CONTENTS 
Page 
Chemistry. — The Oxidation of Hydroquinoi. in the Presence oi^ Ai^iphatic 
Amines . . . By R. N. Harger 57 
Physics. — The Grating Space of Mica and the Intensities of the Spectral 
Orders By B. Davis and H. M. Terrill 59 
Physics. — Ionization and Radiation Potentials and the Size of the Atom 
By B. Davis 61 
Physics. — Periods and Logarithmic Decrement of the Gravitation Needle 
under High Exhaustion By C. Barus 63 
Physics. — Plane Reflection of Sound, as Exhibited by the Pinhole Resona- 
tor ..." By C. Barus 66 
Astronomy. — Note on the Problem of Great Stellar Distances 
By H. Shapley 69 
Statistics. — The Vital Index of the Population of England and Wales, 
1838-1920 By R. Pearl and M. H. Burger 71 
Statistics. — Seasonal Fluctuations of the Vital Index of a Population 
By R. Pearl 76 
Mathematics. — A Solution of the Linear Matrix Equation by Double 
Multiplication . . By F. L. Hitchcock 78 
