Pol. 36 



SEPTEMBER 1868, 



No. 242. 



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 Tilloch's ( Philosophical Magazine, 9 

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



CONDUCTED KY 



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



AND 



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



FOURTH SERIES. 



N° 242.— SEPTEMBER 1868. 



LONDON: 



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



Printers and Publishers to the University of London. 

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

 Co. ; Whittaker and Co. ; and H. Bailliere, London : — and by A. and C. Black, and 

 Thomas Clark, Edinburgh ; Smith and Son, Glasgow : — Hodges and Smith, 

 Dublin : — and Putnam, New York. 



Agency of Smithsonian Institution. 



— <v*-\2AS'- w — 



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bookseller anti ^ubljgJjcr, 



Rt. Fleet Street. ,i,oiKlon. 



