MECHANICS. 13S 



being inversely as the squares of the number of 

 vibrations which they perform in the same time. 



Thus, if l r be the length of a simple pendulum vibra- 

 ting seconds ; x the distance of the centre of oscilla- 

 tion of a compound pendulum from its centre of sus- 

 pension, and n the number of vibrations which it 



3600 x V 



makes in a minute, x = 5 . 



n 2 



Because I' is nearly 39.1386 inches, 



140898.9 . , .. 



a = 2 inches, nearly. In making this ex., 



periment, n may be measured by a watch. See 

 BUTTON'S Math. Diet, article, Centre of Oscilla- 

 tion. 



211. The centres of suspension and oscillation are 

 convertible, that is, if the centre of oscillation in 

 any body or system of bodies be made the point of 

 suspension, the former point of suspension will 

 then become the centre of oscillation. 



The first author who treated of the pendulum and the 

 centre of oscillation, was HUYGENS, in his Horolo- 

 gium- Ostittatorium, Opera Varia, torn. i. p. 51. 

 &c. See also S'GRAVESANDE, 404, and 424, 

 MUSCHENBROEK, 640. BOSSUT, Mecanique, 401, 

 405. 



Heavy 



