being the weight, in pounds, of 1 cu. ft. of earth. The prisms are supposed to be 1 ft. in length perpendicular to the plane of the paper.
These weights are now laid off to the scale of force, vertically downward from
, to points 1, 2, 3, ..., and from these points, lines are drawn parallel to
,
,
, ..., respectively, of lengths equal to