John Tuthill Dreyer

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Major-General John Tuthill Dreyer, C.B., D.S.O., Royal Artillery (24 December, 1876 – 23 May, 1959) was a British Army officer and artillerist, a son of the noted astronomer John Louis Emil Dreyer and the brother of Admiral Sir Frederic C. Dreyer.

Life & Career

Dreyer was born on 24 December, 1876,[1] the son of Dr. John Louis Emil Dreyer, then serving as the Earl of Rosse's astronomer. When he was young, his father was first appointed Assistant Astronomer at the Royal Observatory at Dunsink, and then Astronomer at the Armagh Observatory. John was educated at home with his two brothers Frederic and George until he was sent as a day boy to the Royal School, Armagh.[2] He entered the Royal Military Academy, Woolwich and was commissioned into the Royal Artillery in 1897. During the Boer War he took part in operations in the Transvaal, Orange River Colony and Cape Colony.[1]

Around 1908, he conceived the Dreyer Calculator, a comprehensive slide rule to make range adjustments for a given range, range rate and atmospheric condition for naval use. Some time soon afterward, he devised an enhanced naval gun sight that could apply changes necessitated by wear of the bore. Both systems were being manufactured for use by 1908.[3]

Dreyer was appointed D.S.O. "for services rendered in connexion with military operation in the field" on 1 January, 1916.[4]

He was promoted from the rank of Colonel to Major-General and retired on 1 April, 1930.[5]

Dreyer's two sons, John and Christopher, both served in the Royal Navy as Commanders during the Second World War.[6]


  • "Maj.-Gen. J. T. Dreyer" (Obituaries). The Times. Monday, 25 May, 1959. Issue 54469, col F, pg. 15.
  • Dreyer, Admiral Sir Frederic C. (1955). The Sea Heritage: A Study of Maritime Warfare. London: Museum Press Limited.

See Also

Military Appointments

  1. 1.0 1.1 "Maj.-Gen. J. T. Dreyer" (Obituaries). The Times. Monday, 25 May, 1959. Issue 54469, col F, p. 15.
  2. Dreyer. Sea Heritage. p. 25.
  3. Fire Control, 1908, pp. 5-6.
  4. "Rewards for Service in the Field" (Official Appointments and Notices). The Times. Friday, 14 January, 1916. Issue 41063, col A, p. 12.
  5. "London Gazette" (Official Appointments and Notices). The Times. Wednesday, 2 April, 1930. Issue 45477, col C, p. 27.
  6. Dreyer. Sea Heritage. p. 463.