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 proJwc^ 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. 11. 2 B 



