280 Exjperi7nents on the Vibrations of Pendulums 



From 1^ to J^ in 21m. 45s. 

 Do. ' do, 22 45 

 Do. do. 22 



Do. do. 22 30 



Do. do, 23 



Mean, - - - 22 24 



The mean of the two preceding corresponding results is 23m. 

 12s. The difference may be satisfactorily accounted for; by the 

 difficulty of setting off the pendulum at the precise point intended, 

 and of noting the time when the arc is diminished to the propo- 

 sed quantity. 



It is apparent from these experiments, that when a pendulum 

 is freely suspended, and left to vibrate from its own gravity, the 

 arc of vibration is sooner reduced from %^ to 1^, than from 1*^ to 

 J*^, as might indeed be anticipated from the increased resistance 

 experienced by the bob, while moving through a greater space in 



the same time. 



I attached the pendulum, suspended as before, to a clock, with 



a maintaining power of 61b. 8oz., but the clock stopped in 39 

 minutes; and setting it off again, it stopped in 43 minutes; but 

 on applying a weight of 61b- lloz., the clock continued to go; 

 thus showing that a weight of 61b. lloz. was sufficient to keep 

 the pendulum in vibration, while one only 3oz. lighter was not. 



The arcs of vibration in the preceding experiments being 

 smaller than is desirable in practice, I proceeded to experiment 

 with heavier weights, the pendulum being still suspended by the 

 parallel silk threads, noting in each case the arc of vibration and 

 the rate of the clock, viz., its gain or loss in 24 hours. 



In the following experiments each succeeding pair is to be con- 

 sidered as giving the results for two consecutive days, though 

 more than one day occasionally elapsed between the times at 

 which the sets were taken. 



Weight. Arc of Vibration. Rate. 



141b. 6oz. 2^ 3' — 9s. 



8 1 30 +0 



14 6 2 3 -10 



8 1 30 



11 2 1 I 45 —7 .0 



8 1 30 + 1 .0 



19 . , , . 2 15 -13 .0 



