CONTENTS OF VOL. XVII. — FOURTH SERIES. 



NUMBER CXII.— FEBRUARY. 



Page 

 Prof. Clausius on the Mean Length of the Paths described by 

 the separate Molecules of Gaseous Bodies on the occurrence 

 of Molecular Motion ; together with some other Remarks 



upon the Mechanical Theory of Heat 81 



Prof. Tyndall on Ice and Glaciers 91 



Prof. Trowbridge on Deep-sea Explorations 97 



Prof. Challis on the Direction of the Vibrations of a Polarized 



Ray ••■ 102 



Mr. G. Gore on the Rotation of Metallic Spheres by Electricity. 107 

 Messrs. Quet and Seguin on the Stratifications of the Electric 



Light 109 



Prof. Challis's Proof that every Equation has as many Roots 



as it has Dimensions 112 



Messrs F. C. Calvert and R. Johnson on the Hardness of 



Metals and Alloys 114 



Dr. Wallace on lodo-arseuious Acid 122 



Mr. A. Cayley on Poinsot's four new Regular Solids 123 



Messrs. H. Sainte-Claire Deville and H. Caron on Apatite, 



Wagnerite, and some artificial species of Metallic Phosphates. 1 28 

 Proceedings of the Royal Society : — 



Dr. Hofmann on the Action of Bichloride of Carbon on 



Aniline 131 



Dr. Hofmann's Researches on the Phosphorus-Bases .... 133 

 Dr. Hofmann on the Action of Bisulphide of Carbon on 



Triethylphosphine 136 



Dr. Hofmann on the History of the Monamines 138 



Dr. Pavy on the alleged Sugar-forming Function of the 



Liver 142 



Dr. Marcet on the Action of Bile upon Fats ; with addi- 

 tional Observations on Excretine 145 



Proceedings of the Geological Society : — 



Dr. Dawson on Fossil Plants from the Devonian Rocks of 



Gaspe, Canada 147 



Mr. T. S. Hunt on some Points in Chemical Geology . , 148 

 Mr. H. Rosales on the Gold-field of Ballaarat, Victoria . . 149 

 Mr. J. Harley on a New Species of Cephalaspis (C Astero- 

 lepis) from the Old Red Sandstone of the neighbourhood 



of Ludlow 150 



New Method of Examining and Verifying the Specific Gravity 



of Bodies, by M. A. Meyer 150 



Note on a Theorem in Spherical Trigonometry, by A. Cayley. 151 

 Description of the Methods used to ascertain the Figure of Op- 

 tical Surfaces, by M. L. Foucault 151 



On some large Solar Spots, by W. R. Dawes 152 



