SCIENCE. 



[N. S. Vol. VIII. No. 183. 



deduce respectively from the atomic volume 

 of organic compounds and the limiting 

 density found by Amagat for hydrogen gas 

 under infinite compression. My old experi- 

 ments on the density of hydrogen in palla- 

 dium gave a value for the combined body 

 of 0.62, and it will be interesting to find the 

 real density of the liquid substance at its 

 boiling point. N'ot having arrangements 

 at hand to determine the boiling point, two 

 experiments were made to prove the exces- 

 sively low temperatui-e of the boiling fluid. 

 In the first place, if a long piece of glass 

 tubing, sealed at one end and open to the 

 air at the other, is cooled by immersing the 

 closed end in the liquid hydrogen, the tube 

 immediately fills, where it is cooled, with 

 solid air. The second experiment was 

 made with a tube containing helium. 



The ' Cracow Academy Bulletin ' for 

 1896 contains a paper by Professor Olszew- 

 ski, entitled ' A Research on the Liquefac- 

 tion of Helium,' in which he states ' as far 

 as my experiments go, helium remains a 

 permanent gas and apparently is much 

 more difficult to liquefy than hydrogen.' 

 In a paper of my own in the ' Proceedings 

 of the Chemical Society,' No. 183 (1896-7), 

 in which the separation of helium from 

 Bath gas was efi'ected by a liquefaction 

 method, the suggestion was made that the 

 volatility of hydrogen and helium would 

 probably be found close together, just like 

 those of fluorine and oxygen. Having a 

 specimen of helium which had been extrac- 

 ted from Bath gas, sealed up in a bulb with a 

 narrow tube attached, the latter was placed 

 in liquid hydrogen, when a distinct liquid 

 was seen to condense. A similar experi- 

 ment made with the use of liquid air under 

 exhaustion in the same helium tube (in- 

 stead of liquid hydrogen) gave no visible 

 condensation. From this result it would 

 appear that there cannot be any great dif- 

 ference in the boiling points of helium and 

 hydrogen. 



All known gases have now been con- 

 densed into liquids which can be manipu- 

 lated at their boiling points under atmos- 

 pheric pressure in suitably arranged vacuum 

 vessels. "With hydrogen as a cooling agent 

 we shall get within 20° or 30° of the zero 

 of absolute temperature, and its use will 

 open up an entirely new field of scientific 

 inquiry. Even as great a man as James 

 Clerk Maxwell had doubts as to the possi- 

 bility of ever liquefying hydrogen.* No 

 one can predict the properties of matter 

 near the zero of temperature. Faraday 

 liquefied chlorine in the year 1823. Sixty 

 years afterwards Wroblewski and Olszewski 

 produced liquid air, and now, after a fifteen 

 years' interval, the remaining gases, hydro- 

 gen and helium, appear as static liquids. 

 Considering that the step from the liquefac- 

 tion of air to that of hydrogen is relatively 

 as great in the thermo-dynamic sense as 

 that from liquid chlorine to liquid air, the 

 fact that the former result has been 

 achieved in one-fourth the time needed to 

 accomplish the latter, proves the greatly 

 accelerated rate of scientific progress in our 

 time. 



The efiicient cultivation of this field of 

 research depends upon combination and 

 assistance of an exceptional kind ; but in 

 the first instance money must be available 

 and the members of the Eoyal Institution 

 deserve my especial gratitude for their 

 handsome donations to the conduct of this 

 research. Unfortunately its prosecution 

 will demand a further large expenditure. 

 The handsome contribution made by the 

 Goldsmiths' Company ought also to be men- 

 tioned as very materially helping the pro- 

 gress of the work. 



During the whole course of the low tem- 

 perature work carried out at the Royal In- 

 stitution the invaluable aid of Mr. Robert 

 Lennox has been at my disposal ; and it is 

 not too much to say that but for his engi- 



* See ' Scientific Papers,' Vol. 2, p. 412. 



