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 

 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. Lips. Polit. lib. i. cap. 1 . Not. 



VOL. XXI. 



NEW AND UNITED SERIES OF THE PHILOSOPHICAL MAGAZINE, 

 ANNALS OF PHILOSOPHY, AND JOURNAL OF SCIENCE. 



JULY— DECEMBER, 1842. 



LONDON: 



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



Printers and Publishers to the University of London; 



SOLD BY LONGMAN, BROWN, GREEN, AND LONGMANS ; CADELL; 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 G. W. M. REYNOLDS, PARIS. 



