OBSERVATIONS ON RADIO-ACTIVITY. 389 



A similar instance is that of a meteorite from Virginia, 

 examined by Strutt. 1 In this case, although the presence 

 of helium was detected by analysis, the meteorite failed to 

 give the radium emanation. In the gadolinite, although 

 thoria is not mentioned in the statement of analysis, later 

 investigation by Acting Professor Schofield showed that a 

 small percentage is present, and the activity is probably 

 referable to this. 



Pilbarra mouazite (31 grams tested) gave a definite 

 radium emanation decaying to a half in very slightly under 

 four days. The value of the radium activity cannot yet be 

 assigned until more comparative data are obtainable. 



Monazite from Paradise Creek, Emmaville, N.S.W. (25 

 grams tested) gave an emanation decaying in a very 

 short time, and not measurable with our apparatus. 



Summary. 



A number of Australian minerals have been examined 

 for radio-activity by the ionisation produced in an air gap 

 as measured by the most recent form of a C. T. R. Wilson 

 electroscope. The activities are compared with that of black 

 oxide of uranium. Radium was tested for in four of the 

 minerals by heating them in a vacuum and testing the rate 

 of decay of the radio-activity of the resulting gas. 



A gadolinite in which Professor Norman Oollie found 

 helium to be present was radio-active, but no radium 

 emanation could be detected. A number of monazites were 

 radio-active, one from Pilbarra, W.A., gave the radium 

 emanation. It is intended to continue this work shortly, 

 when all results will be published in amperes. 



For the suggestion of the research, carried out in the 

 Chemical Laboratory, and for constant encouragement we 

 wish to thank Professor David. We are indebted to the 

 Department of Mines for a number of minerals, and especi- 

 ally to Mr. G. W. Card, a.r.s.m., for his cordial help in 

 obtaining us specimens. Our thanks are also due to Acting 

 Professors Schofield and Knibbs for encouragement and 

 interest shown in the research. 



1 Proc. Roy. Soc, 73, p. 193, 1904. 



