142 LIQUID HYDROGEN. 



Duriiit( 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 

 eng-ineering skill, manipulative ainlity, and loyal perseverance, the 

 present successful issue might have been indefinitely delayed. M}^ 

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

 conduct of the experiments. 



