RESEARCH IN BRITISH WEST AFRICA. 305 
points will, therefore, be kept prominently in view in this report when the writer 
is considering in detail the various regions visited. 
(>.) Mountain and River Systems. 
A sketch map (Pl. VII) has been added to illustrate the general contour and 
the river systems in the Protectorate, so that it is necessary here to draw 
attention only to the major features. The dotted contour lines indicate the 
average level of the various regions in the country, and from these it will at once 
be seen that the general altitude is not great. 
The Bauchi plateau, the highest part of the Protectorate, is only between 
4,000 and 5,000 feet above sea-level, and forms the central watershed of the 
Protectorate, whereas Lokoja, 337 miles, and Jebba, over 600 miles from 
the sea, are respectively only 300 and 500 feet above sea-level; so that the 
general fall of the river is only about one foot per mile. 
There are two main river systems in Northern Nigeria ; first the inland 
system which drains into Lake Chad in the north-east corner; and 
second, the Niger-Benue system, with its outlet to the sea through Southern 
Nigeria. > 
(1) Lake Chad is a lake only in name, and consists of nothing but an immense 
marsh with variable stretches of open water nowhere more than twelve 
feet deep. 
The basin of Lake Chad lies curiously between the watersheds of the Niger 
and the Nile, and is supposed to be the remains of a vast shallow inland sea 
which covered most of the region north-east and west of the present lake, and 
which probably communicated with the sea along the basin of the Senegal River. 
A recent French expedition has shown that, at any rate in the rainy season of 
one particular year, there was a continuous water connection between the Benue 
and Lake Chad through the Tuburi marshes into the Logun river, and thus into 
the Shari river, which runs into the Lake. This being so, the lake was then 
nothing but a backwater of a river system in Central Africa, which sent a super- 
fluity of its waters to the Benue and the Niger. 
But, apart from this, Lake Chad merits attention here from the fact that it 
drains roughly one quarter of the Protectorate of Northern Nigeria (the north- 
east portion), and, as will be seen later, is of great interest in connection with the 
distribution of the various species of Glossina, 
(2) The Niger-Benue system drains the rest of the Protectorate—the Benue 
the south-eastern quarter, and the Niger the western half. 
There are two primary watersheds in the Protectorate itself, and these radiate 
from the Bauchi Plateau, the first north-west, and then north-east to the French 
Sudan near Katsena, the other north-east and then south-east to the Kamerun 
