Electricity and Communication
Introduction
Themes for Electricity and Communication:
- the task of the individual inventor
- the rise of science-based industry
- the impact of technology on social
organization,
ideas,
and values
Early history of electricity:
- Benjamin
Franklin was one of many experimenting with static electricity in
the
mid-1700s.
- Alesandro
Volta invented the voltaic pile in 1800. The idea came from Luigi
Galvani, an anatomist, who was dissecting a frog when the frog's
legs
began to twitch. He thought it resulted from electrical action in
the vicinity, such as lightening, stimulating some kind of natural
electricity.
Volta realized that the metal elements touching the frog's nerves might
be the source of the action. Over a period of several years he
worked
out how to use this effect and produced the first continuous flow of
current,
from a wet battery.
- Volta's discovery led quickly to the use of
electric current
to decompose water and to electroplating of metals. In 1810 Davy
created an electric arc between two terminals as a source of
light.
A number of people tried to build telegraphs--using electric current to
ring bells, for example, but at first these were not practical.
- in 1820 Oersted
discovered that an electric current creates a magnetic field, and Ampere
and Faraday
started researching the interactions between the two. Faraday
used
this to make a disk rotate in 1831--the first motor (and generator) but
not a useful one.
- Hippolyte
Pixii invented the first effective generator in 1832, but it was
marginal.
The first application of a magneto generator (one with a permanent
magnet)
to power an arc light was a lighthouse
illuminating the Straits of Dover in 1862.
Cooke
and Wheatstone telegraph
The telegraph
- Practical telegraphs were invented by Baron
Pavel Schilling
and Jacobi in Russia and by Cooke
and Wheatstone in England--a five-needle system was tried in 1837
for
railway use and later simplified--railway signaling is very important
but
not very demanding. The five
needle system used moving needles to point to letters on a
board--the
operator didn't have to read code but you had to have six wires between
the two stations.
- In the U.S. Samuel
F. B. Morse used a simple machine--longer or shorter bursts of
current
pushed a pencil to make a mark on a moving paper tape. The
machine
was rugged and much cheaper to construct, but the operator had to learn
code. By 1837 Morse was transmitting sinals for 10 miles, and in
1843 Congress funded a line between Baltimore and Washington.
That
line was not widely used, but the line between Washington and New York
was profitable.
- By 1850 the telegraph linked all the states
east
of the
Mississippi except Florida. Lines were laid along railroad right
of ways, making it easy to get the infrastructure in place.
- The demand for railroad signaling was
immediate,
and business
news could be profitable. Newspapers competed on having the
lastest
information--it was revolutionary that a St. Louis newspaper could
carry
President Polk's 1848 message to Congress within 24 hours.
1850s
recording telegraph (#55)
There was great eagerness to lay a submarine
telegraph
between Europe and the U.S.--underwater lines already joined England
and
France. (For more of the story see Early
Cable History )
- Retired industrialist Cyrus Field took this
on
as a pet
project, and made his first try in 1857, but the cables were not high
quality
and broke 330 miles out.
- The second attempt with improved cable and
better brakes
for the cable drums started in June 1858, but again the cable broke
repeatedly.
- Another attempt later that year was
successful,
but the
cable ceased to function after about a month due to deterioration by
salt
water.
- In 1865 another attempt set out to lay a
cable
of 2300
nautical miles built in a single length--5000 tons of cable. A
special
ship was built to lay the cable, called The
Great Eastern (picture
of its cable-handling gear) . Only 600
miles
from Newfoundland the cable broke, and while it was grappled a couple
of
times it could not be lifted all the way to the surface.
- In 1866 a new cable was finally successfully
laid (and
the previous year's one was successfully grappled and raised and
repaired
as well).
grappling
the 1865 cable
The telegraph became the basis for an industry:
- During the Civil
War over 6 million messages were transmitted by some 15000
telegraphers,
and by the end of 1865 more than 200,000 miles of telegraph line were
in
service. Increased demand led to the invention of duplex and
multiplex
telegraph systems.
- Thomas Edison's first major invention, in
1870,
was the
stock ticker, a special printing telegraph to transmit stock prices
from
Wall Street.
- arc
lights had been invented early in the century, but without an
effective
power source they weren't very interesting. A few were run by
batteries
in the 1830s and 1840s, but no further improvements were patented
between
1860 and 1870.
- Zenobe
T. Gramme (France) invented the dynamo (generator using
electromagnets)
in 1867 and also showed it could be run backwards as a motor.
Gramme
was a model maker for a manufacturer of electrical devices; he didn't
have
a deep knowledge of the theory involved. He developed his dynamo
into a system particularly for powering an improved arc light invented
in Paris that required alternating current and high voltage. The
system was quite widely used in Europe, though it consumed carbons at a
very high rate.
- In 1878 Charles
F. Brush invented an arc lighting system with a better generator
and
a simple arc light. This was immediately useful for street lights
and other large spaces. Both Brush's company and one started a
year
later by two Philadelphia high school teachers--Elihu
Thomson and Edwin Houston--were commercially successful.
- In 1873 research on generators led to the
invention of
effective electric motors. Simple motors had been built as
scientific
toys 40 years earlier, but power from a battery was over 20 times more
expensive than power from a steam engine.
- Gas
light was fairly sucessful in cities for small-scale lighting,
where
arc lighting was too bright. A number of inventors starting
looking
for an alternative, including Thomas Edison.
This page written and copyright Pamela
E. Mack
History
122
last updated 10/21/2005