The entrance of a Roman army into Arabia Felix under the command of my friend and companion Ælius Gallus,[737] and the traffic of the Alexandrian merchants whose vessels pass up the Nile and Arabian Gulf[738] to India, have rendered us much better acquainted with these countries than our predecessors were. I was with Gallus at the time he was prefect of Egypt, and accompanied him as far as Syene and the frontiers of Ethiopia, and I found that about one hundred and twenty ships sail from Myos-hormos[739] to India, although, in the time of the Ptolemies, scarcely any one would venture on this voyage and the commerce with the Indies. 13. Our first and most imperative duty[740] then, both in respect to science and to the necessities of the man of business, is to undertake to lay down the projection of the different countries on the chart in as clear a style as possible, and to signify at the same time the relation and proportion they bear to the whole earth. For such is the geographer’s peculiar province. It belongs to another science to give an exact description of the whole earth, and of the entire vertebre of either zone, and as to whether the vertebre in the opposite quarter of the earth is inhabited. That such is the case is most probable, but not that it is inhabited by the same race of men as dwell with us. And it must therefore be regarded as another habitable earth. We however have only to describe our own. 14. In its figure the habitable earth resembles a chlamys, or soldier’s cloak, the greatest breadth of which would be indicated by a line drawn in the direction of the Nile, commencing from the parallel of the Cinnamon Country, and the Island of the Egyptian Exiles, and terminating at the parallel of Ierna; and its length by a line drawn from the west at right angles to the former, passing by the Pillars of Hercules and the Strait of Sicily to Rhodes and the Gulf of Issus,[741] then proceeding along the chain of the Taurus, which divides Asia, and terminating in the Eastern Ocean,[742] between India and the Scythians dwelling beyond Bactriana.