CONTENTS OF VOL. XL. SIXTH SERIES. V 



Page 



Dr. E. T. Beatty and Mr. A. Gilmour on the Measurement 

 of Changes in Eesistance by a Valve Method 291 



Mr. G. A. Hemsaleeh on the Character of the Light Eadia- 

 tions emitted by the Vapours of Magnesium, Copper, and 

 Manganese under the Selective Actions of Thermo-chemical 

 and Thermo-electrical Excitations. (Plates VI11. & IX.) 296 



Mr. G. A. Hemsaleeh : Note on a very Convenient Method 

 of Accurately Focussing and Adjusting the Image of a 

 Laboratory Light Source upon the Slit of a Spectrograph . 31b' 



Dr. W. T. David on Heat-loss by Conduction in Explosions 

 of Coal-gas and Air 318 



Mr. Gr. B. Jeffery on the Path of a Eay of Light in the 

 Gravitation Eield of the Sun 327 



Mr. L. C. Jackson on Variably Coupled Vibrations : Gravity- 

 Elastic Combinations. — II. Both Masses and Periods 

 Unequal. (Plate X.) ., 329 



Mr. E. S. Pearson on the Advance of Perihelion of a Planet. 342 



Prof. W. M. Thornton on the Ignition of Gases at Eeduced 

 Pressures by Impulsive Electric Sparks 345 



Prof. G. W. Todd on the Variation of the Specific Heat of a 

 Gas with Temperature 357 



Mr. Cyril 11. Meyers on a Vapour Pressure Equation 362 



Mr. Alex. Erumkin on the Theory of Electrocapillarity. — I. 363 



Mr. Alex. Erumkin on the Theory of Electrocapillarity. — II. 375 



Mr. H. P. Waran on an Improved Design for the Eriction 

 Cones of Searle's Apparatus for the Mechanical Equivalent 

 of Heat 386 



Notices respecting New Books : — 



Prof. J. H. Poynting's Collected Scientific Papers .... 388 



Prof. A. N. Whitehead's The Concept of Nature 389 



Prof. A. Gray's A Treatise on Gyrostatics and Eotational 

 Motion 392 



NUMBEE CCXXXVIII.— OCTOBEE. 



Sir J. J. Thomson on the Scattering of Light by Unsym- 

 metricai Atoms and Molecules 393 



Messrs. G. Stead and B. S. Gossling on the Eelative Ionization 

 Potentials of Gases as observed in Thermionic Valves. . . . 413 



Dr. H. Stanley Allen on Optical Eolation, Optical Isomerism, 

 and the Eing-Electron 426 



Prof. Frank Horton and Miss Doris Bailey on the Effect of 

 a Trace of Impurity on the Measurement of the Ionization 

 Velocity for Electrons in Helium 440 



Prof. "W. M. Thornton on the Ignition of Gases at Eeduced 

 Pressures by Transient Arcs 450 



