388 D. MAWSON AND T. H. LABY. 



New South Wales varieties 1 are of a hyacinth colour, 

 well crystallised, aud exhibit two good cleavages. The 

 Pilbarra monazite in which we have identified the presence 

 of radium 2 is darker in colour than the N.S.W. specimens, 

 and cleavages are not so well defined. It is found in the 

 tin wash in association with euxenite and gadolinite. It 

 will be noticed in referring to the figures in the table that 

 no relation can be traced between radio-activity and thoria 

 contents. This points to the presence of some other active 

 substance in addition to the thoria. 



The gadolinite from the Cooglegong River, W.A. was 

 collected by Mr. B. F. Davis, b.sc, and is described 3 as 

 occurring both with the stream tin in alluvial deposits and 

 in lode formations in Pre-Oambrian gneiss. In the paper 

 cited an analysis is given, and it is stated that Prof. Norman 

 Collie found 1 bubble of helium in the gases obtained by 

 heating 10 grams of the mineral. This is the first 

 authentic case in which radio-activity lias been noticed in 



gadolinite. 



Examination for Radium. 



The method adopted was that used by Hon. R. J. Strutt 

 depending on the decay of the emanation. A preliminary 

 experiment was conducted on 5 grms. of Canotite 4 from 

 Colorado, U.S.A. Its emanation was found to be strongly 

 active, the rate of decay determining it to be due to radium. 

 Three Australian minerals were next tested with the 

 following results : 



Gadolinite from West Australia (38 grams tested) gave 

 no radium emanation. In view of the fact that helium is 

 intimately related to radium, this result is extremely inter- 

 esting, as the gadolinite has been shown to contain helium. 5 



1 Annual Report Dept. Mines, N.S.W. 1903 and Records of Australian 

 Museum 1903. 



2 Vide postea. 3 Journ. Roy. Soc. N.S. Wales, 1902, p. 286. 



4 Since then B. B. Boll wood has published that radium emanation is 

 obtained from this mineral. — Amer. Journ. Sci., 18, p. 97, 1904. 



5 Vide antea. 



