XXxii INTRODUCTION. 
sometimes enormous. In the early morning it may be —4' Cent., and in the afternoon 
as much as 37° Cent. Associated with these extremes there is an ever-recurring 
expansion and contraction of the materials composing the surface of the desert, which 
in time leads to the complete shattering of pebbles, stones, and rocks. The character 
of the climate is brought out in the following brief summaries of the itineraries of 
Cailliaud and other travellers 1 . 
Although much can be learned regarding the physical features of the Libyan desert 
from the writings of Browne 2 and those of succeeding travellers, the names of 
Cailliaud, Rohlfs, Zittel, and Jordan stand out prominently as the most eminent 
authorities on that remarkable and deeply interesting area of North-eastern Africa. 
The first 3 of these distinguished travellers, favoured by the goodwill of Mohammed 
Ali, visited, in 1S19— '20, five of the oases of the Libyan desert, besides the oasis of 
Siwah, where Boutin had lost his life a few years previously. Eohlfs's Expedition 4 , 
of which Zittel 5 , Jordan 6 , Acherson 7 , and Eemele 8 were members, proceeded to 
explore the Libyan desert under the auspices of the Khedive Ismail Pasha, leaving 
Assiut in the latter half of December 1873, and returning to the Nile valley in the end 
of March of the following year. 
Browne, on his visit to the oasis of Siwah 9 , Feb. 1792, followed the coast from 
Alexandria, only losing sight of the Mediterranean when he struck southwards to reach 
his destination. The route was generally smooth and sandy, but many spots were 
marked with verdure that relieved the general aspect of barrenness. In the places 
where he encamped he usually met with a species of jerboa 10 , a land-tortoise (Testudo 
leithii), some lizards and serpents, but not in great numbers. Snails, however, were very 
abundant, attached to the thorny shrubs on which the camels fed. A few hares u were 
observed in the neighbourhood of the springs, and the tracks of antelopes (gazelles) 
1 Phys. Geogr. u. Meteorologie der libysehe Wiiste. Rohlfs'schen Exped. 1873-74. 1870, pp. 127-128. 
2 Browne (W. G.), Travels in Africa, Egypt, and Syria, 1792-98. 
* Cailliaud (M. P.), Voyage a Meroe et au Fleuve Blanc, 1819-22. 4 vols. 1S26. 
Rolilfs (Gerard), Drei Monate in der libysehen Wiiste. 1S75. 
Zittel (Karl A.), Beitraege zur Geologie u. Palaeontologie der libysehen Wiiste, &c. 1S83. 
6 Jordan (W.), o/>. cit. 
7 Acherson (P.), Botanische Zeitung von Dr. Von Barry u. Kraus, 1874, nos. 38-40. 
' Eemele, Pbotographische Album Rohlfs'schen Exped. 1870. 
Since W. G. Browne's day, Siwah has been visited by many Europeans, e. <j. Fr. Hornemann, 1798; 
Boutin, 18 — ?; Belzoni, 1S1U; Cailliaud, 1819-20 ; Drovetti, 1820 ; Minutoli, 1820-21, accompanied by 
Hemprich and Ehrenberg as naturalists, Scholz as orientalist, Gruoe as astronomer; J. R. Pacho, 1826; 
Bayle St. John, 1849; Hamilton, 1850; Rohlfs in 1869, and again in 1874 accompanied by Zittel, Jordan, 
&c. ; Robecchi-Bricchetti, 1880; Weld Blundell, 1894; W. Jenuiugs-Bramly, 1890 ; Silva White, 1898. 
Ehrenberg, on his journey from Siwah to Alexandria, discovered the form known as Scirtomys tetra- 
daclylus (Licht.). 
Ehrenberg recognized the coast hare that he met with on the above route to be Lepus agyptius. The 
hedgehog, which also occur,, he regarded as distinct from Erinacsus uni-it"*. 
