Notices of Memoirs — Permo-Carhoniferous Breccia. 465 



II. — Papers read in Section C {Geology), Meeting of British Association, 

 Australia, August, IQlIj.. 



(1) The Permo-Caeboniferous Breccia, a Desert roRMA.TioN. 

 By H. T. Ferrar, M.A., F.G.S.' 



DURING the meeting of the Association at Birmingham last year 

 members of this Section liad an ample opportunity for A'isiting 

 the chief exposures of the so-called Permian breccia of the midland 

 counties of England, This deposit may be briefly described as a mass 

 of sandstones and marls with occasional sheets of angular breccia, the 

 latter consisting in a large measure of volcanic rocks, grits, slates, and 

 limestones which can be identified with rocks on the borders of Wales. 

 The organic remains which have been recorded are few, hut such as 

 occur are indicative chiefly of terrestrial surfaces. 



The origin of the breccia has given rise to many speculations, 

 amongst which may be mentioned — 



1. Murchison (1839) regarded it as a volcanic or trappoid breccia 

 marking the position of underground masses of volcanic rocks hidden 

 under a cover of their own fragments. 



2. Ramsay (18.55) ascribed its origin to the existence of glacial 

 conditions in Permian times. 



3. Geikie (1892) says with regard to Scotland that the breccia has 

 evidently accumulated in small lakes or narrow fiords during periods 

 of great and rapid denudation following uplift of the Upper Carboni- 

 ferous rocks. 



4. Bonney (1902) concludes that breccias are usually indicative of 

 continental conditions, but that glaciers are necessary for the transport 

 of the larger boulders. 



5. Lapworth (1912) holds that they are the memorials of local 

 Alpine conditions. 



In Egypt a chain of fold-mountains forms the watershed between 

 the Nile and the Red Sea, and the mountains are intersected and 

 drained by steep-sided gorges or wadis. The climate is arid with 

 occasional heavy thunderstorms causing temporary torrents, which 

 sweep forward all rock-material loosened during the prevailing dry 

 climate. The wadi beds receive continuously a fresh supply of angular 

 debris shed from the adjacent bare hillsides, and any fragments which 

 may have become rounded or subangular are often shattered before 

 the next flood sweeps them forward another stage on their journey 

 towards a more permanent resting-place, namely, the alluvial plain at 

 the wadi-mouth. Blocks slipping down the bare hillsides become 

 scratched or they may be scratched by mutual impact during a sudden 

 rush of flood-water. Great blocks are often carried fifty or one hundred 

 miles down the wadi cliannels, and the agency of ice need not be 

 invoked to explain their transport. 



The valley fill of most wadis in the Eastern Desert of Egypt is an 

 unconsolidated breccia so similar to the breccia exposed on Ley Hill, 

 near Birmingham, that there is little room for doubt that the two 

 originated under similar climatic conditions. 



^ By permission of the Director-General, Egyptian Survey Department. 



DECADE VI. — VOL. I. — NO. X. 30 



