The stepped, ribbed lens is one of the most recognisable features of a navigation lantern. It redirects light from the flame towards the horizon instead of allowing so much of it to escape above and below the observer.

Augustin Jean Fresnel (1788–1827) developed his lighthouse lens in the early nineteenth century, completing the design of his flashing apparatus in 1822. His first lighthouse installation followed at Cordouan, at the mouth of the Gironde, in 1823. 

The stepped, ribbed lens is one of the most recognisable features of a navigation lantern. It redirects light from the flame towards the horizon instead of allowing so much of it to escape above and below the observer.

Augustin Jean Fresnel (1788–1827) developed his lighthouse lens in the early nineteenth century, completing the design of his flashing apparatus in 1822. His first lighthouse installation followed at Cordouan, at the mouth of the Gironde, in 1823. 

Thick, curved, ribbed glass is recorded on French ship's lanterns from the 1840s, although the wider adoption of such lenses aboard ship was a later development. The date of Fresnel's lighthouse invention should not be used as a date for every ribbed marine lens.

The American ship-lighting regulations of 1910 are another reference point in the source material for this guide. Their requirements need to be read for the particular class of lantern: a Fresnel lens by itself is not evidence that an American lamp was made after 1910.

American catalogues describe some lenses as a “two-thirds section”. This refers to a lens that extends around the front and sides of the lantern but leaves the back unglazed. It should not be mistaken for a complete circular lens with a piece missing.

The form suits a lantern intended to show forwards and to both sides rather than directly astern. A masthead light has a prescribed sector of 225 degrees, but “two-thirds” should not be read as its exact regulated angle: two-thirds of a circle is 240 degrees, and the housing and screens also determine the sector in which the finished lantern shows light. 

Prismatic glass also occurs in late nineteenth- and early twentieth-century ship's lanterns. The terms used in catalogues and collectors' descriptions need care: “prismatic” and “Fresnel” are not necessarily opposing categories.

A dioptric element redirects light by refraction as it passes through the glass. A catadioptric element uses both refraction and reflection; lighthouse Fresnel systems can contain both kinds of element. A ribbed surface alone is therefore not enough to decide which optical arrangement a lens uses. (National Park Service)

For a ship's lantern, the vertical spread of the light mattered as well as its brightness. A very narrow horizontal beam could move away from an observer as the vessel pitched or heeled. Sailing vessels presented a particular problem because they could remain at an angle for long periods.

A broader vertical spread helped keep the light visible as the vessel moved, although spreading the available light reduced its concentration in any one direction. Gimballed mountings provided another way of keeping a lantern upright. The importance of heel is reflected in the different vertical-sector requirements for sailing-vessel lights in COLREG Annex I.

Coloured glass filters the light produced by the flame or bulb. It absorbs part of that light rather than creating a new colour without loss, so the light source and the glass have to be considered together.

The 1948 rules required a masthead light to be visible at five miles and a sidelight at two. These were requirements for different lights and duties, not a direct measurement of how much light a particular coloured lens absorbed.

Oil flames and early incandescent lamps produced a warm light with a strong yellow and red component. A lens can consequently look different in daylight from the light it transmits when fitted with its intended source. Blue-looking glass occurs in lamps marked “Starboard”, but its transmitted colour should be checked rather than assumed from the unlit glass. The other uses of blue glass are discussed under Blue Glass.

Green glass also occurs in lamps that were not sidelights. The colour alone does not establish a wartime purpose or explain a lantern's visibility range; see Green Glass.

American catalogues also distinguished “ruby” from other red glass and, in examples cited for this guide, charged fifteen cents more for a ruby globe than for red, blue or green. Gold was used to produce some ruby glass, while copper could also produce red glass. The catalogue colour name and price are useful evidence, but do not by themselves establish the recipe used for a surviving globe.

Liquid-filled lenses are recorded in connection with lanterns of the City of Dublin Steam-packet Company. No surviving example has yet been established in the research assembled for this guide, so this remains a documented description rather than an identified object.

Many surviving navigation lanterns have a small triangle enclosing the letters GGG moulded into the glass. This is the mark of Genthe Glas of Goslar, a supplier of optical glass for lighting and signalling.

The Goslar works of Dr. Genthe & Co. were founded in 1926 by Alfred Genthe and Gerhard Weule. The business produced glass for signal and lighting optics, including large optical blanks, and later also supplied the automotive industry. 

The triangle can be difficult to find. It is moulded rather than scratched into the surface and may be partly hidden by a rib or the lantern's frame. In the European collections considered for this guide, it is a particularly familiar glassmaker's mark.

The mark identifies the glassmaker, not the maker of the complete lantern. It is not yet established when the triangle was introduced or whether its design remained unchanged throughout production.

The company encountered insolvency in the late 2000s. The precise year should not be used to date a lantern from its GGG lens alone, particularly where the lens may have been replaced.

Chance Brothers was the other major glassmaker represented in the material assembled for this guide, although its marks are encountered less often on surviving ship's lanterns than the GGG triangle.

Robert Lucas Chance acquired the British Crown Glass Company's Spon Lane works in 1822. After the earlier partnership ended, the business became Chance Brothers and Company in 1836, and lighthouse optics became an important part of its work around the middle of the nineteenth century. (Chance Brothers history)

The company also supplied lenses for ships' lights. On a surviving lens, read the whole inscription rather than simply noting “Chance”: the wording “and Company” or “Limited” can help place a mark within the firm's history, provided it is compared with dated examples.

The later company history is not a simple change of name at the original works. After the Smethwick factory closed in 1981, remaining glass-tube processing moved to Malvern; the operation became independently owned as Chance Glass Limited in 1992.

Look for engraved or scratched numbers as well as moulded names. Some are inspection or approval marks, distinct from the glassmaker's identification. Their meaning depends on the country, the approval system and the way the number is applied.

German collectors use the word “Ritzung” for a scratched inscription. A faint number of this kind is easily overlooked, particularly when it lies against a rib or close to the frame, and aggressive cleaning or polishing can damage it.

German approval registers show that the glass or plastic lens belt could have an approval number separate from that of the complete lantern. In a combined lantern, individual glass sections could also have separate approvals. Several different numbers on one lamp need not therefore mean that its parts were assembled at random.

Not every number is an approval mark, however. A mould number, production code or later owner's marking must be distinguished from an official inspection inscription. For the national systems and examples, see Identifying a Ship's Lamp.

The burner and oil reservoir are often missing from a surviving ship's lantern. When they remain, their construction, size and markings can be as useful as the details of the housing. A replacement burner may fit physically without being the pattern originally supplied.

Three names recur in the marine catalogues and collectors' literature used for this guide:

These names should not be treated as three manufacturers. More than one firm supplied burners of the relevant patterns, and a catalogue description of the regulation a lantern met does not establish its country of manufacture.

Cosmos and Kosmos

“Kosmos” is the familiar German name for a widely manufactured burner design, used in domestic and workshop lamps as well as aboard ship. Its flat wick is formed into a hollow circle at the top of the wick tube, producing a circular flame.

German approval material for paraffin navigation lanterns and collectors' reports refer to ordinary Kosmos burners of specified sizes. The design and size help identify the component, but neither establishes who made it.

American catalogues also record a marine burner sold as “Cosmos” by Plume and Atwood of Waterbury, Connecticut. The spelling and trade description should be recorded exactly: a shared name is not sufficient evidence that every burner sold under it had identical construction.

American catalogue descriptions associate the Glass Cone burner with English-regulation lanterns and a Cosmos burner and chimney with Norwegian-regulation lanterns. One entry even offers a lantern by special order with a Norwegian top and a German burner. Such combinations are useful evidence of the way lanterns were supplied for different markets.

Vortex occurs as an American marine-burner designation. As with the other names, comparison should include the wick arrangement, gallery, reservoir attachment and any stamped marks, rather than the name alone.

The collectors' literature also mentions Barton porcelain burners, Sherwoods, the Wedge burner, Luchaire of Paris and the “brûleur papillon”. These names remain part of the research record, but have not all been checked against marked objects or original manufacturers' catalogues.

British and Norwegian marine specifications discussed in the sources required a lantern to continue burning if its outer glass, lens or globe broke. A flame that depended entirely on the enclosure for its draught could fail when that glass was damaged.

An independent chimney around the burner helped maintain the air path to the flame. It was a working part of the lighting system, not redundant glass inside a second glass enclosure.

This should not be taken to mean that a Kosmos burner normally worked without a chimney ashore. The chimney's profile helps direct the draught on domestic Kosmos lamps as well, and the appropriate chimney belongs with the burner in either setting. 

Ventilation of the housing presented a separate problem. British surveyors inspecting lanterns from 1849 identified poor ventilation as a principal cause of unsatisfactory burning. French technical literature of the 1860s discusses indirect air supplies and hemispherical chimney tops perforated around the base, features worth looking for on a lantern of the period.

The inner glass chimney and the ventilated metal top serve different parts of the system. Both need to be considered when examining an incomplete lantern.

Vaclite was a waxy lighting fuel marketed in the United States in the early twentieth century by the Vacuum Oil Company of Rochester, New York. Its attraction aboard ship was its consistency when cold: it was less liable to spill than liquid oil when a lamp was upset or the vessel rolled.

The company's 1917 publication, The Light of the Seven Seas: The Story of Vaclite, describes the fuel as solid in its unheated state and explains that it required a specially constructed burner. An ordinary oil burner was not sufficient.

The associated burner was called the Minot. Arms extending over the flame conducted heat down towards the fuel, softening it so that it could continue feeding the wick. Those arms are an important feature to look for when identifying a surviving burner.

Lanterns can carry “Vaclite” on the globe or on the body. The word names the fuel, not the manufacturer of the lantern. Perkins Marine Lamp Corporation examples are recorded in the source material for the period 1916–1924.

The bodies were commonly made of coated or galvanised steel rather than brass. Railway-pattern lanterns were also used, their broad, stable form being suited to standing on a deck.

The intended market included the United States Navy and civilian marine users. In civilian service, a specialised lighting fuel had a disadvantage beside kerosene or signal oil, which could also be used for other purposes aboard ship. The account assembled for this guide describes Vaclite as a limited commercial success rather than a widely adopted replacement.

For the wider changes in marine fuels and light sources, see From Oil to Electricity.

The metal housing can help identify a lantern's intended market, but it needs to be read alongside the burner, glass, marks and catalogue description. British and Norwegian requirements cited in the source material specified galvanised steel or copper for certain masthead and anchor lanterns.

Those specifications should not be extended to every British or Norwegian marine lamp of every period. A brass housing is not, by itself, evidence that a lantern is decorative or a reproduction.

After the spread of kerosene in the nineteenth century, round-globed lanterns were made in brass, copper and combinations of the two. Copper and brass do not develop iron rust, although both can corrode. Zinc and zinc coatings also weather and corrode; surviving paint should be examined as part of the lantern's finish, not dismissed simply because the underlying metal can be polished.

For surviving paint and later alterations, see Painted Ship's Lamps.

Some earlier lanterns, including examples made before about 1890, have elaborate tops and decorative castings on handles and hinges. Plainer galvanised-steel models appear in late nineteenth-century catalogues as less expensive alternatives. Ornament and plainness are useful details to compare, but neither gives a date on its own.

Several fittings that can look incidental were part of the lantern's working arrangement. Their position and construction can be useful when the nameplate or burner is missing.

The Sidelight Screen

The inboard screen prevented a sidelight from showing the wrong colour across the bow. The French decree of 1858 specified a screen projecting 0.90 metres ahead of the light; the 1948 rules specified at least three feet. It formed part of the installation and need not have been contained within the loose lantern itself.

A surviving sidelight without its original screen may therefore be only part of the equipment fitted aboard ship. The function and sectors are explained under Types of Navigation Light.

The Guard

The bars around the glass protected an all-round lantern during handling and against contact with rigging or other equipment. This mattered on a lamp that was repeatedly hoisted and lowered on a line, as well as one carried or set down on deck.

The Gimbal

A gimbal allowed the lantern to remain upright as the vessel heeled. Sautter's 1858 price list offered gimballed mountings as an option, providing a contemporary reference for this fitting rather than merely a later collector's description. 

The Internal Wire Cage

A fine wire-gauze enclosure around the flame should not be confused with the external guard around the glass. Its purpose was to act as a flame trap, following the principle used in a miner's safety lamp, rather than to protect the lens from impact.

The bibliography includes regulations, manufacturers' publications and collectors' reference works. Online references are linked beside the relevant passages.

Primary Sources

• United States federal ship-lighting regulations, 1910.
• French decree on ships' lights, 28 May 1858, reproduced in L. Sautter & Cie, Phares et fanaux lenticulaires, Paris, 1858, pp. XIX–XX.
• Regulations for Preventing Collisions at Sea, 10 June 1948, including rule 2(a)(vi), published in the British Treaty Series in 1954.
• L. Sautter & Cie, Phares et fanaux lenticulaires, Paris, 1858, price list.
• Mémoire sur l'éclairage et le balisage des côtes de France, 1864.
• Vacuum Oil Company, The Light of the Seven Seas: The Story of Vaclite, New York, 1917.
• Bundesamt für Seeschifffahrt und Hydrographie, BSH-Zulassungen bis 31.12.1998, See.

Secondary Sources

• A. Hobson, Lanterns That Lit Our World, Book 2, section II.
• B. Mahot, Les lanternes, phares et fanaux.
• R. Bahr, MPhil thesis, University of St Andrews, 1998.
• Pryor, Evolution of Seacoast Navigation Lights, NOAA, for the six orders.
• German collectors' reports on the Pelam forum, 2020 and 2022.
• Reference works on the Fresnel lens and Chance Brothers, supplemented by the National Park Service's account of the Fresnel lens, the French Ministry of Culture's account of Cordouan's first lens, the U.S. Lighthouse Society's lens-order table, and Chance Glass's company history.
• Alfred Genthe biography and glassonweb's Genthe Glas directory entry.
• The Kosmos Burner, Artoluys, and Miles Stair's Kosmos burner reference.
• US Coast Guard, International and US Inland Navigation Rules, for Rule 21 and Annex I; the international and inland provisions are distinguished on the page.