400 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1949 
electromagnetism. Millikan calls Maxwell “the greatest ornament 
of his age’ and points out that “Maxwell’s book has created the 
present age of electricity in much the same way in which Newton’s 
Principia created, a hundred years earlier, the mechanical age in 
which we are still living.” 
The century drew to a close with four very great discoveries which 
have profoundly affected our own times. They are: (1) Roentgen’s 
discovery of X-rays in 1895; (2) Becquerel’s discovery of radioactivity 
in 1896; (3) J. J. Thomson’s demonstration in 1897 of the electron 
as a fundamental constituent of all the atoms in the universe; and 
(4) the quantum theory of radiation enunciated by Planck in Berlin 
in 1900. 
During the period in which such strides were being made in physics, 
the other sciences, notably chemistry, biology, and medicine, were 
not standing still. But, whereas research in physics had enjoyed a 
steady growth for the two centuries preceding the opening of the 
nineteenth, the other sciences lagged somewhat in their development. 
This was partly because in both chemistry and biology there was a 
strong tendency to cling to the classical teachings of the past. But, 
more significantly, progress in these fields and in medicine also was 
dependent to a large extent on the tools and processes being evolved 
by modern physics. 
If one were to review even a partial list of the great names in the 
growth of chemistry prior to this century, it would be necessary to 
mention the Norwegians, Guldberg and Waage, who stated the law 
of mass action; the great Swedish chemist, Arrhenius, who advanced 
the theory of electrolytic disassociation; and the American, Willard 
Gibbs, whose phase rule contributed so much to the development of 
industrial chemistry. There would be the Russian, Mendeleev, who 
first classified the elements in the periodic table, and the Polish 
Marie Curie who, with her French husband, Pierre, made the impor- 
tant discovery of radium. Von Liebig and Wéhler would stand for 
organic chemistry and mention should be made of Hofmann, who 
may be regarded as the father of the German dye industry. To as- 
piring young scientists of today it should be of interest to note that 
one of Hofmann’s students, W. H. Perkin, a boy of 17, is credited 
with discovering the first synthetic dye. The chemical industry in 
the United States today owes much of its start to basic work in dyes 
and synthetics which was done in Germany prior to World War I. 
The emphasis which modern industry and modern warfare also 
have laid upon physical sciences has tended to obscure somewhat in 
the public eye the less spectacular advances of biology and medicine. 
The use of atomic power for both constructive and destructive pur- 
poses has greater interest for the public imagination than that mys- 
terious process by which green plants convert the energy of the sun 
