436 Mr. Bowditch on the motion of a pendulum. 
and gives m= => —=67. The body attached to the point D was 
a sphere of lead of 13 inches diameter. The measures r, 7’, were ta- 
ken to the centre of the sphere, which differed but 0°01 inch from the — 
centre of oscillation. The ball being let fall from the point correspond. 
ing to K (PI. III. Fig. 9) began to vibrate in the parabola KND, which 
gradually changed into the curves marked in Fig. 10, 11, 12, 13. Af- 
ter which the same curves were again described in a contrary order, as 
in Fig. 12, 11, 10,9. By the mean of several trials it was found that 
in 16 vibrations of the pendulum of the length (r+1’) the ball described 
the curve of Fig. 11, according to the order of the letters gf Wdckg. 
In 33 vibrations it described the parabola CSA (Fig. 13). Jn 50 vibra- 
tions it described the curve of Fig. 11, in an opposite direction to its for- 
mer course, or according to the order of the letters gE.cdWig, and in 67 
vibrations it recommenced its former course in the parabola KND, Fig. 
9. The cycle of motions being completed in 67 Yervien Te which | 
agrees with the theory. 
The comparison of the theory of § 19, 20, is not so easy aS that of 
the preceding cases, For the value of 7 is much smaller in compari- - 
son of 7’, consequently the vibrations are quicker, and as the diagonal 
GK is taken much smaller, it becomes difficult to observe the form of 
the curves with any great degree of precision. A few roug’? experi- 
ments were however made in these cases, and the results cgi ¥ 
be sufficiently conformable to the theory. : 
