(5) Yemen. Tehamah. Yemen - Geology.
Yemen
Following the Red Sea coast down to its southernmost extremity at Aden, we have in view the third great geographical section, that of Yemen. It includes two regions, sea-shore and inland, the former of which is commonly called the "Tehamah." This is a wide strip of coast left by the mountain chain, which, continuing on from the Hejaz, runs down as far Aden, but hereabouts recedes somewhat to the east, thus forming an arc, in the curve of which lies the Tehamah. The mountainous district extends far inland, and gives out several minor branches, some of which reach about three hundred miles to the east.
Tehamah
Tehamah is, as might be expected from its topical and geographical conditions, a very hot region; it is one also of but moderate fertility, though the soil, an agglomeration principally of coral debris, is less absolutely barren than that of the Hejaz. The rains here are periodical, their fall coinciding with the epoch of the Indian monsoon; they give rise to numerous torrents, that traverse the plains, and some of which hardly dry up throughout year. The coast-line is indented by several small harbours and road-steads; intricate coral reefs render the approach everywhere difficult, often dangerous.
Yemen under which name the whole south-western quarter of the peninsula is popularly included, possesses many advantages, both of climate and soil, denied to the greater portion of Arabia. It is a highland country, formed by a labyrinth of precipitous hills and fertile valleys. The air is pure and even cool; the seasons are as regular as those of eastern India, and succeed each other in much the same order. No accurate survey has yet been made to determine the elevation of its mountains, some of which have been roughly, but perhaps incorrectly, estimated at five thousand feet in height; their general direction is from north-west to south-east. The largest plains, or rather plateaus, inclosed by them are that of Nejran on the north, that of Sanaa to the south, and that of Mareb to the east, on the frontier of the great desert. The oasis of southern Jowf, a basin-like depression occurring in the sandy waste that reaches inland from the high grounds of Yemen up to Oman, on the other side of Arabia, may also be reckoned as belonging to Yemen.
Geology of Yemen
Though the mountains are well supplied with water, no considerable rivers or streams find their way from them to the Red Sea, tropical evaporation combining with the light and porous quality of the soil to dry up the torrent beds; nor do any natural lakes exist, though artificial pools and tanks, in which water is preserved all the year round, have been constructed in plenty. Indications of volcanic action, long since extinct, abound throughout Yemen, where basalt formations compose a considerable and the most fertile portion of the coffee-bearing district; in other places Jurassic rock predominates, while granite occurs in patches here and there. Spar, agate, onyx, and carnelian are exported from Yemen; silver and gold are reported to have been found on its hills, but on doubtful authority.
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