THE 

 LONDON, EDINBURGH, and DUBLIN 



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.C.S. 



L25 



" Nec 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. XVII.— FIFTH SERIES. 

 JANUARY— JUNE 1884. 



LONDON: 

 TAYLOR AND FRANCIS, RED LION COUKT, FLEET STREET. 



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



AND CO. ; AND WHITTAKER AND CO. ; AND BY ADAM AND CHARLES BLACK, 



AND T. AND T. CLARK, EDINBURGH ; SMITH AND SON, GLASGOW J 



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



YORK; — AND ASHER AND CO., BERLIN. 



