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

| Roadway as late as the middle OF the nine
| tenth century. In the eighth edition Of
| the Encyclopaedia Britannica" publish
| ed in 1856 the immediate predecessor OF
the current issue, heat is defined as "a
material agent of peculiar nature, high
| ly attenuated." And this, In spite of the
| fact that previous to that date the me-
| chanical theory had been completely
! proved by the labors OF Mayer, Joule,
Helmholtz. and William Thomson dord
Kelvin. BY these men solid foundation
! for the theory had been found in great
physical law of such Importance that IT
is Justly considered TO be the most far
reaching generalization In natural philoso-
ply since the time Of Newton Some ac-
count of this law and its discovery will
be given later in this paper.
Among the most important of the cen
tury's contributions to our knowledge of
heat must be included the work of Fou-
rier, as embodied In his "Theorie Analy-
tique de la Chaleur," published in 1872.
Joseph Fourier was born in 17eS and he
died in 1890 He belonged to that splendid
group of philosophers of which the French
nation may always be proud, whose work
constitutes a large part of the lustre Of
intellectual France during her most bril-
liant period, the later years of the eight
zenith and the earlier years OF the nine
teenth centuries. His contemporaries in
cluded such men as Laplace. Arago. La
grange, Fresnel, and Carnot. Fourier
wrote especially of the movement of heat
in solids. and as his thesis depended in
no way on the nature of heat it will
always be regarded as a classic. His as
sumption that conductivity was independ-
ent of temperature was shortly proved to
be erroneous but his general argument
and conclusions were not greatly affected
by this discovery. His work is one of the
most beautiful examples yet produced of
the application of mathematics to physi-
cal research, and mathematical and physi-
cal science were equally enriched by 1t.
In its broader aspects his law of conduc-
ton includes the transfer OF electricity
in good conductors and is the real basis
of Ohm's law.
One of the most skillfui and successful
experimenters in heat was also a French
man. Henri Victor Regnault Qslo-ls7Sl.
He greatly improved the construction and
use OF the thermometer and was the frs.
TO discover that the indications of an air
thermometer and one of mercury did not
exactly agree, because they did not ex-
pand in the same degree for equal in
creases of temperature. His most impor-
tant work was on the expansion of gases,
rapor pressure. specific heat of water, etc,
and for careful, patient measuring he had
a positive genius. Until he proved the con-
trary 1t had been assumed that all gases
had the same coefficient of expansion, and
nversely proportional TO its pressure had
not been questioned. His tables of the |
elastic force of steam have been of i'm
nense practical value, but his studies of
the expansion of gases are of greater in |
terest because they have pointed the way |
TO one of the most important accomplish |
nents of the century, the liquefaction of |
all known gases.
During the earlier years of this century |
L was the custom TO consider vapors and |
gases as quite distinct forms of matter |
Vapors always came by evaporation, from |
liquids and could always be condensed" |
Or reduced to the liquid form without |
difficulty. but 1t was not thought possible |
gases. The first man to attack the prob |
EN- systematically was Michael Faraday,
who. before the end of the first third of
he century had liquefied several gases.
mostly by producing them by chemical
factions under pressure. Several OF the
more easily reducible gases or vapors such
rs ammonia, sulphurous acid, and proba-
by chlorine, had been previously Mquefied
oy cold, but quarter OF a century elapsed |
litter Faraday's researches before the true
relation of the liquid and gaseous states OF
matter was understood and Il was found
hat both increase OF pressure and lower
ng of temperature were, in general, es-
;ential TO the liquefaction of a gas. II
was Thomas Andrews, OF Belfast, who
irst showed in a paper published in 1862
hat there was a continuity in the liquid
md gaseous states of matter, that for
ZACH substance there was a critical tenn
,erature at which it became homo
seneous fluid. neither a liquid nc. a gas:
hat above this temperature great pres
'ure would not liquefy, while below 1t the
substance might exist as partly liquid and
partly gas He pointed out the fact that
or the so-called permanent gases this
'ritical temperature must be exceedingly
ow and If such temperature could be
cached liquefaction would follow.
Subsequent progress in the li1uefaction |
II gases came about by following this
Very low temperatures were
Produced by subjecting the gas to great
in volume by pressure. remoy-
ng the heat Of compression by conductIon
nd nv |
ion its temperature was greatly lowered
IS early as 1877 two Frenchmen, Pic,et
nd Cailletet had succeeded In liquefyine
xygen. hydrogen, nitrogen. and air.
During the past twenty years great i'm
rovements have been made in the meth
DIS of accomplishing these transforma-
Ions, SO that today 1t is easy 10 produce
considerable quantities of all OF the prin-
ipal gases in liquid form and by carry
lg the reduction in temperature still fur
her portions Of the liquid may be changed
D the solid state. The most important |
'ork along this line has been done by |
Vroblewsh and OlszewskI, of the Uni
ersiiy of cracow, and Prof Dewar. of
ne Royal Institution in London Tenn
eratures as low as about $50 degrees C.
Glow the freezing point of water have
cen produced, the absolute zero" being
My 273 degrees c. below that point.
hese experiments promise to throw much
ght ON the nature of matter and they
re especially interesting as revealing its
Extraordinary properties at extremely low
temperatures. Among the most curious
nd suggestive is the fact that The electro
al resistance of pure metals diminlshes ,
rate which indicates that at the alb. ,
Olute zero II would Vanish and ,h.so