assessed, in addition to their taxes in money, for the maintenance of
the King's household and army in kind. Under this assessment the King is
maintained for four months out of the twelve by Babylonia, and for the
remaining eight by the rest of Asia together, so that in wealth the
Assyrian province is equivalent to a third of all Asia."

The "Asia" over which the Achaemenids ruled included Russian Central
Asia and Egypt as well as modern Turkey and Persia, and Egypt, under the
same assessment, merely maintained the local Persian garrison[55]. Its
money contribution was inferior too--700 talents as compared with
Assyria's 1,000; and though these figures may not be conclusive, because
the Persian "province of Assyria" probably extended over the northern
steppes as well as the _Sawâd_, it is certain that under the Arab
Caliphate, when Irak and Egypt were provinces of one empire for the
second time in history, Irak by itself paid 135 million _dirhems_
(francs) annually into Harun-al-Rashid's treasury and Egypt no more than
65 million, so that a thousand years ago the productiveness of the
_Sawâd_ was more than double that of the Nile.

Another measure of the land's capacity is the greatness of its cities.
Herodotus gives statistics[56] of Babylon in the fifth century
B.C.--walls 300 feet high, 75 feet broad, and 58 miles in circuit;
three- and four-storied houses laid out in blocks; broad straight streets
intersecting one another at regular intervals, at right angles or
parallel to the Euphrates. Any one who reads Herodotus' description of
Babylon or Ibn Serapion's of Bagdad, and considers that these vast urban
masses were merely centres of collection and distribution for the open
country, can infer the density of population and intensity of
cultivation over the face of the _Sawâd_. When the Caliph Omar conquered
Irak from the Persians in the middle of the seventh century A.D., and