Cavendish, Henry (1731-1810)

 English chemist and physicist who was shy and absent-minded. He was terrified of women, and communicated with his female servants by notes. He performed numerous scientific investigations, but published only twenty articles and no books. His experiments on electricity  were only published a century after they were performed, when Maxwell rediscovered them in 1879. Cavendish's experiments included the investigation of capacitance  In his experiments, he measured the strength of a current by shocking himself and estimating the magnitude of the pain.

Cavendish perfected the technique of collecting gases above water, publishing his techniques and new findings in On Fractious Airs (1766). He investigated ``fixed air'' and isolated ``inflammable air'' (hydrogen) in 1766 and investigated its properties. He showed that it produced a dew, which appeared to be water, upon being burned. This experiment was repeated by Lavoisier who termed the gas hydrogen. He also found it to be much less dense than air. He investigated air, and found a small volume which he could not combine with nitrogen using electrical sparks. The experiment was ignored until repeated by Ramsay, who is credited with the discovery of argon. Cavendish also used a sensitive  torsion balance  to measure the value of the gravitational constant G . This allowed him to calculate the mass of the Earth.
APS history, June 2008
Cavendish's paper on determining the density of the earth
Cavendish's value for the density of the earth was 5.48 g/cm^3, the current value is 5.57 g/cm^3.

References
Maxwell, J. C. Electrical researches of the Honorable Henry Cavendish  Frank Cass, 1967.
© 1996-9 Eric W. Weisstein
1999-01-22


CAVENDISH'S MEASUREMENT OF THE GRAVITATIONAL CONSTANT G (1798)
 

Measure the angle b with which the light beam reflects off the mirror. This is directly proportional to the torque caused by the gravitational attraction between the masses m on the torsion beam and the fixed masses M. The angle of deflection is easily determined by projecting the beam of light against a distant wall and measuring the distance the spot of light moves on the wall.