﻿APRIL 1869. No. 249. 



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 J 

 Nicholson's 'Journal? and Thomson's ( Annals of Philosophy? 



CONDUCTED BY 



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

 AUGUSTUS MATTHIESSEN, Ph.D. F.R.S. F.C.S. 



AND 



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



FOURTH SERIES, 



N° 249.— APRIL 1869. 



LONDON: 



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



Printers and Publishers to the University of London. 



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

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 Dublin : — and Putnam, New York. 





cy of Smithsonian Institution. 

 WILLIAM WESLEY, 



