Vol. 65.] SANDSTONE, ETC. SOUTH OF KHARGA OASIS. 43 



Distance from Berts, i Bearing from Ben's. 



35| kilometres. 



180° 



47* 



181° 



48 



18-1° 30' 



50 



18S° 



m 



181° 30' 



48i 



165° 30' 



35* 



161 c 



365- 



153 c 



A glance at the accompanying map (PI. II) will show that these 

 granite-bosses, which vary from 100 metres to 3 kilometres in 

 length, lie along well-marked east-and-west lines ; although isolated, 

 the exposures A, G, and H may be regarded as belonging to one and 

 the same crystalline ridge; so also F, B, C, and D must bo looked 

 upon as portions of a second and parallel ridge. The small knob E, 

 although not obviously connected, is probably related to others in 

 the sand-covered country stretching to the west and south-west. 



A. — Although no one of the bosses corresponds with the position 

 assigned to Jebel Abu Bayan on the Egyptian Survey-maps, it is 

 probably this exposure that is referred to and was visited by 

 Capt. Lyons. The name appears to be applied indiscriminately to 

 this and to some of the hills farther south ; but I propose, in order 

 to avoid confusion, to restrict it to this one alone. Approached 

 from the north, Jebel Abu Bayan appears as a dark bun-shaped 

 eminence rising out of the dunes. As a matter of fact, it is situated 

 in an open space quite clear of sand, the ground rising to it from all 

 sides, except possibly on the west. It is an unpicturesque-looking 

 hill, and from a distance shows few of the characteristics of an 

 igneous boss, being indeed less conspicuous than many of the 

 ordinary sandstone-capped hills of this desert. Both coarse- and 

 fine-grained granites occur, although the latter are most in evidence 

 owing to their superior hardness and powers of resistance to 

 weathering. Various dyke-rocks are also to be seen. 



On three sides of the hill the junction with the sedimentary rocks 

 is invisible, but at the western end coarse pink and yellowish false- 

 bedded ferruginous sandstones are met with, dipping away from the 

 granites at a low angle to the north-west. Some of the sandstone- 

 beds are very coarse, containing numerous small subangular pebbles 

 of quartz. The actual junction is observable at one point, the 

 eastern end of the sandstone-ridge immediately west of the igneous 

 slope. There the sandstone appears to pass down into a decomposed 

 granite, reddish in colour, friable, and full of pieces of quartz and 

 powdered felspar. The impression left on my mind by this junction 

 Avould have been in favour of the sandstones having been deposited 

 on the granite, if it had not been for the rather marked tilting of 

 the former ; altogether, I did not feel justified in drawing any 

 definite conclusion from the evidence met with. 



