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out eventually to be of the greatest possible service to mankind. 
The facts on which this method depend are as follows: When 
a gas is subjected to pressure and the pressure is suddenly 
diminished, two things occur simultaneously—(a) The gas expands, 
(6) The temperature of the gas is lowered.” The fall of tem- 
perature is proportional to the fall of pressure. Moreover, the 
lower the temperature originally is, the greater is the fall of 
temperature for the same change of pressure. Consequently 
the lower the original temperature the better the cooling result. 
‘¢ The pressure to which gases can be submitted, by powerful 
engines, is almost unlimited, and thus a most powerful instru- 
ment is placed in the hands of the physicist for refrigerating 
purposes. At present the lowest temperature touched seems to 
be 10° Abs. i.e. —263° C. or about 478° of frost.” 
‘‘Ts there any limit to the degree of cold that can be reached ? 
Is it possible to abstract all the heat from a body, to make it 
absolutely cold ? Scientists believe there is a limit, that limit 
being — 273° C., or in unscientific English, about 490° of frost.” 
‘«In 1835 Thilorier succeeded in reaching a temperature of 
—110° C., and it is only during the last thirty years that lower 
temperatures have been obtained. Hydrogen has now been 
liquefied, and boiling under reduced pressure gives a temperature 
of 16 Abs. — —257° C. Only one known gas—Helium—has not 
succumbed to the recent efforts. It is calculated that it boils at 
5° Absolute, or —268° C.” 
‘In 1813 Sir Humphrey Davy engaged Michael Faraday as 
his laboratory assistant, who, although most renowned for his 
electrical researches, was one of the foremost chemists of his 
time. He succeeded in liquefying all known gases except six.” 
‘*« December 24th, 1877, was a memorable day in the history of 
the French Academy, on that day Cailletet, a French ironmaster, 
and Pictet of Geneva, a manufacturer of ice-making apparatus, 
announced the liquefaction of oxygen.” 
“Tn 1883, Wroblewski and Olszewski, two Russian chemists, 
succeeded in liquefying air by methods similar to that adopted 
by Pictet.”’ 
“James Dewar, the Fullerian Professor at the Royal Institution, 
has spent the last twenty years of his life in low temperature 
investigation, in attempting to reach that final goal—the absolute 
_ zero. The work has been carried on chiefly at the Royal 
Institution, where Faraday was working on similar lines eighty 
years earlier.”’ 
“‘In 1884, Dewar first succeeded in liquefying air in very small 
quantities, and in larger quantities in 1886, ‘lhe method 
