, as to the immediate relation between the power and the
resistance; but the different spaces through which the power and the
resistance move when one exceeds the other, cannot be obvious, without
they pass through much larger spaces than levers will permit.

EXPERIMENT V.

Place the sledge on the farthest end of the wooden road--Plate 2. Fig.
1.--fasten a rope to the sledge, and conduct it through the lowest
pulley P 4, and through the pulley P 3, so as that the boy may be
enabled to draw it by the rope passed over his shoulder. The sledge
must now be loaded, until the boy can but just advance with short
steps steadily upon the wooden road; this must be done with care, as
there will be but just room for him beside the rope. He will meet the
sledge exactly on the middle of the road, from which he must step
aside to pass the sledge. Let the time of this experiment be noted. It
is obvious that the boy and the sledge move with equal velocity; there
is, therefore, no mechanical advantage obtained by the pulleys. The
weight that he can draw will be about half a hundred, if he weigh
about nine stone; but the exact force with which the boy draws, is to
be known by Experiment I.

_The wheel and axle._

This organ is usually called in mechanics, _The axis in peritrochio_.
A _hard_ name, which might well be spared, as the word windlass or
capstan would convey a more distinct idea to our pupils.

EXPERIMENT VI.

To the largest drum, Plate 2. Fig. 1. fasten a cord, and pass it
through the pulley P downwards, and through the pulley P 4 to the
sledge placed at the end of the wooden road, which is farthest from
the machine. Let the boy, by a rope fastened to the extremity of one
of the arms of the capstan, and passed over his shoulder, draw the
capstan round; he will wind the rope round the drum, and draw the
sledge upon its road. To make the sledge advance twenty-four feet upon
its road, the boy must have walked circularly 144 feet, which is six
times as far, and he will be able to draw about three hundred weight,
which is six times as much as in the last experiment.

It may now be pointed out, that the difference of space, passed
through by the power in this experiment, is exactly equal to the
difference of weight, which the boy could draw without the capstan.

EXPERIMENT VII.

Let the rope be now attached to the smaller drum; the boy will draw
nearly twice as much weight upon the sledge as before, and will go
th