505 



THE iw 



LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



LORD KELVIN, LL.D. P.R.S. &c. 

 GEORGE FRANCIS FITZGERALD, M.A. Sc.D. .FR.S. 



AND 



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



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

 vilior quia ex alienis libaraus ut apes." Just. Lips. Polit. lib. i. cap. 1. Not. 



VOL. XXXIIL— FIFTH SERIES, 

 JANUARY— JUNE 1892. 



LONDON: 

 TAYLOE AND FEANCIS, EED LION COURT, FLEET STEEET. 



SOLD BY SIMPKIN, MARSHALL, HAMILTON, KENT, AND CO., LD.J WIIITTAKER AND CO. 



AND BY ADAM AND CHARLES BLACK ; — T. AND T. CLARK, EDINBURGH ; 



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



PUTNAM, NEW YORK;-- VEUVE J. BOYVEAU, PARIS; — 



AND ASIIER AND CO., BERLIN. 



