XXXIV. ABSTRACT OF PROCEEDINGS. 



ford and Soddy's discovery that radium gives off a radio- 

 active gas, the emanation, which decays in activity to half 

 its initial value in four days. A torbernite and euxenite 

 were found highly active, but the specimens were too small 

 to examine for radium. A Western Australian gadolinite, 

 found by Professor Norman Collie to contain one bubble of 

 helium in ten grams, was expected to contain radium, but 

 none could be detected. Twelve monazites were found 

 radio-active ; one, with double the average activity of the 

 others, from Pilbarra, Western Australia, gave on heating 

 the radium emanation ; five monazite and zircon sands were 

 also active. No relation between thoria contents and 

 activity was found, which points to the presence of uranium. 



Remarks were made by Prof. David, Prof. Pollock, Mr. 

 G. H. Knibbs, Mr. F. B. Guthrie, Mr. W. M. Hamlet, the 

 authors, and the President. 



3. "The Flood Silt of the Hunter and Hawkesbury Rivers," 

 by Prof. T. W. Edge worth David, b.a., f.r.s., f.g.s., 

 and Acting-Professor F. B. Guthrie, f.i.c, f.c.s. 



During the floods last July in the Hunter and Hawkesbury 

 rivers, samples of the flood water as well as of the flood silt 

 were collected, at the instance of the authors, by Mr. A. J. 

 Prentice, b.a., of West Maitland, and Mr. W. H. Potts, the 

 Principal of the Hawkesbury Agricultural College. Deter- 

 minations made at the laboratory of the Department of 

 Agriculture show the following to be the chemical com- 

 position of the silts: — 



Analysis of Silt from Hunter River Water. 



Pftr o.f>r\t. 



Insoluble in hydrochloric acid ... ... ... =79*25 



Soluble in hydrochloric acid — 



Oxide of iron and alumina (Fe 2 O s and A1 2 3 ) = 10*02 



Lime (CaO) = 1*55 



Potash (K 2 0) = 0*09 



Phosphoric acid (P 2 5 ) = 0*18 



