. THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



SIR ROBERT KANE 7 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. 



565 



L r ... 



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

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



VOL. XIL— FIFTH SERIES. 

 JULY— DECEMBER 1881. 



—OF ' 



—OFT] 



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SOLD BY LONGMANS, GREEN, READER, AND DYER; KENT AND CO. ; S1MPKIN, MARSHALL 



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