Parts of a Lighthouse

A white lighthouse with the light shining out just after nightfall. A keeper's building is adjacent at the bottom.

What Parts of a Lighthouse give its light, and make it all work? The light source itself can seem mysterious. Especially if you've seen some of those wild films!

We'll find out more about that - what those parts are, and the need for those particular lighthouse components.

But first, let's get a brief background. It's good that we get a sense of the need for each of those lighthouse parts. That helps establish the historical case for how it all happened to begin with.


Background of Lighthouses

Early sea-bound navigators realized they needed coastal aids for  assistance. At first they used signal fires on the highest hills near inlets to ancient ports.1 Later they began building permanent structures.

Early lighthouse architects had the understanding for elevating the light beam. A tower was their solution. Their first raw materials were wood or from local stone quarries. Eventually they began using cut stone and formed bricks.2 The earliest cut carefully to fit together with little or no mortar. Later they used lime mortar.

Through the years, lighthouse construction moved to more modern additions for strengthening. Iron and steel with rebar reinforced concrete were used. In time, even adding the lightweight practicality of aluminum.2


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sailing ship on a foggy oceanNavigation in the Fog - Kind of Scary! Photo by Joel Bengs at Unsplash

We saw the earliest beacons were wood fires, but then sometimes of coal. Not very useful for distance sightings. Slight improvements for parts of a lighthouse came via oil lamps, finally amplified with reflector attachments.1

Fog was a problem for seafarers from time immemorial. Those tending fires, candles or lamps of the earliest lighthouses, realized fog obscured the minimal help of these lights. They provided soundings from drums or large bells when circumstances called for it.1

At the turn of the 18th Century, elevation of lights via towers helped some. But not much. It was when Augustin Fresnel's prisms came into use that the beacon changed dramatically.1


Lighthouse Construction Techniques

Original blueprint plans for a lighthouseThe Plans Outline Measurements for some Parts of the Lighthouse

Light Towers

Diagram of the Eddystone Lighthouse in the English Channel

The first ancient lighthouse tower built in Egypt was massive. Named among the Seven Wonders of the World in antiquity. The Pharos in Alexandria was built of marble and sandstone. The base probably 360 ft. diameter, walls extended 100 ft. wide, 450 ft. tall. Nothing like it at the time!1

Ancient China, meanwhile, used some wooden Pagodas, doubling as light towers. Naturally located at harbor entrances.On occasion, others throughout the world also used wood for constructing parts of a lighthouse.

For instance, the Eddystone Lighthouse, atop rocks in the English Channel. Now that was a tough area! First made of stone, it was destroyed by a 1703 storm. Rebuilt partially of wood in 1709 by John Rudyard, amazingly surviving until 1755. When fire took it down!1

Next they rebuilt with granite blocks. First ensuring the foundation was robust, cobbling pebbles and rocks as a slab. The wodge sections designed to interlock in a splayed edge manner. Making for unique stability that's withstood mighty storms.1

This history reflects the construction parts of lighthouse towers into the 1700s. Types of stone, formed into masonry blocks and bricks, were the most common. However wooden planks were also sourced. 

In the 1800s metal construction was introduced. Concrete reinforced towers became more common in the 1900s. The first in the U.S. was in Point Arena California, built in 1908.7

Lighthouse Foundations

Early lighthouse builders searched best locations for tower construction. Since it needed height, and would be very weighty, a solid foundation would be assessed before the build began. Before 1850, this meant finding impermeable rock, or immovable soil types to build upon.7 Those were always ideal foundation bases for lighthouse building.

Beginning with the early 1800s, the area of construction was considered for a foundation build-up. One early type was built on wooden piles.7 As one could imagine, a strong storm would take the whole structure down. They tried improvements like screw-piles, using iron stilts instead of wood.12

The crib foundation was used for heavy sea influx areas. A crib container was filled with rocks, then loaded with concrete. Becoming the foundational base. Often below water. A similar lighthouse foundation was the cofferdam for low water areas.12

Another foundation material was using stone. This was also used for lighthouses built on ledges in water. 

Caisson style foundations were made from a hollow iron cylinder. Then filled with sand, rock or concrete. This was sunk below the surface, even in 30 ft. of sea. A variation was to add a pneumatic system to pump water away.

chart showing lighthouse constructions types and years in use

Other Parts of a Lighthouse

Lighthouse Lamps, Lens & Reflectors

First Lamps

Lamps are the light source that a lighthouse uses. The beginning of it all, shall we say.

Fires on highest points were the first methods of directing light to mariners at sea for guidance. Imagine the continuous effort this meant. From maintaining the wood fuel needed from dusk to dawn. To feeding that fire through the night. Coal fires were also used. They may have increased efficiency, but still needed constant stoking.

Bad weather could hamper efforts, including wind blowing flames landward. That decreased visibility further still.1

The first lamp alternative was using tallow candles. Then oil lamps were developed. A regular flow of fuel decreased the workload. But the light beam was still weak.

For instance a common type was the Spider Lamp. Whale oil was the fuel used here. A container housed the oil, in which floated. Its problem was the smokiness and fumes emitted. Plus the light output was poor.5

A slight improvement occurred with the invention of parabolic reflectors, which concentrated the light beam.1

Argand Lamp

The first major advancement for parts of a lighthouse was patented in 1783. François-Pierre-Amédée Argand and his brother Jean made the oil lamp's wick flatter and wider. It really brightened the flame. They added flues increasing air flow, intensifying brightness further still. Despite their patent, many copies got into the action.3

Reflectors

Early beacon constructors realized the light alone wasn't enough to project far out to sea for good guidance. The idea of a reflector was promoted when it was noted light could be reflected from a glossy surface, potentially increasing its power. With this principle, they came up with reflectors as parts of a lighthouse for light sources. This is referred to as the Catoptric System for lighthouses.4

Flat Plate

Despite the name, they're not precisely flat. Mostly very early types of reflectors. Like white walls built behind fire platforms. Then using large polished metal plates behind fire platforms. Or behind candle power lamps.4

Their effectiveness is low. The reflection isn't concentrated, not controlled, and very limited.4

Spherical

The shape is a curved arc. Capturing the light waves into a concave section. Reflecting them through the light source, then directing them outward on that continued trajectory.

Light beams bounce from this reflector and return to the light source. To make the light flame seem brighter. But it doesn't project its brightness outward toward the sea, dimming that effectiveness.4

Parabolic

The shape is also a curved arc, but the arc is more deeply curved. The light waves are captured into its concave section. But because of the depth of the arc, they are reflected back on a different trajectory than the spherical.

The reflection's focus is along various points of this deep arc. The beams are returned converging toward the sea's horizon. A drawback is 30% of the rays escape at the reflector's edge, bouncing off to nowhere!4


Lighthouse Lenses

 A lighthouse uses a lens as an optic focusing system. It's the glass gadget that takes the light's electron waves and draws them together in a known direction. Even your eyes have a lens to focus light rays that come in through the pupil, to fix on the retina and optic nerve.

Fresnel Lens

Augustin Fresnel was fascinated by light since boyhood. He studied engineering. Though working in road design, he still worked light formulas himself. Fresnel's thought was light was energy waves. He detected how prisms veered these light waves. He figured he could direct the waves, thus inventing his lens. Fresnel presented his study to the French Academy of Science, which won him an award.1

He tried out his novel idea for a lens at the deluxe lighthouse at Cordouan. He used a basic lamp. Surrounding this was his device, a circular formation of prisms.1 They fit into a brass framework which formed it into a beehive shape. The prisms bent the light into a horizontal beam.7 It could shine out of the lantern room for over 20 miles!1

Close look at a Fresnel lens for a lighthouseOne vital part of a lighthouse is the Lens - Here is a Fresnel

Fog Signals

Fog Cannons, Rockets or Guns6

Another part of a lighthouse first used in Europe in the 1700s.

Then right to the U.S. Use of a Cannon, known as a Fog Gun, for the first time at Boston Harbor in 1719. A ship fired its cannon, then the lighthouse keeper fired the Fog Gun in reply.

On the West Coast, a Fog Gun was mounted in place in 1857 at Point Bonita Lighthouse in California. It's a very foggy area. The man in charge of it was constantly busy. Realizing the impracticality, they decommissioned the signal after two years.

Generally, they saw the unworkability of this. During fog, it's difficult enough to determine distance and location by sound. But using a cannon, since it involved explosive devices, just added to the danger.


Hand Bells

Initially rung by hand, large bells were parts of a lighthouse Put Into Action.

The first in the U.S. was in Rhode Island at the Beavertail Lighthouse.4 Another was actually a triangular shaped contraption. Tried out at West Quoddy Head lighthouse in Maine in 1837. Quite tedious to continuously chime this during fog events.6

Lighthouse with horizontal red and white stripes next to the keeper's house painted white with a red roof.West Quoddy Head Lighthouse in Maine

Also, experiments found that bell sounds didn't efficiently transmit sound. Often quite heavy, up to 5000 lbs. These trials were determining if the size, weight, striking hammer or its timing related to sound transmission. The final discovery was that increasing frequency of strikes per minute increased miles of sound transmission. What also furthered sounding was use of sound concentrating reflectors.4


Automatic Bells

Incessantly attending to a bell was time consuming. Having to warn of fog this way was tedious. Bells were parts of a lighthouse that were in mind as an advancement in form.

The first improvement made the job a little better. Coming in the 1840s, a clock-based set-up was devised, which controlled the bell chime. It needed wind-up, just as a manual clock does. Keepers gave it regular attention, plus gear maintenance. But surrounded by salty air, it often failed, still requiring hand ringing.

The next improvement gained a bit more progress. A winding instrument driven by weights was behind the motion. These heavy plumbs rose up high within an enclosed bell tower. The wind-up method was timed, dropping the weights at required periods. Which caused the bell's strike for sounding.8

The entire apparatus in the bell house was still laborious to manage.8 

Lanterns

This part of a lighthouse confuses many. Maybe because of camping lanterns used, which is a light. Therefore, many think it's the light. But a lighthouse lantern isn't the light. It's the structure at the very top of a lighthouse tower.

The rooms there enclosing the lens and its instruments. The original term was actually Lanthorn.9

Although from a distance it appears as one room, it contains three sections:9

  • Climbing upward, the first part of the lighthouse in the Lantern room you'd reach is the Service Room. Here are fuel tanks and rotation mechanisms. It's the workroom for keepers to clean and prepare the lamp.
  • The next section up is the optical unit. The windows here are storm-strength glass in metal frames called astragals. The all-important lens is protectively housed here.
  • The uppermost part of the lighthouse lantern is the Dome. With a metal frame, often with copper casing. A ball-shaped vent system sits atop, with a concave dish below catching condensation. A weather vane and lightning rod above the ball-vent, at the tip.

Identifying Markings

Poster showing the striped Cape Hatteras Lighthouse. Keeper's house adjacent, ocean in background and lagoon in front.

During the daytime, lighthouses can be observed from the sea, and their painted markings can be seen. These help mariners in various ways.

Painted markings considers the background of the lighthouse's surroundings. For instance, if on a sandy beach, a dark color makes it stand out. Or perhaps a vivid striped pattern. But if it fronts a woodland or dark cliffs, then a light or white color is preferred.10

These are termed "Daymarks." Some become quite well-known. For instance, the North Carolina Outer Banks has several lighthouses. Navigating ship captains find it helpful in distinguishing their location when sighting the vivid black and white stripes of the Cape Hatteras Lighthouse. As opposed to more southerly view of the unique black diamonds dropping down the sides of the Cape Lookout Lighthouse.11


Lighthouse Architects, Builders & Engineers

Sostratus - He's likely responsible for designing the oldest known lighthouse in the world, the Pharos of Alexandria, Egypt. How do we know? He etched his name into one of the stones used for this great structure.1

Emperor Claudius of Rome - Around the 50s AD, he was a creative ancient designer. Anxious to get ships safely to their port, Ostia, he saw usage for an old, huge submerged barge. He directed workers pack boulders and fill rock into the vessel. Then on top, build a 4-level tower, scaffolding narrower as it went upwards. The top level held the signal fires.1

Line drawing of Claudius Caesar, Emperor of Rome

Gaius Sevius Lupus - Designed La Coruna Lighthouse on Spain's north coast. Such an accomplishment. With some renovations and repairs, it hasn't changed much. Today it's still there: you can visit it.1

John Smeaton - British designer and builder, who undertook the mission of the Eddystone Rocks lighthouse in the late 1750s.He originated the interlocking rock system, adding oak pins to connect layers.2

Robert Stevenson - An engineer and builder (author Robert Louis's grandfather) who took on the Bell Rock Lighthouse operation, in the North Sea.1 He based his work on Smeaton's strategies. Completion in 1811,2 still there and functional.



References

1 Jones, R. (2013). The lighthouse encyclopedia. Guilford, Connecticut.: Globe Pequot Publications

2 Dolin, E. J. (2016). Brilliant beacons: A history of the American lighthouse. New York: Liveright Publishing Corp.

3 Sella, A. (2018, Oct. 4). Argand’s lamp: The innovation that gave light to the world. Chemistry World. Retrieved from chemistryworld.com/opinion/argands-lamp/3009536.article

4 Tag, T. (2020). Reflectors by Thomas Tag. United States Lighthouse Society. Retrieved from uslhs.org/reflectors

5 Jenkins, M.B. (1999-2011). Lighthouse lamps and lenses. Chesapeake Bay Lighthouse Project. Retrieved from cblights.com/lights/lampslenses.html

6 Wheeler, W. (2020). The history of fog signals by Wayne Wheeler. United States Lighthouse Society. Retrieved from uslhs.org/history-fog-signals

7 Summary Context Statement (n.d.) NHL Lighthouse Nominations. NPS History. Retrieved from npshistory.com/publications/nhl/special-studies/lighthouses.pdf

D'Entremont, J. (1994-2010). Finicky fog bells. American Lighthouse Foundation. Retrieved from lighthousefoundation.org/light_thoughts/ lal_finickyfogbells.htm

9 Wheeler, W. (2021) The lantern by Wayne Wheeler. United States Lighthouse Society. Retrieved from uslhs.org/lantern

10 Trinity House (2016) Why are lighthouses different colours and heights? Trinity House FAQ. Retrieved from trinityhouse.co.uk/about-us/trinity-house-faq/why-are-lighthouses-different-colours-and-heights

11 Penberthy, B. (2016). Lighthouse frequently asked questions. US Lighthouses. Retrieved from us-lighthouses.com/faq.php

12 Browning, R. (2010) Lighthouse evolution and typology. Sea Shell Shop as referenced from USCG. Retrieved from seashellshop.com/ Lighthouse-Evolution-and-Typology/

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