Monthly Archives: April 2014
353.HOW IS ROPE MADE?
Men have always needed rope for the rigging of ships, for hauling things, and for tying bundles. So rope-making is one of the oldest industries in existence. The first ropes were knotted together from leather thongs, pieces of bark, or even roots. The ancient Egyptians made ropes from vegetable fibers, and these resemble the ropes made today.
352.HOW DOES A WINDMILL WORK?
No one knows where or by whom the windmill was invented. A boat can sail at right angles to the wind by slanting its sail slightly. In the same way, the “fan” or “sail” of a windmill can be driven around in a circle even when placed at right angles to the wind. The windmill is like a huge propeller, with the source of power that turns it coming from the wind instead of a machine.
351.HOW DOES A SUNDIAL TELL TIME?
The sun was man’s first clock. Long ago men guessed at the time of day by watching the sun as it moved across the sky. It was easy to recognize sunrise and sunset, but harder to know when it was noon, the time when the sun is highest above the horizon. In between these times, it was difficult to tell time by the position of the sun.
Then men noticed that the shadow changed in length and moved during the day. They found they could tell time more accurately by watching shadows than by looking at the sun.
CLEOPATRA’S NEEDLE
