CONTENTS OF VOL. XX, 



(FOURTH SERIES.) 



NUMBER CXXX.— JULY 1860. 



Page 



Prof. Kirchhoff on the Relation between the Radiating and 



Absorbing Powers of different Bodies for Light and Heat . . 1 

 Mr. J. C. Maxwell's Illustrations of the Dynamical Theory of 

 Gases :— 



Part it. On the Process of Diffusion of two or more kinds 

 Of moving particles among one another ............ 21 



Part III. On the Collision of Perfectly Elastic Bodies of any 



Form i i 33 



The Rev. S. Earnshaw on a new Theoretical Determination of 



the Velocity of Sound (continued) . . .......... 37 



Dr. Atkinson's Chemical Notices from Foreign Journals . . . i 41 

 Mr. C. J. Burnett on several Forms of Actinometer. (With a 



Plate.) iDiiuvMntttiiii 50 



Notices respecting New Books : — 



Mr. J. B. Smith's Arithmetic in Theory and Practice for 



advanced Pupils. Part the First i n 61 



Mr. J. R. Lunn : Of Motion. An Elementary Treatise . ■. 62 

 Dr. Boole's Treatise on the Calculus of Finite Differences. 62 

 Archdeacon Pratt's Treatise on Attractions, Laplace's 

 Functions, and the Figure of the Earth .......... , » 62 



Proceedings of the Royal Society : — 



Dr. Matthiessen on the Electric Conducting Power of Alloys. 63 

 Rear-Admiral FitzRoy on the Storms of October 25-26 and 



November 1, 1859 ....;.*;.. 64 



Dr. Hofmann on the Diatomic Ammonias i. 66 



Mr. T. Hopkins on the Forces that produce the great Cur- 

 rents of the Air and of the Ocean i.inunt.it 74 



Mr. J. P. Gassiot on the Interruption of the Voltaic Dis- 

 charge in vacuo by Magnetic Force ;....;;*;. ^4 



Proceedings of the Royal Institution : — 



Mr. W. Odling on Acids and Salts 78 



Proceedings of the Geological Society:-— 



Mr. J. Pilbrow on a Well- section at Bury Cross, near 



Gosport 84 



Mr. J. Prestwich on the presence of the London Clay in 



Norfolk 84 



Mr. T. R. Jones and W. K. Parker on some Foraminifera 

 from the Upper Triassic Clays of Chellaston, near Derby 85 



