460 Notices of Memoirs—T. O. Bosworth—The Keuper. 
beheading the longer westward drainages. The highest peaks usually 
consist of granite, which is sometimes foliated, and these high peaks, 
which rise majestically above the denuded schistose rocks, are not 
always on the actual watershed. Forms of rock and mountain 
sculptured by sandblast are not obvious, for the rain which 
occasionally falls destroys these and produces typical water-graded 
slopes. 
The western desert surfaces consist of a thin veneer of waste, 
except where monadknocks or the escarpments of the oases display 
solid rock. This veneer of waste is protected, as in the Antarctic 
regions, by a layer of pebbles, which prevents the wind transporting 
the lighter material and prevents the rain-water from flowing in 
definite channels. 
The eastern, or Etbai, desert shows bare hillsides, and the steep 
cliffs which form the wadi-walls are quite free from débris. The 
wadis or dry watercourses are at present being aggraded, and it is 
only in the wadi-beds that one finds the alluvium. This alluvium of 
boulders and rock-débris is usually from 5 to 50 feet in depth, and 
may be described as a torrential deposit. The only sorting of 
materials that is obvious in this region is that sorting due to water- 
action, where the volume of water and the slope of the ground are the 
determining factors. 
Sorting of fine material from the coarse is not as common as one 
would expect. A high wind (Beaufort scale, force 8) will only move 
pebbles and grit less than 5 mm. in diameter, so that a succession of 
winds of unprecedented force would be necessary to produce ‘ pebble 
beds.’ The pebbles of the gravels on the western plateau, near Wadi 
Natrum, are all rounded and water-worn, and form a heavy mantle 
over the land which prevents the wind from picking up the lighter 
material from below, which they protect. It is only those stones on 
the surface that are wind-etched or show the faceted form. ‘These 
gravels were deposited during the pluvial period, immediately pre- 
ceding the present arid one, and therefore it would seem that the only 
reliable test. to prove that a deposit was a desert formation would be 
to find in it tetrahedral and wind-etched stones. 
Photographs were exhibited to show some of the points referred 
to in this paper. 
III].—Tuer Ortcin or tHe Upper Keuprex or Lercestursurre. By - 
T. O. Boswortu, L.A., F.G.S. 
The Condition of the Rocks beneath the Keuper.—The Charnian 
igneous rocks beneath the Keuper are comparatively fresh right up 
to their surfaces, but where the marl has been denuded and the rocks 
are exposed to the present climate they are decomposed. 
The Surface leatures of the Rocks beneath the Keuper.—Smoothed, 
fretted, and curiously carved surfaces are seen at Mount Sorrel,’ 
Croft, Sapcote, Groby, etc., and usually wherever the marl rests on 
igneous rocks. They are often pitted and sometimes highly polished 
(e.g. at Narborough). But where the rocks are cleaved or broken, as 
1 Professor Watts, Geographical Journal, June, 1903. 
