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. &c. 



AND 



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



505 



" 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. XXIII.— FIFTH SERIES. 



JANUARY— JUNE 1887. 



LONDON: 

 TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 



SOLD BY LONGMANS, GREEN, AND CO. ; 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 ; — 



HODGES, POSTER, AND CO., DUBLIN; PUTNAM, NEW YORK; — 



VEUVE J. BOYVEAU, PARIS ; — AND ASHER AND CO., BERLIN. 



