(or wall produced) at the top of rail parallel to the center line,
and to vary the batter accordingly, using the 2-in. batter previously
mentioned as the minimum. This gave a maximum batter of 3 in. per ft. The
variation is so gradual that it is unnoticeable, and is not sufficient
to introduce any complications in construction.

The wall was designed with a stepped back, primarily to allow the
water-proofing and brick protection to be held in position more readily.
The first step was put at 13 ft. below the surface of the ground. This
gave a vertical back above that point for a 3-in. battered face, and a
slightly battered back for sections having a less batter in front. Below
that point a step was added for each 5 ft. of depth to the elevation
of the top of rail, or to the foundation of the wall if above that
elevation. As the horizontal distance of the heel of the wall, at its
greatest width, from its face at the top of rail would determine the
effective room to be occupied by the wall, it was determined to make the
back vertical below the top of rail and gain the necessary increase in
width below that point by making a heavy batter on the face.

The type of wall having been thus determined, calculations were made
of the width of base required for each ¼-in. batter from 2 to 3 in.,
inclusive, first for a depth of 13 ft. below the top of the curb and
then for each 5 ft. below that elevation, to a depth corresponding to
the distance between the top of the curb and the top of the rail at the
point of greatest variation. These widths of wall were determined for
the two pressures previously decided on, and curves were then plotted
showing the thickness of wall required for each batter calculated and
for each pressure. They are shown on Plate LIV. The curves in broken
lines represent the widths required for saturated material, and the
curves in dotted lines for hydraulic pressure. Mean curves were then