MOBILITY AND DIFFUSION OF IONS. 113 



by an extension of the sphere of force of the ionic nucleus. The 

 expressions given involve only known physical constants of the gas, 

 and are, theiefore, directly comparable with the values as determined 

 experimentally. It is found that the obsei-ved values of the mobilities 

 and diffusion coefficients, as well as certain deviations from the 

 mobility-pressure law, can be approximately explained on the supposi- 

 tion that the ion consists of a single molecule of the gas, with which 

 is associated a charge equal to that carried by the monovalent ion in 

 electrolysis. 



16.— THE THEORY OF THE SMALL ION IN AIR. 



By WILLIAM SUTHERLAND, M.A., B.Sc. 



17.— THE BLEECK-LOVE ELECTRIC BATTERY. 

 By W. A. BLEECK, Brisbane. 



18.— ON. SOME OBSERVATIONS WITH SELENIUM CELLS. 

 By 0. U. VONWILLER, B.Sc, Sydney University, N.S.W. 



19.— THE ELECTRODELESS DISCHARGE IN IMERCURY VAPOUR. 



By S. G. LUSBY, M.A. 



20.— A NOTE ON THE ELECTRON THEORY OF THE CARBON ARC. 



By PROFESSOR J. A. POLLOCK, D.Sc. 



21.— THE SCATTERING OF BETA RAYS. 

 By J. P. r. MADSEN, B.Sc, B.E. 



22.— THE SCATTERING OF X RAYS. 



By PROFESSOR W. H. BRAGG, M.A., F.R.S. 



23.— SHORT NOTES ON— I. TAYLOR'S THEOREM, AND 

 II. ENVELOPES. 



By PROFESSOR E. J. N ANSON. 



24.— UNIVERSAL RADIO-ACTIVITY. NEW EXPERIMENTS WITHOUT 



RADIUM. 

 By J. W. H. RULLETT. 



25.— THE TEACHING OF MATHEMATICS. 



By R. H. ROE, M.A. 



26.— THE PROOF BY PROJECTION OF CERTAIN TYPES OF 

 GEOMETRICAL THEOREMS. 

 By H. TOMKYS. 

 H 



