14 Professor Dewar on Liquid Hydrogen. [Jan. 20, 



Faraday's expressed faith in the potentialities of experimental 

 inquiry in 1852 has been justified forty-six years afterwards by the 

 production of liquid hydrogen in the very laboratory in which all his 

 epoch-makiug researches were executed. The " doubt" has now been 

 settled ; hydrogen does not possess in the liquid state the character- 

 istics of a metal. 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 last of the old 

 permanent gases, hydrogen, appears as a static liquid. Considering 

 that the step from the liquefaction of air to that of hydrogen is 

 relatively as great in the thermodynamic 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 pace of scientific progress in our time. 



The efficient cultivation of this field of research depends on com- 

 bination and assistance of an exceptional kind ; but in the first instance 

 money must be available, and the members of the Royal Institution 

 deserve my especial gratitude for their handsome donations to the 

 conduct of this research. Unfortunately its prosecution will demand 

 a further large expenditure. It is my duty to acknowledge that at 

 an early stage of the inquiry the Hon. Company of Goldsmiths helped 

 low-temperature investigation by a generous donation to the Research 

 Fund. 



During the whole course of the low-temperature work, carried out 

 at the Royal Institution, the invaluable aid of Mr. Robert Lennox 

 has been at my disposal, and it is not too much to say that, but for 

 his engineering skill, manipulative ability and loyal perseverance, the 

 present successful issue might have been indefinitely delayed. My 

 thanks are also due to Mr. J. W. Heath for valuable assistance in the 

 conduct of the experiments. 



[J. D.] 



