This section is from the book "A Treatise On Architecture And Building Construction Vol3: Stair Building, Ornamental Ironwork, Roofing, Sheet-Metal Work, Electric-Light Wiring And Bellwork", by The Colliery Engineer Co.. Also available from Amazon: A Treatise On Architecture And Building Construction.
At the angles, easement curves are necessary, or, at least, advisable. At h is shown a method of drawing an easement curve. From the vertex h lay off equal distances in both directions, as 1, 2, 3, 4, etc. Draw lines from 5 to 6, 4 to 7, etc. Through the points of intersection of these lines, draw a curved line by means of a spline. Otherwise, if the angle at h is sharp, perpendiculars may be drawn until they intersect, as at o; the curve can then be drawn with a compass.