A Brief Primer on Lighthouses (Part 1)

The information that follows was compiled from a number of book and internet sources, along with the author’s accumulated knowledge after more than a decade of serving as a volunteer at lighthouses across the U.S.A. The intent is to provide general background information to other volunteer “keepers” of these important parts of our nation’s maritime history.   It is accurate to the best of the author’s knowledge but represents only the tip of the iceberg to be sure.   With lighthouses, as with most fields of knowledge, one learns that the more you learn the more you learn there is still more to learn. The author stands ready to be corrected and welcomes corrections or additions.                                                                           

The twelve “original” lighthouses in the U.S., those that had been built by the various Colonial governments prior to the adoption of the U.S. Constitution in 1789, are discussed in the section entitled “EARLY LIGHTS.” There may have been a thirteenth colonial lighthouse.  Historians largely agree that a tower was built at Tybee Island, GA as early as 1736, but disagree as to when it became a true lighthouse rather than just a navigational day-mark.   As at many sites, this early tower was replaced several times and the third one, built in 1773, was the one ceded to the new federal government in 1791.  Some authoritative sources state that it was not lit by a lamp system until then.  Staff at Tybee Island Light Station believe that the 1773 tower was lit by candles well before 1789.

Before going any further, there are three lighthouse terms that must be clearly defined.  Sometimes these are incorrectly used as if they are interchangeable.  The first is the Light.  This refers to the source of the light, and as explained below was for decades most likely an oil lamp, and more recently an electric light bulb.  The second term is Lens.  The lens surrounds the light.  Since the 1850s, all lighthouses have had various sizes of reflective “Fresnel” lenses, made up of many prisms set into a frame.  Today many of these have been replaced by plastic/lexan lenses that do basically the same job.  They magnify and redirect the light from the electric bulb and send out a shaft of light to great distance.  The third term is Lantern.  We think of a Coleman-style camping lantern when we hear this word, but in lighthouse parlance, the lantern is the glass-paneled enclosure that surrounds the lens and protects it from weather.

The left photo below shows an electric LIGHT bulb inside a LENS. The right photo shows the LANTERN atop the Au Sable lighthouse in Michigan.

Light Stations   A lighthouse tower was only one component of the larger complex that was known as the “Light Station.”  Typically, in addition to the tower itself, the station would include one or more residences for the head Keeper and any assigned assistants, with associated privies and woodsheds.  Also included was most likely a boathouse with the “ways’’, the ramp and winch system that lowered and returned the station’s boats to and from the protection of the boathouse to the water.   Depending on the severity of the surf, a dock or wharf was commonly built to allow the supply tenders to bring supplies and materials to the stations.  Soon after kerosene was adopted as a lamp fuel, separate “oil houses” of brick or metal were built to store this fuel, much more volatile than lamp oils used previously, away from the other buildings of the station.  By the 1890s, buildings to house the steam whistle fog signals that became common at the major lights were also a part of the station.  The greatly increased workload created by the fog signals often led to the assignment of an additional Assistant Keeper, which in turn might have led to the need for additional quarters.   Another common feature of many of the larger stations was a “tramway,” essentially a small cable car run on tracks that led from the landing wharf to the fog signal building and the residence.   These seemed to appear about the time that coal replaced wood as a fuel for use in the steam boiler and for cooking/heating the houses.  Present too were the barns, sheds, privies and other such buildings that supported the keeper’s life at the station.

Light Sources   The earliest lights as aids to navigation were simply fires kept burning at locations where they could be viewed from a great distance.  By the time lighthouses were built in the U.S., oil lamps and candles were the usual light source.  Greater brightness was achieved by increasing the number of lamps, and by putting some kind of reflective devices behind the burning wicks.  A variety of lard and vegetable based oils were used.  Oils from the Sperm and other great whales became a major lighting fuel in all of the world in the early 1800s, and it was of course used in lighthouses as well.  By mid-century, whale oils had become scarcer and more expensive and lighthouses resumed using primarily lard oils.  By the late 1870s, petroleum based “mineral oil”, or kerosene as it was also known, began to replace lard oil as the fuel of choice because it was plentiful and relatively cheaper.  In 1879, the Light-House Establishment purchased 106,000 gallons of lard oil.  Ten years later, the agency purchased only 14,000 gallons of lard oil, and 332,000 gallons of kerosene.  Kerosene was burned in all lighthouses by the 1890s and continued to be the main fuel until electricity reached these often remote sites.  That didn’t occur until the 1950s at some island and offshore lights.  The Statue of Liberty, which originally served as a lighthouse, was the first one in the U.S. to utilize electricity in 1886.  The first true lighthouse to utilize an electric light in its lantern was at Sandy Hook, New Jersey, in 1889.

About 1910, compressed acetylene gas came into use as a lamp fuel.  This was most often used on buoys and unmanned towers, which then only had to be visited periodically to refill the gas tanks, but it was also used at some larger light stations as well.  The use of acetylene was one of the earliest methods used to automate a light.  These lamps had a pilot light that was always on and a “sun-valve” that turned the gas on and off as temperature fell at dusk and rose at sunrise.

Ami Argand (1750 – 1803), a Swiss scientist, developed the first major advance in lighting in 1792.  It was a nearly smokeless lamp with a glass chimney and a reservoir for oil.  This lamp did not direct the light; it was left to others to come up with various styles of reflectors.  A parabolic-shaped reflector, coated with silver, proved to be the most efficient.  Numerous Argand lamps, each with its own reflector, were mounted in large iron frames and installed in lighthouses.  Some had mechanisms to revolve the frame assembly.

Winslow Lewis (1770 – 1850) patented a lamp that was basically a copy of the Argand lamp, except that it incorporated a parabolic reflector.  This was in 1808.  It was described as a “reflecting and magnifying lantern.”  Lewis’s patent was purchased by the government for $20,000.00   Apparently Lewis’s lamps did consume much less oil than those used previously.  Lewis was also given a seven-year contract for “fitting up and keeping in repair any or all of the light-houses in the United States or territories thereof.”   His contract was renewed in 1816. Lewis was involved in building and repairing US lighthouses until his death in 1850  He was also one of the main suppliers for lamps, reflectors and oil, although the Light-House Establishment contracted with others for these services as well.

In addition to a reflector behind the lamp wicks, Lewis’s lamps also used a magnifying lens in front, something he had apparently copied from early English lighthouses.  The British lighthouse service had concluded the lens was not effective and discontinued their use, yet our American lighthouses continued to use this reflector/lens system for many years. 

Although the lamps Lewis provided were efficient for their times, they did not really produce much useable light.  Tests showed that even with a good quality reflector only about 17% of the light produced actually was sent out as visible light to mariners.  Each lighthouse needed many of the lamps.  An early list of navigational lights, titled “Schedule of the Light Houses and Beacons in the United States”, states that in 1833 there were a total of 160 light stations exhibiting a total of 1,932 lamps, or an average of about 12 lamps per lighthouse.  Thus even though each lamp was stingy with oil, the total number needed resulted in large oil consumption, as well as the associated cost and work of obtaining, transporting, and storing the oil and tending the many lamps. 

By the early 1900s, the IOV (Incandescent Oil Vapor) lamp had supplanted the lamps of Lewis, and improved versions by Funck and Meade.  These were similar to today’s camping lanterns.  The kerosene fuel, under pressure, was pre-heated and vaporized onto a cloth “mantle.”  The burning produced a much brighter light than earlier lamps.  The IOV remained state-of-the-art until electric bulbs replaced oil lamps.

A most interesting book on French lighthouses [ De Phare En Phare, by Jean Guichard, 2007 -translation “From Lighthouse To Lighthouse“ ] states that at least one of the keepers of a light was required to be well experienced in the “preparation and clarification” of oils.   There were three types of oil that were apparently mixed together to give the optimal burning qualities:  olive oil, sperm whale oil, and “rabbet” (?) oil .  I do not know the date of this requirement.  Although no reference has been found as to American lighthouse keepers mixing oils, there is probably no reason to believe that it was not a common practice in lighthouses worldwide.

Types of electric lights have continually evolved since the first incandescent bulb replaced the oil lamps of earlier days. As of the 2020s, various types of LED light units are being installed inside either the classic Fresnel lenses which remain in many lantern rooms, or their “more modern” replacements.

Purpose of A Lighthouse Lighthouses serve one major purpose. They establish a “known point” so that a mariner can establish their location on an otherwise dark and forboding coast. They are a landmark by which to navigate. Secondarily they alert mariners to hazards along the coast such as submerged ledges, rocky outcrops, or shallow shoals, but the mariner must consult either the charts or their own knowledge to know the risks.  A lighthouse also serves this purpose during the day. To accomplish this, a lighthouse must appear different, both by night and by day, than any other lighthouse that can be seen from a given point.  These differences are referred to as the “characteristic” or the “signature” of the lighthouse.  One of the first methods of making one light appear different from another was to build two lighthouses at the same location, thus a mariner would see a double light at night.  The obvious disadvantage of this was the huge cost and expense of building, maintaining, and operating two lighthouses instead of one, particularly in the days when each might have up to a dozen or more lamps.  In a few instances, three separate lighthouses were built at the same place.  Other early methods of distinguishing one light from another was to somehow make the lenses rotate so that the intensity of the beam varied from moment to moment.  The use of opaque or even colored screens in front of some or all of the lamps was tried in some locations.  With the eventual coming of the hugely efficient Fresnel lenses to our lighthouses, the ability to alter the appearance of the lights was greatly simplified.

Some lighthouses were “fixed”, in that the lens did not rotate nor change in appearance.  It was simply “on” and cast a bright shaft of light out over the water.  The largest “first order” Fresnel lenses often displayed a “fixed” (non-flashing) light as they were so big and bright they could not be mistaken for some other lighthouse.  Approximately fifty percent of our U.S. lighthouses had “Fixed” Fresnel lenses. The others had lights that appeared to the viewer from a distance to be “flashing”, and this was accomplished by rotating the entire lens assembly.  In the days of oil lamps, the lamp itself was of course not turning on and off.   Some lenses were made with multiple “bulls-eye” sections, and as the lens rotated the light would appear to give a bright “flash” as the bulls-eye section of the lens passed between the light source and the viewer.  This would then be followed by a period of lesser light intensity until the next bulls-eye section of the lens passed by the light.  The number of seconds between apparent “flashes” was the “characteristic” of this particular lighthouse.  This information would be found on mariners’ navigational charts.  A colored lamp chimney could change the color of the light.  Sometimes colored glass panels were either in the lens or on the outside of the lens, and these gave the light either a continuous color (red and green the most common) or an alternating white and colored  appearance.   The time of white versus colored apparent light would thus be the “characteristic” of that particular light.

Some lights had solid screens that rotated around the lamp or lens, and thus the light would be seen for so many seconds then appear “dark” for so many seconds.  The ways of changing the appearance of the lights were limited only by the technical and mechanical vision of the lighthouse designers and staff.

Fresnel lenses, particularly the large ones, are tremendously heavy.  Some of them rotated on a bed of liquid mercury, others on either a ball-bearing bed, or a system of brass “Chariot wheels.” Actual rotation was achieved by a complicated gear-box system, driven by various designs of clock-work like mechanisms using a heavy weight that slowly descended from the top to the bottom of the lighthouse.  Thus another of the many jobs of the lighthouse Keeper often involved “winding” the weight back to the top from time to time.  .

Daymarks In addition to the differences in their lights, lighthouses also had to be discernable one from another during the daytime, when they also served as a landmark to passing ships.  Painting the towers to make them more identifiable was an innovation of the Light-House Board.  Thus we have some lighthouses that are all white, some colored, and some half and half or with stripes or blocks or diamonds of various design.  These various painting schemes are referred to as the lighthouse’s “daymark”.  Often the design of the light itself was sufficient to distinguish it from others in the area, as was the location on an island or a high bluff. 

This ends Part 1 of this “Primer”. I hope you have found it informative. Please continue on with Part 2.