The Geology of some Regions of Equatorial Africa, 319 



2. ' The Geology of Mount Iluwenzori and some Adjoining 

 Regions of Equatorial Africa/ By G. E. Scott-Elliot, Esq., M.A., 

 B.Sc, E.L.S., and J. W. Gregory, D.Sc, E.G.S. 



Iluwenzori is a mountain between the Albert and Albert 

 Edward Nyanzas. Topographically it is a narrow ridge which 

 extends for about 50 miles in a direction from N.N.E. to S.S.W. 

 Its summit attains a height of 16,500 feet. The western 

 slope is at an angle of 22° ; the eastern slope at about one of 4°. 

 The authors describe sections across the ridge at right angles to 

 its trend. These show that Iluwenzori is not volcanic, nor is it 

 a simple massif of diorite. Epidiorite occurs only as banded, 

 sheets in the schists on the flanks of the mountain, and is not the 

 central rock of the ridge. The strike of the flanking schists seems 

 to run concentrically round the ridge as though the central rock 

 were intrusive into them. The highest rock collected, a coarse- 

 grained granite or granitoid gneiss, may be an intrusive igneous 

 rock, but it may be part of the old Archaean series faulted up ; 

 there is nothing in its microscopical characters to separate it from 

 the Archaean rocks, and the authors think it probable that this 

 rock was raised into its present position by faulting. In this case 

 Iluwenzori is simply composed of an orographic block or ' scholl,' 

 which was at one time probably part of a wide plateau of Archaean 

 rocks. 



There is abundant evidence of volcanic action around Iluwenzori, 

 for the plains, especially to the east and south-east, are studded 

 with small volcanic cones, arranged on lines which radiate from 

 Iluwenzori. 



It is affirmed that evidence points to the former occupation of the 

 Nyamwamba, Mubuku, and Batagu valleys by glaciers, roches 

 moutonnees of typical character having been noted in the two 

 former valleys. 



The country round Buwenzori consists of rocks which may be 

 conveniently grouped into two series — one composed of gneisses and 

 schists, and the other of non-foliated sediments. The former (the 

 Archaean series) are of the type that has an enormous extension in 

 Equatorial Africa, and forms the main plateau on which all the 

 sediments and volcanic rocks have been deposited. 



The sedimentary rocks are probably Palaeozoic, possibly pre- 

 Carboniferous, but in the absence of fossils it would be unsafe to go 

 beyond this statement. 



3. ' On Overthrusts of Tertiary Date in Dorset.' By A. Strahan, 

 Esq., M.A., F.G.S. 



The results given in this paper were obtained during a re-survey 

 of South Dorset on the 6-inch scale. The disturbances can be 

 divided into two groups, — the one being mainly of Miocene date, and 



