CONTENTS.

PART I.

I. On the Bodily Tides original: "Bodily Tides" refers to the deformation of the entire mass of a planet (like Earth) rather than just its oceans. of Viscous and Semi-elastic Spheroids, and on the Ocean Tides upon a Yielding Nucleus A core that is flexible or not perfectly rigid.. By G. H. DARWIN, M.A., Fellow of Trinity College, Cambridge. Presented by J. W. L. GLAISHER, M.A., Fellow of the Royal Society (F.R.S.). . . . page 1

II. On the Spectra of Metalloids In the 19th century, "metalloid" was often used to describe non-metallic elements like oxygen.—Spectrum of Oxygen. By ARTHUR SCHUSTER, Ph.D., Fellow of the Royal Astronomical Society (F.R.A.S.). Presented by J. CLERK MAXWELL, F.R.S., Professor of Experimental Physics in the University of Cambridge . . . . . . . . 37

III. Electrodynamic Qualities of Metals.—Part VII. Effects of Stress on the Magnetization of Iron, Nickel, and Cobalt. By Professor Sir WILLIAM THOMSON, F.R.S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

IV. On Repulsion resulting from Radiation.—Part VI. By WILLIAM CROOKES, F.R.S., Vice President of the Chemical Society (V.P.C.S.) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

V. THE BAKERIAN LECTURE.—On the Illumination of Lines of Molecular Pressure, and the Trajectory of Molecules. By WILLIAM CROOKES, F.R.S., V.P.C.S. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

VI. On the Sensitive State of Electrical Discharges through Rarefied Gases. By WILLIAM SPOTTISWOODE, Doctor of Civil Law (D.C.L.), Doctor of Laws (LL.D.), President of the Royal Society (Pres. R.S.), and J. FLETCHER MOULTON, former Fellow of Christ's College, Cambridge . . . . . . . . . . . . . . . . . . . . . . . . . . . 165

VII. On Stresses in Rarefied Gases arising from Inequalities of Temperature. By J. CLERK MAXWELL, F.R.S., Professor of Experimental Physics in the University of Cambridge . . . . . . . . . . . . . . . . . . . . . . . . . 231

VIII. Researches on the Action of Organic Substances on the Ultra-violet Rays of the Spectrum. By W. N. HARTLEY, Fellow of the Institute of Chemistry, Fellow of the Royal Society of Edinburgh (F.R.S.E.), Fellow of the Chemical Society (F.C.S.), Demonstrator of Chemistry, King's College, London; and A. K. HUNTINGTON, F. Inst. Chem., Associate of the Royal School of Mines (A.R.S.M.), F.C.S. Presented by Professor G. G. STOKES, Secretary of the Royal Society (Sec. R.S.) . . . . . . . . . . . . . . . . . . . . . . 257

IX. On the Microrheometer An instrument used to measure the flow of liquids through very small tubes.. By J. B. HANNAY, F.R.S.E., F.C.S., recently Assistant Lecturer on Chemistry at Owens College, Manchester. Presented by H. E. ROSCOE, Ph.D., Professor of Chemistry at Owens College, Manchester . . . . . . . . . . . . . . . . . 275