CONTENTS OF VOL. V. FIFTH SERIES. V 



NUMBEE XXX.— MAECH. 



Page 

 Dr. J. Kerr on Eefiection of Polarized Light from the Equa- 

 torial Surface of a Magnet 161 



Prof. J. J. Sylvester's Proof of the hitherto undenionstrated 



Fundamental Theorem of Invariants , . . 178 



Prof. H. F. Weber on Electromagnetic and Calorimetric Abso- 

 lute Measurements : the Absolute Value of Siemens'sUnit of 

 Eesistance in Electromagnetic Measure; the Eelation be- 

 tween the Current-work and the Heat-evolution in stationary 

 Gralvanic Currents ; and the Absolute Values of some con- 

 stant Hydroelectromotive Forces in Electromagnetic Mea- 

 sure 189 



Professors W. E. Ayrton and J. Perry on Eain-Clouds and 



Atmospheric Electricity 197 



Mr. H. C. Eussell on a new Modification of the Bichromate 



Battery (Plate VIII. fig. 14.) 201 



M. A. Eitter's Contributions to the Study of States of Aggre- 

 gation. (Plate VIII. figs. 1-13.) 202 



Mr. W. H. Walenn on Unitation. — VIII. Practical Eemarks 



thereon, together with Examples 214 



Professors W. E. Ayrton and J. Perry on the Contact Theory 



of Voltaic Action 219 



Mr. T. Bayley on the Colour Eelations of Copper and its Salts. 222 

 Notices respecting New Books : — 



Mr. J. E. Capron's Photographed Spectra 225 



Mr. E. A. Proctor's Other Worlds than Ours 228 



Mr. E. J. Eouth's Treatise on the Stability of a given 



State of Motion, particularly steady Motion 230 



Proceedings of the Greological Society : — 



Mr. H. Hicks on some Precambrian (Dimetian and Pebi- 



dian) Eocks in Caernarvonshire 231 



Prof. T. M'Kenny Hughes on the Precambrian Eocks of 



Bangor 232 



Mr. W. A. E. Ussher on the Chronological Value of the 



Pleistocene Deposits of Devon 233 



Dr. C. Le Neve Foster on the Great Flat Lode south of 

 Eedruth and Camborne ; and on some Tin-mines in the 



Parish of Wendron, Cornwall 234 



Dr. C. Le Neve Foster on some of the Stockworks of 



Cornwall „ 235 



The Eevs. E. Hill and T. Gr. Boaney on the Precarboni- 



ferous Eocks of Charnwood Forest 236 



On some Measurements of the Polarization of the Light coming 

 from the Moon and from the Planet Venus, bv the Earl of 



Eosse, F.E.S 237 



Glass-engraving by Electricity, by M. Plante 238 



On the Photometric Comparison of Light of different Colours, 

 by Professor 0. N. Eood, of Columbia College, H. S. A. . . 239 



