case just mentioned was the lid of the box. At the other end we apply
our strength, force, or power. The edge of the box against which the
chisel is worked serves as a fulcrum and lies between the handle where
the power is applied and the bevelled edge which moves the resistance or
weight. A pair of ordinary weighing scales also exemplifies the first
order of levers. The knife edge on which the beam is balanced serves as
a fulcrum; it is placed exactly in the middle of the beam, which we
shall suppose to be 10 inches long. If we place a 1-lb. weight in one
scale to represent the resistance to be overcome, the weight will be
lifted the moment that a pound of sugar has been placed in the opposite
scale--the sugar thus representing the power. If, however, we move the
knife-edge or fulcrum so that it is only 1 inch from the sugar end of
the beam and 9 inches from the weight end, then we find that we have to
pour in 9 lb. of sugar to equalise the 1-lb. weight. The chisel used in
prying open the box lid was 10 inches long; it was pushed under the lid
for a distance of 1 inch, leaving 9 inches for use as a power lever. By
using a lever in this way, we increased our strength ninefold. The
longer we make the power arm, the nearer we push the fulcrum towards the
weight or resistance end, the greater becomes our power. This we shall
find is a discovery which Nature made use of many millions of years ago
in fashioning the body of man and of beast. When we apply our force to
the long end of a lever, we increase our power. We may also apply it, as
Nature has done in our bodies, for another purpose. We have just noted
that if the weight end of the beam of a pair of scales is nine times the
length of the sugar end, that a 1-lb. weight will counterpoise 9 lb. of
sugar. We also see that the weight scale moves at nine times the speed
of the sugar scale. Now it often happens that Nature wants to increase,
not the power, but the speed with which a load is lifted. In that case
the "sugar scale" is placed at the long end of the beam and the "weight
scale" at the short end; it then takes a 9-lb. weight to raise a single