T H E 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE, 



CONDUCTED BY 



SIR DAVID BREWSTER, K.H. LL.D. P.R.S.L. & E. &c. 

 RICHARD TAYLOR, F.L.S. G.S. Astr. S. Nat. H. Mosc. &c. 

 SIR ROBERT KANE, M.D., F.R.S., IVLR.I.A. 

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

 JOHN TYNDALL, F.R.S. &c. 



" Nee aranearum sane textus ideo melior quia ex se fila gignuut, nee nostei 

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



VOL. XV.~ FOURTH SERIES. 

 JANUARY— JUNE. 1858. 



LONDON. 



TAYLOU AND FRANCIS, UKI) LION COUUT, FLIiRT STRKKT, 

 Printers and Puhlishers to the University of Lnndoii ; 



SOLD IIY LONGMAN, BIIOWN, GKKEN, LONGMANS, AND HOBEKTS ; SIMPKIN, 

 MARSHALL AND CO.; WHITTAKKH AND CO.; AND IMl'KH AND CO., 



LONDON : BY ADAM AND CHAULliS BLACK, AND THOMAS 



CI.AKK, EDINBUIIGH; smith AND SON, GLASGOW ; 



HODGES AND SMITH, DUBLIN; AND 



PUTNAM, NEW YORK. 



