to cross a river, probably often fordable
during the summer, in order to be in Persia. Hyrcania and Parthia had
indeed a certain amount of protection from the Kharesmian Desert; but
the upper valleys of the great streams--the satrapies of Sogdiana and
Bactria--must have suffered considerable annoyance from such attacks.

On the side of India, the Empire enjoyed a twofold security. From the
shores of the Indian Ocean in the vicinity of the Runn of Cutch to the
31st parallel of north latitude--a distance of above 600 miles--there
extends a desert, from one to two hundred miles across, which
effectually shuts off the valley of the Indus from the rest of
Hindustan. It is only along the skirts of the mountains, by Lahore,
Umritsir, and Loodiana, that the march of armies is possible--by this
line alone can the Punjabis threaten Central India, or the inhabitants
of Central India attack the Punjab. Hence in this quarter there was but
a very narrow tract to guard; and the task of defence was still further
lightened by the political condition of the people. The Gangetic
Indians, though brave and powerful, were politically weak, from their
separation into a number of distinct states under petty Rajahs, who
could never hope to contend successfully against the forces of a mighty
Empire. Persia, consequently, was safe upon this side, in the division
of her adversaries. Nor had she neglected the further security which was
obtainable by an interposition between her own actual frontier and her
enemies' dominions of a number of half-subject dependencies. Native
princes were allowed to bear sway in the Punjab region, who acknowledged
the suzerainty of Persia, and probably paid her a fixed tribute, but
whose best service was that they prevented a collision between the Power
of whom they held their crowns and the great mass of their own nation.

The Great Arabian Peninsula, which lay due south of the most central
part of the Empire, and bordered it on this side for about thirteen
degrees, or (if we follow the line of the boundary) for above a thousand
miles, might seem to have been the most important of all the adjacent
countries, since it contains an area of a million of square miles, and
is a nursery of brave and hardy races. Politically, however, Arabia is
weak, as has been shown in a former volume; while geographically she
presents to the north her most arid and untraversable regions, so that
it is rarely, and only under very exception