Vol. 32. 



SEPTEMBER 1891 



No. 196, 



Published the First Day of every Month. — Price 2s. 6d. 



THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



AND 



JOURNAL OF SCIENCE. 



Being a Continuation of TillocKs l Philosophical Magazine,' 

 Nicholsons 'Journal] and Thomson's ' Annals of Philosophy.' 



CONDUCTED BY 



SIR WILLIAM THOMSON, Knt. LL.D. P.R.S. &c. 

 GEORGE FRANCIS FITZGERALD, M.A. F.R.S. 



AND 



WILLIAM FRANCIS, Ph.D. F.L.S. F.RA.S. F.C.S. 



FIFTH SERIES. 



N° 196.- SEPTEMBER 1891. 



WITH THEEE PLATES. 



Illustrative of Dr. A. Eicbardson's Paper on the Expansion of Chlorine 

 by Light as applied to the Measurement of the Intensity of Pays of 

 High Eefrangibility, and Mr. A. P. Chattock's on the Electrification 

 of Steel Needle-Points in Air. 



LONDON: 



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Sold by Simpkin. Marshall, Hamilton, Kent, and Co., Ld. ; and Whittaker and Co. ; — 

 and'by A. and C. Black, and T. and T. Clark, Edinburgh; Smith and Son, 

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 Boyveau, Paris : — and Asher and Co., Berlin. 



