356 Capt. Kater’s experiments for determining the variation 
The invariable pendulum furnishes a means of severely 
checking the rate of the clock ; for should any alteration 
occur, it immediately indicates it. Thus on referring to the 
preceding table of “ vibrations of the pendulum at 62°/’ it 
appears that from the 23d to the 28th of July, a gradual in- 
crease in the rate of the clock had taken place, amounting in 
the whole to a quantity equal to 2,5 vibrations of the pendulum, 
or 0,5 of a vibration in every 24 hours. 
The rate of the clock, is that due to the middle time of the 
interval between the transits from which it is deduced. The 
number of vibrations of the pendulum is obtained for the 
mean of the times at which the coincidences were observed. 
If this mean should not coincide with the time for which the 
rate of the clock is obtained, and the rate of the clock should 
be variable, the number of vibrations of the pendulum com- 
puted on such given rate must evidently be erroneous. If 
the mean of the interval of the transits should be before the 
mean of the times of the coincidences, the number of vibra- 
tions will, in the present case of an accelerating rate, be in 
defect. If after the mean of the coincidences, they will be in 
excess; and the proportionate change of rate must be added 
or subtracted accordingly. On this principle the corrections 
were calculated and the results obtained, which are contained 
in the following table. 
