761. 11. MAY 1881. No. 69. 



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THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



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JOURNAL OF SCIENCE. 



Being a Continuation of Tilloch's 'Philosophical Magazine/ 

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

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



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FIFTH SERIES. 



N° 69.— MAY 1881. 



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