)--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 settlement
with resultant leaning of the Tower was considered a dangerous
possibility.[2] 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 19th 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.[3] Not until the invention of a
device which would positively 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.

[Illustration: Figure 5.--Correcting erection discrepancies by raising
pier member--with hydraulic press and hand pump--and inserting shims.
(From _La Nature_, Feb. 18, 1888, vol. 16, p. 184.)]

[Illustration: Figure 6.--The promenade beneath the Eiffel Tower, 1889.
(From _La Nature_, Nov. 30, 1889, vol. 17, p. 425.)]

[Illustration: Figure 7.--Teagle elevator in an English mill about 1845.
Power was taken from the line shafting. (From _Pictorial Gallery of Arts_,
Volume of Useful Arts, London, n.d. [ca. 1845].)