DEVELOPMENTS IN PHYSICAL SCIENCE 449 
force and potential energy, and reduce a universe to ether movement. 
Space and time were not fundamental ideas, but, as Kant had said, 
mere subjective notions. We measure time by a change of space rela- 
tion; that is, a movement of a star, of the earth, of a clock hand. “In 
a world void of all kind of movement there would not be seen the 
slightest sequence in the internal state of substance. Hence the aboli- 
tion of the relation of substances to one another, carries with it the 
annihilation of sequence and of time.” Thus everything was made to 
depend upon movement. The equations of motion became the chief 
instruments of physical research, and the criterion by which the results 
of experiments were interpreted. Galileo lost his professorship because 
he dared to dispute the authority of Aristotle. Daguerre was, for a 
time, placed in an asylum because he said he could take a picture on a 
tin plate. Galvani was ridiculed by his friends, and dubbed “ the 
frog’s dancing master.” Franklin’s paper on lightning conductors was 
considered foolish, and refused publication by the Royal Society. 
Fifteen years ago it would have been almost as disastrous for a physicist 
to question the authority of La Grange or Maxwell. Not only were the 
results of experiments subjected to mathematical analysis, the direction 
of scientific investigation was largely so determined. The question was 
first put to mechanics. If a positive answer was indicated the question 
was put to nature and the research went on. If the equations indicated 
a negative result the question was dropped and the research abandoned. 
Physics was an exact science. Other sciences were not exact 
sciences because their theories and hypotheses could not be mathemat- 
ically expressed—the relation between cause and effect was not expres- 
sible in algebraical symbols. Physics was an exact science whose 
fundamental principles had been discovered and its laws expressed by 
equations. All that remained to be done was to make more accurate 
measurements of physical quantities for use as coefficients and 
exponents. 
Let me quote from the 1894 catalogue, and later catalogues, of one 
of the largest universities in the United States. 
While it is never safe to affirm that the future of physical science has no 
marvels in store ..., it seems probable that most of the grand underlying 
principles have been firmly established and that further advances are to be 
sought chiefly in the rigorous application of these principles to all the phe- 
nomena which come under our notice... . An eminent scientist has remarked 
that the future truths of physical science are to be looked for in the sixth 
place of decimals. 
The foregoing is a verbatim quotation from the introductory state- 
ment preceding the list of courses in physics offered at one of our great 
universities, written, I think, in 1894. “ Underlying principles firmly 
established.” “ Future truths in sixth decimal place,” 1894. Then 
came the discovery of Réntgen rays, 1895; Becquerel rays, 1896; Zee- 
VOL. LXXVU.—31. 
