Vlll CONTENTS OF VOL. XIX. SIXTH SERIES. 



Messrs. J. C. Chapman and S. H. Piper on Secondary 



Homogeneous X Radiation 897 



Mr. J. W. Waters on Radioactive Minerals in Common Eocks 903 

 Mr. J. W. Waters on the Rate of Decay of Radioactivity of 



Polonium 905 



Mr. W. J. Harrison on the Decay of Waves in a Canal .... 906 

 Mr. W. A. Scoble : Further Tests of Brittle Materials 



under Combined Stress 908 



Proceedings of the Geological Society 917-918 



Index 919 



PLATES. 



I. Illustrative of Mr. W. A. Scoble's Paper on Ductile 

 Materials under Combined Stress. 

 II. Illustrative of Mr. P. V. Bevan's Paper on the Absorption 



Spectrum of Potassium Vapour. 

 HI. Illustrative of Mr. F. E. Smith's Paper on Cadmium 



Amalgams and the Weston Normal Cell. 

 IV. Illustrative of Mr. T. Royd's Paper on Further Experi- 

 ments on the Constitution of the Electric Spark. 

 V. Illustrative of Mr. C. A. Sadler's Paper on Homogeneous 

 Corpuscular Radiation. 

 VI. Illustrative of Mr. E. E. Baynes's Paper on Saturation 

 Specific Heats, &c, with van der Waals's and Clausius's 

 Characteristics. 

 VTI. Illustrative of Mr. H. R. Nettleton's Paper on a New- 

 Method of Determining Thermal Conductivity. 

 VIII. & IX. Illustrative of Prof. J. Joly and Mr. A. L. Fletcher's Paper 

 on Pleochroic Halos. 

 X. & XI. Illustrative of Mr. G. H. Berry's Paper on the Striking 

 Point of Pianoforte Strings. 

 XII. Illustrative of Mr. and Mrs. Soddy and Mr. Russell's Paper 

 on the Question of the Homogeneitv of y-Rays. 

 XIII. Illustrative of Prof. H. Rubens and Mr. H. Hollnagel's 

 Paper on Measurements in the Extreme Infra-Red 

 Spectrum. 



ERRATUM. 



Page 605. in the title to Mr. Borodowsky's paper for Tourjew 

 read Iourjew. 



