Experiments on the Vibrations of Pendulums. 283 



With it the arc of vibration was from 



2^ to 1° in Ih. 47m. 



Applying maintaining power of 41b. loz. and 21b. 2oz. respec- 

 tively, with -97 inch effective length of the following results were 

 noted : — 



Weight. Arc. Rate. 



41b. loz. 2° 6' —2s. -2 



2 2 1 30 +1-2 



Even with this comparatively stiff spring, the arc of vibration 

 is greater with a maintaining power of 41b. loz., than it was with 

 141b. 6oz., when the pendulum was suspended by two parallel 

 silk threads. But the rate appears to vary more with the arc of 

 vibration, than it did when No. 3 was used. 



Reducing the length of this spring to -68 inch, the following 

 results were obtained : — 



Sliding up the isochronal piece still further, till the length of 

 the efifective part of the spring was reduced to -50 inch, the fol- 

 lowing were the results : 



Weight. Arc. Rate. 



41b. loz. 2P Z' - IBs. -0 



2 2 1 12 -14 -5 



This further shortning of the spring appears to have had a per- 

 ceptible effect on the arc of vibration, when the lighter weight 

 was applied. 



I lastly attached the strongest spring. No. 5, and with effective 

 length 1-0 inch. 



Weight. Rate. 



41b. 13oz. -15s. -5 



2 10 -13-5 



Reducing the length of this spring to '8, the following results 

 were obtained : 



