53. Double Platforms. — Fig. 49 is a plan of a platform stairway making a half turn, one riser at the center of the cylinder dividing the space into two platforms. Where the run will permit, it is always advisable to dispense with this central riser, thus adding breadth to the platform, and avoiding the danger of stumbling at the step placed where it is not expected.
54. Quarter Platform With Step. — Fig. 50 is a plan of a quarter-platform stairway with a 15-inch cylinder having a regular step at its center.
55. Three-Quarter Turn. — Fig. 51 is a plan of a winding stairway making a three-quarter turn, the entrance being at one end of the staircase.