IN CENTRAL AFRICA. 251 
and M. Caillie's route perfectly coincides. The French 
traveller met with the Dhioliba, for the first time, at 
Couroussa^ and observed its course. This point and this 
course, from the mere construction of the new map of 
the route, are found to continue that traced by the English 
traveller. At the point of meeting, there appears to be 
a very small interval left, and I have therefore had no dif- 
ficulty in supplying this hiatus. Henceforward our know- 
ledge of the thirty-five or forty first leagues of the course 
of this great river may be considered as perfectly esta- 
blished. 
The second expedition of Major Laing, as all the 
world knows, had for its object the city of Timbuctoo, 
which he endeavoured to reach by way of Tripoli, not 
across the Bornou, like his immediate predecessors, but 
by the direct route of the oasis of Agably. The work, 
which, in the course of this paper, I have had frequent 
occasion to quote, has made the reader acquainted with 
VItin4raire de Tinjmli, de Barbaric a la ville de Tem- 
boctou, by the sheik Hagg-Cassem, revised by M. Dela- 
porte, vice-consul of France 3 an itinerary which I con- 
gratulate myself upon having submitted, in 1818, to the 
Institute, since my learned colleague M. Walckenaer, 
declares that it induced him to favour the public with his 
Recherches g^ographiques sur rint^7'ieur de V Afrique 
septentrionale. This document places Timbuctoo at eighty- 
one days' distance from Tripoli, and the oasis of Ain- 
Salah and Agably at thirty-three days, or three sevenths 
of the way. We are yet ignorant what observations 
