West of Egypt was a dry and sandy tract, dotted with oases, but otherwise only habitable along the shore, which in the time of the Persian Empire was occupied by a number of wild tribes who were mostly in the lowest condition to which savage man is capable of sinking.  The geographical extent of this tract was large, exceeding considerably that of Egypt; but its value was slight.  Naturally, it produced nothing but dates and hides.  The inhumanity of the inhabitants made it, however, further productive of a commodity, which, until the world is christianized, will probably always be regarded as one of high value—­the commodity of negro slaves, which were procured in the Sahara by slave-hunts, and perhaps by purchase in Nigritia.

Still further to the west, and forming the boundary of the Empire in this direction, lay the district of the Cyrenaica, a tract of singular fertility and beauty.  Between Benghazi, in east longitude 20 deg., and the Ras al Tynn (long. 23 deg. 15’), there rises above the level of the adjacent regions an extensive table land, which, attracting the vapors that float over the Mediterranean, condenses them, and so abounds with springs and rills.  A general freshness and greenness, with rich vegetation in places, is the consequence.  Olives, figs, carobs, junipers, oleanders, cypresses, cedars, myrtles, arbutus-trees, cover the flanks of the plateau and the hollows which break its surface, while the remainder is suitable alike for the cultivation of cereals and for pasturage.  Nature has also made the region a special gift in the laserpitium or silphium, which was regarded by the ancients as at once a delicacy and a plant of great medicinal power, and which added largely to the value of the country.

Such was the geographical extent of the Persian Empire, and such were the chief provinces which it contained besides those previously comprised in the empires of Media or Babylon.  Territorially, the great mass of the Empire lay towards the east, between long. 50 deg. and 75 deg., or between the Zagros range and the Indian Desert.  But its most important provinces were the western ones.  East of Persepolis, the only regions of much value were the valleys of the Indus and the Oxus.  Westward lay Susiana, Babylonia, Assyria, Media, Armenia, Iberia, Cappadocia, Asia Minor, Cyprus, Syria, Palestine, Egypt, the Cyrenaica—­all countries of great, or at least considerable, productiveness.  The two richest grain tracts of the ancient world, the best pasture regions, the districts which produced the most valuable horses, the most abundant of known gold-fields, were included within the limits of the Empire, which may be looked upon as self-sufficing, containing within it all that man in those days required, not only for his necessities, but even for his most cherished luxuries.