242 MR. A. WADE ON THE EASTERN DESERT OF EGYPT. [May 19II. 



thickness, common in the Bunter Pebble-Beds of Lancashire and 

 Cheshire ; the angular breccias of Hilbre Island, and so on ; even 

 the striking eccentricity of the bedding- planes, as well as other 

 minor features, are all characteristic both of the Triassic pebble- 

 beds and of the ' gravels ' of the Red-Sea coasts. 



The Permian conglomerates of Shropshire and South Stafford- 

 shire 1 appear to show close resemblances with the coarse beds here 

 described. Calcareous conglomerates and breccias of igneous rocks, 

 which pass into more sandy beds, have been described ; while 

 Prof. Hull 2 has expressed an opinion that these beds originated in 

 the very manner that I have suggested for the Red-Sea igneous 



gravels. 



VI. Distribution of Pebbles. 



Despite the fact that the conditions already described will explain 

 many points in Triassic geography, those observers who account 

 for the distribution of pebbles in the Triassic Pebble-Beds, by 

 transportation by means of a large river, receive some support from 

 a study of the ' gravels ' on the western side of the Red-Sea Hills. 

 That a river should carry stones of moderate size for a distance 

 of 300 miles or more has seemed to be impossible. 



I have already shown that, on the eastern side of the Red-Sea 

 ranges, the fragments found in the ' gravels ' are derived from the 

 hills near to which they lie, and that they have travelled very 

 little in most cases. A similar state of things is observed in certain 

 localities in England, where the pebbles of the Bunter Beds can be 

 traced to neighbouring Mountain Limestones, cherts, sandstones, 

 and even veinstones. Fragments in the Permian breccias of 

 Staffordshire have also a local origin. 



On the western side of the igneous hills of the Red-Sea coast a 

 different set of circumstances has affected the distribution of the 

 rock-fragments ; they appear to have been carried along the main 

 wadis and old lines of drainage, to distances which compare very 

 well with those to wdiich some of the more widespread pebbles — 

 such as the liver-coloured quartzites — in the British Bunter Beds 

 may have been borDe. 



The distribution of these rocks from the igneous ranges of the 

 Red-Sea districts in the gravels of the valley of the Nile and 

 adjoining areas is shown very well in the accompanying sketch- 

 map (fig. 1, p. 243), which I have constructed from details given 

 by Barron & Hume. 3 These authors trace the pebbles from four 

 main centres of distribution : — 



(1) Jirra-Jidami Eange Granite. 



(2) Ai.eteq Range Gneiss. 



(3) J"bel Abu Garahish Schist. 



(4) . .ri District Schist. 



1 W. Wickham King, Q. J. G. S. vol. lv (1899) p. 97. 



2 ' The Triassic & Permian Rocks of the Midland Counties of England ' 

 Mem. Geol. Surv. 1869, pp. 14 et seqq. 



3 Egypt. Geol. Surv. Rep. 1902, pp. 121 et scqq. 



