From what has been said, it will be clear that the Euphrates is, _par excellence_, the river of Southern Mesopotamia or Babylonia, while the Tigris may be regarded as the river of Assyria. It was the Euphrates that made possible the high degree of culture, that was reached in the south. Through the very intense heat of the dry season, the soil developed a fertility that reduced human labor to a minimum. The return for sowing of all kinds of grain, notably wheat, corn, barley, is calculated, on an average, to be fifty to a hundred-fold, while the date palm flourishes with scarcely any cultivation at all. Sustenance being thus provided for with little effort, it needed only a certain care in protecting oneself from damage through the too abundant overflow, to enable the population to find that ease of existence, which is an indispensable condition of culture. This was accomplished by the erection of dikes, and by directing the waters through channels into the fields. Assyria, more rugged in character, did not enjoy the same advantages. Its culture, therefore, not only arose at a later period than that of Babylonia, but was a direct importation from the south. It was due to the natural extension of the civilization that continued for the greater part of the existence of the two empires to be central in the south. But when once Assyria was included in the circle of Babylonian culture, the greater effort required in forcing the natural resources of the soil, produced a greater variety in the return. Besides corn, wheat and rice, the olive, banana and fig tree, mulberry and vine were cultivated, while the vicinity of the mountain ranges furnished an abundance of building material--wood and limestone--that was lacking in the south. The fertility of Assyria proper, again, not being dependent on the overflow of the Tigris, proved to be of greater endurance. With the neglect of the irrigation system, Babylonia became a mere waste, and the same river that was the cause of its prosperity became the foe that, more effectually than any human power, contributed to the ruin and the general desolation that marks the greater part of the Euphrates Valley at the present time. Assyria continued to play a part in history long after its ancient glory had departed, and to this day enjoys a far greater activity, and is of considerable more significance than the south. II.