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Amos Dolbear

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Amos Dolbear
Amos Dolbear, c. 1880
Born(1837-11-10)November 10, 1837
Norwich, Connecticut
DiedFebruary 23, 1910(1910-02-23) (aged 72)
Medford, Massachusetts
Known forDolbear's law
Signature

Amos Emerson Dolbear (/ˈeɪmɒs ˈɛmərsən ˈdɒlbɛər/;[1] 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.[2] 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

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Amos Dolbear was born in Norwich, Connecticut, on November 10, 1837.[3] 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.[citation needed] 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:

[...] had he been observant of patent office formalities, it is possible that the speaking telephone, now so widely credited to Mr. Bell would be garnered among his own laurels.[4]

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

Circuit of Dolbear's wireless telephone, from his 1882 patent. The transmitter (A) consisted of an electrostatic microphone (T) and battery in the primary circuit of an induction coil (G). One side of the high voltage secondary winding is earthed (C) the other side connected to an elevated capacitance (H1). The receiver (B) consists of a battery, earphone (R) and capacitor (H) connected in series between an elevated capacitor (H2) and earth (D).

In 1883, Dolbear was able to communicate over a distance of a quarter of a mile without wires in the Earth.[5][6] His device relied on conduction in the ground, which was different from later radio transmissions that used electromagnetic radiation.[citation needed] 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[7] and he received a patent for this device, U.S. patent 350,299, 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.[8] However, in March 1901, a United States Circuit Court dismissed the suit.[9] 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.[10] 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.[11]

In 1868 Dolbear (while a professor at Bethany College) invented the electrostatic telephone.[citation needed] 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.[citation needed] 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.[3]

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.[12] Apparently in 1897, widespread newspaper reports of a cigar-shaped flying object started to circulate in the Midwest and Southwest.[13][14] 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."[12] The two operators performed minor repairs on their electrically powered lighter-than-air craft, then again flew away.[15][16]

Publications

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Books

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Journal articles

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  • "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

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References

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  1. ^ "What is the definition of Amos emerson dolbear?". Dictionary.net. Retrieved January 24, 2024.
  2. ^ "Tufts Digital Library". Archived from the original on January 4, 2014. Retrieved April 14, 2014.
  3. ^ a b "Prof Dolbear Passes Away". The Boston Globe. Medford. February 24, 1910. p. 9. Retrieved March 14, 2022 – via Newspapers.com.
  4. ^ Dolbear, Amos (June 18, 1881). "A new telephone system". Scientific American. 44 (25). The Scientific American Publishing Co.: 384. JSTOR 26075824. Retrieved June 15, 2022.
  5. ^ Fahie, John Joseph (1902). A History of Wireless Telegraphy, 3rd Ed. New York: Dodd, Mead, and Co. pp. 94–99. Alt URL
  6. ^ Sarkar, T. K.; Mailloux, Robert; Oliner, Arthur A. (2006). History of Wireless. John Wiley and Sons. pp. 254–255. ISBN 978-0471783015.
  7. ^ "Mode of Electric communication" U.S. patent 350,299 October 5, 1886. Lines 51–55.
  8. ^ "A Suit Against Marconi". The Washington Times. New York. October 18, 1899. p. 4. Retrieved March 14, 2022 – via Newspapers.com.
  9. ^ "Suit Against Marconi Dismissed". New-York Tribune. March 23, 1901. p. 7. Retrieved March 14, 2022 – via Newspapers.com.
  10. ^ "Petition of the American Wireless Telegraph and Telegraph Company, of Philadelphia, Pa., Praying the Extension for Ten Years of Letters Patent No. 350,299, Being the Basic Patent for the Art of Wireless Telegraphy and Telephony Granted to Amos Emerson Dolbear in 1886", United States Senate Documents, Volume 26 (4245), 57th Congress, 1st Session, Document No. 346, pages 1–3.
  11. ^ "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.
  12. ^ a b Biffle, Kent (February 4, 2008). "Stephenville area's had its share of UFO sightings". Dallas Morning News. Archived from the original on October 28, 2008. Retrieved April 26, 2009.
  13. ^ Cohen, Daniel (1981). The great airship mystery: A UFO of the 1890s. Dodd, Mead. ISBN 0-396-07990-3.
  14. ^ Busby, Michael (January 2004). Solving the 1897 Airship Mystery. Pelican Publishing Company. ISBN 1-58980-125-3.
  15. ^ Cabinet of Wonders (February 3, 2008). "The Stephenville phantom airship". Cabinet of Wonders blog. Archived from the original on March 3, 2008. Retrieved April 26, 2009.
  16. ^ Cabinet of Wonders (February 13, 2008). "The faces of phantom airship pilots". Cabinet of Wonders blog. Archived from the original on February 18, 2008. Retrieved April 26, 2009.
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