486 EEPORT— 1881. 



region of Arabia. Few of the perennial streams reach the shore in the 

 dry season — most of them are fiumaras. 



The eastern end of the island is most destitute of water. Here in 

 the dry season are no rivers, and, springs being rare, it is the most arid 

 region. 



Igneons, metamorphic, and sedimentary rocks compose the island. 

 The fundamental rock is granitic. This crops out, as I have mentioned, 

 towards the middle of the island, forming a series of bare pinnacles and 

 crags, projecting, with singularly fantastic look, from the plateau, below. 

 This rock also shows on the slopes of the valleys and ravines below the 

 compact limestone which caps it and forms the surface rock of the hill 

 plateaux. This limestone attains in places, as seen on the cliff faces, a 

 thickness of two or three hundred feet. Superficially over wide areas it 

 is rotted and broken into a jagged surface, over which progression is by 

 no means easy, while at other spots it forms broad, smooth slabs. A shaley 

 rock and coarse-textnred purple sandstone, in beds dipping at all angles, 

 crop out in the valleys and on the shore, whilst forming the shore-plains 

 and the bases of the valleys is a recent breccia and conglomerate. Cutting 

 through all these rocks and altering them to a considerable extent, occur 

 dykes and extensive masses of doleritic rocks and felstones, which vary 

 much in texture. 



Professor Bonney, who is working out the rock specimens, tells me he 

 has nearly completed his report, and we may therefore soon hope for 

 more definite knowledge of the geology of the island. 



The soil resulting from such petrological conditions is correspondingly 

 varied, correlated with which is a varjing character in vegetation and 

 scenery. 



In the valleys on the banks of the streams, especially in the granitic 

 region, a deep rich red soil is found, and where there is water perennially 

 it is covered by a luxuriant growth. As the limestone composes the 

 greater part of its superficies the plateau appears barren. Where, 

 however, the limestone has rotted, a series of nooks and crevices occur, 

 in which, where a soil has collected, an Aloe, Kalanclwe, or other 

 succulent finds a congenial habitat. But upon the limestone plateau, 

 especially at the eastern and western ends of the island, occur depressions 

 varying in width from some hundi-ed yards up to a mile or more, girt on 

 every side by the cavernous limestone cliff, with perhaps a narrow outlet 

 through it at one or more points. These, which have all the appearance 

 of lagoons, or at least of enclosed water-basins, are floored now by a rich 

 red soil on which a crop of coarse grass, small herbs, and low trees vege- 

 tates. On the shore-plains the soil is light and sandy. 



In its climate Socotra contrasts favourably with the adjacent shores 

 of Arabia and Africa. 



During the N.B. monsooD, from October to April, it is cool. January 

 and February are the most pleasant months. But during the rest of the 

 year it is exceedingly disagreeable. Rain falls twice in the year, at the 

 changes of the monsoons, at which times the stream-courses are filled 

 with mighty torrents. The temperature of course varies much with the 

 altitude, and one may pass in the course of a few hours from the tropical 

 heat of the shore plains to the cool temperate air of the mountain ranges. 

 The average temperature on the plains in January is said to be about 70°, 

 but in the hotter months it is as much as 86°. But on the plateau the 

 temperature at nights often goes down to 52°. The higlier peaks are, at 



