Henry Cavendish
1731-1810
English Chemist and Physicist
Henry Cavendish made many significant contributions to a wide range of scientific endeavors and is regarded as one of the greatest scientist of his day. He is best known for his work with the chemistry of gases, the discovery of hydrogen, the determination of the composition of water, the synthesis of water, and his contributions to electrical theory.
Henry Cavendish was born into one of England's most prominent families; two of his grandfathers were dukes. When he received his inheritance, he became one of the wealthiest people of his time. He was educated at exclusive Hackney School and attended Peterhouse College at Cambridge University. He never received a degree, refusing to declare his acceptance of the Church of England, a requirement of all graduates. Instead he returned home to assist his father in the laboratory that the elder Cavendish, a well-known amateur scientist, maintained in their home. He subsequently followed in his father's footsteps, working for the rest of his life in his own private laboratory in his home.
Cavendish was an extremely shy and eccentric person, an introvert and recluse who seldom left his house. It is not surprising that he also was reluctant to publish the results of his scientific work, most of which remained unpublished until the Scottish physicist James Clerk Maxwell (1831-1879) edited and published it after Cavendish's death.
He was among the first scientists to use quantitative methods in chemistry. He performed extensive experiments with gases, especially hydrogen ("inflammable air") and carbon dioxide ("fixed air"). He determined that hydrogen is a separate substance and that water is not an element but is made up of hydrogen and oxygen. He succeeded in synthesizing water from its constituent elements. He also discovered nitric acid.
Cavendish made significant groundbreaking contributions to the study of electricity. He suggested that an electric atmosphere surrounds a charged substance, providing the basis for the development of electric field theory. He proposed the concept of electrical potential and discovered that the potential across a conductor is proportional to the current through it. He was one of several scientists who independently worked out the inverse square law of electrical attraction and repulsion: the attraction between opposite charges or the repulsion between two charges having the same sign is inversely proportional to the distance between the charges. He was first to determine and study the electrical conductivity of salt solutions. It is interesting to note that Cavendish had no instrument to measure electric current. Instead, he used the reaction of his own body to the electrical shock to measure the intensity of the current, developing a quantitative scale based on the intensity of his reaction to the shock.
As a part of a research effort he undertook late in life, he invented an extremely sensitive torsion balance and used it to determine the constant in Isaac Newton's (1642-1727) universal law of gravitation. He was also able to measure the density of Earth using data obtained with this balance.
Cavendish also performed extensive experiments with heat. His work with the calibration of thermometers, the measurement of vapor pressures, latent heats, and specific heats is particularly noteworthy. He rejected the theory thatheat is a substance that flows from one object to another. Instead he championed the explanation of heat as the motion of particles within substances.
Cavendish died at age 78, a recluse with neither close friends nor any direct descendants to inherit his vast wealth. The various relatives who became his heirs honored him by endowing the Cavendish Laboratory at Cambridge University. This laboratory quickly became a major center for developments in experimental and theoretical physics and remains so today.
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