these annual inundations lies one of several
resemblances between the valley of the Euphrates and that of the Nile.
But there are important differences. The time of the annual flood is
reversed, the Nile being highest in autumn and winter, and lowest in
spring and early summer. The periodical overflows of the Nile, regulated
by the great lake basins in the south, are usually punctual in arrival,
gradual in growth, and beneficial in operation. No lakes are interposed
between the mountain torrents of the upper basis of the Tigris and the
Euphrates and their lower courses. Hence, heavy rain, or an unusually
rapid thaw in the uplands, gives rise to the sudden irruption of a vast
volume of water which not even the rapid Tigris, still less its more
sluggish companion, can carry off in time to prevent violent and
dangerous overflows. Without an elaborate system of canalisation,
providing an escape for such sudden excesses of the supply of water,
the annual floods of the Euphrates, and especially of the Tigris, must
always be attended with risk, and often prove harmful.

There are other peculiarities of the Euphrates valley which may
occasionally tend to exacerbate the evils attendant on the inundations.
It is very subject to seismic disturbances; and the ordinary
consequences of a sharp earthquake shock might be seriously complicated
by its effect on a broad sheet of water. Moreover the Indian Ocean lies
within the region of typhoons; and if, at the height of an inundation,
a hurricane from the south-east swept up the Persian Gulf, driving its
shallow waters upon the delta and damming back the outflow, perhaps for
hundreds of miles up-stream, a diluvial catastrophe, fairly up to the
mark of Hasisadra's, might easily result. [2]

Thus there seems to be no valid reason for rejecting Hasisadra's
story on physical grounds. I do not gather from the narrative that the
"mountains of Nizir" were supposed to be submerged, but merely that they
came into view above the distant horizon of the waters, as the vessel
drove in that direction. Certainly the ship is not supposed to ground on
any of their higher summits, for Hasisadra has to ascend a peak in order
to offer his sacrifice. The country of Nizir lay on the north-eastern
side of the Euphrates valley, about the courses of the two rivers Zab,
which enter the Tigris where it traverses the plain of Assyria some
eight or nine hundred feet above the sea; and, so far as I can judge
from m