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.
In Fig. 56 is shown a plan of an elliptic stairway. The usual method of providing a uniform width for the treads along the wall stringer, and also along the front stringer, causes some of the risers to stand at such an angle with the line of travel as to diminish the width of treads at that point. It has the advantage, however, of giving the hand rail a uniform pitch from end to end. In the plan shown, the treads are divided equally on the line of travel, and the risers are drawn as nearly as possible normal to the front stringer.