244 ME. A. AVADE ON THE [May I9II, 



The pebbles have travelled in more or less westerly directions 

 down the wadis, into the important north-and-south wadi which 

 continues the line of the Nile north from Qena. They are 

 abundant for some distance to the north and south of Qena. 

 Thence they have been carried northwards down the Nile Valley. 

 They were found by Mr. Beadnell x on the western side of the Nile, 

 this fact having been used in the determination of the age of that 

 river. The most interesting occurrences of these rocks, which the 

 Survey geologists say ' could only come from the Red Sea ', 2 are 

 at Heluan, a few miles south of Cairo, where they were noted by 

 Mr. Beadnell, and in the Delta itself, where they were found in 

 the Royal Society's boring at Zagazig. 3 Thus these rocks have 

 been river-borne for at least 400 miles. 



A careful examination of the Jubal and Gaysum groups of 

 islands showed that these ' gravels ' do not exist upon them. 

 This suggests that these islands have come into existence since 

 Pleistocene times, the age generally assigned to the ' gravels.' 



A very thin bed of ' gravel,' containing pebbles of igneous rocks, 

 does occur beneath the Upper "White Limestone Series on Jubal 

 Island. The pebbles are evidently derived from the igneous rocks 

 of the mainland, and consist of pink granite, felsite, andesites, and 

 porphyries. Since the age of the limestone ranges perhaps from 

 Upper Miocene to Pleistocene, the presence of this gravel suggests 

 a local extension of the land-area at some time immediately prior 

 to those periods. This has an important bearing upon the sequel. 



VII. Sands and Maels. 



The Gulf of Suez, with its parallel ranges of hills, appears to act 

 as a funnel down which cooled air from the north is drawn towards 

 the Equator. Thus there is an almost constant northerly wind, 

 which frequently blows with violence. 



Zeit Bay and the Gulf of Jemsa are both directly in continuation 

 of sandy tracts of country, from which there is a continuous passage 

 of dust and sand. Both are at certain seasons bordered with 

 saline mud containing very much fine material, along with some 

 coarser sand-grains. 4 The passage of the dust must be checked 

 by the water of these bays, and the fine mud is the result of the 

 accumulation which necessarily takes place under these conditions. 

 Here, then, we have in actual progress the state of things adduced 

 theoretically by Mr. H. C. Beasley 5 to account for the Keuper Marls 

 (so-called) of South Lancashire and Cheshire. In these districts 



1 J. W. Dawson, 'Notes on the Geology of the Nile Valley' Geol. Mag. 

 dec. 3, vol. i (1884) p. 289 ; see also T. Barron & W. F. Hume, Egypt. Geol. 

 Surv. Eep. 1902, p. 121. 



2 T. Barron & W. F. Hume, op. cit. p. 128. 



3 J. W. Judd, ' Second Eeport on a Series of Specimens of the Deposits of 

 the Nile Delta ' Proc. Eoy. Soc. vol. lxi (1897) p. 32. 



4 T. Barron & W. F. Hume, op. cit. pp. 78 & 79. 



5 Proc. Liverp. Geol. Soc. vol. x, pt. 2 (1905-1906) pp. 79 et seqq. 



