621 [=646] (V.1)

621

from Rajbuhas irrigation it will
be necessary to reduce the slopes
of the Rajbuha channels to a
minimum, which I should
fix at six inches per mile. This
in the first seventy miles of the
branch, would on each mile, 621
give the Rajbuha channel a
command over that of the reser-
voir from which it was supplied
of nine inches. Supposing there-
fore, that the average level of
the canal or reservoir bed was
seven feet below the surface of
the country the Rajbuha channel
must lie 9 1/3 miles in length be-
fore its bed would strike out
upon the surface of the country.
From the 70th mile downwards,
where from the surface slope being
only 12 inches per mile, we
could only give six inches of
command on each mile in
length of the Rajbuha; fourteen
of the miles in length would be
necessary to obtain the result
above described. With a depth
of water in the Rajbuha equal
to three feet, which we may
fairly take as an average,
the above length will be re-
duced in the first case to 5 1/3
and in the latter to 8 miles;
which we may consider as
the points at which [Tor ?] or
surface irrigation would be
available with slopes of 15 and 12 inches p mile *. It will be very
evident therefore, that if a
proper use is made of the
main lines of Rajbuha which
come from the higher levels of
the upper country, and if
these main lines are kept
well
This is a continuation of [?]
* At the Kylunpoor [bridge ?] however the fall of [?]
[?] will [?] [?] command to the Rajh
lying [along ?] it : in this case the distance at
which Tor water will be delivered becomes [reduced ?]
from 5 1/3 to 2 2/3 miles. Advantages of an equal
favorable nature will exist at the 91st mile
from whence Tor water will be delivered to
a distance of 5 1/3 instead of 8 miles.