CONTENTS OF VOL. XXXVL 



(FOURTH SERIES.) 



NUMBER CCXL.— JULY 1868. 



Page 



Mr. J. Gill on the Dynamical Theory of Heat 1 



Prof. R. Ball on Vortex-rings in Air 12 



On C. S, Lyman's new form of Wave-apparatus 14 



M. A. Kundt on the Velocity of Sound in Tubes 22 



Mr. R. Moon on the Theory of Pressure in Fluids 27 



Prof. F. Guthrie's Description of a new Thermostat 30 



M. H. Fizeau on the Expansion of Solids by Heat 31 



Mr. E. C. Pickering on the comparative Efficiency of different 



Forms of the Spectroscope 39 



Mr. J. C. Douglas on an Optical Experiment .... 43 



Mr. G. W. Wigner on Purification of Sewage 46 



Notices respecting New Books : — 



Dr. H. Watts's Dictionary of Chemistry and the Allied 



Sciences 47 



The Rev. T. W. Webb's Celestial Objects for Common Te- 

 lescopes 51 



Proceedings of the Royal Society : — 



Dr. W. J. M. Rankine on Waves in Liquids 52 



Mr. W. Huggins on the Spectra of the Sun, and of some 

 of the Stars and Nebulae, with an attempt to determine 

 therefrom whether these Bodies are moving towards or 

 from the Earth, and on the Spectrum of Brorsen's Comet, 



1868 55 



Mr. T. Graham on the Occlusion of Hydrogen Gas by Metals. 63 

 Proceedings of the Royal Institution : — 



Dr. W. Odling on some Effects of the Heat of the Oxyhy- 



drogen Flame 68 



Proceedings of the Geological Society : — 



Mr. H. Woodward on Palaeozoic Crustacea from the Upper 

 Silurian rocks of Lanarkshire, &c 71 



