THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE 



A X 1) 



JOURNAL OF SCIENCE. 



CONDUCTED BY 



SIR WILLIAM THOMSON, Knt. LL.D. F.R.S. Ac. 

 GEORGE FRANCIS FITZGERALD, M.A. F.R.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 libannus ut apes." Just. Lips. Polit. lib. i. cap. 1 . Not. 



VOL. XXX.— FIFTH SERIES. 



JULY— DECEMBER 1890. 



LONDON: 

 TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET. 



SOLI) BY SIMPKIN, MAKSHALL, HAMILTON, KENT, AND CO., LD.; AND WHITTAKEB 



AND CO. ; AND BY ADAM AND CHARLES BLACK, AND T. AND T. CLAUK, 



EDINBURGH; SMITH AND SON, GLASGOW; — HODGES, FIGGIS, 



AND CO., DUBLIN; PUTNAM, NEW YORK ;-- VEUVE J. BuYVKAU, 



PARTS; AND ASIIEE AND CO., BERLIN. 



