CONTENTS OF VOL. XX. 



(SIXTH SERIES). 



NUMBER CXV.— JULY 1910. 



Page 



Mr. John Satterly on the Amount of Radium Emanation in 

 the Lower Regions of the Atmosphere and its Variation 

 with the Weather. (Plates I. & II.) 1 



Mr. A. L. Eletcher on the Radioactivity of the Rocks of the 

 Transandine Tunnel 36 



Messrs. C. Barus and M. Barus on the Interference of the 

 Reflected-Diffracted and the Diffracted-Reflected Rays of 

 a Plane Transparent Grating:, and on an Interferometer . . 45 



Mr. A. Whitwell on the Lengths of the Focal Lines of 

 Cylindrical Lenses 59 



Mr. E. Howard Smart on a Formula for the Spherical Aber- 

 ration in a Lens-System correct to the Fourth Power of 

 the Aperture , 82 



Messrs. G. Stead and H. Donaldson on the Problem of Uni- 

 form Rotation treated on the Principle of Relativity .... 92 



Prof. A. H. Gibson on a Rational Formula for the Discharge 

 over a Broad-crested Weir 95 



Prof. W. E. Story on Partial Pressures in Liquid Mixtures. . 97 



Prof. Harold A. Wilson on the Statistical Theory of Heat 

 Radiation 121 



Prof. J. Joly on the Amount of Thorium in Sedimentary 

 Rocks. — I. Calcareous and Dolomitic Rocks 125 



Dr. W. H. Eccles on an Oscillation Detector actuated solely 

 by Resistance-Temperature Variations 128 



Dr. G. Bakker on the Theory of Surface Forces. — V. Thermo- 

 dynamics of the Capillary Layer between the Homogeneous 

 Phases of the Liquid and the Vapour 135 



Dr. J. W. Nicholson on the Bending of Electric Waves round 

 a Large Sphere : II 157 



Profs. O. W. Richardson and H. L. Cooke on the Heat 

 developed during the Absorption of Electrons by Platinum. 

 (Plate III.) .' 173 



Dr. S. W. J. Smith on the Limitations of the Weston Cell as 

 a Standard of Electromotive Force 206 



Dr. R. D. Kleeman on the Shape of the Atom 229 



Sir J. J. Thomson on the Theory of Radiation 238 



Notices respecting New. Books : — .... 

 C. Tissot's Les Oscillations electriques, and E. Jouguet's 

 Theorie des Moteurs Thermiques 247 



