306 Dr. C. Chree on Deductions from 



Uranium. 



I 



UrX. 



I 

 ? 



Radium and its family of rapidly-changing products, viz., 

 the emanation, radium A, B, and 0. 



f 



Radium D = primary constituent in radio-lead. 



Radium E. 



\ 

 Radium F = active constituent in radio-tellurium and po- 

 lonium. 



No evidence has been obtained that any further active 

 products exist after radium F has been transformed. If the 

 a particle is a helium atom, remembering that five products 

 are present in radium which emit a particles, the atomic 

 weight of the transformation product of radium F should be 

 225 — 20 or 205. This is very close to the atomic weight of 

 lead, 206*7. The view r that lead is the final or end product of 

 the transformation of radium is supported by the fact that 

 lead is always found in the radioactive minerals in about the 

 amount to be theoretically expected from the content of 

 uranium, when the quantity of helium, present in the mineral, 

 is used to compute its probable age*. A similar suggestion 

 has recently been advanced by Boltwoodf. 



McGill University, Montreal, 

 May 1, 1905. 



XXXVIII. Deductions from Magnetic Disturbances at 

 Greenwich. By C. Chree, Sc.D., LL.D., F.R.S.^ 



§ 1. TX three recent papers in the Monthly Notices § of 

 A the Royal Astronomical Society, Mr. E. W. Maunder 

 has discussed the phenomena of magnetic storms at Green- 

 wich. In the first paper he concluded that magnetic storms 

 tend to follow one another at an interval of 27*275 days. 

 In a review of this paper in the March number of ' Terrestrial 

 Magnetism/ p. 12, I pointed out that "With the S storms 



* A full discussion of this question was given by the writer in the 

 Silliman Lectures, Yale University, March 1905. 

 t Phil. Mag-. April 1905. 

 X Communicated by the Author. 

 § November 1904, April 1905, May 1905. 



