CONTENTS OF VOL. XXXIII.- — FIFTH SERIES. Vll 



NUMBER CCV.— JUNE. 



Page 

 Mr. A. M c Aulay on Quaternions as a practical Instrument of 



Physical Besearch 477 



Mr. W. Baily on the Construction of a Colour Map. (Plate 



VIII.) 496 



Dr. G. J. Stoney on an Analysis of the Spectrum of Sodium, 



including an Inquiry into the true place of the Lines that 



have been regarded as Satellites. (Plates VI. & VII.) .... 503 

 Prof. E. E. Herroun on the Electromotive Eorces of Gold 



and of Platinum Cells 516 



Dr. C. Ludeking on the Action of the Electric Discharge on 



G-ases and Vapours , 521 



Dr. E. T. Trouton and Mr. W. E. Lilly on a Method for deter- 

 mining the Specific Inductive Capacity of Dielectrics .... 529 

 Mr. J. Brown on the Difference of Potential at the Contact of 



Mutually Eeacting Liquids 532 



Proceedings of the Geological Society : — 



Rev. E. Hill and Prof. T. G. Bonney on the Hornblende- 

 schists, Gneisses, and other Crystalline Rocks of Sark 539 

 Messrs. J. R. Dakyns and J. J. H. Teall on the Plutonic 



Rocks of Garabal Hill and Meall Breac 540 



On the Value of the Brightness of Spectral Colours with 



different absolute Intensity, by A. Konig and R. Ritter . . 541 



On the Glow-Discharge, by E. Warburg 543 



Prize for Researches in Physics, offered by Schnyder von 



Warten see's Eoundation for Science and Art, Ziirich .... 544 



Index 545 



