404 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1909. 
the banks of the rivers, which can be followed to-day for miles upon 
miles, with a width never under 100 feet. 
The great value of water free of silt for the early development of 
the country is the first serious lesson I have learned from an exami- 
nation of the ancient systems of irrigation, and you will see later on 
how we propose to utilize this knowledge. 
The Tigris and Euphrates carry in flood during a few days every 
year over four times as much silt as the Nile. Irrigation with such 
water will be no easy task even to-day. It was terribly difficult in 
the old days when they had no cement, and were ignorant of every 
kind of weir or barrage, except an earthen dam completely shutting off 
the waters and causing convulsions among the people living lower 
down. 
While the development of the country was confined to the low- 
lying lands blessed with water clear of silt, everything in the delta 
went on smoothly enough. Pressure of population made the work of 
‘development advance into the parts where there was no clear water, 
and then the difficulties began. In the language of Genesis, the 
world became full of violence. A strong central government only 
could have dealt with the question, and there was no strong govern- 
ment. Now the Euphrates and Tigris floods come down with extraor- 
dinary force, and both rivers, but especially the Euphrates, overflow 
their banks in a way a dweller in the Nile Valley could have no 
knowledge of. Joseph’s famine would have been impossible in the 
Tigris-Euphrates delta. Noah’s flood would have found no place 
in Kgypt. 
As men crowded up the two rivers, the necessity of protecting 
themselves from the floods and at the same time keeping their canals 
free of silt, compelled the early more powerful communities to resort 
to the only kind of regulation they knew of, and that was the bold 
one of bodily shutting off the waters of certain of the branches by 
earthen dams. Judging from the levels, I should say that the first 
head to be shut off was that of the Hiddekel, or the modern Sakh- 
lawia. Until this was closed nothing could be done with the upper 
half of the delta. The struggle between the different communities, 
and the terrible consequences which might result, intimidated the 
more thoughtful members of the community, of whom Noah was one, 
and he prepared for the worst. He built an ark of the poplar wood 
so common in the Euphrates Valley, and pitched it inside and out 
with bitumen from Hib, just as the boats and corracles on the 
Euphrates are pitched to-day. A settler probably in the lower part 
of the delta south of Kerbela, where the deserts, moreover, are 
strangely degraded and low, he felt the full force of the inundation. 
A massive earthen dyke was thrown across the head of the Sakhlawia, 
the flood discharge of the Euphrates was doubled, and instead of 
