PROCEEDINGS 



OF 



THE ROYAL IRISH ACADEMY. 



1843. No. 37. 



January 9. 



SIR Wm. R. HAMILTON, LL.D., President, in the Chair. 



Stewart Blacker, Esq, Thomas Gather, Esq., William V 

 Drury, M. D., William Gore, M. D., Thomas Hodder, Esq. 

 R. N., Rev. John Homan, Henry Hutton, Esq., Robert Leslie 

 Ogilby, Esq., the Hon. Frederick Ponsonby, and George Sal- 

 mon, Esq., F.T.C.D., were elected members of the Academy. 



Rev. H. Lloyd, V. P., read a paper " on the Determina- 

 tion of the Intensity of the Earth's Magnetic Force in abso- 

 lute Measure." 



The means of determining the intensity of the earth's mag- 

 netic force in absolute measure consist, it is well known, in 

 observing the time of vibration of a freely-suspended hori- 

 zontal magnet, under the influence of the earth alone, and 

 then employing the same magnet to act upon another, which 

 IS also freely-suspended, and noting the effects of its action 

 combined with that of the earth. From the former of these 

 observations we deduce the product of the horizontal com- 

 ponent of the earth's magnetic force into the moment of free 

 magnetism of the first magnet,— from the latter, the ratio of 

 the same quantities; and, the product and the ratio being 

 thus known, the two factors are absolutely determined. The 

 former part of this process involving no difficulty which may 



VOL. II. 2 B 



