrubs, palms, ferns, pandani, etc., in the background, the former 
diminishing, the latter increasing in number and extent the higher one ascends. 
Onwards from Barijali no mangroves are seen, and different parts of the bank 
show a varying preponderance of scrub, palms, etc., mentioned above (fig. 8). 
21367 A 2 
