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Deck Lights Gallery
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Deck lights come in six basic styles: bull's-eye, round prismatic, hexagonal pyramid ("pointed" or "spike"), reamer ("melon"), ribbed ("reeded") and a several styles of rectangular prism.

Bull's-Eye

Bull's-eye lenses (flat on one side, convex on the other) are the oldest style, pre-dating prismatic shapes. When used in a deck light, the flat surface would be flush with the deck and the curved lens hung below, diffusing the light. They are not to be confused with the bull's-eye at the center of crown window glass, which is too thin to be load-bearing and has no desirable optical properties. I have no examples of original bull's-eye deck lights, alas.

Bull's-eye lantern
Bull's-eye lantern
Youth's Companion, 1891
Smith & Lovett coal-hole cover with bull's-eye lenses
Smith & Lovett 14" coal cover:
Bull's-eye lenses w/protecting knobs
Bull's-eye deck light
6" Bull's-eye deck light
Classic Marine #107
Bull's-eye deck light
Replacement bull's-eye lens
Davey & Co via TOPLICHT GmbH

Apsley Pellat's 1807 British patent "Lighting the Interior of Ships, Buildings, &c." uses a bull's eye lens curved-side up: "This illuminator is a piece of solid glass of a circular or elliptical form at the base, but the circular form is the most productive of light, and the strongest against accident; it is convex on the side to be presented outwards to receive and condense the rays of light, and has a flat or plane surface on the inside of the room or apartment, which it is intended to light."

Earlier patents (Wyndus 1684, Cole 1704) do not give any detail about the shape of the glasses used. Thaddeus Hyatt's famous 1845 patent ("Vault Cover"), the basis of the "Hyatt Lights" which made his fortune, used small bull's-eyes: "I prefer to make my illuminating glasses circular, and convex on one side".

Davey & Company still makes bull's-eye deck lights with 6" and 8" lenses; see their Deck Hardware catalog.


Shown below is Henry Lanergan's modified bull's-eye lens of 1861 (Patent No. 31,247) which features threaded sides and a protruding octagonal boss, allowing damaged lenses to be quickly replaced by simply unscrewing the old lens and screwing in a new one. The smaller Lanergan shown below (3" diameter, 2" thick) is heavily worn on the working surface and was presumably removed from service and replaced. The larger lens (4" diameter, 2" thick) is only lightly worn and still perfectly useable. Lenses cost $0.60 for 3" and $0.70 for 4" in 1862 (Annual report of the Secretary of the Navy), but a set of tools to replace them was $275 (United States Congressional serial set, Volume 1221, 1865)!

3" Lanergan's deck light (bottoms)
3" Lanergan's deck light (tops)
Lanergan's patent deck light
3" Lanergan's deck light (threaded side)
3" Lanergan's deck light (embossing, large) 3" Lanergan's deck light (embossing, small)

LANERGAN'S DECKLIGHT.
For lighting the saloons of vessels below the deck it is customary to cut small openings through the deck and fill them with blocks of glass. When inserted in the deck of a vessel it has been held in place by cement or by means of a frame of metal screwed to the deck and arranged so as to lap over the edges of the decklight. Breakage of a decklight is a very common occurrence on shipboard, and beside, when the decklight is fixed in place by means of putty or cement the latter is likely to become either loosened or cracked. Lanergan's Decklight The consequence of either breakage of the decklight or loosening of the cement is leakage of water through the deck whenever it is washed. Furthermore, the securing of a decklight into the deck by means of putty or a metallic frame, or both, is a matter of much trouble and care. All these evils are overcome most completely by the simple device illustrated by the accompanying engraving.
A circular block of glass has a thread formed upon it in the mold so that it can be screwed into the plank of the deck. Above the thread the block is enlarged and left in the form of a smooth cylinder, to fill the hole perfectly and make a tight, smooth joint. Below the screw the glass is made hemispherical or convex, to disperse the light and diffuse it in the room beneath. At the lower end of the block is a polygonal projection, e, to fit a wrench for turning the screw into place. In case the block should become loose, from the shrinking of the deck plank, it is easily tightened by giving it an additional turn. In place of the polygonal projection, recesses may be formed in the block to receive projections on the wrench; but this plan is objectionable, as the recesses interfere with the dispersion of the light, and the glass about them is liable to crack.
We are informed that this decklight is meeting with the universal approval of mariners and ship builders, and that it is regarded as a more important improvement than, from its simplicity, it might at first sight appear to be.
The patent for this invention was granted to the inventor, Henry Lanergan, Jan. 29, 1861, and further information in relation to it may be obtained by addressing Charles Smith* (to whom it has been assigned) at No. 6 Central Wharf, Boston, Mass.
Scientific American: N.S. Vol.5, No.1, July 6, 1861
*"Smith Charles, commission merchant, 6 Central Wharf, house 15 Chambers" —The Boston Directory, 1859

Round Prismatic
This is my only example of an original round prismatic deck light. It has a Fresnel look to it, but the prisms on the lower side are triangular in cross-section and all the same profile. There's a bull's eye at the center. Overall diameter is 9½" and it's the usual ¾" thick, so a bit larger than the largest currently made which is 8" in diameter. There's no wear on the top surface (still smooth and shiny) so it must have been installed somewhere with no traffic.
Round prismatic deck (top) Round prismatic deck (closeup of prisms) Round prismatic deck (bottom)
Top view Closeup of prisms and bull's-eye center Bottom view
Luxfer deck prisms What is that unusual flat round deck light at the top left of this group of Luxfer-Prismen-Gesellschaft schiffsprismen? Are those 66 small bull's-eyes on the bottom surface?? It's shown in Anzeiger zum Zentralblatt der Bauverwaltung No. 8 from 1925 (Digitale Landesbibliothek Berlin) but nowhere else I've seen.

Hexagonal Pyramid aka "Pointed" or "Spike"

Pyramids usually in two nominal sizes, 3" and 4" (measured across the flats), although Thomas Laughlin Co. lists them in 3½" and 4½". This style has been reproduced in vast numbers, mostly copying the lone surviving original prism on the 1840s whaler Charles W. Morgan, now at Mystic Seaport Museum.

My originals (shown below) all have sharp base edges and are somewhat crude, unlike the modern reproductions which have smooth, rounded base edges and are of uniformly higher production quality. Reproductions come in many beautiful but unauthentic colors which would be useless for anything except mood lighting.

3" hex pyramid deck prism 3" hex pyramid deck prism 3" hex pyramid deck prism 3" hex pyramid deck prism 3" hex pyramid deck prism 3" hex pyramid deck prism
W: 3 1/8"; H: 3½"; B: 1 1/8" W: 3 1/8"; H: 3½"; B: 1" W: 3 1/8"; H: ~3¼"; B: ¾"

Hexagonal deck prism (Tiebout catalog) Hexagonal deck prism (Durkee catalog) Hexagonal deck prism (Durkee catalog)
Hexagonal deck prism (Durkee catalog)
Hexagonal deck prism (Thomas Laughlin catalog)

Triple-Spike Deck Prism Triple-Spike Deck Prism Triple-Spike Deck Prism
Bezel: 14¼" × 6½" × 1½"; prisms 3 7/8" across the flats × 4" high

Single-Spike Deck Prism Single-Spike Deck Prism Single-Spike Deck Prism
Bezel: About 57/8" across the flats × 1½" deep; prism 37/8" across the flats × about 4¼" hiigh

Single-Spike Deck Prism bezel Single-Spike Deck Prism bezel
Bezel: Outside: 6½" across the flats × 1¾" deep
Inside: 4½" × 19/16" deep
New Old Stock.

Reamer aka "Melon"

This style prism looks like an orange juicer, aka reamer, but is styled "melon" by its makers. I don't know the design's origins; it's not shown in any of my catalogs, nor do I know of a patent which covers it. My larger example has a yellow tint that looks to be caused by selenium, the decolorizer which replaced manganese around WWI. Like manganese, which turns pink/purple after prolonged UV exposure (solarizing), selenium also changes color, turning "straw", a light yellow. Selenium was used mainly post-war, around 1920-1930, with usage tapering off by mid-century.

The Mother of All Reamers below is 7¾" in diameter, 5" high and weights 10¼#. This is much larger than the typical units which are 3 - 4" in diameter. It was reported to have been retrieved from the bottom of the Baltic. Is it Russian? There are no markings.

Reamers in a variety of sizes and depths are still made today by Davey & Company and Marine Skylights, but nobody is making them this large.

7¾" reamer-style deck prism 7¾" reamer-style deck prism 7¾" reamer-style deck prism

This purple reamer is about the same height, but 6¼" in diameter and 5½# (without the original bronze bezel), which is still large for this style, but much smaller than the Mother. It has no provenance and no markings. Because of its purple color, we can assume it's pre-WWI.
6¼" reamer-style deck prism 6¼" reamer-style deck prism 6¼" reamer-style deck prism

Size comparison:
Comparison of 7¾" and 6¼" reamer-style deck prisms


6" Melon deck prism w/bull's-eye 6" Melon deck prism w/bull's-eye 6" Melon deck prism w/bull's-eye
Melon variant with bull's-eye (6" wide, 5" tall). Photos: humbleseabird (eBay)

Rectangular Prism
Rectangular deck prism
Rectangular deck prism
Rectangular deck prism
Stepped-pyramid style deck prism
Stepped-pyramid style deck prism
Stepped-pyramid style deck prism
Typical design, still made today Unusual step-pyramid pattern

Ribbed or Reeded
This style appears in three of my early marine hardware catalogs (Durkee, Laughlin and Tiebout) dating from 1915 to 1920. They all list the same set of sizes, 6"×3", 9½"×2½", 10"×3", 10½"×3½" and 12"×4", and the illustrations are very similar. Were they all selling the same manufacturer's products? I haven't seen any original examples in situ, but Capt. Dan Berg recovered the one at right from the wreck of the Cornelia Soule, a three-master schooner which ran aground in 1902. Reeded deck prism recovered from the wreck of the Cornelia Soule
Capt. Dan Berg holding reeded deck light from the wreck of the Cornelia Soule.
Ribbed deck prism (Durkee catalog)
Durkee
Ribbed deck prism (Laughlin catalog)
Laughlin
Ribbed deck prism (Tiebout catalog)
Tiebout