Thus the axes of the two chains are nearly at right angles to one another, the triangular basin of Van occurring at the point of contact, and softening the abruptness of the transition.

Again, whereas the Zagros mountains present their gradual slope to the Mesopotamian lowland, and rise in higher and higher ridges as they recede from the mountains of Armenia ascend at once to their full heignt from the level of the Tigris, and the ridges then gradually decline towards the Euxine.
It follows from this last contrast, that, while Zagros invites the inhabitants of the Mesopotamian plain to penetrate its recesses, which are at first readily accessible, and only grow wild and savage towards the interior, the Armenian mountains repel by presenting their greatest difficulties and most barren aspect at once, seeming, with their rocky sides and snow-clad summits, to form an almost insurmountable obstacle to an invading host.

Assyrian history bears traces of this difference; for while the mountain region to the east is gradually subdued and occupied by the people of the plain, that on the north continues to the last in a state of hostility and semi-independence.
West of Assyria (according to the extent which has here been given to it), the border countries were, towards the south, Arabia, and towards the north, Syria.

A desert region, similar to that which bounds Chaldaea in this direction, extends along the Euphrates as far north as the 36th parallel, approaching commonly within a very short distance of the river.

This has been at all times the country of the wandering Arabs.