THE 
LONDON, EDINBURGH, an» DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
CONDUCTED BY 
SIR, DAVID BREWSTER, K.H. LL.D. F.B.S.L. & E. &. 
SIR ROBERT KANE, M.D., F.R.S., M.R.LA. 
WILLIAM FRANCIS, Pu.D. F.L.S. F.B.AS. F.C.S. 
JOHN TYNDALL, F.RS. &c. 
“Nec aranearum sane textus ideo melior quia ex se fila gignunt, nec noster 
vilior quia ex alienis libamus ut apes.” Just. Lres. Poli, lib. i. cap. 1. Not. 
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VOL. XXL=FOURTH SERIES. 
JANUARY—JUNE, 1861. 
LONDON. 
TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 
Printers and Publishers to the University of London ; 
SOLD BY LONGMAN, GREEN, LONGMANS, AND ROBERTS ; SIMPKIN, MARSHALL 
AND CO.3 WHITTAKER AND CO.; AND PIPER AND CO., LONDON :—— 
BY ADAM AND CHARLES BLACK, AND THOMAS CLARK, 
EDINBURGH; SMITH AND SON, GLASGOW ; HODGES 
AND SMITH, DUBLIN; AND PUTNAM, 
NEW YORK, 
