Secondly, by slope walls laid up with an inclination cor-
responding to that of the bank on which they rest. The
first kind are much the most massive, being necessarily
proportioned in strength to the pressure of the earth behind
them, while the second recline upon the face of the bank,
and are supported by it, merely protecting its surface
from the action of the water. The most feasible arrange-
ment of the latter method, for the purpose now in view,
is believed to be that represented (with different dimen-
sions) in the annexed diagrams No. 1 and 2, consisting
of a narrow reversed arch and slope walls of brick, the
whole resting upon a layer of beton or concrete, six

Detiiiliofthii • i • .1 • ■

arraD£«meot. mches m thickness.
The sectional area of masonry for this profile, in the
case of No. 1, is 27 J square feet (including the beton),
and the sectional area of its water-way, at the level of
the upper line, 28J feet. A channel of equal capacity,
constructed with regular side walls, as first mentioned,



J. No. 44*



Hope wallf pr«»



Ixample, No. L



'•pacity.
<8timate.
xample, No. 2.
apacity.
Doc. No.
Deemed. conelvS'
live,.
2. Open choline]
with protection
or slope walls.
Details of this
arran^emeot.
<

^

m

]



<

t
C



S






/



425



[Doc. No. 44»



contain, at least, 44 square feet sectional area of ?^®p« ^•^J* ?'•"
1 . 11 . 11 I 1 . f««w«-

iry ; and its- cost, allowing all the advantage it

gain, from the circumstance of stone masonry
less expensive than brick, would be to that of the

just described, in the ratio of at least 10 to 7.
