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