Cut out the figure of a horse, and having fixed a curved iron wire to
the under part of its body, place a small ball of lead upon it. Place
the hind legs of the horse on the table, and it will rock to and fro.
If the ball be removed, the horse would immediately tumble, because
unsupported, the center of gravity being in the front of the prop;
but upon the ball being replaced, the center of gravity immediately
changes as position, and is brought under the prop, and the horse is
again in equilibrio.
TO CONSTRUCT A FIGURE, WHICH BEING PLACED UPON A CURVED SURFACE, AND
INCLINED IN ANY POSITION, SHALL, WHEN LEFT TO ITSELF, RETURN TO ITS
FORMER POSITION.
The feet of the figure rest on a curved pivot, which is sustained
by two loaded balls below; for the weight of these balls being much
greater than that of the figure, their effect is to bring the center of
gravity of the whole beneath the point on which it rests; consequently
the equilibrium will resist any slight force to disturb it.