IV CONTENTS OF VOL. XXXIV. SIXTH SERIES. 



Page 

 Mr. E. A. Biedermann on the Energy in the Electromagnetic 

 Eield 142 



Dr. S. Chapman on the Partial Separation bj Thermal 



Diffusion of Grases of Equal Molecular "Weight 146 



Notices respecting New Books : — 



Dr. W. H. Bragg and Mr. L. W. Bragg's X-Rays and 



Crystal Structure 151 



Proceedings of the Geological Society : — 



The President's Anniversary Address 151 



NUMBER CCL— SEPTEMBER. 



Sir E. Rutherford on the Penetrating Power of the X Ra- 

 diation from a Coolidge Tube 153 



Prof. A. S. Eddington on Astronomical Consequences of the 

 Electrical Theory of Matter. Note on Sir Oliver Lodge's 

 Suggestions 163 



Mr. W. J. Walker oa Thermodynamic Cycles with Variable 

 Specific Heat of "Working Substance 168 



Prof. A. Anderson on some Properties of the Nul Point of 

 Thin Axial Pencils of Light directly refracted through a 

 Symmetrical Optical System 174 



Prof. R. W. "Wood and Mr. S. Okano on the Ionizing 

 Potential of Sodium Vapour 177 



Dr. Balth. van der Pol on the Relation of the Audibility 

 Eactor of a Shunted Telephone to the Antenna Current as 

 used in the Reception of Wireless Signals 184 



Dr. J. R. Airey on the Numerical Calculation of the Roots 

 of the Bessel Function J n (x) and its first derivate J n '(x) . . 189 



Mr. H. H. Poole on the Temperature Variation of the 

 Electrical Conductivity of Mica 195 



Dr. L. Isserlis on the Variation of the Multiple Correlation 

 Coefficient in Samples drawn from an Infinite Population 

 with Normal Distribution . . . . 205 



NUMBER CCII.— OCTOBER. 



Mr. Gr. A. Hemsalech on the Origin of the Line Spectrum 

 emitted by Iron Vapour in the Explosion Region of the 

 Air-Coal Gas Elame. (Plates II. & III.) 221 



Mr. Gr. A. Hemsalech on the Production of Coloured Elames 

 of High Luminosity for Demonstration and Experimental 

 Purposes , ... 243 



