813 REPORT—1899" 
6. On Sand-Dunes bordering the Delta of the Nile. 
Ly Vaucuan Cornisy, J.Sc., F.R.G.S., FCS. 
The author visited Egypt in April-May, 1899, in continuation of his work 
upon Sand-dunes (see ‘ Geographical Journal, March 1897, the first of a series of 
papers upon ‘Kumatology’). Observations of sand-dunes and allied phenomena 
were made upon twenty-three days along the line of the Suez Canal between Port 
Said and Serapeum, on the Syrian route from Kantara, in the neighbourhood of 
Ismailia, and on the line from Ismailia to Abu Hammad, between Cairo and 
Terieh, on the western margin of the Delta, and in the neighbourhood of Helwan 
and Sakara. About fifty photographs and eight drawings, suitable for reproduc- 
tion, were obtained of sand-dunes, wind-erosion structures, and of tree-planting 
directed against the encroachment of sand. The photographs of dunes include 
both Barchanes (or Medanos) and the curious hollows which, in Arabia, are called 
Fuljes, as well as gently undulating surfaces, covering the country like a mantle 
of snow, with no sharp ridge or slipping lee cliff. Measurements of ripples and 
dunes were made, and samples of sand were taken, from which (two only at 
present) micro-photographs have been prepared. 
Ripples—The author had previously measured twelve wind-formed ripples in 
the blown sea sand on the Dorset coast.. The average ratio of length to height 
was ‘ft = 184. The least height was ‘06 inch, and the greatest ‘34 inch. These 
measurements were, for the most part, of one or two individual ripples. Mr. E. 
A. Floyer measured six of the largest kind of ripples on the El Arish route, and 
obtained Pai ‘7 with H from 6 to 10°6 inches. The author measured thirty- 
seven consecutive ripples to leeward of a sand-dune near Ismailia. The ripples 
had an average height of 1°43 inches, and the average ze was 16:57. The appear-_ 
ance of these was intermediate between that of ripples where accumulation is rapid 
(which never grow large), and the large and nearly symmetrical ripples (? analogous 
to sastrugi), as much as 11] feet in wave-length, the formation of which 1s 
apparently accompanied by a considerable lowering of the general level. 
Dunes.—A tract of a few hundred acres of small, but true, dunes (not ripples) 
on a sandy foreland, exposed during the fall of the Nile, afforded an opportunity 
for similar measurements. 
Higher and lower dunes succeeded one another, and viewed transversely, the 
ridges were strongly undulating. Nevertheless, a line having been marked out in 
the up-and-down-wind direction, the average za for twenty-four consecutive dunes 
was found to be 18:04, average height 20 inches. Another set of measurements 
taken near the same line on the succeeding day, gave s 17:89 for twenty-three 
consecutive dunes. Apparently the ridges are formed of the nearly uniform e =18) 
shape, and lateral inequalities are subsequently developed in the manner explained 
in the ‘ Geographical Journal,’ June 1898, pp. 637-9, but these do not affect the 
average x The author hopes to make similar measurements of trains of larger 
dunes. 
The straight, slipping lee cliff of dunes is caused by the undercutting of the 
eddy. In the dunes near Ismailia a progressive development of the profile form 
was observed. At first both windward and lee slopes are very gentle, and the 
highest point is near the middle. Thesummit apparently moves to leeward, and the 
lee slope becomes steeper; a slipping cliff is formed on the upper part of the lee 
slope. This pushes back towards the summit, and the windward slope grows 
steeper. Finally, windward and average leeward slope become of nearly equal 
steepness, and the top of the cliff coincides with the summit of the dyne, 
