55 



ijth March^ i8gj. 



Professor J. D. Everett, f.r.s., d.cl., in the Chair. 



Mr. John Finnegan, b.a., b.sc, delivered a lecture on 



" THE HISTORY AND PROPERTIES OF THE 

 RONTGEN RAYS." 



Mr. Finnegan said — About sixteen months ago Rontgen read 

 a short paper before the Physico-Medical Society at Wiirzburg, 

 to which he gave the title, "A new kind of rays." They all 

 remember the great excitement produced by his discovery, and 

 how eagerly experiments were made in almost every scientific 

 laboratory in the world. He would lay before them the most 

 prominent steps in the history of that discovery — show them 

 some experiments on the X rays, and finally discuss their 

 nature. The apparatus required consisted of an induction coil 

 and exhausted glass tubes, of which he should show them several 

 in the course of the evening. The lecturer here showed a glass 

 tube thirty inches long and two inches diameter. Into its ends 

 were fused platinum wires. These were connected with the 

 coil. The positive terminal was called the anode, and the 

 negative the cathode. The air could be removed from the tube 

 by this pump. When rioo part of the air remained, a thin 

 purple line of light traverses the tube. As the pump continued 

 to work this line got wider, and filled the tube, and when about 

 I "1 500 of the air was left a velvety glow covered the cathode. 

 Then they had a dark space, called the Crookes's space. Adjoin- 

 ing this space was a luminous column — the negative glow, then 

 another dark space, and finally a luminous column stretching 

 right up to the positive electrode. The positive column was 



