There are several plaques of this type in
Bloomsbury that appear to have been erected in preference to blue plaques. They
do appear to have more character to them.
The plaque is cast from metal and has maintained clean sharp edges of the text
and relief work above and below the inscription. The inscription reads:
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Honble
Henry Cavendish
Natural Philosopher
Lived here
Born Died
1731 1810
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The Notable Biographies website (visit
link) tells us:
"The English physicist and chemist Henry
Cavendish determined the value of the universal constant of gravitation, made
noteworthy electrical studies, and is credited with the discovery of hydrogen
and the composition of water.
Early years
Henry Cavendish was born in Nice, France, on
October 10, 1731, the oldest son of Lord Charles Cavendish and Lady Anne Grey,
who died a few years after Henry was born. As a youth he attended Dr. Newcomb's
Academy in Hackney, England. He entered Peterhouse, Cambridge, in 1749, but left
after three years without taking a degree.
Cavendish returned to London, England to
live with his father. There, Cavendish built himself a laboratory and workshop.
When his father died in 1783, Cavendish moved the laboratory to Clapham Common,
where he also lived. He never married and was so reserved that there is little
record of his having any social life except occasional meetings with scientific
friends.
Contributions to chemistry
During his lifetime Cavendish made notable
discoveries in chemistry, mainly between 1766 and 1788, and in electricity,
between 1771 and 1788. In 1798 he published a single notable paper on the
density of the earth. At the time Cavendish began his chemical work, chemists
were just beginning to recognize that the "airs" that were evolved in many
chemical reactions were clear parts and not just modifications of ordinary air.
Cavendish reported his own work in "Three Papers Containing Experiments on
Factitious Air" in 1766. These papers added greatly to knowledge of the
formation of "inflammable air" (hydrogen) by the action of dilute acids (acids
that have been weakened) on metals.
Cavendish's other great achievement in
chemistry is his measuring of the density of hydrogen. Although his figure is
only half what it should be, it is astonishing that he even found the right
order. Not that his equipment was crude; where the techniques of his day
allowed, his equipment was capable of precise results. Cavendish also
investigated the products of fermentation, a chemical reaction that splits
complex organic compounds into simple substances. He showed that the gas from
the fermentation of sugar is nearly the same as the "fixed air" characterized by
the compound of chalk and magnesia (both are, in modern language, carbon
dioxide).
Another example of Cavendish's ability was
"Experiments on Rathbone-Place Water"(1767), in which he set the highest
possible standard of accuracy. "Experiments" is regarded as a classic of
analytical chemistry (the branch of chemistry that deals with separating
substances into the different chemicals they are made from). In it Cavendish
also examined the phenomenon (a fact that can be observed) of the retention of
"calcareous earth" (chalk, calcium carbonate) in solution (a mixture dissolved
in water). In doing so, he discovered the reversible reaction between calcium
carbonate and carbon dioxide to form calcium bicarbonate, the cause of temporary
hardness of water. He also found out how to soften such water by adding lime
(calcium hydroxide).
One of Cavendish's researches on the current
problem of combustion (the process of burning) made an outstanding contribution
to general theory. In 1784 Cavendish determined the composition (make up) of
water, showing that it was a combination of oxygen and hydrogen. Joseph
Priestley (1733–1804) had reported an experiment in which the explosion of the
two gases had left moisture on the sides of a previously dry container.
Cavendish studied this, prepared water in measurable amount, and got an
approximate figure for its volume composition.
Electrical research
Cavendish published only a fraction of the
experimental evidence he had available to support his theories, but his peers
were convinced of the correctness of his conclusions. He was not the first to
discuss an inverse-square law of electrostatic attraction (the attraction
between opposite—positive and negative—electrical charges). Cavendish's idea,
however, based in part on mathematical reasoning, was the most effective. He
founded the study of the properties of dielectrics (nonconducting electricity)
and also distinguished clearly between the amount of electricity and what is now
called potential.
Cavendish had the ability to make a
seemingly limited study give far-reaching results. An example is his study of
the origin of the ability of some fish to give an electric shock. He made up
imitation fish of leather and wood soaked in salt water, with pewter (tin)
attachments representing the organs of the fish that produced the effect. By
using Leyden jars (glass jars insulated with tinfoil) to charge the imitation
organs, he was able to show that the results were entirely consistent with the
fish's ability to produce electricity. This investigation was among the earliest
in which the conductivity of aqueous (in water) solutions was studied.
Cavendish began to study heat with his
father, then returned to the subject in 1773–1776 with a study of the Royal
Society's meteorological instruments. (The Royal Society is the world's oldest
and most distinguished scientific organization.) During these studies he worked
out the most important corrections to be employed in accurate thermometry (the
measuring of temperature). In 1783 he published a study of the means of
determining the freezing point of mercury. In it he added a good deal to the
general theory of fusion (melting together by heat) and freezing and the latent
heat changes that accompany them (the amount of heat absorbed by the fused
material).
Cavendish's most celebrated investigation
was that on the density of the earth. He took part in a program to measure the
length of a seconds pendulum close to a large mountain (Schiehallion).
Variations from the period on the plain would show the attraction put out by the
mountain, from which the density of its substance could be figured out.
Cavendish also approached the subject in a more fundamental way by determining
the force of attraction of a very large, heavy lead ball for a very small, light
ball. The ratio between this force and the weight of the light ball would result
in the density of the earth. His results went unquestioned for nearly a century.
Unpublished works
Had Cavendish published all of his work, his
already great influence would undoubtedly have been greater. In fact, he left in
manuscript form a vast amount of work that often anticipated the work of those
who followed him. It came to light only bit by bit until the thorough study
undertaken by James Maxwell (1831–1879) and by Edward Thorpe (1845–1925). In
these notes is to be found such material as the detail of his experiments to
examine the conductivity of metals, as well as many chemical questions such as a
theory of chemical equivalents. He even had a theory of partial pressures before
John Dalton (1766–1844).
However, the history of science is full of
instances of unpublished works that might have influenced others but in fact did
not. Whatever he did not reveal, Cavendish gave other scientists enough to help
them on the road to modern ideas. Nothing he did has been rejected, and for this
reason he is still, in a unique way, part of modern life."