THE 

 LOiVDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



SIR ROBERT KANE, LL.D. 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. 



" Nee aranearum sane Lextus ideo melior quia ex se fila gignunt, nee no&ter 

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



VOL. XLVIL— FOURTH SERIES. 

 JANUARY— JUNE 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. J AND WI1ITTAKER 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. 



