Moving belt machines work at other jobs, too. They load sand into trucks
and cargo into ships.
On some piers, huge vacuum cleaners empty ships full of sugar or wheat.
At ports on the Great Lakes, machines reach down into ore-carrying ships
and unload them with great speed. At the end of each of these unloaders
hangs a clamshell bucket. Just above the bucket is a little room where a
man sits and watches what goes on. He signals to the operator, telling
him just where to drop the bucket so it can pick up a mouthful of ore.
The ship can be unloaded by two men who do nothing but signal to each
other and push levers. But usually there are several machines working at
the same time so that the job goes as quickly as possible.
When iron ore has been turned into steel bars or wheels or gears,
another kind of lifter can handle them. This one does its work with a
huge electro-magnet that holds heavy weights when electricity is running
through it. The operator drops the magnet onto the load of iron or steel
that he wants to lift. Then he turns on the electricity which makes the
magnet and the piece of metal stick together. The operator moves the
load wherever it is supposed to go. Then he turns off the electricity.
The magnet lets loose and is ready for another job.