I grew up near the railroad tracks in a small Kansas town and would lie awake at night listening to the trains and their mournful whistle as they passed through. It was a lonesome, haunting tone.

When I moved here to Maine for graduate school, I did not expect to hear anything similar. That is, until I made my first visit to a lighthouse during a particularly heavy fog. It was then that I heard my first foghorn on the coast.

Fog and foghorns, sea smoke and lonely bell buoys clanging in the dark. How powerful are those things? They evoke a haunting feeling, something visceral or primeval. Like that darn train whistle at night that I’d hear as a kid.

This is why I guess lighthouses can kind of creep me out. Or a fog-bound wharf, even in daylight, can bring to mind a Scooby-Doo ghost dressed like the Morton fisherman chasing Velma and me along a foggy dock.

Fog rolls in over Penobscot Bay at the wharf in Bayside, Northport. Photo by Charles H. Lagerbom

Anyone familiar with the coast of Maine knows we get fog. Researching the state’s maritime history, I began to realize how much of a part that particular phenomena played — and continues to play.

The fogs of Maine have resulted in many tragic happenings along its coast causing groundings, shipwrecks, and numerous disasters. Advances in navigational aids and onboard equipment have made foggy conditions here not as dire or dangerous as maybe they once were.

Still, fog can make it quite difficult for mariners.

But what exactly is fog? When and how does it occur? Why does it distort sound and make things seem so mysterious or creepy?

Fog is a visible aerosol made up of water drops or ice crystals suspended in the air or near the surface, kind of like a low-lying cloud bank. It comes when water vapor in the air condenses. Sea fog tends to be even thicker than land fog because of the presence of salt. Water vapor condenses on these tiny salt crystals; the result is wicked thick fog at sea and along the coasts.

Sea fog is heavily influenced by sea spray, which puts those salt crystals into the air. Waves send spray into the air and water vapor condenses around them. Breaking waves along the coast send up the greatest concentrations of airborne salt crystals, which explains why coastlines like Maine can get such heavy fog.

There is no sign of Islesboro in the fog, in this view from Warren Keith Wharf in Bayside. Photo by Charles H. Lagerbom


I was surprised to discover that another source of condensation nuclei for coastal fog is seaweed. Researchers have discovered that kelp can release iodine particles into the air when under stress. Water vapor will then condense around these particles, much like they do ice and salt. So, we get seaweed fog. Huh, who knew?

There are actually all kinds of fog. Radiation fog is formed by land cooling after sunset. Ground fog obscures less than 60% of the sky. Advection fog has moist air passing by wind over cooler surfaces. Evaporation fog forms over water covered by much colder air. Frontal fog forms the same way as stratus clouds near a front. Ice fog forms in extremely low temperatures. Freezing fog deposits rime. Precipitation fog is the result of precipitation falling into drier air below it. Hail fog occurs around significant hail accumulations, and upslope fog forms when moist air travels up a mountain slope.

Fog is also about air temperature and dew points. It forms when the difference between the two is less than 4.5 degrees Fahrenheit. Then you add water vapor. This happens a bunch of different ways, such as by wind, precipitation from above, or daytime heating evaporating water. The vapor then begins to condense on the salt or ice or iodine crystals and forms clouds or banks.

Fog thickness is mostly set by the altitude of the inversion boundary, a fancy way of saying the top of the fog bank or marine layer. Above this layer, the air mass is much warmer and drier, making a clear distinction between the two.

Visibility in fog depends on how concentrated the condensation is, it can range from just an appearance of haze to complete zero visibility. My first visit to the lighthouse in heavy fog and hearing that foghorn was in zero visibility. We still laugh about how we had to grope our way back to the car in the parking lot, never having really seen anything.

Visibility drops as the fog comes in at Bayside. Photo by Charles H. Lagerbom


Even though fog is liquid water, there are gaps between the droplets. This tends to mess with sound. Sound travels fastest and farthest through solid mediums, less so through liquids, and even lesser than that through gases. During thick fog, sounds are distorted due to gaps between these water vapor droplets and the differences in air temperature.

Short-wavelength higher-pitched sounds get reflected and refracted in fog. They are partially, or sometimes completely, canceled — their energy scattered or dissipated. This is known as damping. Distorted sounds in heavy fog add to that creepy weirdness feeling, which make up a big part of the atmosphere with horror movies, haunted lighthouses, and Scooby-Doo mysteries.

On the other hand, lower pitched notes with a low frequency do not lose as much energy to these water droplets. They are less affected by fog and can therefore travel way farther, which explains the evocative low-pitched tone of many foghorns and bell-buoys.

All foghorns use a vibrating column of air to create their audible tone. The Daboll trumpet used vibrating plates, like a car horn. Others used air forced through holes in a rotating cylinder, like a siren.

Before foghorns, early lighthouses used small cannon to signal danger. But this method proved impractical. Whistles and bells were then used. A regular bell striker was developed, much like in a clock. These were implemented throughout the 1800s with the use of a governor. In Maine in 1837, they used a giant triangle with 4-foot-long sides.

The first automated steam-powered foghorn was invented by Robert Foulis, a Scotsman living in Saint John, New Brunswick. On a foggy night, he heard his daughter playing the piano and noticed the lower notes were more audible than the higher ones.

Foulis developed a low-frequency device but could not get the attention of anyone official. Someone else was later given credit for the idea. Eventually Foulis was recognized as the true inventor, but he was never able to secure a patent so never profited from his invention.

Automation of lighthouses throughout Maine and New England became common in the 1960s and 1970s. Most of the older foghorn equipment was removed and replaced with electrically powered diaphragm or compressed air horns. These would automatically activate during heavy fog conditions. The need for lightkeepers and attendants, or even full-time on-site maintenance personnel, proved no longer necessary. It was the end of an era.

But the fogs of Maine continue to come. And the foghorns continue to sound out their doleful tone as the marine layer creeps in and muffles the coast. Sounds are dulled and distorted. Damp and clammy air covers you like a cloak. The sun is blotted out. It is difficult to make out shapes and forms in the smothering dampness.

Some tend to find this comforting and tranquil; for others it is stifling, making their neck hair tingle and stand on end. Goosebumps might even form on an arm from the sudden chill. I really hope that Morton fisherman is not around the corner, right Shaggy?

Charles Lagerbom teaches AP U.S. History at Belfast Area High School and lives in Northport. He is author of “Whaling in Maine” and “Maine to Cape Horn,” available through Historypress.com.