18 *
EXPERIMENTS WITH
TRACT 30'.
of shape in the afterpart of the figure should not make somesensible difference; a circumstance still remaining to betried. Accordingly, the experiments show this to be pre-cisely the case, the difference in the times of revolution, be-tween the globe and the hemisphere, being considerable withthe small weights, but gradually and continually decreasing,so as nearly to vanish, in comparison with the whole times.So that it appears there is almost no difference, whether aflat side or a round one is hindmost, at least none that isvery sensible in the svdftest of these velocities. Those thatare set down above, are the mediums of the last 20 revolu-tions with each weight. Where it is to be noted, that, bymistake in measuring, the centre of the ball w'as placedof an inch too near the axis; so that the times should be avery little more than are here set down, viz, more in theproportion nearly of 53x to 53|, which however will not sen-sibly alter them.
32. June 29, 1786.
Weather much the same as yesterday.
Used the cone this day. Its weight was 8 oz 6 dr, andits height 6-§. inches, being rather more than its diameter,which was 6|, being the same diameter as the former figures.Tried it with the vortex foremost this day, as follows.
Wt.
Time
wt.
Time
Wt.
Time
Wt.
Time
oz
2
3
4
5
6
7
sec.
13-50
8-65
6-95
5-97
5-30
4-77
oz
8
9
10
12
14
16
sec.
4-42
4-15
3-87
3-57
3-25
3-00
oz
18
20
24
28
32
40
sec.
2-80
2-67
2-40
2-17
2-07
1-85
oz
48
56
64
72
80
100
sec.
1 '651-521-42T351-303-17
33. It was found that 2 oz was the least weight thatwould give motion to the machine.—By comparing thesenumbers with those of the day before, for the globe, it ap-pears that the times to day are nearly equal to, but somewhat