CONTENTS OF VOL 



(SIXTH SERIES), 



^ ^^cg iQQs 



NUMBER XXXI.— JULY 



Prof. L. T. More on Electrostriction. (Plate I.) . . TT^**^ ^^ 

 Prof. H. Nagaoka on the Potential and Lines o£ Eorce of a 



Circular Current 19 



ProF. A. L. Kimball on the Application of Cornu's Spiral to 



the Diffraction-Grrating. — A Greometrical Method of ob- 

 taining the Intensity Formula for a Flat Diffraction-Grating. 30 

 Mr. A. Campbell on Measurements of Small Resistances. ... 33 

 Dr. J. A. Harker on a Direct-reading Potentiometer for 



Thermoelectric Work. (Plate IL). . 41 



Mr. A. Whitwell on Refraction at a Cylindrical Surface. 



(Plate III.) 46 



Prof. J. Trowbridge on Spectra of G-ases and Metals at High 



Temperatures. (Plate IV.) 58 



Dr. W. Marshall Watts on the Atomic Weight of Radium. . 64 

 Mr. H. Hilton on the Grraphical Solution of Astronomical 



Problems , 6Q 



Hon. R. J. Strutt on the Absorption of Light by Mercury 



and its Vapour 76 



Dr. S. R. Milner on a New Form of Vacuum Stopcock 78 



Mr. O. W. Richardson on the Positive Ionization produced by 



Hot Platinum in Air at Low Pressures. (Plate V.) 80 



Prof. R. W. Wood on the Anomalous Dispersion, Absorption, 



and Surface-Colour of Nitroso-dimethyl-aniline, with a Note 



on the Dispersion of Toluine. (Plates A^I.-VIII.) 96 



Hon. R. J. Strutt on the Preparation and Properties of an 



Intensely Radioactive Gras from Metallic Mercury 113 



Dr. J. Stark on the Theory of Ionization by Collision of Ions 



with Neutral Molecules 116 



Prof. F. L. O. Wadsworth on the Aberration of the Concave 



Grrating, when used as an Objective Spectroscope 119 



Mr. T. H. Havelock on the Pressure of Radiation 157 



Prof. R. C. Maclaurin on the Influence of Stiffness on the 



Form of a Suspended Wire or Tape 166 



Mr. Gr. F. C. Searle on a Simple Rheostat 173 



Dr. K. Przibram on the Point-Discharge in Mixtures of Gases. 176 

 Dr. H. A. Wilson on the Electric Intensity in the Uniform 



Positive Column in Air 180 



Prof. W. Watson on the Construction and Attachment of 



Thin Galvanometer Mirrors 188 



