M CONtffiNTS OP VOL. XX. — FOURTH SERIES. 



Page 



Prof. Challis on a Theory of the Force of Electricity . ; . i 280 



Dr. Atkinson's Chemical Notices from Foreign Journals .... 290 

 Mr. T. Tate on the Construction of a new Air-thermometer , . 298 

 Mr. D. Campbell on the presence of Arsenic and Antimony in 



the sources and beds of Streams and Rivers 304 



Mr. J. J. Sylvester: Meditation on the Idea of Poncelet's 



Theorem. .' i 307 



Proceedings of the Royal Society : — 



Prof. W. Thomson on the Measurement of the Electro- 

 motive Force required to produce a Spark in Air between 



parallel metal plates at different distances 316 



On the difference in size of Medals of different Metals obtained 

 by Stamping, and by Casting in the same Mould, by Ht. W. 



Dove 327 



On Atmospheric Electricity, by M. Volpicelli 327 



On a Magnetic Phenomenon, by M. Ruhmkorff 328 



NUMBER CXXXIV.— NOVEMBER. 



M. F. August on a new Species of Stereoscopic Phenomenon. 



(With a Plate.) i ; . . . 329 



Mr. A. Cayley on a Problem of Double Partitions 337 



Mr. A. Cayley on a System of Algebraic Equations 341 



M. R. Schneider on the Volumetric Determination of Antimony. 342 

 The Rev. It. Carmichael's Illustrations of Symmetrical Integra- 

 tion 348 



Prof. Dove on the Dichrooscope. (With a Plate.) 352 



Prof. W. Thomson's Notes on Atmospheric Electricity 360 



Mr. T. Tate's Experimental Researches on the Laws of Ab- 

 sorption of Liquids by Porous Substances. (With a Plate.) 364 



Mr. J. Cockle's Note on Transcendental Roots 369 



MM. A. and F. Dupre : Spectrum-analysis of London Waters. 373 

 Dr. Atkinson's Chemical Notices from Foreign Journals .... 374 

 Proceedings of the Royal Society : — 



Sir David Brewster and Dr. Gladstone on the Lines of 



the Solar Spectrum * 385 



Dr. Crace Calvert on some New Volatile Alkaloids given 



off during Putrefaction 387 



Prof. Matteucci on the Electrical Phenomena which accom- 

 pany Muscular Contraction 388 



Dr. RadclifFe on the Muscular Movements resulting from 



the action of a Galvanic Current upon Nerve * ; . 390 



Proceedings of the Geological Society : — 



M. E. Lartet on some Arrow-heads and other Instruments 

 found with Horns of Cervus megaceros in a Cavern in 



Languedoc ...;.;..:. 400 



Mr. T. F. Jamieson on the occurrence of Crag Shells 

 beneath the Boulder- clay in Aberdeenshire 401 



