The giant shovel digs; the overhead crane lifts; the pile driver pounds.
All machines multiply the power that’s in the muscles of men--or of
animals. The pushingest animal is an elephant. In some places in the
world, elephants are trained to clear land by putting their foreheads
against a tree and heaving until the tree topples over.
A tree-dozer can out-push an elephant. The one in the picture has a
special forehead built in front. With a slow, steady shove, it clears
the way for roads or opens up fields for farms.
[Illustration: tree-dozer]
Farmers used to dig their fields by hand. Then they hitched horses to
plows. Now a tractor does the work, but we still measure its strength in
horsepower.
[Illustration: elephant]