Mills
Have you ever seen a mill?
By "mill" I mean a water mill.
It usually looks like a small cottage with a big wooden wheel - like a small Ferris wheel - beside it.
The wheel is always over a stream - otherwise it wouldn't be a water wheel, would it?
Ice melts in the mountains, and the water flows downhill (down hill).
People put this big wooden wheel that has paddles on it, and when the water flows under the wheel, the water turns the wheel.
The wheel has an axle that turns --- oh you get the general idea - one turning thing turns another. You can end up with interlocking cogs and all sorts of things.Like a mechanical version of electricity, a mill makes it possible to power devices - to get work done.
Where there is not an all year stream, people some time use windmills (wind mills).
Windmills are large paddles that are turned by the wind. This turns an axel, which turns other things. It makes "mechanical energy" - the ability to power things.
Usually windmills here work a pump which pulls water from a well to water cattle.
But windmills can be used to make electricity, that can run your computer.
Dams hold back water, but some water is let through, which turns turbines - much like a water wheel - and so really, it is much like you are still using the same idea to produce power today, as long ago.
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