iver bridge between New York and
Brooklyn, was supplanted by the cantilever type, consisting of trusswork
beams poised upon piers and meeting each other mid-stream. Iron and
steel construction also made elevated railways possible. In 1890 the
elevated roads of New York City alone carried over 500,000 passengers
daily. Steel lent to the framework of buildings lightness, strength, and
fire-proof quality, at the same time permitting swift construction.
Walls came to serve merely as covering, not sustaining the floors, the
weight of which lay upon iron posts and girders.

At the time of the Centennial, electricity was used almost exclusively
for telegraphic communication. By 1893 new inventions, as wonderful as
Morse's own, had overlaid even that invention. A single wire now
sufficed to carry several messages at once and in different directions.
Rapidity of transmission was another miracle. During the electrical
exposition in New York City, May, 1896, Hon. Chauncey M. Depew dictated
a message which was sent round the world and back in fifty minutes. It
read:

"God creates, nature treasures, science utilizes electrical power for
the grandeur of nations and the peace of the world." These words
travelled from London to Lisbon, thence to Suez, Aden, Bombay, Madras,
Singapore, Hong-Kong, Shanghai, Nagasaki, and Tokio, returning by the
same route to New York, a total distance of over 27,500 miles.

[Illustration: Three vertical generators about thirty feet in diameter.]
Interior of the Power House at Niagara Falls.

Self-winding and self-regulating clocks came into vogue, being
automatically adjusted through the Western Union telegraph lines, so
that at noon each day the correct time was instantly communicated to
their hands from the national observatory. Another invaluable use of the
telegraph was its service to the Weather Bureau, established in 1870. By
means of simultaneous reports from a tract of territory 3,000 miles long
by 1,500 wide, this bureau was enabled to make its forecasts
indispensable to every prudent farmer, traveller, or mariner.

The three great latter-day applications of electrical force were the
telephone, the electric light, and the electric motor. In 1876, almost
simultaneously with its discovery by other investigators, Alexander
Graham Bell exhibited an electric transmitter of the human voice. By the
addition of the Edison carbon transmitter the same year the novelty was
assured swift success. In