THE 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



SIR OLIVER JOSEPH LODGE, D.Sc, LL.D., F.R.S. 

 hi JOSEPH JOHN THOMSON, O.M, M.A., Sc.D, LL.D., F.R.S. 

 JOHN JOLY, M.A., D.Sc, F.R.S., F.G.S. 

 GEORGE CAREY FOSTER, B. A./ LL.D, F.R.S. 



AND 



WILLIAM FRANCIS, F.L.S. 



"Nee aranearum sane textus i<leo melior quia ex sc fila gignunt, nee nostor 

 vilior (iiiia ex alienis libamus ut apes." Just, lit vs. Polit. Ii!>. i. cap. 1. Not. 



VOL. XXX.— SIXTH SERIES, 

 JULY— DECEMBER 11)15. 



t l-\*5 



LONDON-. 

 TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 



SOLD BY SIUPSXK, MARSHALL, HAMILTON, KKNT. AN!> CO., LD. 



SMITH AND SON, GLASGOW I — HODGBS, PJGOJS, AXD CO., DUBLIN; — 



AND YKKVE J. BOYVBAU, PARTS. 



