Vol. 30. DECEMBER 1890. No. 18 



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



THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



AND 



JOURNAL OF SCIENCE. 



Being a Continuation of Tilloclis 'Philosophical Magazine/ 

 Nicholson's l Journal f and Thomson s i Annals of Philosophy.' 



CONDUCTED BY 



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

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



AND 



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



FIFTH SERIES. 



N» 187.— DECEMBER 1890. 



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