CONTENTS. 



VOL. XV. 



Page 



On the Colouring and Extractive Matters of Urine. — Part I. By Edward 

 Schunck, F.R.S 1 



Sixth Memoir on Radiation and Absorption. By Professor J. Tyndall, F.R. S. 5 



On the Spectrum of Comet 1, 1866. By William Huggins, F.R.S ih. 



Note on the Secular Change of Magnetic Dip, as recorded at the Kew Ob- 

 servatory. By Balfour Stewart, M.A., LL.D, F.R.S., Superintendent of 

 the Observatory 8 



On the Specific Gravity of Mercury. By Balfour Stewart, M.A., LL.D., 

 F.R.S., Superintendent of the Kew Observatory 10 



On the Forms of Graphitoidal Silicon and Graphitoidal Boron. By W. H. 

 Miller, M.A., For. Sec. R.S., and Professor of Mineralogy in the Univer- 

 sity of Cambridge 11 



On the Viscosity or Internal Friction of Air and other Gases, being the Ba- 

 kerian Lecture, delivered by James Clerk Maxwell, M.A.^ F.R.S 14 



Further Observations on the Spectra of some of the NebulEe, with a Mode 

 of determining the Brightness of these Bodies. By William Huggins, 

 F.R.S 17 



Account of Experiments on the Flexural and Torsional Rigidity of a Glass 

 Rod, leading to the determination of the Rigidity of Glass. By Joseph 

 D. Everett, D.C.L., Assistant to the Professor of Mathematics in the Uni- 

 versity of Glasgow 19 



Note on the relative Chemical Intensities of direct Sunlight and difiuse 

 Daylight at Different Altitudes of the Sun. By Henry E. Roscoe, F.R.S., 

 and Joseph Baxendell, F.R.A.S 20 



Researches on Acids of the Lactic Series. — No. I. Synthesis of Acids of the 

 Lactic Series. By E. Frankland, F.R.S., and B. F. Duppa, Esq 25 



Note on a Correspondence between Her Majesty's Government and the Pre- 

 sident and Council of the Royal Society regarding Meteorological Obser- 

 vations to be made by Sea and Land. By Lieutenant-General Sabine, 

 P.R.S 29 



On the Action of Compasses in Iron Ships. By Mr. John Lilley 38 



On the Tidal Currents on the West Coast of Scotland. By Archibald 

 Smith, M.A., F.R.S 42 



