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عدد الرسائل : 65
تاريخ التسجيل : 13/06/2008
 |  موضوع: Alexander Graham Bell -- Telephone  الثلاثاء يوليو 01, 2008 2:07 am | |
| Bell speaking into prototype model of the telephoneTelephoneBy 1874, Bell's
initial work on the harmonic telegraph had entered a formative stage with progress
it made both at his new Boston
"laboratory" (a rented facility) as well as at his family home in Canada
a big success..[51]
While working that summer in Brantford, Bell experimented with a
"phonautograph," a pen-like machine that could draw shapes of sound
waves on smoked glass by tracing their vibrations. Bell thought it might be possible to generate
undulating electrical currents that corresponded to sound waves.[52]
Bell also
thought that multiple metal reeds tuned to different frequencies like a harp
would be able to convert the undulatory currents back into sound. But he had no
working model to demonstrate the feasibility of these ideas.[53]In 1874, telegraph message traffic was rapidly
expanding and in the words of Western Union
President William Orton, had become "the nervous system of commerce."
Orton had contracted with inventors Thomas Edison
and Elisha Gray
to find a way to send multiple telegraph messages on each telegraph line to avoid the great
cost of constructing new lines.[54]
When Bell mentioned to Gardiner Hubbard and
Thomas Sanders that he was working on a method of sending multiple tones on a
telegraph wire using a multi-reed device, the two wealthy patrons began to
financially support Bell's
experiments.[55]
Patent matters would be handled by Hubbard's patent attorney, Anthony Pollok.[56]In March 1875, Bell
and Pollok visited the famous scientist Joseph Henry,
who was then director of the Smithsonian Institution, and asked Henry's
advice on the electrical multi-reed apparatus that Bell hoped would transmit the human voice by
telegraph. Henry replied that Bell
had "the germ of a great invention". When Bell said that he did not have the necessary
knowledge, Henry replied, "Get it!" That declaration greatly
encouraged Bell
to keep trying, even though he did not have the equipment needed to continue
his experiments, nor the ability to create a working model of his ideas.
However, a chance meeting in 1874 between Bell
and Thomas A. Watson, an experienced electrical
designer and mechanic at the electrical machine shop of Charles Williams,
changed all that.With financial support from Sanders and
Hubbard, Bell
was able to hire Thomas Watson as his assistant and the two of them
experimented with acoustic telegraphy. On 2 June 1875, Watson accidentally
plucked one of the reeds and Bell,
at the receiving end of the wire, heard the overtones of the reed; overtones
that would be necessary for transmitting speech. That demonstrated to Bell that only one reed
or armature was necessary, not multiple reeds. This led to the "gallows"
sound-powered telephone, which was able to transmit indistinct, voice-like
sounds, but not clear speech.Later inventionsAlthough Alexander Graham Bell is most often
associated with the invention of the telephone, his interests were extremely
varied. According to his biographer, Charlotte Gray, Bell's work ranged "unfettered across
the scientific landscape" and he often went to bed voraciously reading the
Encyclopaedia Britannica, scouring it for new areas of interest.[89]
The range of Bell's
inventive genius is represented only in part by the 18 patents granted in his
name alone and the 12 he shared with his collaborators. These included 14 for
the telephone and telegraph, four for the photophone,
one for the phonograph,
five for aerial vehicles, four for "hydroairplanes" and two for selenium
cells. Bell's inventions spanned a wide range of interests and included a metal
jacket to assist in breathing, the audiometer
to detect minor hearing problems, a device to locate icebergs, investigations
on how to separate salt from seawater, and work on finding alternative fuels.Bell worked extensively in medical research and invented
techniques for teaching speech to the deaf. During his Volta Laboratory period,
Bell and his
associates considered impressing a magnetic field on a record as a means of
reproducing sound. Although the trio briefly experimented with the concept,
they were unable to develop a workable prototype. They abandoned the idea,
never realizing they had glimpsed a basic principle which would one day find
its application in the tape recorder, the hard disc
and floppy disc
drive and other magnetic media.Bell's own home used a primitive form of air conditioning,
in which fans blew currents of air across great blocks of ice. He also
anticipated modern concerns with fuel shortages and industrial pollution. Methane
gas, he reasoned, could be produced from the waste of farms and factories. At
his Canadian estate in Nova Scotia,
he experimented with composting toilets and devices to capture water
from the atmosphere. In a magazine interview published shortly before his
death, he reflected on the possibility of using solar panels to heat houses.AeronauticsMain article: Aerial Experiment AssociationMain article: AEA Silver Dart  AEA Silver Dart c.1909Bell was a supporter of aerospace engineering
research through the Aerial Experiment Association (AEA),
officially formed at Baddeck, Nova Scotia, in October 1907 at the suggestion of
Mrs. Mabel Bell and with her financial support. The AEA was headed by Bell and
the founding members were four young men: American Glenn H. Curtiss,
a motorcycle manufacturer who later was awarded the Scientific American Trophy
for the first official one-kilometre flight in the Western hemisphere and became a world-renowned
airplane manufacturer; Frederick W. Baldwin, the first Canadian and
first British subject to pilot a public flight in Hammondsport, New York; J.A.D. McCurdy;
and Lieutenant Thomas Selfridge, an official observer from the
U.S. government. In 1891, Bell
began experiments to develop motor-powered heavier-than-air aircraft.In 1898, Bell
experimented with tetrahedral box kites and wings constructed of multiple compound tetrahedral kites
covered in silk. The tetrahedral wings were named Cygnet I, II and III,
and were flown both unmanned and manned (Cygnet I crashed during a
flight carrying Selfridge) in the period from 1907–1912. Some of Bell's kites are on
display at the Alexander Graham
Bell National Historic Site.The AEA's work progressed to heavier-than-air
machines, applying their knowledge of kites to gliders. Moving to Hammondsport,
the group then designed and built the Red Wing,
framed in bamboo and covered in red silk and powered by a small air-cooled
engine.[94]
On 12 March
1908, over Keuka Lake,
the biplane lifted off on the first public flight in North
America.[95]
The innovations that were incorporated into this design included a cockpit
enclosure and tail rudder (later variations on the original design would add
ailerons as a means of control). One of the AEA project's inventions, the aileron,
is a standard component of aircraft today. (The aileron was also invented
independently by Robert Esnault-Pelterie.) The White Wing
and June Bug were to follow and by the end of 1908, over 150 flights
without mishap had been accomplished. However, the AEA had depleted its initial
reserves and only a $10,000 grant from Mrs. Bell allowed it to continue with
experiments.[96]Their final aircraft design, the Silver Dart
embodied all of the advancements found in the earlier machines. On 23 February
1909, Bell was present as
the Silver Dart flown by J.A.D. McCurdy from the frozen ice of Bras
d'Or, made the first aircraft flight in Canada. Bell had worried that the flight was too
dangerous and had arranged for a doctor to be on hand. With the successful
flight, the AEA disbanded and the Silver Dart would revert to Baldwin
and McCurdy who began the Canadian Aerodrome Company and would later
demonstrate the aircraft to the Canadian Army.[97]..DeathBell died of pernicious anemia
on 2 August
1922, at his private
estate, Beinn Bhreagh, Nova Scotia, at age 75.[101]
While tending to her husband after a long illness, Mabel whispered, "Don't
leave me." By way of reply, Bell
traced the sign for "No" – and promptly expired.[102]Dr. Alexander Graham Bell was buried atop Beinn
Bhreagh mountain overlooking Bras
d'Or Lake.
He was survived by his wife and his two daughters, Elisa May and Marion.[103] | |
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