Vol. 23. APRIL 1887. No. 14£ 



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THb APR 18 1687 

 LONDON, EDINBURQH^Mil^gLIN 



PHILOSOPHICAL MAGAZINE, 



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JOURNAL OF SCIENCE. 



Being a Continuation of TillocKs l Philosophical Magazine? 

 Nicholson's i Journal, and Thomson's 'Annals of Philosophy.' 



CONDUCTED BY 



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

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



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



FIFTH SERIES. 



N° 143.— APRIL 1887. 



WITH TWO PLATES. 



Illustrative of Prof. S. P. Thompson's Paper on an Arc-Lamp, and 

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