LOW-TEMPERATURE RESEARCHES 



to Olzewski in 1884. Thus forty years of effort had 

 been required to conquer five of Faraday's refractory 

 gases, and the sixth, hydrogen, still remains resistant. 

 Hydrogen had, indeed, been seen to assume the form 

 of visible vapor, but it had not been reduced to the so- 

 called static state that is, the droplets had not been 

 collected in an appreciable quantity, as water is col- 

 lected in a cup. Until this should be done, the final 

 problem of the liquefaction of hydrogen could not be 

 regarded as satisfactorily solved. 



More than another decade was required to make 

 this final step in the completion of Faraday's work. 

 And, oddly enough, yet very fittingly, it was reserved 

 for Faraday's successor in the chair at the Royal In- 

 stitution to effect this culmination. Since 1884 Pro- 

 fessor Dewar's work has made the Royal Institution 

 again the centre of low - temperature research. By 

 means of improved machinery and of ingenious de- 

 vices for shielding the substance operated on from the 

 accession of heat, to which reference will be made 

 more in detail presently, Professor Dewar was able to 

 liquefy the gas fluorine, recently isolated by Moussan, 

 and the recently discovered gas helium in 1897. And 

 in May, 1898, he was able to announce that hydrogen 

 also had yielded, and for the first time in the history 

 of science that elusive substance, hitherto "perma- 

 nently" gaseous, was held as a tangible liquid in a 

 cuplike receptacle; and this closing scene of the long 

 struggle was enacted in the same laboratory in which 

 Faraday performed the first liquefaction experiment 

 with chlorine just three-quarters of a century before. 



It must be noted, however, that this final stage in 



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