396 



(II.) i and ^ reduced to 1840*0. 





Lat. 



Long. E. 

 from Paris. 



i. 



di 



dt 





48 



1 



50 











67' 



/ 



II'24 



1 



— 3*2700 





50 



51 



2 



22 



68 



2I*l6 



— 2-8772 





51 



31 



— 2 



25 



69 



13*36 



-2*5572 





51 



31 



7 



34 



67 



46-83 



-2*6434 





52 



31 



II 



2 



67 



58-12 



-2*5394 



Copenhagen 



55 



41 



10 



15 



69 



55*07 



-1*5495 





59 



55 



S 



23 



71 



49*36 



-1*8597 





59 



30 



IC 



J 



44 



71 



27'q6 



-1-6578 





59 



57 



27 



59 



70 



56*17 



— 1*1098 





55 



48 



47 



I 



68 



2I-02 



+0-8169 



Catharinenburg . . 



56 



50 



58 



14 



69 



47*67 



+0-8739 



Nertschinsk .... 



51 



18 



117 



I 



67 



6-II 



+4*1819 





39 



54 



114 



5 



55 



33*11 



+3*8466 





57 



3 



222 



25 



75 



46*16 



+ 1*4892 





40 



43 



283 



31 



72 



48-27 



-1*1307 



These variations are in good harmony with the general motion 

 of the magnetical system from west to east in the northern hemi- 

 sphere. C. H. 



3. A letter was also read fi'om Dr. Rigby addressed to the 

 Secretary, communicating a circular from the Committee of the 

 Seckenberg Society of Natural History at Frankfort, respecting the 

 celebration of the 50th Anniversary of Prof. Tiedemann's doctorate. 



February 2, 1854. 

 COLONEL SABINE, R.A., Treas. & V.P., in the Chair. 



The following papers were read : — 



I. " Sur la Theorie de I'orientation du Plan oscillatoire du 

 Pendule simple, et son application k la recherche de I'aplatissement 

 du spheroide terrestre." By M. Oliveira. Communicated by 

 Charles Babbage, Esq., F.R.S. &c. Received January 18, 1854. 



In this memoir the author first deduces a formula upon geometrical 

 considerations alone, expressing the deviation of a free pendulum 

 (like Foucault's) in terms of the latitude and difference of 

 meridians, or hour-angle ; and this is done (as far as appears) with- 

 out any reference to the dynamical considerations on which Foucault's 

 formula is deduced, assuming only the inertia of the pendulum. 



The author's formula assumes the earth to be a sphere. If now, 

 observation should give a slightly different deviation, the author 

 infers that this would be due to the ellipticity of the earth ; and in- 



