generally known years after his
death; yet in spite of the absence of anything approaching
self-advertisement he acquired a very high reputation within his own
country and abroad, recognized by the Institute of France in 1803 when
it chose him as one of its eight foreign associates. Arsenic formed the
subject of his first recorded investigation, on which he was engaged at
least as early as 1764, and in 1766 he began those communications to the
Royal Society on the chemistry of gases, which are among his chief
titles to fame. The first (_Phil. Trans._, 1766) consists of "Three
papers containing experiments on Factitious Airs," dealing mostly with
"inflammable air" (hydrogen), which he was the first to recognize as a
distinct substance, and "fixed air" (carbon dioxide). He determined the
specific gravity of these gases with reference to common air,
investigated the extent to which they are absorbed by various liquids,
and noted that common air containing one part in nine by volume of fixed
air is no longer able to support combustion, and that the air produced
by fermentation and putrefaction has properties identical with those of
fixed air obtained from marble. In the following year he published a
paper on the analysis of one of the London pump-waters (from Rathbone
Place, Oxford Street), which is closely connected with the memoirs just
mentioned, since it shows that the calcareous matter in that water is
held in solution by the "fixed air" present and can be precipitated by
lime. Electrical studies seem next to have engaged his attention, and in
1771 and 1772 he read to the Royal Society his "Attempt to explain some
of the principal phenomena of electricity by an elastic fluid," which
was followed in 1775 by an "Attempt to imitate the effects of the
Torpedo (a fish allied to the ray)" (_Phil. Trans._, 1776). But these
two memoirs contain only a part of the electrical researches he carried
out between 1771 and 1781, and many more were found after his death in a
number of sealed packets of papers. The contents of these for a long
time remained unknown, but ultimately by permission of the duke of
Devonshire, to whom they belonged, they were edited by James Clerk
Maxwell and published in 1879 by the Cambridge University Press as the
_Electrical Researches of the Hon. Henry Cavendish_. About 1777 or 1778
he resumed his pneumatic inquiries, though he published nothing on the
subject till 1783. In that year he described a new eud