l&YfT 



THE 



XI 



LONDON, EDINBURGH, an ' ^BLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



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

 SIR WILLIAM THOMSON, Knt. LL.D. F.R.S. &o. 



AND 



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



" 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. XL— FIFTH SERIES. 

 JANUARY— JUNE 1881. 



C 



LONDON: 

 TAYLOE AND FEANCIS, EED LION COUET, FLEET STREET. 



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



AND CO. ; AND WHITTAKER AND CO. ; — AND BY ADAH AND CHARLES BLACK, 



AND THOMAS CLARK, EDINBURGH J SMITH AND SON, GLASGOW ; — 



HODGES, FOSTER, AND CO., DUBLIN; — PUTNAM, NEW 



YORK ;— AND ASHER AND CO., BERLIN. 



