206 Capt. H. Lynes & W. Campbell Smith— 
Preliminary Note on the Rocks of Darfur. 
By Captain Husert Lynss, C.B., C.M-G., R.N., and 
W. CampBeLL Situ, M.A., F.G:S. 
Published by permission of the Trustees of the British Museum. 
i the course of a journey from El Obeid to Jebel Marra, in 
Darfur, Captain Hubert Lynes collected a number of the rocks 
from the volcano of Dereiba and from various other points on 
the route, shown in the map (Fig. 1). The rocks of this area have 
not been described hitherto. The following notes give a brief 
description of the nature of the country, with petrological details 
of the rocks collected. 
Darfur is a vast plain, clad with bush and scrub, about one-fifth 
as large as the combined area of the British Isles, with a mean 
altitude of some 2,300 feet above sea-level. The highest part of this 
plain lies in the centre of the Province, whence it slopes very gradually 
downwards in all directions, except, perhaps, to the north. The 
surface is undulating with huge mile-long sweeps of almost 
imperceptible gradient, broken only in a few places by shorter and 
steeper undulations, which form low rolling hills. 
The only important structural features which rise from the plain 
of Darfur are the mountains of Jebel Marra, including the extinct 
volcano of Dereiba, some high ground observed by Tilho round 
Mount Durbulla, in approximately lat. 14° N., long. 234° E., and 
numerous groups of lower hills, maimly in the northern part of the 
Province, rising on the average to about 1,500 feet above the plain. 
Of the last the most isolated and singular group is that of Jebel 
Meidob, some 130 miles N.E. of Hl Fasher, which 1s reported to 
contain a crater and a salt-lake. 
Between the eastern borders of Darfur and the White Nile stretches 
the Province of Kordofan, also in the main a vast bush and scrub- 
clad plain partly studded with denuded hills and kepjes, which to the 
south merge into the mountainous country of the Nuba Mountain 
Province. Some of the rocks of this area have already been described 
by Linck.? Before starting on his main expedition,Captain Lynes went 
south to Dilling, following a route some 12 miles to the west of the 
El] Obeid—Kadero route taken by Linck. The first rocks noticed 
by Lynes on the El-Obeid—Dilling route were at Khor el Haggis. 
The specimen collected here (48)? is a typical troctolite, consisting of 
equigranular (2mm. grain) olivine and basic labradorite, near 
Ab,, An,. The felspar is quite fresh, and is traversed by radial 
cracks emanating from the olivine, which is partly serpentinized, 
though less so than in the troctolite of Coverack Cove (Cornwall). 
? 
1 G. Linck, “ Beitrage zur Geologie und Petrographie von Kordofan ”’ : 
Neues Jahrbuch fiir Min., etc., B.B. xvii, 1903, pp. 391-463. 
2 The numbers in brackets are the serial numbers of the specimens as 
recorded in the rock-registers of the Department of Minerals, British Museum 
(Natural History). 
