intersect it contain many fertile stretches of
alluvial soil, where cultivation is possible and which support a
considerable settled population, with several large towns and numerous
villages.

The third or southern division contains the highland plateaus of Asir
and Yemen in the west, and J. Akhdar in the east, which with a temperate
climate, due to their great elevation and their proximity to the sea,
deserve, if any part of Arabia does, the name of Arabia Felix--the
population is settled and agricultural, and the soil, wherever the
rainfall is sufficient, is productive. The Batina coast of Oman,
irrigated by the mountain streams of J. Akhdar, is perhaps the most
fertile district in the peninsula; Hadramut, too, contains many large
and prosperous villages, and the torrents from the Yemen highlands
fertilize several oases in the Tehama (or Tihama) or lowlands of the
western and southern coast. These favourable conditions of soil and
climate, however, extend only a comparatively short distance into the
interior, by far the larger part of which is covered by the great
southern desert, the Dahna, or Ruba el Khali, empty as its name implies,
and uninhabitable.

_Exploration._--Before entering on a detailed description of the several
provinces of Arabia, our sources of information will be briefly
indicated. Except in the neighbourhood of Aden, no regular surveys
exist, and professional work is limited to the marine surveys of the
Indian government and the admiralty, which, while laying down the coast
line with fair accuracy, give little or no topographical information
inland. For the mapping of the whole vast interior, except in rare
cases, no data exist beyond the itineraries of explorers, travelling as
a rule under conditions which precluded the use of even the simplest
surveying instruments. These journeys, naturally following the most
frequented routes, often cover the same ground, while immense tracts,
owing to their difficulty of access, remain unvisited by any European.

The region most thoroughly explored is Yemen, in the south-west corner
of the peninsula, where the labours of a succession of travellers from
Niebuhr in 1761 to E. Glaser and R. Manzoni in 1887 have led to a fairly
complete knowledge of all that part of the province west of the capital
Sana; while in 1902-1904 the operations of the Anglo-Turkish boundary
commission permitted the execution of a systematic topographical survey
of the British protect