Architect, Landscape Architect, Urban Designer, Land Use Planner, Environmental Observer

Friday, July 10, 2009

The Lure and Lore of Lighthouses.....

(drawings above and
photos below are from the

Historic American Building Survey)

Pigeon Point Lighthouse

Pescadero, California

What is it about these structures that make them so compelling?

For about four years I was a docent at this (my local) lighthouse. I enjoyed my trips down this beautiful stretch of the unspoiled California coast. I never tired of telling visitors the story. For me, this is what I think makes lighthouses so popular -


These structures were put in some of the most beautiful parts of the American coast. Sometimes , they were actually put out at sea on a rock outcropping (such as St. Georges Reef Lighthouse). But the ones on the edge of the land and sea draw us to visit that special interface.


The lighthouses take us back to the eighteenth and nineteenth centuries. It was a time of sailing ships and the cargoes that they carried. The shipping lanes up and down the coast of California were important to the beginning of the Golden State (remember the 49ers? no, not the football team - the gold miners).

In the case of Pigeon Point, a ship was lost (SS Carrier Pigeon) on the rocks below the point in 1852. Who complained? ... the insurance companies, of course! No
one was drowned, but all the cargo was lost. Congress authorized a lighthouse here in 1855. Why wasn't in built then? What happened from 1860 to 1865 in America?...yep, civil war. So the lighthouse was begun after that, in 1871 and finished in 1872.


Ever see the lens on a lighthouse? is a marvel. In 1822, a French physicist who specialized in optics took out a patent on a new lens design. His name was Augustine Fresnel. This lens was a cylinder made of prisms. The light emanated in 360 degrees from a central light (the fuel was first whale oil, then kerosene and then electicity). The prisms bent the light into straight lines which emanated from the lantern room. The light came out in rays. These rays of light could be seen 20 miles out to sea !!!

The lens turned on gears which were driven by a large weight at the bottom of the tower. The lighthouse keeper would wind the weight up and then let it go down with a kind of clock work mechanism. The weight turned gears which spun the lens around. It took four hours before the weight had to be lifted up again. The design was calculated so that a beam spun past the same point. The timing of this differed from lighthouse to lighthouse. It occurred at Pigeon Point every eight seconds.

That meant if you were a captain at sea, you could look up Pigeon Point in your Book of Lights and it would tell you that it was an eight second light. If it was another timing you were in the wrong place.


The style of lighthouse that is used at Pigeon Point is fairly standard, but there are lights built into buildings, up on pilings in Delaware Bay, etc. The basic design was repeated in five other lighthouses. The lantern is 100 feet above the base, and the base is plus or minus 50 feet above the ocean. The base is octagonal and cut from granite. Attached is a small house-like structure. In it were two rooms - one for tools and one for storage of whale oil. The main structure is shaped like a chimney, in that it tapers toward the top. It's a brick column with over 50,000 bricks. The lantern room was prefabricated in New Jersey and shipped to the site. Inside the tower is a wrought iron circular stairway with three landings.


I used to like to remind people that the construction happened in the 1870's. That meant that Highway One was the Coast Stage Road. A dirt road, that barely could be passed in some places. We believe that the brick came from clay deposits outside the town of Pescadero, but the wrought iron stairway had to come down from San Francisco (in numbered pieces). When I say that, of course, I hope that people envision putting these things on carts and having it brought by horses about 50 miles on not so great dirt roads.

The chimney-shaped shaft was probably built by the masons who built smoke stacks in San Francisco. The shaft is about 4 1/2 feet thick at the base and 18 inches thick at the top. So, it's really a double taper - the walls taper inward and they get thinne
r as you get up further. How was this done? Probably with an iron pipe column in the middle and a string to get the circles right. You had to be pretty good with math as a mason in these times. The shaft is really two walls with an air space in the middle. That way bolts needed for the platform above could be in the walls, but not penetrate all the way through. The masonry walls allow the moisture from the fog to condense, penetrate the brick, but the air space in the middle creates a way for the moisture to run down between the two walls and out weep holes at the base. The inside of the tower is never damp or clammy.

So, they built the base by leveling the rock that forms the point. Then put cut granite to form a base. The granite base has a hole in the middle for the weight to drop in. Remember the weight? Then the brick sits on that. And how did the staircase get in there?. In pieces (right?), but the walls had to be built just high enough for each section before the stair piece was lowered in - then the next section of masonry could be done. How was it hoisted up and lowered in? Probably by a team of horses pulling rope on pulleys.

The lighthouses of America (and there are over 1100 of them!) are truly remarkable feats of engineering and construction. This one has withstood two big earthquakes - 1904 and 1989. Why? ....because the base was solid rock, the granite was larger than the tower, and the tapered shape creates stability from rocking back and forth (it's kinda like a triangle...hard to tip over).


(my digitized photo from the point
showing the Fog Horn Building
and the tower )
for more West Coast lighthouses check out
. . .

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