Vol. 9. 



APRIL 1880. 



No. 56. 



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 'Philosophical Magazine, 

 Nicholson's ( Journal f and Thomson's 'Annals of Philosophy.'' 



CONDUCTED BY 



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

 SIR WILLIAM THOMSON, Knt. LL.D. F.R.S. Ac. 



AND 



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



FIFTH SERIES. 



N° 56.— APRIL 1880, 



LONDON: 



PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 



Sold by Longmans, Green, Reader and Dyer j Kent and Co. ; Simpkin, Marshall and 

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