Vol. 12. SEPTEMBER 1881. No. 74. 



Published the First Day of every Month — Price 2s. 6d. 



THE 

 LONDON, EDINBURGH, and DUBLIN 



PHILOSOPHICAL MAGAZINE, 



AND 



JOURNAL OF SCIENCE. 



Being a Continuation of Tilloch's 'Philosophical Magazine, 

 Nicholson's 'Journal? and Thomson's 'Annals of Philosophy.' 



CONDUCTED BY 



SIR ROBERT KANE, LL.D. F.R.S. M.R.I.A. F.C.S. 

 SIR WILLIAM THOMSON, Knt. LL.D. F.R.S. &c. 



AND 



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



FIFTH ^ERIESYy 





r*& 



N° 74.— SEPTEMBER 1881. #>X V $ 



WITH A PLATE. 



Illustrative of Mr. T. Gray's Paper on Instruments for Measuring and 

 Eecording Earthquake-Motions. 



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