Henry Cavendish, FRS (10 October 1731 - 24 February 1810) was a British
scientistA scientist, in the broadest sense, is any person who engages in a systematic activity to acquire knowledge or an individual that engages in such practices and traditions that are linked to schools of thought or philosophy. In a more restricted sense, a scientist is an individual who uses the...
noted for his discovery of
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
or what he called "inflammable air". He described the density of inflammable air, which formed water on combustion, in a 1766 paper "On Factitious Airs".
Antoine LavoisierAntoine-Laurent de Lavoisier ; ), the father of modern chemistry, was a French noble prominent in the histories of chemistry and biology...
later reproduced Cavendish's experiment and gave the element its name. Cavendish is also known for the
Cavendish experimentThe Cavendish experiment, done in 1797–98 by British scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory, and the first to yield accurate values for the gravitational constant and the mass of the Earth. However, these were...
, his measurement of the Earth's density, and early research into electricity.
Personal life
Henry Cavendish was born on 10 October 1731 in
NiceNice is a city in southern France located on the Mediterranean coast, between Marseille, France, and Genoa, Italy, with 347 060 inhabitants in the 2006 estimate...
, France, where his family was living at the time. His mother was Lady Anne Grey, daughter of the
Duke of KentHenry Grey, 1st Duke of Kent KG , PC , was a British courtier and one of the Lords Justice appointed during the absence, in Germany, of George I....
and his father was
Lord Charles CavendishLord Charles Cavendish FRS was a British nobleman, Whig politician and scientist.He was the youngest son of William Cavendish, 2nd Duke of Devonshire and Rachel Russell.- Marriage and children :...
, son of
2nd Duke of DevonshireWilliam Cavendish, 2nd Duke of Devonshire KG, PC was a British nobleman and politician, the eldest son of William Cavendish, 1st Duke of Devonshire and Lady Mary Butler. A prominent Whig, he was sworn of the Privy Council in 1707, and served as Lord President of the Council from 1716 to 1717 and...
. The family traces its lineage across eight centuries to
NormanThe Normans were the people who gave their names to Normandy, a region in northern France. They descended from Viking conquerors of the territory and the native population of mostly Frankish and Gallo-Roman stock...
times and was closely connected to many aristocratic families of Great Britain.
At age 11, Cavendish was a pupil at Peter Newcome's School in
HackneyHackney Central is the central district of the London Borough of Hackney in East London. It comprises the area roughly surrounding, and extending north from Mare Street. It is situated north east of Charing Cross...
. At age 18 (on 24 November 1749) he entered the
University of CambridgeThe University of Cambridge , located in the City of Cambridge, Cambridgeshire, United Kingdom, is the second oldest university in the English-speaking world and the fourth oldest in Europe...
in St Peter's College, now known as Peterhouse, but left four years later on 23 February 1753 without graduating. His first paper, "Factitious Airs", appeared thirteen years later, in 1766.
Cavendish was silent, and solitary, viewed as somewhat eccentric,he only spoke to his female servents by notes and formed no close personal relationships outside his family. By one account, Cavendish had a back staircase added to his house in order to avoid encountering his housekeeper because he was especially shy of women. The contemporary accounts of his personality have led some modern commentators, such as
Oliver SacksOliver Wolf Sacks, CBE, FRCP , is a British neurologist residing in New York City. Sacks is the author of several bestselling books, including several collections of case studies of people with neurological disorders...
, to speculate that he had
Asperger syndromeAsperger syndrome is an autism spectrum disorder, and people with it therefore show significant difficulties in social interaction, along with restricted and repetitive patterns of behavior and interests. It differs from other autism spectrum disorders by its relative preservation of linguistic and...
, though he may merely have been painfully shy. His only social outlet was the Royal Society Club, whose members dined together before weekly meetings. Cavendish seldom missed these meetings, and was profoundly respected by his contemporaries. However his shyness made those who "sought his views... speak as if into vacancy. If their remarks were...worthy, they might receive a mumbled reply." He also enjoyed collecting fine furniture exemplified by his purchase of a set of "ten inlaid satinwood chairs with matching
cabriole legA cabriole leg is one of vertical supports of a piece of furniture shaped in two curves; the upper arc is convex, while lower is concave; the upper curve always bows outward, while the lower curve bows inward. The axes of the two curves must lie within the same plane...
ged sofa" documented to have been acquired by Cavendish himself.
Because of his asocial and secretive behaviour, Cavendish often avoided publishing his work, and much of his findings were not even told to his fellow scientists. In the late nineteenth century, long after his death,
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
looked through Cavendish's papers and found things for which others had been given credit. Examples of what was included in Cavendish's discoveries or anticipations were
Richter's Law of Reciprocal ProportionsJeremias Benjamin Richter was a German chemist. He was born at Hirschberg in Silesia, became a mining official at Breslau in 1794, and in 1800 was appointed assessor to the department of mines and chemist to the royal porcelain factory at Berlin, where he died.-Developer of titration:To him...
,
Ohm's LawIn electrical circuits, Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them....
,
Dalton's Law of Partial PressuresIn chemistry and physics, Dalton's law states that the total pressure exerted by a gaseous mixture is equal to the sum of the partial pressures of each individual component in a gas mixture...
, principles of electrical conductivity (including Coulomb's Law), and
Charles's Law of GasesCharles's law is an experimental gas law which describes how gases tend to expand when heated. It was first published by French natural philosopher Joseph Louis Gay-Lussac in 1802, although he credits the discovery to unpublished work from the 1780s by Jacques Charles...
.
Cavendish died in 1810 and was buried, along with many of his ancestors, in the church that is now
Derby CathedralThe Cathedral of All Saints , is a cathedral church in the City of Derby, England. It is the seat of the Bishop of Derby, and with an area of around is the smallest Anglican cathedral in England.-History:...
(and the road he used to live on in Derby has been named after him. The University of Cambridge's
Cavendish LaboratoryThe Cavendish Laboratory is the University of Cambridge's Department of Physics, and is part of the university's School of Physical Sciences. It was opened in 1874 as a teaching laboratory and was initially located on the New Museums Site, Free School Lane, in the centre of Cambridge. After...
was endowed by one of Cavendish's later relatives,
William Cavendish, 7th Duke of DevonshireWilliam Cavendish, 7th Duke of Devonshire, KG, PC , known as Lord Cavendish of Keighley between 1831 and 1834 and 2nd Earl of Burlington of the 2nd creation between 1834 and 1858, was the great-grandson of the 4th Duke of Devonshire, grandson of the 1st Earl of Burlington, and son of William...
(Chancellor of the University from 1861 to 1891).
Gases and the atmosphere
Cavendish is considered to be one of the so-called
pneumatic chemistsPneumatic chemistry is a term most-closely identified with an area of scientific research of the seventeenth, eighteenth, and early nineteenth centuries. Important goals of this work were an understanding of the physical properties of gases and how they relate to chemical reactions and,...
of the eighteenth and nineteenth centuries, along with, for example,
Joseph PriestleyJoseph Priestley was an 18th-century English theologian, Dissenting clergyman, natural philosopher, educator, and political theorist who published over 150 works...
,
Joseph BlackJoseph Black was a Scottish physician, physicist, and chemist, known for his discoveries of latent heat, specific heat, and carbon dioxide. He was a founder of thermochemistry who developed many pre-thermodynamics concepts, such as heat capacity, and was the mentor for James Watt...
, and
Daniel RutherfordProfessor Daniel Rutherford was a Scottish chemist and physician who is most famous for the isolation of nitrogen in 1772.- Isolation of nitrogen :...
. By combining metals with strong acids, Cavendish made
hydrogenHydrogen is the chemical element with atomic number 1. It is represented by the symbol H. At standard temperature and pressure, hydrogen is a colorless, odorless, nonmetallic, tasteless, highly flammable diatomic gas with the molecular formula H
2...
(H
2) gas, which he isolated and studied. Although others, such as
Robert BoyleRobert Boyle was a natural philosopher, chemist, physicist, inventor, and gentleman scientist, also noted for his writings in theology. He is best known for the formulation of Boyle's law...
, had prepared hydrogen gas earlier, Cavendish is usually given the credit for recognizing its elemental nature.
Cavendish observed that hydrogen, which he called "inflammable air", reacts with oxygen, then known as "dephlogisticated air", to form water.
James WattJames Watt FRS was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the changes brought by the Industrial Revolution in both the Kingdom of Great Britain and the world.-Biography:James Watt was born on 19 January 1736 in Greenock,...
and
Antoine LavoisierAntoine-Laurent de Lavoisier ; ), the father of modern chemistry, was a French noble prominent in the histories of chemistry and biology...
made a similar observation, resulting in a controversy as to who should receive credit for it.
Cavendish also accurately determined the composition of Earth's atmosphere. In a 1785 paper, he described experiments in which hydrogen and ordinary air were combined in known ratios, and then exploded with a spark of electricity. In each case, Cavendish observed both the formation of water and that the gas volume after the explosion was always less than it was before it. By careful measurements he was led to conclude that, "common air consists of one part of dephlogisticated air [oxygen], mixed with four of phlogisticated [nitrogen]".
The same paper described an experiment in which Cavendish was able to remove, in modern terminology, both the oxygen and nitrogen gases from a sample of atmospheric air until only a small bubble of unreacted gas was left in the original sample. From this experiment Cavendish concluded that not more than 1/120 of the Earth's atmosphere was other than oxygen and nitrogen. Although a seemingly small fraction, about 100 years later
William RamsaySir William Ramsay, KCB was a Scottish chemist who discovered the noble gases and received the Nobel Prize in Chemistry in 1904 "in recognition of his services in the discovery of the inert gaseous elements in air" .-Early years:Ramsay was...
and
Lord RayleighJohn William Strutt, 3rd Baron Rayleigh OM was an English physicist who, with William Ramsay, discovered the element argon, an achievement for which he earned the Nobel Prize for Physics in 1904...
showed that this residual gas contained
argonArgon is a chemical element designated by the symbol Ar. Argon has atomic number 18 and is the third element in group 18 of the periodic table . Argon is present in the Earth's atmosphere at 0.94%. Terrestrially, it is the most abundant and most frequently used of the noble gases...
, an element that was unknown at the time.
Density of the Earth
In addition to his achievements in chemistry, Cavendish is also known for the
Cavendish experimentThe Cavendish experiment, done in 1797–98 by British scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory, and the first to yield accurate values for the gravitational constant and the mass of the Earth. However, these were...
, the first to measure the force of gravity between masses in a laboratory and to produce an accurate value for the Earth's density. His work led others to accurate values for the
gravitational constant (G)The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. It is also known as the universal...
and the Earth's mass. Based on his results, one can calculate a value for G of 6.754 × 10
−11N-m
2/kg
2 , which compares favourably with the modern value of 6.67428 × 10
−11N-m
2/kg
2.
The equipment Cavendish used was designed and built by geologist
John MichellJohn Michell was an English natural philosopher and geologist whose work spanned a wide range of subjects from astronomy to geology, optics, and gravitation. He was both a theorist and an experimenter....
, who died before he could begin the experiment. The apparatus was sent in crates to Cavendish, who completed the experiment in 1797 – 1798, and published the results. Cavendish noticed that Michell's apparatus would be sensitive to temperature differences and induced air currents so he made modifications by isolating the apparatus in a separate room with external controls and telescopes for making observations.
The experimental apparatus consisted of a torsion balance to measure the gravitational attraction between two 350-pound lead spheres and a pair of 2-inch 1.61-pound lead spheres. Using this equipment, Cavendish found that the Earth's average density is 5.48 times greater than that of water.
John Henry PoyntingJohn Henry Poynting was an English physicist. He was a professor of physics at Mason Science College from 1880 until his death.Poynting was the youngest son of Thomas Elford Poynting, a Unitarian minister...
later noted that the data should have led to a value of 5.448, and indeed that is the average value of the twenty-nine determinations Cavendish included in his paper.
It is not unusual to find books that erroneously describe Cavendish's work as a measurement either of the
gravitational constant (G)The gravitational constant, denoted G, is an empirical physical constant involved in the calculation of the gravitational attraction between objects with mass. It appears in Newton's law of universal gravitation and in Einstein's theory of general relativity. It is also known as the universal...
or the Earth's mass, and this mistake has been pointed out by several authors. In reality, Cavendish's stated goal was to measure the Earth's density, and his result was later used to calculate
G. The first time that this constant was used was in 1873, almost 100 years after the Cavendish experiment. Cavendish's results also can be used to
calculate the Earth’s massThe Cavendish experiment, done in 1797–98 by British scientist Henry Cavendish, was the first experiment to measure the force of gravity between masses in the laboratory, and the first to yield accurate values for the gravitational constant and the mass of the Earth. However, these were...
.
Cavendish performed his experiment in an outbuilding in the garden of his Clapham Commons estate. For years afterward, his neighbours would point out the building and tell their children that it was where the world was weighed.
Electrical researches
Cavendish wrote papers on electrical topics for the Royal Society but the bulk of his electrical experiments did not become known until they were collected and published by
James Clerk MaxwellJames Clerk Maxwell was a Scottish theoretical physicist and mathematician. His most significant achievement was the development of the classical electromagnetic theory, synthesizing all previous unrelated observations, experiments and equations of electricity, magnetism and even optics into a...
a century later, in 1879, long after other scientists had been credited with the same results. Among Cavendish's discoveries were the following:
- The concept of electric potential
At a point in space, the electric potential is potential energy divided by charge that is associated with a static electric field. It is a scalar quantity, typically measured in volts....
, which he called the "degree of electrification"
- An early unit of capacitance
In electromagnetism and electronics, capacitance is the ability of a body to hold an electrical charge.Capacitance is also a measure of the amount of electric charge stored for a given electric potential. A common form of charge storage device is a parallel-plate capacitor...
, that of a sphere one inch in diameter
- The formula for the capacitance of a plate capacitor
A capacitor or condenser is a passive electronic component consisting of a pair of conductors separated by a dielectric. When a voltage potential difference exists between the conductors, an electric field is present in the dielectric. This field stores energy and produces a mechanical force...
- The concept of the dielectric constant
The relative static permittivity of a material under given conditions is a measure of the extent to which it concentrates electrostatic lines of flux. It is the ratio of the amount of stored electrical energy when a potential is applied, relative to the permittivity of a vacuum...
of a material
- The relationship between electric potential and current, now called Ohm's Law
In electrical circuits, Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference or voltage across the two points, and inversely proportional to the resistance between them....
. (1781)
- Laws for the division of current in parallel circuits, now attributed to Charles Wheatstone
Sir Charles Wheatstone FRS , was a British scientist and inventor of many scientific breakthroughs of the Victorian era, including the English concertina, the stereoscope , and the Playfair cipher...
- Inverse square law of variation of electric force with distance, now called Coulomb's Law
Coulomb's law, sometimes called the Coulomb law, is an equation describing the electrostatic force between electric charges. It was studied and first published in the 1780s by French physicist Charles Augustin de Coulomb and was essential to the development of the theory of electromagnetism...
Selected writings
- edited by James Clerk Maxwell and revised by Joseph Larmor - edited by James Clerk Maxwell and revised by Joseph Larmor - edited by James Clerk Maxwell
Further reading
- Dictionary of National Biography, Vol. 3, p.1261.
- Cavendish: The Experimental Life, C. Jungnickel and R. McCormmach, Bucknell University Press, 1999.
External links
- The Life of the Honourable Henry Cavendish by George Wilson, London, 1851.
- Experiments on Air by Henry Cavendish, Edinburgh: William F. Clay (1893) - Alembic Club reprint number 3.
- "The Mean Density of the Earth" by J. H. Poynting, London: Charles Griffin and Company (1894).
- The Laws of Gravitation: Memoirs by Newton, Bouguer and Cavendish, edited and translated by A. Stanley MacKenzie, New York: American Book Company (1900).
- A History of Chemistry by F. J. Moore, New York: McGraw-Hill (1918) - See especially pages 34 – 36.
- Henry Cavendish, English Scientist (1731-1810) from the Encyclopaedia Britannica, 10th Edition (1902).
- "Cavendish" by Christa Jungnickel and Russell McCormmach, 1996, 414 pages