can be carefully examined, all speculation as to their date and origin must be vague and unreliable. It seems most probable that the rude savages who fashioned them for their own use deliberately chose positions offering the best security against attack, either from human enemies or wild beasts. Whether to facilitate entrance they used a rude ladder, such as the notched trunk of a tree, or relied on the superior climbing power which the freer use of the foot confers on most savage people, must remain uncertain. As usual in this country the Moors refer these, as well as all other antique remains, to the ‘Christians,’ and stories of concealed treasure connected with all such monuments, of whatever date, make it almost impossible to attempt to explore or examine them. The work can be undertaken only by a traveller authorised by a special order of the Sultan, who should also be prepared by handsome presents to secure the goodwill of the local authorities. We halted for luncheon in a convenient spot, and gave some time to botanising on the rocks, where, along with other plants, we found a beautiful variety of the _Stachys saxicola_ of Cosson, densely covered with very long, white, silky hairs. It was near to five o’clock before we were again under way. For some time the defile continued, the cliff-like walls still showing at intervals excavated rock dwellings, and at one point it receives a tributary stream, with a bed now dry, which had cut a similar trench, and whose cliffs also showed the traces of rock dwellings. As we advanced, always ascending, we gradually emerged from the defile, and found ourselves on the slope of the hills that extend northward from the base of the Great Atlas for a distance of thirty or forty miles, and are probably continuous with the low range that we crossed between Shedma and Aïn Oumast. There must be some change hereabouts in the mineral composition of the limestone rock, if not in its geological age; as from about this point the surface was much less barren, and the vegetation more varied. Among other fine _Cynaraceæ_ we saw here _Atractylis macrophylla_ of Desfontaines, only once before met in our journey.