The times. [volume] (Washington [D.C.]) 1897-1901, 1901-02-17

| improvement VI the SltdUl tL6lllN. 4 -
science was created by Carnot, who.
spite of the fact that his views regardin
| the nature of heat were erroneous, dis
| covered some of the most interesting re
lations among the quantities involved an
discussed their applications to the heat en-
| gines with great skill. Subsequent contrib
utors to the theory and practice of Their
modynamics were Clausius, RANKING
| Lord Kelvin. and Prof. TAFT.
The mechanical theory of heat naturall
led up to what has already been referre
| to as the most important generalization
| in physical science since the time of New
ton, the doctrine of
THE CONSERVATION OF ENERGY.
This principle puts physics in its relation
to energy where chemistry has long beef
In its relation TO matter. If matter wer
not conservative, if 1t could he created o
destroyed at will, chemistry would be al
impossible science. Physics is put upon
solid foundation by the assumption of {
like conservatism in energy; ii can nelthe
be created nor destroyed, although 1t MAJ
appear in many different forms which are
in general. mutually interconvertible.
Many men have contributed to the es'
Establishment of this great principle. but II
was actually discovered and proved by the
labors of three or four. Although II wa:
practically all done before the middle OF
the nineteenth century, its general popu-
lar recognition did not come until n quar-
ter of a century later. The doctrine was
first distinctly formula ted by Robert
Mayer, a German physician, who publish
ed in 1912 a suggestive paper on The
Forces of Inorganic Nature" which. how
ever, attracted little or no attention.
Mayer had not approached the problem
from an experimental standpoint. but at
about the same time II was attacked most
successfully from this side by a young
Englishman, James Prescott Joule, son of
wealthy brewer of Manchester, Eng
land. Joule made the first really accurate
determination of the mechanical eduiva-
lent of a given quantity of heat, ply
steal constant which Rumford had tried
to measure, reaching only rough ap-
Proclamation. Substantially Joule's result
was that the heat energy necessary to
raise the temperature of any given mass
of water l degree +. is the equivalent of
the mechanical energy required to lift
that mass through a height OF III feet
against the force of the earth's attrac-
ton; and conversely, If a mass of water
be allowed TO fall through distance of
772 feet under the action of gravity and
at the end of its motion be instantly ar
rested, the heat generated will suffice to
raise Its temperature i degree F. or such
vast importance is this numerical CO.
efficient that it has been called the golden
number OF the nineteenth century. Since
Joules time II has been predetermined by
several physicists, notably by Prof. Row
land Of Baltimore, the general conclusion
being that Joules number was some
what, but not greatly, too small.
The first clear and full exposition of the
doctrine of the conservation OF energy
was given by Joule In a popular lecture
In Manchester In 1884,, but 1t attracted
little attention until a few months later
when the author presented his theory at
a meeting of the British Association for
he Advancement of Science. Even among
men 1t would have passed with
put comment or consideration had II not
been for the presence of another young
then as little known as Joule
himself, who began a series of remarks,
appreciative and critical, which resulted
N making Joule's paper the sensation OF
he meeting. This was William Thorn
ION, who had been only year before, .
he age of twenty-five years. appointed
professor of natural philosophy at the
of Glasgow. now known as
ord Kelvin, the most versatile. brilliant.
nd profound student of physical science
which the century has produced. From
hat day TO the death of Joule qsSs) these
wo men were closely associated in the
and exploitation of a great
principle of which they were at first al
most the sole opponents among English
peaking people.
By an interesting coincidence, in the
anne year In which Joule announced the |
esult OF his experiments. the Physical |
society of Berlin listened to a paper al |
most identical with Joule's In character |
nd conclusions. but prepared quite indie |
by young German physician, |
herman Won Helmholtz, destined to rank |
/ the time of his death, in 1893. as one OF |
he very first mathematician of the age. |
oub;less the first psychologist Of his time. |
nd as a physicist with whom not more |
nan one other of the nineteenth century
lay be compared. Helmholtz's paper was
elected by the editor of the leading scien-
fc journal of Germany, but his work was
o important that he must always share
18th Joule and Kelvin in the glory OF this
pooh making generalizati ton.
Even a brief sketch of the history of
ne doctrine of the conservation of energy |
-ould be incomplete If mention were not
iade of the work of Tyndall. Although |
Y original research he contributed in no
mall degree to the demonstration of the
leory. 1t is mainly through his wonder
al skill In popular presentation of the
rincipies of physical science that he be-
ONES related to the great movement OF
lie middle of the century. His masterful
xposition of the new theory in a course
Z lectures at the Royal Institution, given
1862 and published in 1863 under the
tie Heat as a Mode OF Notion" was the
cans OF making the intelligent public ac-
tainted with its beauty and profound sig
fcance, and the history of science af-
,rds no more admirable example of the
and wisdom of popular scien-
fic writing than this book. As for the
rinclple of the conservation of energy
self 1t is not too much to say that dur
& the last half Of the century it has been
lie guiding and controlling spirit of all
ientifc discovery or of invention through
e application OF scientific principles.
LIGHT.
The revival and final establishment of
e undulatory or wave theory of light is
IL of the glories of the nineteenth CEN
ny, and the credit for 1t is due to Thorn