Another 'whats it" mystery?

[redbeardrelics]

Here are a couple photos of another old glass item I am trying to learn about. This item is solid clear glass,(weighs about 2 pounds), and was recovered from the bottom of the Chesapeake Bay by commercial fishermen. It has an 8 sided raised octagon shape on the top, and embossed on this octagon is " H .....RGAN / JAN 29 / 1861 / PAT'D".
The bottom side is flat, and the edges/sides have raised glass screw threads. It is pretty chipped up and cracked, but would have been about 4 inches in diameter.
At first glance it appears to be a glass lid to a container of some type, but why is it solid and heavy glass?
Maybe it was some part of a ship or boat that allowed light to enter the vessel under the watre level, hence the need for thick solid glass? Maybe part of a secret Confederate or Union submarine?? lol.
A quick check on the internet did not come up with a match for the patent date of Jan 29 1861, but I am not very good at patent searches.
Any ideas?
thanks in advance,
Chris

 

[redbeardrelics]

side view

 

[redbeardrelics]

Bottom view

 

[deepbluedigger]

Could it be a lens, maybe for a maritime light of some kind?

 

[epackage]

The NUT shaped part on the top makes me think it could be turned with a wrench...

 

[RED Matthews]

Hello redbeardrelics; I think your glass item is a light source devise that was used to supply light to a cabin in a ships cabin. I have been to the ship museum on the south coast of Connecticut ( Mystic Seaport ) There - there was a ship named the "Morgan"; where the ships cabin was lighted by a prism glass piece. They had reproduced these glass items, and I bought one at that time. Your piece seems to have a CT (Continuous Thread), which would have permitted it to be screwed up or down into a formed ring or holder to make it possible to seal it from leaking - but allow light to enter the cabin.

I have never seen one like this - but that is what I think it is. RED Matthews

 

[cyberdigger]

I agree with Red M, especially his last line.. [] ..nautical cabin light.. prolly got blown off by enemy cannon..

 

[vivid2012]

ORIGINAL: redbeardrelics

Bottom view

wow, I love it.

 

[Sodasandbeers]

Chris, The patent was number 31,247 by Henry Lanergan of East Cambridge, Massachusetts for a deck light on January 29, 1861. I can send you the description if interested.

 

[GuntherHess]

nice job finding that