382 D. MAWSON AND T. H. LABY. 



Preliminary OBSERVATIONS on RADIO-ACTIVITY 



and the OCCURRENCE OF RADIUM in 



AUSTRALIAN MINERALS. 



By D. Mawson, b.e., Junior Demonstrator in Chemistry, 



and T. H. Laby, Acting-Demonstrator in Chemistry 



in the University of Sydney. 



[Read before the Royal Society of N. S. Wales, October 5, 1904.'] 



Literature. 

 Professor H. Becquerel, as is well known, was the first to 

 observe what is now called radio-activity in uranyl-potas- 

 sium sulphate. Schmidt 1 extended the observations to 

 thorium minerals. Madame Curie,' 2 who independently 

 made the same discovery, has published values of the radio- 

 activity of thirteen minerals 3 of high uranium and thorium 

 content, as measured by the ionisation produced in an air 

 gap. Sir W. Crookes 4 looked for radio-activity by a photo- 

 graphic method in his collection of minerals, especially 

 among the barium ones; but found only euxenite, alvite, 

 arrhenite, sipilite, and hiebnite to be active. These 

 minerals contain either uranium or thorium. No instance 

 of the comparatively intense activity of minerals contain- 

 ing these elements, has been found in their absence. The 

 Hon. R. J. Strutt 5 examined the activity of samarskite, 

 fergusonite, pitchblende, malacone, monazites, and zircon 

 by a different method, depending on the rate of decay of 

 the activity of the gas given off when the minerals were 

 heated. 



1 Wied. Annal. 65, p. 141, 1898. 



s Coinptes Rendus, 126, p. 1601, 1898. 



3 These presentee a la Faculte des Sciences de 1' Universite de Paris. 



* Proc. Roy. Soc, 66, p. 409, 1900. 6 Loc. cit., 73, p. 193, 1904. 



