699
that the longitudinal axis of
the inlet is at a distance of 3045
feet from that of the outlet, with
a slope, therefore, of 8.23 feet in the
mile, the sill of the inlet ought,
that it may correspond with the
slope of the bed of the river, to
be 1.87" x 3.045 or 5.69 inches above
that of the outlet. There is an
advantage, however, in maintain-
-ing the sill of the inlet at a
moderate height, as it enables us
to reduce the extent of sluice area,
and by so doing to give us greater
facilities for adapting the means
of opening and shutting the
gates, an increased velocity of
current at this particular point
so as to expedite the passage of
silt and alluvial matter through
the canal channel may possibly
be an advantage. At any rate,
but chiefly with reference to
the effective slope above mentioned,
and to the desire of reducing
the height of the sluice openings;
the sills of the inlet are raised
24 inches above the horizontal
level: that of the dam being
flush with the above level, with
the exception of a masonry step
of 10 inches which the piers for
the gate [calls for, struck through] require. I am by no
means certain that it may
not be found advisable hereafter
to raise the sills of the dam,
by which two advantages will
be gained; 1[?] a reduction to the
dimensions of gate necessary
for opening and shutting the
sluice; 2nd a fixed channel to
a depth equal in amount to
that
EN