THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



■ — i 



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. 

 R [CHARD TAUNTON FRANCIS 



AND 



WILLIAM FRANCIS, F.L.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. XLIIL— SIXTH SERIES. 

 JANUARY— JUNE 1922. 



LOUDON: 

 TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 



SOLD BY SMITH AND SON, GLASGOW; — HODGES, FIGGIS, AND CO., DUBLIN - 

 AND VEUVE J. BOYVEAU, PARIS. 



