THE 



PHILOSOPHICAL MAGAZINE 

 AND JOURNAL. 



30 th SEPTEMBER 1824. 



XXVII. Remarks on the Experiments of the Pendulum made 

 by Captain Kater, M. Biot, fyc. By William Gal- 

 braith, Esq. A.M. 



r T , HE determination of the figure and magnitude of the earth 

 -*- has long formed to the philosopher an interesting object 

 of research. The attempts of the ancients were very rude 

 and inaccurate; but still they kept alive that spirit of successive 

 improvement by which each observer endeavoured to surpass 

 his immediate predecessor, both in the accuracy of his instru- 

 ments and the exactness of his results, till in our times it 

 would appear that a very high degree of precision has been 

 attained. 



This is sufficiently established by the extensive systems of 

 operations lately performed in this country, and in France and 

 Spain ; by which the Shetland and Balearic Isles have been con- 

 nected by actual mensuration, comprehending an arc of 

 22° 5' 29'' of latitude. In the execution of this sm*vey, the 

 British on their part have employed the largest and most ac- 

 curate instruments ever constructed; by this means cutting off 

 all those sources of inaccuracy not essentially involved in the 

 nature of the question : while the French have used instru- 

 ments of small dimensions, but of great ingenuity, correcting 

 the errors to which they are thus liable, by ingenious expe- 

 dients and appropriate formula?. 



In the prosecution of the survey, too, the length of the pen- 

 dulum oscillating seconds at the more important stations, has 

 been deemed an object worthy of being attained, in order to 

 promote the objects of science by unfolding the laws that re- 

 gulate the structure and figure of the earth ; and the instru- 

 ments and methods employed by the men of science engaged, 

 were as characteristic of the genius and habits of the two na- 

 tions in this case as in the former. 



Captain Kater, by selecting a particular property of the 

 pendulum, or of an oscillating body, was enabled to dispense 

 with fbrmulaj necessarily employed by Borda and Biot, by 

 that means avoiding the possibility of error to which the me- 



Yol. 64. No. 3 1 7. Sept. 1 82*. X thods 



