230 ANNUAL RECORD OF SCIENCE AND INDUSTRY. 



perature falls to 23. If a current of air be passed through 

 it, a temperature of 55 is obtained, in which mercury 

 freezes. Placed in a closed vessel and the air exhausted, 

 a very low temperature is obtained, which may be utilized 

 in the production of ice. Methyl chloride is sold in the liquid 

 form in Paris at four francs the kilogram. 



The close of the year 1877 was distinguished by a series 

 of remarkable discoveries in the liquefaction of gases. In 

 November, Cailletet announced to the French Academy the 

 liquefaction of acetylene, ethyl hydride, marsh gas, and nitro- 

 gen dioxide, the last under a pressure of 104 atmospheres at 

 11 C. On the 22d of December a despatch to the Acad- 

 emy announced the liquefaction of oxygen by Raoul Pictet,of 

 Geneva, under a pressure of 320 atmospheres at 140. At 

 the meeting on the 24th a sealed communication from Caille- 

 tet, deposited with the Secretary on the 3d of December, was 

 opened and found to contain a statement that upon the pre- 

 vious day he had compressed oxygen and carbonous oxide 

 to 300 atmospheres at 29, and had then allowed them to 

 expand suddenly; a thick mist appeared, which was evident- 

 ly a liquid in droplets. Hence both these physicists appear 

 as original and independent discoverers, their methods being 

 entirely different, though attaining the same result. Pictet, 

 however, obtained an amount of liquid oxygen which occu- 

 pied one third of the length of a glass tube one meter long 

 and a centimeter in interior diameter. On the 31st of De- 

 cember, at the Ecole Normale, in Paris, and in presence of 

 Berthelot, Boussingault, II. Sainte -Claire Deville, Mascart, 

 and others, Cailletet liquefied nitrogen, hydrogen, and then 

 atmospheric air. The nitrogen was compressed to two hun- 

 dred atmospheres at +13, and, when the pressure was sud- 

 denly relieved, the gas condensed into distinct droplets. Hy- 

 drogen yielded a mist when expanded suddenly from 280 at- 

 mospheres. On trying the experiment with carefully puri- 

 fied air, a stream of liquid air issued from the jet, resembling 

 the spray from an atomizer. Thus disappears the last of the 

 permanent gases, and molecular cohesion assumes its sway 

 over all the forms of matter. 



Cailletet has given subsequently the details of his experi- 

 ment of liquefying air. Enclosing in his glass tube air dry 

 and free from carbon dioxide, he cooled this tube with liquid 



