Large masses of tabular basalt, and irregular precipices, common to this formation, are scattered over this range of hills, and extend over all the plains which environ them. The most lofty hills are those which present the most massive façades of tabular basalt; the sides sometimes exhibit a step-like appearance, and in many instances are overhung by pillars, curved, inclined, and perpendicular: these produce a singular effect, not devoid of grandeur. The lower stratum of all these hills is invariably limestone, mixed with a reddish clay. Hills of the same are found bordering upon, and in some cases joining, the basaltic ones; some of these are strewed over with a covering of basalt stones of various sizes and forms, none of them large, from three to eighteen inches in circumference, but still showing the colour and structure of the soil on which they are spread. Other hills of limestone are also indiscriminately found without the slightest particle of basalt on them, although in the immediate vicinity of what could easily be imagined the ancient crater of a volcano, which had showered a sombre covering heaved from the very bowels of the earth, on all the then existing hills and plains which surrounded it. Some of these limestone hills have been cut through, either by the falling of masses of rock from the higher hills, or by violent watercourses; and a section of them reveals nothing but pure limestone mixed with clay. The Souda, or Gibel Assoud[4], extend from north to south, three days’ journey, but in so winding a direction, as not to exceed thirty-five miles at the utmost in a straight line: to the west, as far as the well called Assela, on the road to the Shiati, where the red clay hills continue alone, and join the hills at Benioleed: to the east, they extend three days on the road to Zella, or Bengagi, to a wadey called Temelleen.