6 
Proceedings of the Royal Society 
just referred to led to the discovery of cases of isomerism of great 
theoretical importance. 
Regnault’s investigations of specific heat of metals reduced the 
number of apparent exceptions to the law of Dulong and Petit, and 
induced him to propose (in 1840-41, and again in 1849) the change 
in the atomic weights of silver and of the alkali metals, which was 
afterwards strongly advocated by Cannizaro, and is now generally 
adopted. 
In physical work Regnault was distinguished rather for extreme 
skill in manipulation and patient study of details (especially in the 
investigation of necessary corrections) than for brilliance or novelty 
in discovery. He was an admirable experimenter, and may he said 
to have done almost as much good to science by training a school 
of skilled experimenters as by his own extended researches. He 
devoted himself specially to the accurate determination of physical 
constants, such as latent and specific heats, to the laws of expansion 
of gases and vapours, to the determination of the densities of gases, 
and specially to the accurate measurement of temperature. 
His greatest work, forming Volume XXI. of the Memoir es de 
VAcademie des Sciences , was undertaken for the French Govern- 
ment, and contains most elaborate experimental determinations of 
the various physical data required for investigations of the working 
of steam engines. Besides numerous other chemical and physical 
papers (a complete list of which will be found in the Royal Society’s 
catalogue of scientific papers), Regnault published, in four volumes, 
an “Elementary Course of Chemistry,” which has been long and 
deservedly successful 
The death, during the siege of Paris, of his only son, who was 
rapidly advancing to high distinction as a painter, seems to have 
clouded his later years, and he died on January 19, 1878, at the 
age of 67. 
Claude Bernard. — By the recent death of Claude Bernard, 
France has lost her greatest physiologist, and this Society one of the 
most distinguished of its Foreign Associates. 
Bernard was horn in 1814, at St Julien in France; he studied 
medicine in Paris, became assistant to Magendie, resolved to devote 
