Note 18 — Chapter I · FROM MOURZUK TO KOUKA IN BORNOU.

We had a fine wadey the greater part of the way, and many patches of saline incrustations; some exposed beds of red sandstone, containing numerous nodules of iron ore. Hills of much blacker colour; and a few have the appearance as of ruins of towns and castles, on their summits. Passed three springs, like the oozings at Traghen. A large tract of black surface, as if the situation of an extensive salt bed, from which the salt had only been removed a few years; it extends more than four or five miles to the eastward, and was more than a mile across, on our road. It is black and crispy, but has none of the irregular heapings taken notice of in other salt plains.

There is another small town about two miles to the westward, of the same name. Round it are a number of mud elevations, which appear as if produced by mud volcanoes; but these are artificial, and made for the preparation of salt. I had long wished to see the extensive salt plain that afforded such copious supplies: originally, no doubt, the large spaces I have several times noticed afforded abundance, but the re-production could not keep up with the quantity taken away. Art was employed to obtain Nature; shallow pits were dug, which soon filled with water, and its evaporation left thick layers of salt: high embankments were raised round these, evidently to prevent currents of air. These places have much the look of our tanyards, with small pits partitioned from each other. The water is now strongly impregnated; in summer a thick crust is formed, which is the salt in use. One of these works apparently yields a large quantity of salt every year. When removed, the sordes are heaped up on the embankments. In the recesses there are many stalactites, of a beautiful white colour, which consist of muriate and carbonate of soda.

The great mystery is, the origin of the salt in all situations in which the water is near the surface, and the inclemency of the water prevented by shelter. It is highly probable all this vast country was once a salt ocean; its height is nothing, considering its distance inland. What effect has the want, or almost want of rain,—for, as far as I can learn, no salt formations exist within the boundaries of the rains? There are many fine fresh springs issuing from the soil, and none of the wells are brackish; when the water, however, remains some time stagnant, it gets impregnated with saline matter.—W. O.