﻿Yol. 6 1.] GEOLOGY OF PART OF THE CONGO FREE STATE. 641 



30. Notes on the Geological Aspect of some of the North-Eastern 

 Territories of the Congo Free State. By Gaston Felix 

 Joseph Pretjmont (communicated by J. A. Howe, B.Sc, F.G.S.); 

 with Petrological Notes by John Allen Howe, B.Sc, F.G.S. 

 (Bead April 19th, 1905.) 



[Plates XLII-XLIV.] 

 I. Introduction. 



In 1902 I had the honour of being commissioned by the Govern- 

 ment of the Congo Free State, as mining-engineer and geologist, to 

 accompany an exploratory mission sent to their north-eastern 

 territories, and I had the opportunity of taking a few notes on the 

 geological aspect of that part of Africa, which is as yet little known 

 to the geologist. 



It has occurred to me that the observations recorded during nearly 

 two years spent in that region, although no doubt very incomplete, 

 might possibly be found of some interest. 



The Government of the Congo Free State have given me in Africa 

 in a very generous way, through all their officials, every assistance to 

 carry out the investigation of that large tract of country : and I beg- 

 to be allowed here to mention my debt of gratitude towards them, 

 as also to thank the Secretary-General of the Interior, Commandant 

 Liebrecht, for the kind permission which he has granted me to bring 

 these notes before this Society. 



I am also greatly indebted to Mr. J. Allen Howe, who has kindly 

 undertaken the petrological description of the rocks, for his valuable 

 assistance and advice. 



The Uelle district and the Lado Enclave are the north-eastern- 

 most provinces of the Congo Free State. They cover an area 

 at least six times as large as Belgium, and the Uelle district 

 alone extends over 72,000 square miles. On the map it presents 

 the shape of a long and broad belt of country nearly parallel to 

 the Equator, stretching approximately from lat. 2° 30' to 5° north, 

 and from long. 23° 30' to 32° east of Greenwich. Eastward it 

 reaches as far as the Nile, and adjoins there the Uganda Protectorate. 

 Northward it is bounded by the Egyptian province of Bahr-el- 

 Ghazal, and farther west is divided from the French Congo by 

 the River Mbomu, which by joining the Uelle River forms the 

 Ubangi. On the south-west and south it is contiguous to other 

 provinces of the Free State. The south-eastern extremity of the 

 country so described reaches to Lake Albert. 



From Boma, the capital of the State, on the Lower Congo, access 

 is gained to the Uelle district by the usual route to the interior, 

 namely, from Boma to Matadi by steamboat on the Lower Congo ; 



Q. J. G. S. No. 243. 2 t 



