n full flood till quite
the end of May or the beginning of June; it then continues high for
above a month, and does not sink much till the middle of July, after
which it gradually falls till September. The country inundated by the
Tigris is chiefly that on its lower course, between the 32d and 31st
parallels, the territory of the Beni Lam Arabs. The territory which the
Euphrates floods is far more extensive. As high up as its junction with
the Khabour, that stream is described as, in the month of April,
"spreading over the surrounding country like a sea." From Hit
downwards, it inundates both its banks, more especially the country
above Baghdad (to which it is carried by the Saklawiyeh canal), the
tract west of the Birs Nimrud and extending thence by way of Nedjif to
Samava and the territory of the Affej Arabs, between the rivers above
and below the 32d parallel. Its flood is, however, very irregular,
owing to the nature of its banks, and the general inclination of the
plain, whereof mention was made above. If care is taken, the inundation
may be pretty equally distrib uted on either side of the stream; but if
the river banks are neglected, it is sure to flow mainly to the west,
rendering the whole country on that side the river a swamp, and leaving
the territory on the left bank almost without water. This state of
things may be traced historically from the age of Alexander to the
present day, and has probably prevailed more or less since the time when
Chaldaea received its first inhabitants.

The floods of the Tigris and Euphrates combine with the ordinary action
of their streams upon their banks to produce a constant variation in
their courses, which in a long period of time might amount to something
very considerable. It is impossible to say, with respect to any portion
of the alluvial plain, that it may not at some former period have been
the bed of one or the other river. Still it would seem that, on the
whole, a law of compensation prevails, with the result that the general
position of the streams in the valley is not very different now from what
it was 4000 years ago. Certainly between the present condition of things
and that in the time of Alexander, or even of Herodotus, no great
difference can be pointed out, except in the region immediately adjoining
on the gulf, where the alluvium has grown, and the streams, which were
formerly separate, have united their waters. The Euphrates still flows
by Hit a