THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



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

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

 RICHARD PHILLIPS, F.R.S.L.&E. F.G.S. &c. 

 SIR ROBERT KANE, M.D. M.R.I.A. 



" Nee aranearum sane textus ideo melior quia ex se fila gignunt, nee noster 

 vilior quia ex alienis libamus ut apes. ' Just. Lirs. Polit. lib. i. cap. 1. Not. 



VOL. XXXL 



NEW AND UNITED SERIES OF THE PHILOSOPHICAL MAGAZINE, 

 ANNALS OF PHILOSOPHY, AND JOURNAL OF SCIENCE. 



.JULY— DECEMBER, 1847. 



LONDON: 



RICHARD AND JOHN E. TAYLOR, RED LION COURT, FLEET STREET, 



Printers and Publishers to the University of London; 



SOLD BY LONGMAN, SHOWN, GREEN, AND LONGMANS J SIMPKIN, MARSHALL 

 AND CO.; S. HIGHLEY ; WHITTAKER AND CO.; AND SHERWOOD, 



GILBERT, AND PIPER, LONDON : BY ADAM AND CHARLES 



BLACK, AND THOMAS CLARK, EDINBURGH ; SMITH AND SON, 



GLASGOW ; HODGES AND SMITH, DUBLIN ; AND 



WILEY AND PUTNAM, NEW YORK. 



^K 



