1872.] Heat. 125 
sequently, while water is always a solid or a liquid in all parts of the earth, 
ether would be a permanent gas in any place where the highest tropical tem- 
perature prevailed, and sulphurous acid is always a gas except in the cold of 
the polar regions. Even the dense and brilliant metal mercury, when 
exposed to a temperature sufficiently high, becomes, in reality, a perfectly 
colourless and transparent gas, and carbonic acid gas, when exposed to a 
temperature sufficiently low, becomes first a yellowish, oily-looking liquid, and 
then a beautiful snow-white solid. The only difference, then, between common 
snow and carbonic acid snow is, that the one is much colder than the other, 
while, on the other hand, the only difference between carbonic acid gas and 
mercury gas is, that the one requires a higher temperature for its existence 
than the other. There are certain gases, however, which no degree of cold 
yet reached has reduced to the liquid, far less to the solid form. Prominent 
among these are oxygen and hydrogen—the two gases that when combined 
form water. But, after it had been observed that intense cold tended to 
reduce all gases and vapours to the liquid form, it was supposed that, if 
hydrogen and oxygen could only be made cold enough, they would become 
liquid too. So they were cooled with freezing mixtures, but still they remained 
in the gaseous state. Thena still more powerful freezing agent (solid carbonic 
acid) was used. But, although mercury became solid, and alcohol, unless 
very pure, became thick and pasty, instead of clear and limpid, still hydrogen 
remained unaltered. After a time a still more powerful freezing agent 
(liquefied laughing-gas) was discovered. Natterer, of Vienna, made a powerful 
steel pump and pumped laughing-gas into a large iron receiver or bottle 
until it became liquefied with the pressure. When a little of this liquid was 
poured into the air it evaporated and produced the greatest degree of cold ever 
observed—a degree of cold 257° below the zero of Fahrenheit’s thermometer. 
Of such a temperature we have but a very faint idea. Let us begin at the 
temperature of our own bodies, and gradually descending by well-known 
stages, see if we can realise the fearful degree of cold that is expressed by 
257° below zero. Human existence requires a temperature in the neighbour- 
hood of 100°—a temperature which, under ordinary circumstances, is easily 
maintained by the chemical and vital actions going on in the system, whenever 
the external atmosphere does not sink below 60°. When the temperature of 
the surrounding air falls below 60°, the animal carries on acontinual fight for 
the maintenence of its normal temperature. At 32° the contest becomes 
more energetic. Warm clothing is called into requisition, and, if the air should 
be agitated by keen winds, the clothing must be warm and the fuel (food) 
liberal, or the animal will suffer. When the temperature sinks to zero, even 
on a clear, still day, there are few persons that do not feel it keenly, and, if 
any wind should be stirring, ugh! how cold itis! But, keenly though we feel 
it, we have just begun to descend the scale. Let us take a leap down to — 40°. 
The mercury in our thermometers will now congeal, and, if we find it necessary 
to expose ourselves, we must encase our persons in triple layers of fur. Let 
us take another leap of equal magnitude, and descend to —80°. This is lower 
than any natural temperature ever observed, and it is improbable that human 
life could be long sustained in an atmosphere cooled to this degree. At six 
degrees below this point, carbonic acid condenses to a liquid, and the breath 
of our nostrils would condense as it issued forth, and would fall to the ground 
in streams. Forty-four degrees below this point carries us to —130°. If such 
a temperature could be produced over a large area, what strange phenomena 
would present themselves! The air would be dry—drier than the summer 
dust—for all moisture would have been precipitated from it long ere this tem- 
perature had been reached. No animal could breathe such air, and if plants 
could live and perform their functions at such a low temperature, they could 
find no sustenance in an atmosphere as cold as this, for all the carbonic acid 
would descend to the earth as beautiful white snow. The breath from the 
nostrils of every animal, provided animals could exist, would yield a shower of 
these flakes, and the air would be entirely purified from the produéts of respi- 
ration. And yet we are not half way down to the point reached by Natterer. 
