﻿666 GEOLOGY OF PART OF THE CONGO FREE STATE. [Aug. I905. 



Dr. John W. Evans referred to the occurrence of similar hills of 

 iron-ore in connection with the crystalline schists in British Central 

 Africa and Southern India. He thought that the word laterite 

 should be confined to the products of the alteration of alumina- 

 bearing silicates, in the course of which the silica was wholly or 

 partly removed. He also remarked on the interest of the occur- 

 rence, in the country dealt with in the paper, of the north-westerly 

 and south-easterly strike which was so common in the Equatorial 

 regions of the earth's surface. 



Mr. Howe, in reply to Mr. Gibson, said that some of the rocks 

 described undoubtedly bore a resemblance to certain gold-bearing 

 rocks of South Africa ; but no gold had been noticed in the area 

 covered by the paper, although it had been discovered in the region 

 somewhat to the south. 



The results of M. Preumont's traverses brought forward no facts in 

 favour of an extension of the so-called Karroo type of deposit in 

 the Upper Uelle Basin ; on the contrary, these rocks appeared to be 

 absent over the whole area east of the granite-ridge which separates 

 the Uelle from the Rubi. The specimen of chert from Suronga 

 was obtained from loose blocks, therefore nothing certain could be 

 deduced from that occurrence. The 'Karroo' line on Mr. Hudleston's 

 map would still remain broken, so far as the evidence now presented 

 was concerned. 



With regard to the word laterite, it was not proposed to use 

 that name for the conglomeratic deposits directly derived from the 

 breaking-down of the iron-ore-beds of Mount Tena, Mount Graima, 

 Mount Angba, etc. : ' limonitic conglomerate ' was the term used by 

 M. Preumont in all cases. But there seemed to be no doubt that 

 some of the laterite described by Cornet was correctly so named, 

 and was represented, along with other forms, in that part of the 

 Congo Basin. 



