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 Deck Prisms 
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Post Deck Prisms
Does anyone know when deck prisms were first used? In the 19th century were they used on naval ships as well as merchant ones?

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susan


Tue Oct 27, 2009 7:25 am
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Post Re: Deck Prisms
susan wrote:
Does anyone know when deck prisms were first used? In the 19th century were they used on naval ships as well as merchant ones?

What a great question Susan! I cannot believe that we don't already have a thread on deck prisms. Another simple piece of technology from the age of wooden ships.

I have a wonderful replica that I purchased at Mystic Seaport, CT when I visited the whaling vessel "Charles W. Morgan." My replica was modeled from a prism from that ship. She made her maiden voyage in 1841 so it, at least, existed then on whalers. My replica is a very pale green but I have noted images on-line of colors that are very dark. I cannot believe that such dark colors would be of any benefit. Could anyone suggest a reason for such dark glass?

I also noted deck prisms when I visited the warship USS Constitution which was launched in 1797.

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Tue Oct 27, 2009 10:11 am
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I was curious about them because I found one on the Falls of Clyde: Deck Prism

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Tue Oct 27, 2009 4:20 pm
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Post Deck Prism
susan wrote:
I was curious about them because I found one on the Falls of Clyde: Deck Prism

Susan, your deck prism seems to be a much simpler design that the one I have. Yours appears to be one flat pane of glass surrounded by a rectangular frame above a hollow chamber leading down to the cabin. It looks like your example could be a much earlier design than the ones I have encountered. Mine seems to be formed in a mold. Here is an image of a deck prism nearly identical to mine Click Here

The dates that deck prisms were used might depend on the design or (as you mentioned in your original post) the types of ships utilizing them.

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Wed Oct 28, 2009 1:32 am
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The earlier type were bullseyes, I think - usually round, of thick ground glass.


Wed Oct 28, 2009 4:09 am
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IONIA wrote:
The earlier type were bullseyes, I think - usually round, of thick ground glass.

Thanks to IONIA's comment about bullseyes, I found some additional images.

If you scroll down, a round bullseye deck prism is illustrated. Just below that is a rectangular prism that looks like the one that Susan referenced. I originally thought that the one from the Falls of Clyde was a flat piece of glass but, after seeing this image, I went back and looked at it again and it appears to be a prism just like the one at the following site. I'm now not so sure which type could be the earliest based on design. Although I suspect that IONIA's comment might be correct. CLICK HERE

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Wed Oct 28, 2009 5:56 pm
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timoneer wrote:
t below that is a rectangular prism that looks like the one that Susan referenced. I originally thought that the one from the Falls of Clyde was a flat piece of glass but, after seeing this image, I went back and looked at it again and it appears to be a prism just like the one at the following site.

Hi Don,

I can confirm that it is a prism, not flat. Sorry that the angle of the photo wasn't the best. I was trying to watch my footing, as the prism is near an open hatch and the deck isn't in the best shape.

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susan


Thu Oct 29, 2009 1:00 pm
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susan wrote:
Hi Don, I can confirm that it is a prism, not flat. Sorry that the angle of the photo wasn't the best. I was trying to watch my footing, as the prism is near an open hatch and the deck isn't in the best shape.

Good morning Susan. I think it was the dirt that threw me as well as the difference in shape from the ones in my experience. Thanks for the confirmation.

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Thu Oct 29, 2009 1:19 pm
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Post Re: Deck Prisms
susan wrote:
Does anyone know when deck prisms were first used? In the 19th century were they used on naval ships as well as merchant ones?

Susan, I did some additional searching on the Internet and found information that there was a British patent granted to Edward Wyndus in 1684. You can click on the patent name on the webpage below but only legal verbiage is present, no image.

The earliest U.S. patent is listed as one granted to E. Rockwell in 1834 (boy, were we late!). Click on the words "drawing page" and an image associated with the patent is available.

I found another webpage that stated glass is difficult to date scientifically so dating prisms taken from old ships might be problematical.

Poking around in Admiralty records might be the only way to connect deck prisms with specific types of ships in the British navy. I have no idea where such information can be gathered for merchant ships.

CLICK HERE

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Don Campbell
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Last edited by timoneer on Wed Nov 04, 2009 6:20 am, edited 2 times in total.



Sat Oct 31, 2009 8:02 am
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Thanks for the additional information, Don. I've been busy this week, so I haven't had the time to really look.

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Sat Oct 31, 2009 8:21 am
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