﻿Vol. 6 1.] TERRITORIES OF THE CONGO FEES "STATE. 665 



Plate XLIV. 



Fig. 1. Ferruginous oolitic limestone, from Buta, on the Eiver Eubi. Magnified 

 15 diams. Specimen No. 51 (see p. 656). 

 2. Oolitic limestone, from the same locality. Magnified 10 diams. 

 Specimen No. 42 (see p. 655). 



Discussion. 



The Chairman (Mr. H. B. Woodward) referred to the fact that 

 the area examined by M. Preumont extended over 70,000 square 

 miles, in a country where a geological survey was rendered difficult, 

 and often impossible, by the dense vegetation. Nevertheless, he 

 had made an important and interesting series of observations, which 

 had been ably elucidated with the help of Mr. Howe. 



Mr. Walcot Gibson said he was sure that all interested in African 

 geology would be indebted to the Authors for their paper on this little- 

 known region. Once again the absence of fossiliferous deposits from 

 Central Africa was demonstrated, from a region where it might havo 

 reasonably been expected that such would occur. This paucity of 

 fossil evidence, on which to base the age of the dynamic and volcanic 

 phenomena in East-Central Africa, should be kept in mind. The 

 iron-bearing schists and accompanying rocks described by the Authors 

 recalled a sequence in Griqualand West which, there was good reason 

 to believe, approximated in age to the Eand gold-bearing deposits. 



Mr. Hudleston welcomed this paper, since it supplemented the 

 observations of Cornet and Barrat in their several descriptions of 

 different portions of the Congo Basin. It also served to confirm, 

 towards the north, their conclusions as to the relations between the 

 ring of old crystalline rocks, which form the periphery of the Congo 

 Basin, and the red-and-white grits described by Cornet under the 

 general term ' formations post-primaires,' which fill up the vast 

 interior of that basin. In the sketch-map which he (the speaker) 

 had ventured to publish, a gap had been left in the line indicating 

 the approximate limits of the red-and-white grits towards the 

 north ; and he had indulged in the hope that there might be a break 

 in the ring of crystalline rocks towards the watershed between the 

 basins of the Congo and Lake Chad, so that these grits might be 

 traced into the system of the Biver Shari, the principal feeder of that 

 lake. The results obtained by the Authors were unfavourable to 

 this view, and it seemed as though the ring of crystalline rocks was 

 as complete on the north as elsewhere. 



The description of the iron-ores in relation to the plutonic massif 

 was of great interest, though possibly (from an economic point of 

 view) not of much importance at present, since * iron-mountains ' 

 existed in other parts of the world, in regions more accessible than 

 this. Yet the abundance of iron occurring in these old crystalline 

 rocks might, in part, account for the great spread of laterite noticed 

 by Barrat and others in connection with the superficial deposits of 

 the Congo Basin. 



Q.J. G.S. No. 213. 3 a 



