ON ARTIFICIAL EEFRIGERATION. 921 



liquid was seen on the surface of the quicksilver, in quantity about infou 

 part of the volume of air. The gasometer was at another time charged 

 witli carburetted hydrogen," and " it was subjected to ditierent i)ressures, 

 and it began to liquefj' at about 40 atmospheres, and at 1,200 atmos- 

 pheres the whole was liquefied." 



"These instances of apparent condensation of gaseous fluids were first 

 observed in January, 1822 ; but for want of chemical knowledge requisite 

 to ascertain the exact nature of the liquids produced, I did not pursue 

 the inquiry further; and as the subject has been. taken up by those who 

 are eminently qualified for the investigation, I need not regret my ina- 

 bility to make full advantage of the power I had the means of applying." 



Jacob Perkiris knew probably more than any of his contemporaries 

 as to the means whereby an apparatus could be constructed to stand 

 such pressures. He afterwards invented the steam-gun, and no doubt 

 his knowledge of the liquefaction of gases led him directly to the recou- 

 densation of the ether vapor in the ice-machine patented, a drawing of 

 which is appended to this paper. Sir Humphrey Davy appeared in no 

 admirable Ught on this question in relation to Faraday. He was presi- 

 dent of the Eoyal Society in 1823, and in this year he asked his pui:)il 

 and assistant to liquefy chlorine. Can Perkins's important pai)er, draw- 

 ings and all, have been lost by mere accident ? Dr. Andrews lia^ pointed 

 out that to determine the certainty of the liquid and solid state of matter 

 is a much more difficult subject for experiment than the relation between 

 gases and liquids. In this relation Mr. Perkins's observations of the 

 crj'stalization of acetic acid under i)ressure is at all events interesting. 



However this may be, we may repeat in Mr. Wurtz's words that "the 

 experiments of MM. Eaoul Pictet and Cailletet have removed from 

 science the distinction between permanent and condensable gases." 

 Cailletet liquefied oxygen and carbonic oxide on the 2d of December, 

 1877. Being a candidate for election to a seat in the Academy of 

 Sciences he delayed the announcement, after having consigned a state- 

 ment of the discovery to a sealed packet, till the session of the 24th of 

 December. At the same time Eaoul Pictet's results by low temperature 

 jiroduced with the combined aid of sulphurous and carl)onic acid gases 

 were xniblished, and confirmed Cailletet's experiments in which lique- 

 faction has been induced by " detente" or expansion of the gas compressed 

 at low temperature. On the last day of 1877 Cailletet liquefied hydrogen, 

 nitrogen, and atmospheric au', and on the 11th of January" ]\f. Pictet 

 solidified hydrogen, pr(^ing it to be a metal, as previously supposed by 

 Professor Dumas. 



This suspicion had been almost transformed into certainty by the ad- 

 mirable work of Graham, in forming hydrogcnium alloys — notably with 

 palladium: and while palladium itself was known to be capable of but 

 feeble magnetism, its hydrogeuium alloy was found to become strongly 

 magnetic. 



Space forbids that I should prolong this history, but it is important 



