[ iv ] 
VI. On the Absorption-Spectra of Bromine and of Iodine Monochloride. By H. E. 
Roscoe, F.R.S., and T. E. Thorpe, F.B.S. page 207 
VII. On the Organization of the Fossil Plants of the Coal-measures. — Part VIII. 
Ferns (continued) and Gymnospermous Stems and Seeds. By W. C. Williamson, 
F.B.S. , Professor of Natural History in the Owens College , Manchester . 213 
VIII. On the Influence of Geological Changes on the Barth's Axis of Potation. By 
George H. Darwin, M.A., Fellow of Trinity College , Cambridge. Communicated 
by Professor J. C. Adams, F.B.S. 271 
IX. The Action of Light on Selenium. By Professor W. G. Adams, M.A., F.B.S., 
and R. E. Day, M.A 313 
PART II. 
X. On Hyperjacobian Surfaces and Curves. By William Spottiswoode, M.A., LL.I)., 
Treas.R.S. . . 351 
XI. On a new Form of Tangential Equation. By John Casey, LL.I)., F B.S., 
M.B.I.A., Professor of Mathematics in the Catholic University of Ireland 367 
XII. On the Bicircular Quartic. — Addition to Professor Casey’s Memoir “ On a new 
Form of Tangential Equation By A. Cayley, LL.D., F.B.S., Sadlerian Pro- 
fessor of Pure Mathematics in the University of Cambridge 441 
XIII. Contributions to Terrestrial Magnetism. — No. XV. By General Sir Edward 
Sabine, B.A., K.C.B., F.B.S 461 
XIV. On Friction between Surfaces moving at Low Speeds. By Fleeming Jenkin, 
F.B.SS.L. & E., Professor of Engineering in the University of Edinburgh , and 
J. A. Ewing 509 
XV. On the Structure and Development of the Skull in the Urodelous Amphibia . — Part I. 
By William Kitchen Parker, F.B.S 529 
XVI. Besidual Charge of the Leyden Jar. — Dielectric Properties of different Glasses. 
By J. Hopkinson, M.A., D.Sc. Communicated by Professor Sir William 
Thomson, F.B.S. ................... 599 
