The accompanying illustration shows the method of finding the tion ot a curved wing wall for a bridge. It is a helical or screw surface. Draw the plan, and divide the wing wall coping into any number of equal angles by radial lines from the centre of the curve. Where these lines cut the inner and outer edge of coping pro-jed rertical Lines to the elevation. Then in the elevation set off the height a b, which the coping will occupy, and by means of the ordinary device of practical geometry shown on the left divide it into the same number of equal parts as the coping was divided in plan. Now draw horizontal lines to intersect with the verticals from the plan, and draw the required curve through the intersections. The visible edge or the underside of the coping is obtained by setting off the thickness vertically at each point below the curve of the upper edge.

Projection of Curved Wing Wall.