The use of levers
is an old discovery; more than 1500 years before Christ, Englishmen,
living on Salisbury Plain, applied the invention when they raised the
great stones at Stonehenge and at Avebury; more than 2000 years earlier
still, Egyptians employed it in raising the pyramids. Even at that time
men had made great progress; they were already reaping the rewards of
discoveries and inventions. But none, I am sure, surprised them more
than the discovery of the lever; by its use one man could exert the
strength of a hundred men. They soon observed that levers could be used
in three different ways. The instance already given, the prying open of
a lid by using a chisel as a lever, is an example of one way (Fig. 1);
it is then used as a lever of the first order. Now in the first order,
one end of the lever is applied to the point of resistance, which in the
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.
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