THE 



505 



LONDON, 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 textus ideo melior quia ex se fila gignunt, nee noster 

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



VOL. XLV.— FOURTH SERIES. 

 JANUARY— JUNE 1873. 



ik S 



?* 



LONDON. 



TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 



Printers and Publishers to the University of London ; 



SOLD BY LONGMANS, GREEN, READER, AND DYER; KENT AND CO. ; SIMPKIN, MARSHALL, 



AND CO. ; AND WIIITTAKER AND CO. ; AND BY ADAM AND CHARLES BLACK", 



AND THOMAS CLARK, EDINBURGH J SMITH AND SON, GLASGOW! — 



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



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