190 Geological Society : — 



currents. Eventually the upward movement ceased, and the hollow 

 below the fault was filled up, so that the Dogger was laid down as 

 a continuous bed over the whole area. The uplift to the north was 

 probably much greater ; consequently the whole of the Upper Lias 

 was removed, and the Middle Lias reached and denuded. Pebbles 

 derived from the Middle Liassic Ironstone occur in the basement- 

 conglomerate of the Wainstones, according to Prof. P. F. Kendall. 



2. * Notes on the Geological Aspect of some of the North-Eastern 

 Territories of the Congo Free State.' By Gaston Felix Joseph 

 Preumont. 



This paper is a brief sketch of the geological structure of the 

 northern part of the Congo State, from Buta on the River Rubi and 

 Bima on the Uelle in the west, to Lado and Dufile on the Nile. 



In the whole of this region, the only post-Primary rocks met 

 with, other than those of comparatively-modern alluvial origin, were 

 chocolate-coloured shales (Buta Shales) and sandstone, and an oolitic 

 limestone, on the extreme west. 



From the Lipodongu Falls on the Rubi, and thence through Poko 

 to Rungu, on the Bomokandi River, none but granitic rocks (gneisses) 

 were observed. Along the Uelle, from Bima to Bomokandi, the 

 same rocks were seen. 



In the centre of the region mica-schists, quartzites, and similar 

 metamorphic rocks replace the granite wholly or in part. A 

 noticeable feature here is the presence of a range of isolated hills, 

 composed almost completely of great beds of magnetite and haema- 

 tite occurring in the schistose series. 



In the south-eastern portion of the region visited, between the 

 Uelle-Kimbali and Bomokandi rivers, a great plutonic massif is laid 

 bare in the mountainous district of Arebi. 



From the presence of iron-ore and schists at Mount Tena on the 

 south-west and analogous rocks at Mount Gai'ma on the north-west 

 side of the massif, and from the fact that the dip is in each case 

 strongly away from the intervening country, it is suggested that 

 these rocks have been uplifted and tilted by the plutonic complex, 

 and that the beds of Mount Tena and Mount Gai'ma are identical 

 in age. 



The plutonic massif itself contains microclinic gneiss, and 

 abundant diabasic rocks, and the same rocks in all stages of 

 dynamo-metamorphism. 



On the boundary between the Congo State and the Bahr-el- 

 Ghazel, several hills made up of rocks of coarse gneissose and schistose 

 character are described ; some of these rocks are rich in tourmaline, 

 kyanite, and garnet in large crystals. 



From the region of the Enclave de Lado and the western side of 

 the Nile between Lado and Dufile, mica-schists, quartzites, and 

 microcline-gneisses are described. 



The alluvium of a large part of the Uelle is covered, on the 

 higher ground, by a deposit of limonitic conglomerate ; in places 



