the length of the pendulum at Madras. 131 
The clock was then set in motion. This was on the 2 2d of 
March, and the observations commenced two days after- 
wards. 
The following is the mode pursued in making the obser- 
vations. 
The pendulum was lifted up from the Y’s by myself and 
an assistant, and the knife edges wiped with a cloth saturated 
with oil. The pendulum was then replaced, and the Y's 
lowered, so that the knife edges rested upon the agates. The 
telescope was then adjusted (care being taken that the O on the 
arc of vibration coincided with the point of the slip), so that 
the edges of the slip were exactly embraced by the edges of 
the diaphragm. The height of the barometer, of the thermo- 
meter fixed near the middle of the pendulum, and that of 
the hygrometer, were taken and registered. The point of the 
slip at the end of the pendulum was then brought and kept 
by the hand to about i°,3 upon the arc ; and an instant be- 
fore the pendulum of the clock was at its highest point on 
the same side, the hand was withdrawn, and the pendulum 
thereby allowed to vibrate freely. I stationed the head Bra- 
min assistant* to take down the time, and the youngest 
Bramin assistant to count the clock, which he does with the 
greatest correctness. Having placed myself at the telescope, 
I found there was a sensible portion of time, more or less, 
as the arc of vibration was greater or smaller, between the 
disappearance of the disc behind the slip, and its reappear- 
ance ; I therefore noticed the seconds, and parts of a second, 
when the disc disappeared, and also the instant when it 
* The name of the head assistant is Senavassaehary, and that of the other Teroo- 
vencatachary. 
