Whazzit..

[Ben H]

Ooh, is it a light house diffuser, you know, the thing that creates the narrow beam of light for a lighthouse? If no, I give up.

[Rob Amaral]

It is a glass diffuser of some kind that is inset into the floor with a white-washed box around it to direct light into the cellar..

I know they used things like these in the decks of old ships.. but I've never seen one like this one.. The ones I've seen are octagonal jewel-shaped..

In other words, it's an 'antique light fixture from 1819.."

[resqman]

Oh, it is a 200 yr old Solatube.

[Rob Amaral]

sort of..