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I 



THE 



I 



LONDON, EDINBURGH, an.d DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



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

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



AND 



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



u Nee aranearum sane textus ideo melior quia ex se fila gignunt, nee noster 

 vilior quia ex alienis libamus ut apes." Just. Lips. Polit. lib. i. cap. 1 . Not. 



VOL. XLVIII.— FOURTH SERIES. 

 JULY— DECEMBER 1874. 



LONDON. 



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. J SIMPKIN, MARSHALL. 



AND CO. ; AND WniTTAKER AND CO. ; — AND BY ADAM AND CHARLES BLACK, 



AND THOMAS CLARK, EDINBURGH; SMITH AND SON, GLASGOW: — 



HODGES, FOSTER, AND CO, DUBLIN: PUTNAM, NEW 



YORK: — AND ASHER AND CO., BERLIN. 



