Sea Kayaking and Fog: How Foghorns Work

That haunting, slightly mournful sound you hear alongshore on foggy days is likely a foghorn attached to a lighthouse like the light at Gurnet Point in Duxbury, Massachusetts, an hour or so north of Cape Cod and overlooking Cape Cod Bay. Located high a high of a bluff about 150 feet above sea level, Gurnet Light's fog signal was once manned by a Coast Guard crew, but is now automated.

Climb the bluffs adjacent to any lighthouse on a cold and raw, foggy day and you'll soon learn how foghorns work. This is a good exercise for sea kayakers. Not only does the exercise give you good reason to get out of the cockpit, one can learn how foghorns work, and how useful they are. Because truth to be told, sea kayaking marks the first exposure for many paddlers to the oceangoing environment, and it wasn't until we discovered sea kayaking that we found ourselves in the ocean environment with its wide variety of signals and signaling devices, rules of the road and so on.

Fog horns signals work on a basic principle. When visibility is reduced, the fog signal goes to work. In previous eras, when lighthouses and their foghorns were manned by keepers, and included lightships anchored off Nantucket Shoals, activating the fog signal was a simple matter of looking out the window. If the designated landmark was obscured by rain or a deep bank of fog, and when the dew point reached a certain level, the dutiful keeper activated the signal for as long as the landmark remained invisible or the dew point remained at the pre-determined level.

In the modern age, things run differently. Fog signals are fully automated. They turn themselves on and off when visibility is reduced.

At Gurnet Point lighthouse overlooking Cape Cod Bay, for example, the intrepid sea kayaker who lands at Gurnet Beach and takes the short walk to the lighthouse will notice, about three quarters of the way up the western side of the shingled tower, an electronic eye. It emits a signal reflected back by a designated landmark. As long as the designate landmark is picked up, the foghorn stays off.

Foghorns emit a sound perhaps most accurately described here as a bleat. It's a loud, very modern tonal sound which does a good job of piercing the sound muffling characteristics of fog and, perhaps thankfully, lacks that mournful sound fog signals made in earlier centuries.

So next time next time you're feeling groggy in the morning at a coastal Maine bed and breakfast after a foggy night, tired because you didn't sleep because of the local foghorn blaring all night, don't hold anyone human for your sleeplessness. It's done automatically, by way of the mechanical indifference, efficiency and low cost of an electronic eye and a solar panel array.