vi Contents. 



PAGE 



Professor J. J. Thomson, On the motion of a charged ion in a magnetic 



field 49 



Mr John S. Townsend, The formation of clouds with ozone ... 52 

 Mr H. C Pocklington, On the Symbolic Integration of certain Differential 



Equations in Quaternions 59 



Mr H. C. Pocklington, On the conditions of sensitiveness in Detectors of 



Radiant Heat 66 



-Mr J. Stanley Gardiner, On the Anatomy of a supposed New Species of 



Coenopsammia from Lifu ........ 72 



Professor J. J. Thomson, On the Conductivity of Gases exposed to Ent- 



ladungsstrahlen 74 



Mr W. Bateson and Miss D. F. M. Pertz, Notes on the inheritance of 



Variation in the Corolla of Veronica Buxbaumii (Plate I) 78 



Mr W. M C F. Orr, On the product J m (x)J n (x) . . . . .93 



Rev. H. J. Sharpe, On the Reflection of Sound at a Paraboloid . . 101 

 Mr A. C. Seward, Notes on the Binney Collection of Coal-Measure Plants. 



Plates III to VII 137 



Mr D. Sharp, The Modification and Attitude of Idolum diabolicum, a 



Mantis of the hind called " floral simulators." Plate II . .175 



Mr J. Larmor, On the Origin of Magneto -optic Rotation . . . 181 



Proceedings at the Meetings held during the Session 1898 — 1899 . .183 



Mr W. M C F. Orr, On Semi-convergent Series 189 



Mr C. T. R. Wilson, An Experiment on the Condensation of Clotids . 189 

 Mr J. J. Lister, The Skeleton of Astrosclera compared with that of the 



Pharetronid Sponges 189 



-Dr S. F. Harmer, Note on the name Balanoglossus . . . .190 



Miss E. Dale, On certain outgroivths {Intumescences) on the green parts of 



Hibiscus vitifolius Linn. Plates VIII, IX, X 192 



Mr H. W. Richmond, On the condition that five straight lines situated in 



a space of four dimensions shotdd lie on a quadric .... 210 

 Professor Liveing, On the Influence of Temperature, and of Various 



Solvents, on the Absorption Spectra of Didymium and Erbium 



Salts 213 



Mr H. Jackson, Researches in the Sugar Group 215 



Mr A. Hutchinson, On a New Mineral 216 



Mr John S. Townsend, Secondary Rontgen Rays 217 



-Mr J. Graham Kerr, Note on hypotheses as to the origin of the Paired 



Limbs of Vertebrates 227 



Mr J. S. Budgett, Observations on Polypterus and Protopterus . . 236 

 Mr J. A. M°Clelland, On the Conductivity of Gases from an Arc and 



from Incandescent Metals 241 



Miss D. F. M. Pertz and Mr Francis Darwin, Experiments on the 



Periodic Movement of Plants 259 



Mr A. C. Seward, On the Wealden Plants from Bernissart . . , 259 



