PHYSICAL FEATURES. xxxix 
descent to the first of the fertile spots on this side of the depression is extremely 
steep and rugged. At the foot an abundance of Alhagi manniferum was met with, 
along with clamps of tamarisk, Calligonum, and wild palms. 
No mention has been made of any animal life having been observed by the members 
of Rohlfs's expedition along this route, but the comparative abundance of vegetable life 
evinced by the number of species recorded sanctions the supposition that animal life is 
equally well represented. The disturbance necessarily created by the passage of a 
large caravan through the intense and noiseless repose of the desert would scare 
animals away, and this doubtless largely accounts for the meagre reference to their 
presence by travellers. Moreover, the winter, as has been before pointed out, is a 
season of torpidity with reptiles, and, besides, not a few are nocturnal in their habits 
and have to be specially sought for by turning over stones and by searching carefully 
in crevices of rocks and at the roots of plants. 
The desert between Farafreh and Dakhel begins to rise at Bir-Dikker, 95 metres 
above the sea, and at this point a great zone of sand extends nearly to the northern 
escarpment of the oasis of Dakhel. In the neighbourhood of Bir-Dikker, Jordan met 
with Zygophyllum album, Acacia nilotica, Juncvs maritimus, tamarisks, isolated date- 
palms, and some other desert plants ; but between this portion of the Farafreh 
depression to near the Dakhel escarpment he saw no vegetation. However, at the 
southern end of the zone of sand he found some bushes of Fagonia arabica; and at 
this part of the plateau, 370 metres above the level of the sea, Rohlfs afterwards observed 
Anabasis articulata. Two species of Acanthodactylus 1 , viz. A. boskianus and A. partialis, 
were obtained by the Rohlfs Expedition, probably either at Bir-Dikker or to the 
southward of the sand zone. Cailliaud describes the route as traversing at first a more 
or less sandy limestone plain, and afterwards a tract of sand many kilometres in length, 
forming a narrow valley along which it passes. It then ends in another plain strewn 
with irregularly-shaped little rocks, its surface cut up and waved superficially as if by 
water flowing towards the north. The summit of this plain is covered with jagged 
conical hillocks, giving a wild and imposing aspect to the scene and constituting a 
perfect labyrinth of rocks. The highest part just before the descent is made into the 
depression of Dakhel lies 445 metres above the level of the sea. From the edge of the 
escarpment the traveller, for about half an hour, descends through magnificent scenery, 
between the upper Pass or Bab-el-Jasmund, and the lower Pass or Bab-el-Cailliaud 
(Introd. PI. V.), so called by Rohlfs in honour of the French traveller. In these 
passes, but especially in the lower, sand accumulates in great drifts, very difficult to 
traverse owing to its loose and shifty character. 
Sir Archibald Edmonstone and his companions seem to have been the first Europeans 
who, in modern times, visited this oasis of Dakhel (Introd. PL VI.). Their visit took 
1 These two species have been included in the Table of Distribution under Oasis of Dakhel, as they were 
found in that neighbourhood. 
