Vol. 44. SEPTEMBER 1872. No. 292 



Published the First Day of every Month. — Price %s. Qd. 



THE 

 LONDON, EDINBUEGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



AND 



JOURNAL OF SCIENCE, 



Being a Continuation of Tilloch's ^Philosophical Magazine,' 

 Nicholson's 'Journal/ and Thomson's ' Annals of Philosophy/ 



CONDUCTED BY 



SIR ROBERT KANE, LL.D. F.E.S. M.R.I.A. F.CS. 

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



AND 



WILLIAM FRANCIS, Ph.D. F.L.S. F.R.A.S. F.CS. 



FOURTH SERIES. 



N° 292.— SEPTEMBER 1872. 



LONDON: 



PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FX,EET STREET, 



Printers and Publishers to the University of London. 



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