Attock, and the Panjob. He every where took advantage of this commerce, not
by plundering and thus destroying it for the purpose of filling his
coffers, but by nourishing and increasing it, and thus at once benefitting
himself and the inhabitants who wore engaged in it. By means of the
commerce in which the natives of the Panjob were engaged on the Indus,
Alexander procured the fleet with which he sailed down that river. This
fleet is supposed to have consisted of eight hundred vessels, only thirty
of which were ships of war, the remainder being such as were usually
employed in the commerce of the Indus. Even before he reached this river,
he had built vessels which he had sent down the Kophenes to Taxila. By the
completion of his campaign at the sources of the Indus, and by his march
and voyage down the course of that river, he had traced and defined the
eastern boundary of his conquests: the line of his march from the
Hellespont till the final defeat of Darius, and his pursuit of that
monarch, had put him in possession of tolerably accurate knowledge of the
northern and western boundaries; the southern provinces alone remained to
be explored: they had indeed submitted to his arms; but they were still,
for all the purposes of government and commerce, unknown.

"To obtain the information necessary for the objects they had in view, he
ordered Craterus, with the elephants and heavy baggage, to penetrate
through the centre of the empire, while he personally undertook the more
arduous task of penetrating the desert of Gadrosia, and providing for the
preservation of the fleet. A glance over the map will show that the route
of the army eastward, and the double route by which it returned, intersect
the whole empire by three lines, almost from the Tigris to the Indus:
Craterus joined the division under Alexander in the Karmania; and when
Nearchus, after the completion of his voyage, came up the Posityris to
Susa, the three routes through the different provinces, and the navigation
along the coast, might be said to complete the survey of the empire."