Amos Dolbear

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Amos Dolbear
Amosedolbear1880.jpg
Amos Dolbear, ca. 1880
Born (1837-11-10)November 10, 1837
Died February 23, 1910(1910-02-23) (aged 72)

Amos Emerson Dolbear (November 10, 1837 – February 23, 1910) was an American physicist and inventor. His patents interfered with Guglielmo Marconi's planned activities in the United States. 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.[1]

Biography[edit]

Dolbear was a graduate of Ohio Wesleyan University, in Delaware, Ohio. While a student at Ohio Wesleyan, 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 of 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:

"had [Dolbear] 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."

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

In 1882, Dolbear was able to communicate over a distance of a quarter of a mile without wires in the Earth. It is interesting to note that the Tufts professor was ahead of Hertz and Marconi. He received a U.S. patent for a wireless telegraph in March of that year. His device relied on conduction in the ground, a type of radio transmission. 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[2][3] and he received a patent for this device, U.S. Patent 350,299, in 1886. But more importantly the Dolbear patent prevented the Marconi Company from operating in the United States. In the end Marconi had to purchase Dolbear's patent, primarily because it was:

  1. Similar to the 1896 model of Guglielmo Marconi.[4]
  2. Tractable in specific applications (such as transmission in the earth).

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.

Publications[edit]

Books
  • The Art of Projecting, Boston, 1876
  • The Speaking Telephone, 1877
  • Sound and its Phenomena, 1885.
  • First Principles of Natural Philosophy, Boston, 1897.
  • Modes of Motion, Boston, 1897.
  • Matter, Ether, and Motion
Journal articles
  • "The Cricket as a Thermometer". The American Naturalist, Vol. 31, No. 371 (Nov., 1897), pp. 970–971. Published by The University of Chicago Press for The American Society of Naturalists
Patents

External articles[edit]

Citations
  1. ^ http://dl.tufts.edu/catalog/tei/tufts:UA069.005.DO.00001/chapter/D00047
  2. ^ "Mode of Electric communication" U.S. Patent 350,299 Oct 5, 1886. Lines 51-55.
  3. ^ "Dolbear - Overlooked Radio Pioneer" 25-Aug-1999. - (cf., "Dolbear [...] appears to have successfully sent and received signals using Hertzian waves over a distance of 13 miles - more than a decade before Marconi did".)
  4. ^ John J. O'Neill, "Prodigal Genius:The Life of Nikola Tesla". Ives Washburn, New York, 1944; Great Britain by Neville Spearman Ltd., 1968; United States by Angriff Press, Los Angeles, 1973.
General