Note 58 — 11. The Sand-Dunes.

The hot and disagreeable south and south-west winds which blow during the “khamsins” of the spring are much less constant in their direction; and though they produce thick sandstorms, they have always seemed to me to occasion rather a general scattering of the sand over the surface of the desert than to form deposits having very definite arrangement; moreover, they blow on relatively few days of the year. The far more prevalent cool strong north-north-west winds, on the other hand, often scarcely vary a point in direction for days together, and their coincidence with the direction of the dune-lines is very pronounced.