When I first thought of writing the Zodiac Mysteries, featuring San Francisco astrologer Julia Bonatti, I knew that the city itself, its history, its atmosphere, its constantly changing faces should play a big part in Julia’s world.  And one of the most important features of San Francisco is its fog, especially where Julia lives on the outer avenues close to Land’s End and the Pacific.
Julia doesn’t mind the billows of fog that arrive almost every day around three o’clock in the afternoon.  She loves the way it carries the smells of the sea and the silence it creates.  She adores the mist on her face and the way it softens the hard contours of buildings.  And she particularly loves the deep voices of the foghorns as they lull her to sleep at night.Bridge Fog
What causes all that fog?  Well, California’s very hot in the summer months, while San Francisco is perched on a peninsula at the edge of the continent surrounded by water, water that brings freezing cold Alaskan currents.  When the cold air of the ocean meets the rising inland heat, fog is formed and it occurs most heavily in the months from July through October.

City FogFor many years, the compressed air horns under the Golden Gate Bridge sounded with deep two-tone baritone voices.  There were two fog horns on the south tower of the Golden Gate Bridge that made a single blast every twenty seconds, while a mid-channel foghorn sounded two blasts every forty seconds.  During the foggy season, July through October, they sound more than five hours a day.
Inbound ships heading east into the Bay would steer left of the foghorns on the south tower and right of the mid-channel horn.  Outbound ships would stay to the right of the mid-channel foghorn.  Their voices guided hundreds of thousands of vessels safely through the Gate and forewarned San Franciscans when fog was about to envelope their city.
SF.1But nothing lasts forever and in the mid 1970’s the two-tone horn at mid span stopped working.  Replacement parts were impossible to find.  So for the next ten years, only a one-tone horn continued to sound.  Eventually that horn too began to show signs of wear and tear and had to be replaced.  The replacement horns are one-tone horns that differ in frequency but operate with compressed air, like the originals.  Each horn has a different pitch and marine navigational charts give the frequency or signature of each.
Then, in 1992, the Coast Guard decided to stop operating the fog horns and replaced them with electronic signals!  Romantics of the city arose and protested loudly until the horns were finally reinstituted.  You can listen to them here:
They don’t quite sound the same as the originals but they still lull Julia to sleep at night and their voices can be heard in the city once again.

[This post first appeared at A Holland Reads on June 30, 2017]

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