Figure 4. — The proposed i , 000-foot iron tower 

 designed by Clarke, Reeves & Co. for the Cen- 

 tennial Exhibition of 1876 at Philadelphia. 

 (From Scientific American, Jan. 24, 1874, vol. 30, 

 P- 47-) 



two widely separated points by the deep bands of 

 trussing which formed the first and second platforms. 

 A slight curvature inward was gi\en to the main piers 

 to further widen the base and increase the stability 

 of the structure. At a point slightly above the second 

 platform, the four members converged to the extent 

 that conventional bracing becaine more economical, 

 and they were joined. 



That this theory was successful not only practically, 

 but visually, is evident from the resulting work. 

 The curve of the legs and the openings beneath the 

 two lower platforms are primarily responsible for the 

 Tower's graceful beauty as well as for its structural 

 soundness. 



The design of the Tower was not actually the work 

 of Eiffel himself but of two of his chief engineers, 

 Emile Nouguier (1840-?) and Maurice Koechlin 

 (1856-1946) — the men who had conducted the high 

 pier studies — and the architect Stephen Sauvestre 

 (1847-?). 



In the planning of the foundations, extreme care 

 was used to ensure adequate footing, but in spite of 

 the Tower's light weight in proportion to its bulk, and 

 the low earth pressure it exerted, uneven pier settle- 

 ment with resultant leaning of the Tower was con- 

 sidered a dangerous possibility.^ To compensate 

 for this eventuality, a device was used whose ingenious 

 directness justifies a brief description. In the base of 

 each of the 16 columns forming the four main legs 

 was incorporated an opening into which an 800-ton 

 hydraulic press could be placed, capable of raising 

 the member slightly. A thin steel shim could then 

 be inserted to make the necessary correction (fig. 5). 

 The system was used only during construction to 

 overcome minor erection discrepancies. 



In order to appreciate fully the problem which 

 confronted the Tower's designers and sponsors when 

 they turned to the problem of making its observation 

 areas accessible to the fair's visitors, it is first necessary 

 to investigate briefly the contemporary state of 

 elevator art. 



Elevator Development before the Tower 



While power-driven hoists and elevators in many 

 forms had been used since the early years of the 1 9th 

 century, the ever-present possibility of breakage of 

 the hoisting rope restricted their use almost entirely 

 to the handling of goods in mills and warehouses.' 

 Not until the invention of a device which would posi- 

 tively prevent this was there much basis for work 

 on other elements of the system. The first workable 

 mechanism to prevent the car from dropping to the 

 bottom of the hoistway in event of rope failure was the 

 product of Elisha G. Otis (1811-1861), a mechanic 

 of Yonkers, New York. The invention was made 

 more or less as a matter of course along with the 

 other machinery for a new mattress factory of which 

 Otis was master mechanic. 



The importance of this invention soon became 

 evident to Otis, and he introduced his device to the 



2 The foundation footings exerted a pressure on the earth of 

 about 200 pounds per square foot, roughly one-sixth that of the 

 Washington Monument, then the highest structure in the world. 



3 A type of elevator known as the "teagle" was in use in 

 some multistory English factories by about 1835. From its 

 description, this elevator appears to have been primarily for 

 the use of passengers, but it unquestionably carried freight as 

 well. The machine shown in figure 7 had, with the exception 

 of a car safety, all the features of later systems driven from line 

 shafting — counterweight, control from the car, and reversal 

 by straight and crossed belts. 



BULLETIN 228: CONTRIBUTIONS FROM THE MUSEUM OF HISTORY AND TECHNOLOGY 



