146 — ANNUAL REPORT \ & 
crete. Not only in business houses but also in the finest residences con- 
crete stairways are used. 
George W. Vanderbilt’s fine residence on Fifth Avenue, in New 
York City, is just being erected with a fine double spiral stairway. These 
spiral stairways curving in opposite directions intersect midway between 
floors, then swinging apart again continue to curve to the upper floor. 
They are self supporting, without beams, girders or columns. ‘They are 
of exceptionally light construction, the concrete spiral, being 64 inches 
wide and 4 inches thick, with side panels or vertical edges 4 inches thick 
and 14 inches high. Ransome twisted bars 14 inch square are used, 
Fig. 83.—Steel Skeleton for Spiral Stairway, Geo. W. Vanderbilt’s residence, New York. 
