LOW-TEMPERATURE RESEARCHES 



But in 1844 Faraday returned to them, armed now 

 with new weapons, in the way of better air-pumps and 

 colder freezing mixtures, which the labors of other 

 workers, chiefly Thilorier, Mitchell, and Natterer, had 

 made available. With these new means, and without 

 the application of any principle other than the use of 

 cold and pressure as before, Faraday now succeeded in 

 reducing to the liquid form all the gases then known 

 with the exception of six ; while a large number of these 

 substances were still further reduced, by the applica- 

 tion of the extreme degrees of cold now attained, to 

 the condition of solids. The six gases which still 

 proved intractable, and which hence came to be spoken 

 of as "permanent gases," were nitrous oxide, marsh 

 gas, carbonic oxide, oxygen, nitrogen, and hydrogen. 



These six refractory gases now became a target for 

 the experiments of a host of workers in all parts of the 

 world. The resources of mechanical ingenuity of the 

 time were exhausted in the effort to produce low tem- 

 peratures on the one hand and high pressures on the 

 other. Thus Andrews, in England, using the bath of 

 solid carbonic acid and ether which Thilorier had dis- 

 covered, and which produces a degree of cold of 80 

 Centigrade, applied a pressure of five hundred at- 

 mospheres, or nearly four tons to the square inch, 

 without producing any change of state. Natterer in- 

 creased this pressure to two thousand seven hundred 

 atmospheres, or twenty-one tons to the square inch, 

 with the same negative results. The result of Andrews' 

 experiments in particular was the final proof of what 

 Cagniard de la Tour had early suspected and Faraday 

 had firmly believed, that pressure alone, regardless of 



