Masterpieces of Science 



cyanide. I was. thus being shown the first phe- 

 nomenon which attracted the discoverer's at- 

 tention and led to his discovery, namely, the 

 passage of rays, themselves wholly invisible, 

 whose presence was only indicated by the effect 

 they produced on a piece of sensitized photo- 

 graphic paper. 



A moment later, the black darkness was pene- 

 trated by the rapid snapping sound of the high- 

 pressure current in action, and I knew that the 

 tube outside was glowing. I held the sheet ver- 

 tically on the shelf, perhaps four inches from the 

 plate. There was no change, however, and 

 nothing was visible. 



"Do you see anything?" he called. 



"No." 



"The tension is not high enough; " and he pro- 

 ceeded to increase the pressure by operating an 

 apparatus of mercury in long vertical tubes acted 

 upon automatically by a weight lever which 

 stood near the coil. In a few moments the 

 sound of the discharge again began, and then 

 I made my first acquaintance with the Rontgen 

 rays. 



The moment the current passed, the paper 

 began to glow. A yellowish green light spread 

 all over its surface in clouds, waves and flashes. 

 The yellow- green luminescence, all the stranger 

 and stronger in the darkness, trembled, wavered, 

 and floated over the paper, in rhythm with the 

 snapping of the discharge. Through the metal 

 plate, the paper, myself, and the tin box, the 

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