The New Physics and Its Evolution | Page 5

has enriched physics."
Shortly afterwards, our amateur would learn that Carlisle and
Nicholson had decomposed water by the aid of a battery; then, that
Davy, in 1803, had produced, by the help of the same battery, a quite
unexpected phenomenon, and had succeeded in preparing metals
endowed with marvellous properties, beginning with substances of an
earthy appearance which had been known for a long time, but whose
real nature had not been discovered.
In another order of ideas, surprises as prodigious would wait for our
amateur. Commencing with 1802, he might have read the admirable
series of memoirs which Young then published, and might thereby
have learned how the study of the phenomena of diffraction led to the
belief that the undulation theory, which, since the works of Newton
seemed irretrievably condemned, was, on the contrary, beginning quite
a new life. A little later--in 1808--he might have witnessed the
discovery made by Malus of polarization by reflexion, and would have
been able to note, no doubt with stupefaction, that under certain
conditions a ray of light loses the property of being reflected.

He might also have heard of one Rumford, who was then promulgating
very singular ideas on the nature of heat, who thought that the then
classical notions might be false, that caloric does not exist as a fluid,
and who, in 1804, even demonstrated that heat is created by friction. A
few years later he would learn that Charles had enunciated a capital law
on the dilatation of gases; that Pierre Prevost, in 1809, was making a
study, full of original ideas, on radiant heat. In the meantime he would
not have failed to read volumes iii. and iv. of the Mecanique celeste of
Laplace, published in 1804 and 1805, and he might, no doubt, have
thought that before long mathematics would enable physical science to
develop with unforeseen safety.
All these results may doubtless be compared in importance with the
present discoveries. When strange metals like potassium and sodium
were isolated by an entirely new method, the astonishment must have
been on a par with that caused in our time by the magnificent discovery
of radium. The polarization of light is a phenomenon as undoubtedly
singular as the existence of the X rays; and the upheaval produced in
natural philosophy by the theories of the disintegration of matter and
the ideas concerning electrons is probably not more considerable than
that produced in the theories of light and heat by the works of Young
and Rumford.
If we now disentangle ourselves from contingencies, it will be
understood that in reality physical science progresses by evolution
rather than by revolution. Its march is continuous. The facts which our
theories enable us to discover, subsist and are linked together long after
these theories have disappeared. Out of the materials of former edifices
overthrown, new dwellings are constantly being reconstructed.
The labour of our forerunners never wholly perishes. The ideas of
yesterday prepare for those of to-morrow; they contain them, so to
speak, in potentia. Science is in some sort a living organism, which
gives birth to an indefinite series of new beings taking the places of the
old, and which evolves according to the nature of its environment,
adapting itself to external conditions, and healing at every step the
wounds which contact with reality may have occasioned.

Sometimes this evolution is rapid, sometimes it is slow enough; but it
obeys the ordinary laws. The wants imposed by its surroundings create
certain organs in science. The problems set to physicists by the
engineer who wishes to facilitate transport or to produce better
illumination, or by the doctor who seeks to know how such and such a
remedy acts, or, again, by the physiologist desirous of understanding
the mechanism of the gaseous and liquid exchanges between the cell
and the outer medium, cause new chapters in physics to appear, and
suggest researches adapted to the necessities of actual life.
The evolution of the different parts of physics does not, however, take
place with equal speed, because the circumstances in which they are
placed are not equally favourable. Sometimes a whole series of
questions will appear forgotten, and will live only with a languishing
existence; and then some accidental circumstance suddenly brings them
new life, and they become the object of manifold labours, engross
public attention, and invade nearly the whole domain of science.
We have in our own day witnessed such a spectacle. The discovery of
the X rays--a discovery which physicists no doubt consider as the
logical outcome of researches long pursued by a few scholars working
in silence and obscurity on an otherwise much neglected subject--
seemed to the public eye to have inaugurated a new era in the history of
physics. If, as is the case, however, the extraordinary scientific
movement