t per minute.[6]

[Illustration: Figure 12.--Final development of the Baldwin-Hale water
balance elevator, 1873. The brake, kept applied by powerful springs, was
released only by steady pressure on a lever. There were two additional
controls--the continuous rope that opened the cistern valve to fill the
bucket, and a second lever to open the valve of the bucket to empty it.
(From _United States Railroad and Mining Register_, Apr. 12, 1873, vol.
17, p. 3.)]

In addition to the element of potential danger from careless operation or
failure of the brake, the Baldwin system was extremely expensive to
install as a result of the second shaft, which of course was required to
be more or less watertight.

Much of the water-balance elevator's development and refinement was done
by William E. Hale of Chicago, who also made most of the installations.
The system has, therefore, come to bear his name more commonly than
Baldwin's.

The popularity of the water-balance system waned after only a few years,
being eclipsed by more rational systems. Hale eventually abandoned it and
became the western agent for Otis--by this time prominent in the
field--and subsequently was influential in development of the hydraulic
elevator.

The rope-geared system of hydraulic elevator operation was so basically
simple that by 1880 it had been embraced by virtually all manufacturers.
However, for years most builders continued to maintain a line of steam and
belt driven machines for freight service. Inspired by the rapid increase
of taller and taller buildings, there was a concentrated effort,
heightened by severe competition, to refine the basic system.

[Illustration: Figure 13.--Vertical cylinder, rope-geared hydraulic
elevator with 2:1 gear ratio and rope control (about 1880). For higher
rises and speeds, ratios of up to 10:1 were used, and the endless rope was
replaced by a lever. (Courtesy of Otis Elevator Company.)]

By the late 1880's a vast number of improvements in detail had appeared,
and this form of elevator was considered to be almost without defect. It
was safe. Absence of a drum enabled the car to be carried by a number of
cables rather than by one or two, and rendered overtravel impossible. It
was fast. Control devices had received probably the most attention by
engineers and were as perfect and sensitive as was possible with
mechanical means. Cars with lever control could be run at the high speeds
required for high buildin