Cypress trees with a lean from the prevailing winds off the seaCabrillo Point is a lighthouse that was once manned by three families to steer ships away from the treacherous rocks along the coast south of Mendocino. It reminded me in many ways of Prince Edward Island.
In speaking to a historian at the lightkeeper's house, we discovered an interesting connection between these two opposite ends of the continent. The historian had come across a photo of the Presbyterian minister who performed the lightkeeper's wedding in Mendocino. Mendocino's one Protestant church was Presbyterian because one of the founding elders was from Prince Edward Island, where that denomination was prominent.
Did you ever wonder how a lighthouse works? The light at the top is surrounded by angled lenses which reflect the light outward. They're set up almost like a shutter, so that the light is amplified in as many directions as possible. See here for how it looks and works.
Every lighthouse flashes at its own unique rate. Cabrillo Point put out its flash of light every ten seconds. By timing it, mariners could tell which lighthouse they were looking at. Even in storms, they could know where they were along the coast. See here and here for why a lighthouse's flashing is important.
We liked seeing a model of the machinery that turned the light. Here's a picture:
At the bottom of the string is a weight. This motor mechanism had a hand crank to wind the cable (represented by the string) onto the drum. This had to be done every 1 & 1/2 hours. Now you know why there had to be a lighthouse keeper on duty all the time!
The weight pulls down on the cable and slowly turns the drum at a steady speed. This is the motor which drives the gears, which turn the optic. If you looked at the links about the light (you should look at the links about the light!) you saw the lenses that turn and catch the light. Look at the gears in the picture above. The gears start out vertical, and the last one is horizontal. This would be attached to the optic assembly to turn it.
1 comments:
Driving home from being in town when I was a child often meant driving past a small airport. If an arrival was expected at night, the "search light" (that's what we called it) would be on. I always marveled that the light would sweep over us quite rapidly, but seem to take forever to return. This phenomenon would be a fun geometry exploration with your kids.
The Corning Museum of Glass in Corning, New York, has a great display of lighthouse lens optics, too.
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