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wider than the others, that they may have more power
to resist the action of the wedges, which, loaded with
the weight of the superincumbent wall, press towards
the centre, and have a tendency to thrust out the
abutments. But if the outer piers be of large dimensions,
by restraining the power of the wedges they will give
stability to the work. Having paid due attention to these
points, care must next be taken, and particularly is it to
be observed, that the work be carried up perpendicularly
and without inclination in any part. The greatest at¬
tention must be bestowed on the lower parts of the
walls, which are often damaged by the earth lying
against them. This is not always of the same weight
as in summer; for in the winter season, imbibing a great
quantity of water from the rain, it increases in weight
and bulk, and breaks and extrudes the walls. To re¬
medy this evil, the thickness of the wall must be pro¬
portioned to the weight of earth against it, and, in
front, counterforts (anterides) or buttresses (erismæe)
are carried up with the wall, at a distance from each other
equal to the height of the foundations, and of the same
width as the foundations. Their projection at bottom
is equal in thickness to the wall, and diminishing as
they rise, their projection at top is equal to the thick¬
ness of the work : adjoining the inside of the wall, to¬
wards the mass of ground, teeth similar to those of a
saw are constructed, each of which projects from the wall
a distance equal to the height of the foundations, and
their thickness is to be equal to that of the foundation
wall. An extent equal to the height of the foundations
is taken at the outer angles, and marked by points on