D W. S. DUN. 



chiefly on the rare earths. Of his more recent work, in 

 connection with radio-activity he first effected the separa- 

 tion of the product resulting from the disintegration of 

 uranium, calling it uranium X, and discovered in 1903 that 

 a zinc sulphide target phosphoresces under the influence 

 of a bombardment of a particles. The effect is seen in the 

 4 Spintharoscope' which Orookes invented for the purpose,, 

 and through the agency of this fascinating little instrument 

 the phenomenon is well known. This discovery has im- 

 portant applications in connection with radio-active deter- 

 minations. 



Much of Orookes' work dealt with practical matters. In 

 1859 he started the "Chemical News" which he edited 

 until the end of his life, and he published many papers and 

 books on technical subjects covering a wide range. For 

 some years he devoted much attention to the study of the 

 origin and properties of diamonds. He was given unique 

 opportunities to visit De Beers' mines, and to examine the 

 famous blue clay. Several papers and a most interesting 

 book record the results of his investigations of these pre- 

 cious stones. In 1914 he completed a comprehensive study 

 of the effects of adding various metallic oxides to the con- 

 stituents of glass in a search for glasses for spectacles 

 which, though transparent in the ordinary sense, would be 

 opaque to the rays which have been found injurious to the 

 eyes of workers exposed to furnace glare. The result is a 

 table giving the composition and appropriate use of nine- 

 teen glasses which are valuable, out of more than 300 kinds 

 investigated. To many workers glasses made to these 

 prescriptions will prove an inestimable boon. Sir William 

 Orookes during his life time received many honours. He 

 served as President of several Societies, including the 

 Chemical Society, the British Association, and the Institu- 

 tion of Electrical Engineers. He was President of the 

 Royal Society from 1913 to 1915, and was one of the few 



