35 



a part of his theory that the phenomena exhibited by the 

 tube is caused by the rectilineal motion of the atoms of 

 residual eras, charged with negative electricity from the 

 kathode. Dr. Lenard, a pupil of the celebrated physicist Hertz, 

 constructed a Crooke's tube partly of glass and partly of 

 aluminium. He then found that the kathode radiation would 

 pass through the aluminium window and would then excite 

 fluorescence in certain substances such as the platino- cyanide of 

 potassium, and moreover act upon a photographic plate. Accord- 

 ing to modern views as we have said chemical decomposition and 

 electrical discharge invariably accompany one another. The 

 atoms of the substance between the anode and kathode undergo 

 some change of position or groupiug ; some going to the one 

 pole and some to the other. In the electric arc lamps, now so 

 familiar to us, the positive electrode is quite the hottest place on 

 earth. Gold, platinum, and carbon are vaporized at it. The 

 temperature is probably about 3,500" C. As the arc of light can 

 deflected by a magnet it is assumed that the discharge is partly 

 carried by particles torn off the electrodes and partly by the 

 conducting carbon vapour. 



Dr. Clutterbuck, at the conclusion of Mr. Bower's paper, 

 described the process of making the tube or bulk in which the 

 Kontgen rays are generated, and by means of a large coil 

 exhibited them. He also showed how they passed through 

 opaque subjects such as wood, and since they passed through the 

 fleshy parts of the hand but were obstructed by the bones, a 

 photographic plate placed beneath the hand was affected in some 

 parts and not in others. Hence a shadow of the bones was 

 obtained, which could by the methods ordinarily followed by the 

 photographer be fixed, and a permanent impression of them be 

 thus obtained. 



