Sir J. TV. Dawson — Hocks of Assouan on the Nile. 101 



of its existence is during the " Lost Interval." It was then a large 

 land-mass of unknown size and shape, but evidently of continental 

 proportions. 3. At the beginning of the Palaeozoic this continental 

 mass was nearly lost by submergence ; all that remained being the 

 well-known Archaean areas, with a large extension on the eastern 

 margin of the present continent. The masses formed the nucleus 

 from which grew the present continent, with more regularity than 

 before, but with some very large oscillations, the greatest of which 

 was at the end of the Palaeozoic, and the last of which was at the end 

 of the Tertiary and beginning of the Quaternary. 

 Berkeley, California, January lith, 1886. 



II. — Note on the Geological Eelations of'Eocks prom Assouan 

 and its Neighbourhood. 



By Sir J. William Dawson, C.M.G., L.L.D., F.R.S. 



DB. BONNEY having been so kind as to examine microscopically 

 and describe a collection of crystalline rocks which I made 

 in the vicinity of Assouan on the Nile, I have prepared the following 

 notice of the geological conditions, to accompany his descriptions, 

 referring, however, to the notes on the locality given in my paper 

 in the Geological Magazine for Oct. 1884. Eeference may also 

 be made to the paper of Lieut. Newbold in the Journal of the 

 Geological Society, vol. iv., and to that of Mr. Hawkshaw in the 

 same journal, vol. xxiii. Lartet has given in his Geology of Pales- 

 tine a summary of the observations of Eussegger, Eiviere and Figari 

 Bey on the crystalline rocks of the Nile, and the allied rocks of the 

 Sinaitic Peninsula have been described by him, by Bauerman 1 and 

 by Holland, 2 and more recently by Hull. 3 All these authors have 

 given, more or less distinctly, a series of gneisses and micaceous 

 and hornblendic schists associated with intrusive granites and 

 diorites as the oldest rocks of these districts, and succeeding these 

 in geological age, certain slates and associated rocks, with porphyry 

 and basanite in beds and veins. 



The best section which I had an opportunity to examine of the 

 older series was near the town of Assouan, in a railway cutting 

 crossing the ridge between the river and the valley lying to the 

 east of the town, and which exposed the beds in a perfectly fresh 

 and unweathered state for about a quarter of a mile, beyond which 

 they were more or less imperfectly seen for about 800 yards, until 

 they were covered by the lower beds of the Nubian Sandstone un- 

 conformably superimposed on them. 



I have given a section of the beds exposed in this cutting in the 

 paper above cited. They are nearly vertical with a strike N. 10° E. 

 As seen in the cutting, about four-fifths (Series A in Note) of the 

 thickness exposed consisted of schists with black mica and black 

 hornblende, the remainder being orthoclase gneiss regularly strati- 

 fied and numerous dykes of reddish hornblendic granite (Series B. 

 in Note). Further to the south the same rocks are seen to be 



1 Quart. Journ. Geol. Soc. vol. xxv. 2 Ord. Survey Sinai. 3 Mount Seir. 



