DISCOVERIES PRECEDING X-RAYS 33 



great chance of coming nearer to the secret of the 

 meaning of electricity. The great Maxwell insisted 

 on the importance of this view, and the multiplicity 

 of the researches which have been made on the 

 question is an evidence that experimenters generally 

 have been of the same mind. In many cases no 

 doubt the beauty and varied interests of the experi- 

 ments have been an inducement to researchers ; 

 but that would not have been enough in itself. 

 Such an amouut of attention would not have 

 been concentrated on the question had there not 

 been a feeling that important secrets were gradually 

 being disclosed. Let us go backwards along the 

 line of advance in order to be consistent to our 

 plan, which is to show that there is such a line and 

 only one natural way along it. 



The particular research of Rontgen was con- 

 cerned with the attempt to clear up the question 

 of radiation from the seat of electric discharge, 

 which question had been prompted by the result 

 of researches immediately preceding such as those 

 of Lenard and Herz. Lenard had actually found 

 that if he caused an electric discharge to pass 

 through a highly exhausted glass tube, in the walls 

 of which he had inserted a "window" of very 

 thin aluminium foil, and if the window was placed 

 in the right position with respect to the discharge, 

 a very feeble radiation seemed to stream from the 

 window into the air outside. Before him Herz 

 had shown that the same sort of radiation existed 



