3 I /• 



THE f*lllj 



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 

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



VOL. XLIL— FOURTH SERIES. 

 JULY— DECEMBER 1871. 



u^ 



LONDON. 



TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 



Printers and Publishers to the University of London ; 



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



WHITTAKER AND CO.; AND KENT AND CO., LONDON: — BY ADAM AND 



CHARLES BLACK, AND THOMAS CLARK, EDINBURGH ; 



SMITH AND SON, GLASGOW; HODGES AND 



SMITH, DUBLIN ; AND PUTNAM, 



NEW YORK. 



