As the surface-soil of Babylonia did not originate there, but was brought down by the rivers and deposited by them as their currents lost impetus in approaching the sea, and were thus unable to carry their burden further, it is well to trace this soil to its original source. Both the Euphrates and the Tigris rise in the mountains of Armenia,[5] the geological formation of which is chiefly granite, gneiss and other feldspathic rocks. These rocks were gradually decomposed by the rains, their detritus being hurried rapidly down-stream; the rivers in the course of their career travel through a variety of geological formations including limestone, sandstone and quartz, all of which contribute something to the silt which is destined to form part of the delta’s soil; the latter being composed mainly of chalk, sand, and clay, is extremely fertile, which won for it a reputation testified to even by the classical writers: thus Herodotus who flourished in the seventh century B.C. tells us (I, 293) that “of all the countries that we know, there is none which is so fruitful in grain. It makes no pretension indeed, of growing the olive, the vine, or any other trees of the kind; but in grain it is so fruitful as to yield commonly two hundredfold, and when the production is greatest even three hundredfold. The blade of the wheat-plant and barley is often four fingers in breadth. As for millet and the sesame, I shall not say to what height they grow, though within my own knowledge, for I am not ignorant that what I have already written concerning the fruitfulness of Babylonia, must seem incredible to those who have never visited the country.... Palm trees grow in great numbers over the whole of the flat country, mostly of the kind that bears fruit, and this fruit supplies them with bread, wine and honey.” However exaggerated this account may be, all ancient writers agree in ascribing to Babylonian soil a fertility and productivity surpassing that of any other country with which they were acquainted.