Note 9 — Chapter I · FROM MOURZUK TO KOUKA IN BORNOU.

The surface is of a dark colour, with here and there patches and streaks of a snowy white. It is uneven from the heaping, as it were, of large flat clods on each other: these are all hollow underneath, and have a very uneven surface, from the number of projections. What I have remarked was observed in all the salt fields we have seen. The heaping of the salty clods, and the circulation of air underneath, are phenonema attending this formation which it is difficult to explain—Are they the production of art, or of nature alone? In the numerous gardens at Traghan, and other places left fallow, we observe, on the small scale, an appearance like this, and the earthy clods soon became strongly impregnated with salt: the degree is not comparable to what is seen in the large salt plain. The salt is of two kinds; one a white snowy-looking efflorescence, that is often several inches thick, the other with an earthy-coloured shining surface.—W. O.