The two rivers which determine the character and nature of the depression between the Syrian plateau and the tableland of Iran rise at no great distance from each other on the mountains of Armenia. The Euphrates rises to the north, the Tigris to the south. After leaving the mountains of Armenia--the Euphrates, by a broad circuit to the west, the Tigris by a direct course to the south--both rivers enter a tolerably lofty steppe, where the uniform surface is broken by ridges of rock, by ranges of hills, pastures, and fruitful strips of land, while the banks of the rivers are overgrown with forests of plane-trees, tamarisks, and cypresses, and shut in by meadows. As the soil becomes more level, these fruitful depressions by the rivers become somewhat broader, but the land between the streams becomes more sterile and treeless, and supports only nomad tribes and herds of wild asses, ostriches, and bustards.[307] When the Euphrates has left behind the last spurs of this desolate hill country, at the place where the two rivers approach each other most nearly--about 400 miles from their mouths--there commences a plain of brown rich soil. Through this the Euphrates passes with a quiet stream, but the Tigris hurries to the sea down a bed which is both narrower, and often inclosed by rocks, while at the same time the river is increased by copious additions from the western edge of the tableland of Iran. In spite of the excellent soil this flat would remain unfruitful unless the two rivers, year by year, when the snow melted on the Armenian mountains, overflowed their banks, and thus irrigated the land for the summer. In the Tigris the inundation commences about the beginning of June, in the Euphrates, whose sources lie far higher, about the beginning of July. But this inundation does not take place nearly so calmly and regularly as that in the Nile. Instead of fertilising water, the Tigris often sends down destructive floods over the plain, and changes it, down to the marshy Delta at the mouth, into a broad and rolling sea.