On July 4, for the third and last time, I crossed the line that separates the waters of the Chad basin from that of the Mediterranean, at the Kowra Pass, which is at an altitude of about 4000 feet; then, coming down from spur to spur across the Djebel Kowra I reached the Djebel Om, a very broken region, chaotic in appearance and covered with scanty scrub, stunted, prickly, and almost leafless, where our exhausted camels found but little sustenance. From place to place we crossed recently worked deposits of salt. The salt is very much mixed with earth, and the richest beds are indicated by the swollen, cracked, and friable character of the soil. As in other salt-producing regions in Central Africa, the salt-bearing earth is washed for a longer or shorter time in washing and filtering baskets; then, when the saline solution has become concentrated enough, it is heated in clay jars, on the inside of which the salt crystallizes as the water evaporates. The product thus obtained, though impure and grey-coloured, is pleasant to the taste, and supplies a great part of the market in Dar Four and the neighbouring countries. In the afternoon of the 5th, leaving behind us the last salt-beds of Om Bakour, we got clear away from the mountainous zone and made our way for four days across the undulating plains that stretch eastwards beyond El Fasher. The further I went the clearer grew the panorama of the chain I had just crossed. Spur after spur, fantastically shaped, extended in long succession to the north, while towards the west and the south the summits of the Dourboullé and the Djebel Marra towered above the rest of the mountains and stood out boldly against the sky, especially at dusk, a moment at which the light was particularly favourable for the observations required for determining their position and altitude. In the plain of shifting sand, dotted here and there with isolated rocks of huge size, real natural geodetic signals, the landscape stretched away monotonously, almost without trees or even grass. The fertilizing rains of the first few days of July not having reached further than the djebels I had just crossed, the sowing had not begun, and the inhabitants of the villages that succeeded one another at regular intervals down the valleys I traversed were feeling a little uneasy.