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THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



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



SIR 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. 



5 



/ 



"Nee aranearutn sane textus ideo melior quia ex se fila gignunt, nee noster 

 vilior quia ex alienis iibamus ut apes." Just. Lrps. Polit. lib. i. cap. 1. Not. 



VOL. XXIX.— SIXTH SERIES. 

 JANUARY— JUNE 1915. 



LONDON: 



TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, 



SOLD BY SIMPKIN, MARSHALL, HAMILTON, KKNT. AND CO., !.!>. 



SMITH AND SON, GLASGOW; — HODGES, FIGGIS. AND CO., DUBLIN | — 



AND VKUVK J. BOYVKAU, PARIS. 



