58 ELISHA MITCHELL SCIENTIFIC JOURNAL 



radioactive body, one can show with its salts in the best man- 

 ner the action of the Becquerel rajs. 



According to the investigations of Rutherford and his col- 

 laborators, the different actions of the radioactive bodies are 

 not caused by one kind of rays, but by different ones. The 

 rays which cause the discharge of the electroscope he called 

 a-rays. They are easily absorbed by different substances and 

 only slightly deflected by a magnet. 



The /8-rays on the other hand produce chiefly the photo- 

 graphic action, even penetrating- thin metal sheets, wood, and 

 so on, and are deviated easily in a magnetic field. Rutherford 

 found also a third kind of rays, the y-rays, the source of which 

 is not clearly denned. Perhaps these, according- to the sug- 

 gestion of Dr. Baskerville, are derived from the /3-rays, as 

 the Roentgen rays arise from the cathode rays. A discussion 

 of this matter need not hold our attention today however. 



It is noteworthy indeed, that the radioactive substances 

 emit not only rays, but material particles too, in form of a gas. 

 It may be swept along by a stream of air blown over the sub- 

 stance and follows its course, unlike the light rays. It also 

 diminishes the conductivity of the air. As a real gas it has 

 been condensed to a liquid boiling at about 135° below zero. 

 Rutherford called this very interesting property of the radio- 

 active bodies "emanation". 



Rutherford performed his preliminary experiments not with 

 Radium, Uranium or Polonium, but with another radioactive 

 substance, Thorium. Mrs. Curie and G. C. Schmidt had 

 found, independently of each other, that the Thorium com- 

 pounds are also radioactive. Some time later Debierne dis- 

 covered in Pitchblende a body similar to Thorium. It gave 

 all the reactions of real Thoria: precipitation by Ammonia, 

 Alkali, Ammonium sulphide, also by oxalic acid, strong acids 

 being present, and in neutral solution by Sodium thiosulphate 

 and Hydrogen dioxide. Its hydroxide was insoluble in hydro- 

 fluoric acid and Potassium fluoride. But differing from the 

 ordinary Thorium it was extremely and permanently active. 



