Amos Dolbear

Amos Emerson Dolbear (; November 10, 1837 – February 23, 1910) was an American physicist and inventor. Dolbear researched electrical spark conversion into sound waves and electrical impulses. He was a professor at University of Kentucky in Lexington from 1868 until 1874. In 1874 he became the chair of the physics department at Tufts University in Medford, Massachusetts. He is known for his 1882 invention of a system for transmitting telegraph signals without wires. In 1899 his patent for it was purchased in an unsuccessful attempt to interfere with Guglielmo Marconi's wireless telegraphy patents in the United States.

Biography

Amos Dolbear was born in Norwich, Connecticut, on November 10, 1837. He was a graduate of Ohio Wesleyan University, in Delaware, Ohio. While a student there, he had made a "talking telegraph" and invented a receiver containing two features of the modern telephone: a permanent magnet and a metallic diaphragm that he made from a tintype. He invented the first telephone receiver with a permanent magnet in 1865, 11 years before Alexander Graham Bell patented his model. Later, Dolbear couldn't prove his claim, so Bell kept the patent. Dolbear lost his case before the U. S. Supreme Court, (''Dolbear et al. v. American Bell Telephone Company''). The June 18, 1881, edition of ''Scientific American'' reported:

In 1876, Dolbear patented a magneto electric telephone. He patented a static telephone in 1879.

In 1883, Dolbear was able to communicate over a distance of a quarter of a mile without wires in the Earth.Alt URL
/ref> His device relied on conduction in the ground, which was different from later radio transmissions that used electromagnetic radiation. He received a U.S. patent for a wireless telegraph in March of that year. His set-up used phones grounded by metal rods poked into the earth. His transmission range was at least as much as a half a mile and he received a patent for this device, , in 1886. (He did not patent his system in Europe.)

In 1899, The New England Wireless Telegraph and Telephone Company, a subsidiary of the American Wireless Telephone and Telegraph Company, purchased Dolbear's 1886 patent, and filed a suit against Marconi for infringement. However, in March 1901, a United States Circuit Court dismissed the suit. In April 1902, American Wireless petitioned Congress to extend the 1886 patent by ten years, but was unsuccessful, so it duly expired on October 4, 1903. In 1905, the New York Circuit Court further noted that the Dolbear patent was "inoperative, and that, even if operative, it operates by virtue of radically different electrical laws and phenomena" than the radio signaling used by Marconi."Marconi Wireless Telegraph Co. of America v. De Forest Wireless Telegraph Co. (Circuit Court, S. D. New York. April 11, 1905.)", ''The Federal Reporter. Volume 138. Cases Argued and Determined in the Circuit Courts of Appeals and Circuit and District Courts of the United States. July–September, 1905'', page 668.

In 1868 Dolbear (while a professor at Bethany College) invented the electrostatic telephone. He also invented the opeidoscope (an instrument for visualizing vibration of sound waves, using a mirror mounted on a membrane) and a system of incandescent lighting. He authored several books, articles, and pamphlets, and was recognized for his contributions to science at both the Paris Exposition in 1881 and the Crystal Palace Exposition in 1882.

In 1897, Dolbear published an article "The Cricket as a Thermometer" that noted the correlation between the ambient temperature and the rate at which crickets chirp. The formula expressed in that article became known as Dolbear's Law.

In 1899, after the demonstration by Ernest A. Hummel of the telediagraph, an apparatus allowing the transmission of pictures by wire, Dolbear claimed to have invented such an apparatus in 1864
''Norwich Bulletin'', 26 April 1899
.

He died at his home in Medford on February 23, 1910.

In 2008, Kent Biffle of the Dallas Morning News reported receiving newspaper clippings from a local lawyer and historian on the subject of UFO sightings in Stephenville, Texas. Apparently in 1897, widespread newspaper reports of a cigar-shaped flying object started to circulate in the Midwest and Southwest. Responding to sightings previously reported in the Morning News, on April 17, 1897, one respected Erath County farmer, C.L. McIlhany discovered such a craft had landed on his property, and reported two human operators, a pilot and an engineer, who gave their names as " S.E. Tilman" and "A.E. Dolbear." The two operators performed minor repairs on their electrically powered lighter-than-air craft, then again flew away.

Publications

Books

* Dolbear, A. E
''The Art of Projecting: A manual of experimentation in physics, chemistry, and natural history, with the porte lumière and magic lantern''
Boston, Lee and Shepard, 1877
* Dolbear, A. E
''The Telephone''
Boston, Lee and Shepard, 1877
* Dolbear, A. E
''The Telephone and how to make it''
London, Sampson Lowe, 1878
* Dolbear, A. E
''Matter, Ether, and Motion''
Boston, Lee and Shepard, 1892
* Dolbear, A. E
'' First Principles of Natural Philosophy''
Boston, Ginn and Co., 1897
* Dolbear, A. E
''Modes of Motion: Mechanical conceptions of physical phenomena''
Boston, Lee and Shepard, 1897

Journal articles

*
The Cricket as a Thermometer
. ''The American Naturalist'', Vol. 31, No. 371 (November 1897), pp. 970–971. Published by The University of Chicago Press for The American Society of Naturalists

Patents

*
Apparatus for transmitting sound by electricity
' April 5, 1881.

References

External links

*
*

Concise Encyclopedia of Tufts History - Dolbear, Amos Emerson, 1837–1910

Roxbury's Professor Dolbear

A portrait of Prof. Dolbear

{{DEFAULTSORT:Dolbear, Amos Emerson
1837 births
1910 deaths
19th-century American inventors
20th-century American inventors
19th-century American physicists
Ohio Wesleyan University alumni
University of Kentucky faculty
Tufts University faculty
20th-century American physicists
People from Norwich, Connecticut
Inventors from Connecticut
Scientists from Connecticut