John Hadley (16 April 1682 – 14 February 1744) was an
English
English usually refers to:
* English language
* English people
English may also refer to:
Peoples, culture, and language
* ''English'', an adjective for something of, from, or related to England
** English national ...
mathematician, and laid claim to the invention of the
octant, two years after
Thomas Godfrey claimed the same.
Biography
He was born in
Bloomsbury
Bloomsbury is a district in the West End of London. It is considered a fashionable residential area, and is the location of numerous cultural, intellectual, and educational institutions.
Bloomsbury is home of the British Museum, the largest ...
,
London
London is the capital and List of urban areas in the United Kingdom, largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary dow ...
the eldest son of George Hadley of
Osidge
Osidge is a district in the London Borough of Barnet, between Brunswick Park and Southgate, just west of the border with the London Borough of Enfield. It may be loosely defined as the part of postal district N14 that is in Barnet. Osidge has n ...
,
East Barnet,
Hertfordshire
Hertfordshire ( or ; often abbreviated Herts) is one of the home counties in southern England. It borders Bedfordshire and Cambridgeshire to the north, Essex to the east, Greater London to the south, and Buckinghamshire to the west. For gov ...
and his wife Katherine FitzJames. His younger brother
George Hadley
George Hadley (12 February 1685 – 28 June 1768) was an English lawyer and amateur meteorologist who proposed the atmospheric mechanism by which the trade winds are sustained, which is now named in his honour as Hadley circulation. As a key ...
became a noted
meteorologist
A meteorologist is a scientist who studies and works in the field of meteorology aiming to understand or predict Earth's atmospheric phenomena including the weather. Those who study meteorological phenomena are meteorologists in research, while t ...
.
In 1717 John became a member (and later vice-president) of the
Royal Society of London
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, r ...
. In 1729 he inherited his father's East Barnet estate.
He died in East Barnet in 1744 and is buried in the local churchyard with other members of his family. He had married Elizabeth, daughter of Thomas Hodges, FRS (former
Attorney General of Barbados) and had one child, a son and heir John, born in 1738.
Work
In 1730 Hadley invented the reflecting octant, which could be used to measure the altitude of the sun or other
celestial
Celestial may refer to:
Science
* Objects or events seen in the sky and the following astronomical terms:
** Astronomical object, a naturally occurring physical entity, association, or structure that exists in the observable universe
** Celes ...
objects above the horizon at sea. A mobile arm carrying a mirror and pivoting on a graduated arc provides a reflected image of the celestial body overlapping the image of the horizon, which is observed directly. If the position of the object on the sky and the time of the observation are known, it is easy for the user to calculate his own
latitude
In geography, latitude is a coordinate that specifies the north– south position of a point on the surface of the Earth or another celestial body. Latitude is given as an angle that ranges from –90° at the south pole to 90° at the north ...
. The octant proved extremely valuable for navigation and displaced the use of other instruments such as the
Davis quadrant
The backstaff is a navigational instrument that was used to measure the altitude of a celestial body, in particular the Sun or Moon. When observing the Sun, users kept the Sun to their back (hence the name) and observed the shadow cast by the u ...
. An
American
American(s) may refer to:
* American, something of, from, or related to the United States of America, commonly known as the "United States" or "America"
** Americans, citizens and nationals of the United States of America
** American ancestry, pe ...
,
Thomas Godfrey, independently invented the octant at approximately the same time.
Hadley also developed ways to make precision aspheric and
parabolic objective
Objective may refer to:
* Objective (optics), an element in a camera or microscope
* ''The Objective'', a 2008 science fiction horror film
* Objective pronoun, a personal pronoun that is used as a grammatical object
* Objective Productions, a Brit ...
mirrors for
reflecting telescope
A reflecting telescope (also called a reflector) is a telescope that uses a single or a combination of curved mirrors that reflect light and form an image. The reflecting telescope was invented in the 17th century by Isaac Newton as an alternati ...
s. In 1721 he showed the first parabolic
Newtonian telescope
The Newtonian telescope, also called the Newtonian reflector or just a Newtonian, is a type of reflecting telescope invented by the English scientist Sir Isaac Newton, using a concave primary mirror and a flat diagonal secondary mirror. Newto ...
to the Royal Society. This Newtonian, with a
primary mirror
A primary mirror (or primary) is the principal light-gathering surface (the objective) of a reflecting telescope.
Description
The primary mirror of a reflecting telescope is a spherical or parabolic shaped disks of polished reflective meta ...
, compared favorably with the large
aerial refracting telescopes of the day. He also made
Gregorian telescope
The Gregorian telescope is a type of reflecting telescope designed by Scottish mathematician and astronomer James Gregory in the 17th century, and first built in 1673 by Robert Hooke. James Gregory was a contemporary of Isaac Newton. Both oft ...
s with accurately shaped mirrors.
Honors
Mons Hadley and
Rima Hadley
Rima, also known as Rima the Jungle Girl, is the fictional heroine of W. H. Hudson's 1904 novel '' Green Mansions: A Romance of the Tropical Forest''. In it, Rima, a primitive girl of the shrinking rain forest of South America, meets Abel, a pol ...
on the
Moon
The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...
are named after him.
The
Oasis Trust
Oasis Charitable Trust, commonly known as Oasis, is a UK-based Christian registered charity. It was founded by the Reverend Steve Chalke in September 1985. Chalke had been assistant minister at Tonbridge Baptist Church, Kent, for four years. He ...
Academy in
Ponders End
Ponders End is the southeasternmost part of Enfield, north London, centred on the Hertford Road. Situated to the west of the River Lee Navigation, it became industrialised through the 19th century, similar to the Lea Valley in neighbouring E ...
in north London is called
Oasis Academy Hadley in his honour.
Oasis Academy in NE Enfield
Retrieved 5 February 2009
See also
* List of largest optical telescopes in the 18th century
References
Further reading
*
External links
Biography from the School of Mathematics and Statistics at the University of St Andrews, Scotland
{{DEFAULTSORT:Hadley, John
1682 births
1744 deaths
People from Chipping Barnet
18th-century British astronomers
18th-century British inventors
Fellows of the Royal Society
People from Bloomsbury
British scientific instrument makers