Deck Prism Recovered from Iberia Wreck

[wreckvalle]

I ran a winter charter to the wreck of the Iberia this morning (2-17-08). Had to break through some ice in the creek on the way out and deal with 2-4' seas and only 5' vis but Capt. Ed Slater recovered this intact deck prism. One of my customers Rob Urban came up with an intact wine bottle.

Safe diving
Capt. Dan Berg
www.shipwreckexpo.com

 

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[TidePool]

What is a deck prism?

From Glassian.org-

A deck prism is a prismatic glass set into a ship's deck, to let natural light below. They are especially useful when an open flame would be hazardous, such as with a cargo of coal or gunpowder. On colliers (coal ships), prisms were also used to spy on the cargo hold; light from a fire would be collected by the prism and be make visible on the deck¹ even in daylight.

In normal usage, The prism hangs below the ceiling and disperses the light sideways; the top is flat and installed flush with the deck, becoming part of the deck. A plain flat glass would just form a single bright spot below-- not very useful general illumination-- hence the prismatic shape.

The names "deck light" and "dead light" or "deadlight" are sometimes used, though the latter seems to be uncommon as a reference to prisms, as more often refers to plain-glass panels.

The earliest deck prisms with provenance are from the 1840s. Presumably they were used earlier, but how much earlier is unknown; the origin of the idea is lost, and glass is difficult to date. Very few original specimens remain. The Charles W. Morgan (1841), last surviving American wooden whaler and National Historic Landmark, had a single deck prism left. This ship has now been restored and is residing at Mystic Seaport. The original deck prism has been reproduced and is widely available.

This idea was later borrowed for use in urban sidewalks, to light underground spaces. In that application, they are called "vault lights" or "sidewalk lights". Model Shipways makes a model of the Charles W. Morgan that includes 21 tiny deck prisms!

Deck prisms are alive and well today. They are still being made, some in the original form (or close to it), and some in a newer tank-periscope-like rectangular design.

 

[PhipsFolly]

What a fantastic and rather rare find! Nice work and in those weather and water conditions... more power to you guys!!!!!!!! Phips

 

[diverlynn]

wreckvalle
That is a great find and thats is a very pretty stone! Would make a cool necklace....

Diverlynn

 

[Copperhead]

A really cool and interesting find...'course I didn't know what it was either till TidePool explained it..
I learn something new everyday here....sounds like some hardcore diving wreckvalle..but worth the reward
Congrats..

 

[bradyboy]

That is so.......... very cool - Ive never heard of one but sure makes sense.
Congrats on your find.
Whats your guess on value?
What is the prisim made of?

 

[wreckvalle]

That is so.......... very cool - Ive never heard of one but sure makes sense.
Congrats on your find.
Whats your guess on value?
What is the prisim made of?

Unfortunetely, I did not find the Iberia deck prism today. My good friend Capt. Ed Slater recovered the artifact. Only thing I got today was cold!! They are not a common artifact. After over 20 years I found just one a few years back on the Frank Buck wreck. (See attached photo). Im on the right. Its not the best image but deck prism is small octogon shapped. (Other artifacts are dead eyes). Anyway, I think the prisms are made of glass.

Safe Diving
Capt. Dan Berg
www.shipwreckexpo.com