410 



Sir W. Crookes. 



radium, bodies of enormous radio-active powers, it was suggested that 

 uranium might possibly owe its power to the presence of a small 

 quantity of one of these bodies. But in a paper published in the 

 ' Revue Generale des Sciences ' for January, 1899, Mdme. Curie says : — 

 " This does not appear probable, for if such were the case different 

 samples of uranium compounds would have very different radio- 

 activities, but in the course of a number of experiments made with 

 various samples of metallic uranium, as well as with oxides and salts 

 from various sources, I have never found any marked difference 

 between the relative activities of the same compound." 



In another paper* the same author says that "the property of 

 emitting rays . . . which act on photographic plates is a specific 

 projperty of uranium and thm'ium." " The physical condition of the 

 metal seems to be of an altogether secondary importance." " Uranium 

 and thorium alone are practically active." 



3. When the discovery of radium was announced, and it was said 

 to have " to all appearance the properties of almost pure barium,"! it 

 occurred to me that radium might be found in detectable quantities in 

 some barium minerals were search made among them from different 

 localities. Accordingly specimens of the following minerals were put 

 on sensitive plates, a sheet of black paper separating them from the 

 sensitive surface. As it was probable that the radio-active substance 

 would be present, if at all, in very minute quantities^ the sensitive 

 plate was exposed to their influence for forty-eight hours. 

 Barytes (Heavy Spar). 



„ from Hungary. (Three specimens.) 



„ „ Cumberland. (Eight.) 



„ „ Westmorland. (One.) 



„ „ Cumberland. (A fine crystal.) 



,, ,, Derbyshire. (Three.) 



„ „ Arkendale. (One.) 



„ „ Hartz. (One.) 



„ „ Scotland. (One.) 



„ Ireland. (Two.) 



„ „ Northumberland. (Two.) 



„ „ Arran. (One.) 



„ ,, Cherbourg. (One.) 



,, Several unnamed, but finely crystallised, specimens* 



Witherite from Lancashire. (One.) 

 „ „ Cumberland. (Four.) 

 „ „ Northumberland. (One.) 



,* M. and Mdme C arie, ' Comptes Rendus,' vol. 127, p. 175; 'Chem. Newa/ 

 vol. 78, p. 49, July 29, 1898. 



, f M, and Mdme. Curie gnd M. Bemont, ' Comptes Eendus,', vol. 127, p. 1215 j 

 Chem, News,' vol. 79, p. 1, January 3, 1899. 



