SEPTEMBER 11, 1902] 
phers have adopted the view ‘‘ that every palpable elastic fluid 
in nature is produced and preserved in this form by the action 
of heat. Mr. Amontons, an ingenious member of the late 
Royal Academy of Sciences, at Paris, was the first who proposed 
this idea with respect to the atmosphere. He supposed that it 
might be deprived of the whole of its elasticity and condensed 
and even frozen into a solid matter were it in our power to | 
apply to it a sufficient cold; that it is a substance that differs 
from others by being incomparably more volatile, and which is 
therefore converted into vapour and preserved in that form by a 
weaker heat than any that ever happened or can obtain in this 
globe, and which therefore cannot appear under any other form 
NATURE 
than the one it now wears, so long as the constitution of the | 
world remains the same as at present.” The views that Black 
attributes to Amontons have been generally associated. with 
the name of Lavoisier, who practically admitted similar 
possibilities as to the nature of air; but it is not likely 
that in such matters Black would commit any mistake as 
to the real author of a particular idea, especially in 
his own department of knowledge. Black’s own 
special contribution to low-temperature studies was his explana- 
tion of the interaction of mixtures of ice with salts and acids by 
applying the doctrine of the latent heat of fluidity of ice to 
account for the frigorific effect. In a similar way, Black ex- 
plained the origin of the cold produced in Cullen’s remarkable 
experiment of the evaporation of ether under the receiver of an 
air-pump by pointing out that the latent heat of vaporisation in 
this case necessitated such a result. Thus, by applying his own 
discoveries of latent heat, Black gave an intelligent explanation 
of the cause of all the low-temperature phenomena known in 
his day. 
After the gaseous laws had been definitely formulated by Gay- 
Lussac and Dalton, the question of the absolute zero of tempera- 
ture, as deduced from the properties of gases, was revived by 
Clement and Desormes. These distinguished investigators 
presented a paper on the subject to the French Academy in 
1812, which, it appears, was rejected by that body. The authors 
subsequently elected to publish it in 1819. Relying on what we 
know now to have been a faulty hypothesis, they deduced from 
observations on the heating of air rushing into a vacuum the 
temperature of 272s 267 degrees as that of the absolute zero. 
They further endeavoured to show, by extending to lower tem- 
peratures the volume or the pressure coefficients of gases given 
by Gay-Lussac, that at the same temperature of mzzas 267 
degrees the gases would contract so as to possess no appreciable 
volume, or, alternatively, ifthe pressure was under consideration, 
it would become so small as to be non-existent. Although full 
reference is given to previous work bearing on the same subject, 
yet, curiously enough, no mention is made of the name of 
Amontons. It certainly gave remarkable support to Amontons’ 
notion of the zero to find that simple gases like hydrogen and 
compound gases like ammonia, hydrochloric, carbonic and 
sulphurous acids should all point to substantially the same value 
for this temperature. But the most curious fact about this re- 
search of Clement and Desormes is that Gay-Lussac was a bitter 
opponent of the validity of the inferences they drew either from 
his work or their own. The mode in which Gay-Lussac re- 
garded the subject may be succinctly put as follows: A quick 
compression of air to one-fifth volume raises its temperature to 
300 degrees, and if this could be made much greater and instan- 
taneous the temperature might rise to 1000 or 2000 degrees. 
Conversely, if air under five atmospheres were suddenly dilated, 
469 
| able, for the same reason we ought to accept the reality of the 
absolute zero. We know now that Gay-Lussac was wrong in 
supposing the increment of temperature arising from a given 
gaseous compression would produce a corresponding decrement 
from an identical expansion. After this time the zero of tem- 
perature was generally recognised as a fixed ideal point, but in 
order to show that it was hypothetical a distinction was drawn 
between the use of the expressions, zero of absolute temperature 
| and the absolute zero. 
| _ The whole question took an entirely new form when Lord 
Kelvin, in 1848, after the mechanical equivalent of heat had 
| been determined by Joule, drew attention to the great principles 
underlying Carnot’s work on the ‘* Motive Power of Heat,” 
and applied them to an absolute method of temperature measure- 
ment, which is completely independent of the properties of any 
particular substance. The principle was that for a difference of 
one degree on this scale, between the temperatures of the source 
and refrigerator, a perfect engine should give the same amount 
of work in.every part of the scale. Taking the same fixed 
points as for the Centigrade scale, and making 100 of the new 
degrees cover that range, it was found that the degrees not 
only within that range, but as far beyond as experimental 
data supplied the means of comparison, differed by only minute 
quantities from those of Regnault’s air thermometer. The zero 
of the new scale had to be determined by the consideration that 
, when the refrigerator was at the zero of temperature the perfect 
engine should give an amount of work equal to the full 
mechanical equivalent of the heat taken up. This led to a 
zero of 273 degrees below the temperature of freezing water, 
substantially the same as that deduced from a study of the 
gaseous state. It was a great advance to demonstrate by the 
application of the laws of thermodynamics not only that the 
zero of temperature is a reality, but that it must be located at 
273 degrees below the freezing-point of water. As no one has 
attempted to impugn the solid foundation of theory and experi- 
ment on which Lord Kelvin based his thermodynamic scale, the 
existence of a definite zero of temperature must be acknowledged 
as a fundamental scientific fact. 
Liquefaction of Gases and Continuity of State. 
In these speculations, however, chemists were dealing 
theoretically with temperatures to which they could not make 
any but the most distant experimental approach. Cullen, the 
teacher of Black, had indeed shown how to lower temperature 
by the evaporation of volatile bodies, such as ether, by the aid 
of the air-pump, and the later experiments of Leslie and Wol- 
laston extended the same principle. Davy and Faraday made the 
most of the means at command in liquefying the more con- 
| 
| 
| pressure all the gases were liquefied by the year 1844, with the 
it would absorb as much heat as it had evolved during compres- | 
sion, and its temperature would be lowered by 300 degrees. 
Therefore, if air were taken and compressed to fifty atmospheres 
or more, the cold produced by its sudden expansion would have 
no limit. In order to meet this position, Clement and Desormes 
adopted the following reasoning : They pointed out that it had 
not been proved that Gay-Lussac was correct in his hypothesis, 
but that in any case it tacitly involves the assumption that a 
limited quantity of matter possesses an unlimited supply of 
heat. If this were the case, then heat would be unlike any 
other measurable thing or quality. It is, therefore, more 
consistent with the course of nature to suppose that the amount 
of heat in a body is like the quantity of elastic fluid filling a 
vessel, which, while definite in original amount, one may make 
less and less by getting nearer to a complete exhaustion. 
Further, to realise the absolute zero in the one case is just as 
impossible as to realise the absolute vacuum in the other ; and 
as we do not doubt a zero of pressure, although it is unattain- 
NO. 1715, VOL. 66] 
densable gases, while at the same time Davy pointed out that 
they in turn might be utilised to procure greater cold by their 
rapid reconversion into the aériform state. Still the chemist 
was sorely hampered by the want of some powerful and acces- 
sible agent for the production of temperatures much lower than 
had ever been attained. That want was supplied by Thilorier, 
who in 1835 produced liquid carbonic acid in large quantities, 
and further made the fortunate discovery that the liquid could 
be frozen into a snow by its own evaporation. Faraday was 
prompt to take advantage of this newand potent agent. Under 
exhaustion he lowered its boiling-point from m2nes 78° C. to 
minus 110 C., and by combining this low temperature with 
exception of the three elementary gases—hydrogen, nitrogen, 
and oxygen, and three compound gases—carbonic oxide, marsh 
gas, and nitric oxide; Andrews some twenty-five years after 
the work of Faraday attempted to induce change of state in the 
uncondensed gases by using much higher pressures than Faraday 
employed. Combining the temperature of a solid carbonic acid 
bath with pressures of 300 atmospheres, Andrews found that 
none of these gases exhibited any appearance of liquefaction 
in such high states of condensation; but so far as change of 
volume by high compression went, Andrews confirmed the 
earlier work of Natterer by showing that the gases become pro- 
portionately less compressible with growing pressure. While 
such investigations were proceeding, Regnault and Magnus had 
completed their refined investigations on the laws of Boyle and 
Gay-Lussac. A very important series of experiments was made 
by Joule and Kelvin ‘‘On the Thermal Effects of Fluids in 
Motion” about 1862, in which the thermometrical effects of 
passing gases under compression through porous plugs furnished 
important data for the study of the mutual action of the gas 
