INGENUITY AND LUXURY 



struction. Four flights of stairs, to reach a fifth story, 

 represent about the limit to which man would ascend 

 for pleasure or business except when absolutely nec- 

 essary. The case stood thus: higher buildings were 

 absolutely necessary; muscular exertion refused to 

 carry man higher. The implication was obvious- 

 some substitute for muscle must be found. 



The substitute took the form of the passenger ele- 

 vator, introduced in 1853 by Elisha G. Otis; and this 

 invention, and one other that came a quarter of a cen- 

 tury later, made possible the modern skyscraper. 



The development of the elevator will be referred to 

 presently. The other invention was that of the steel- 

 frame construction, with which it was possible to erect 

 high buildings having relatively thin walls. 



THE STEEL FRAME 



By the old method of constructing with stone or 

 brick, the walls of a twenty-story building would have 

 to be so thick near the base that the rooms on the ground 

 floor would be reduced to mere tunnels, scarcely wide 

 enough for the staircases and elevator shafts. But 

 by using steel girders and braces, and filling in the 

 spaces with some such substances as tile, brick, or 

 stone, a thin veneer on the outside, or a surrounding 

 shell, the walls of a tall building may be kept of almost 

 uniform thickness from base to top. 



The steel frame of a modern skyscraper is really 

 "a cantilever bridge stood on end." Perhaps the 

 improved bridges of the early eighties suggested the 



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