Following on from the references to lighhouses, some people may be interested to see: http://www.uklighthouse.info
which has some info about lighthouse lenses made by the Lighthouse Works, Chance Brothers, Smethwick.
I originally learned of the lighthouse glass connection to the Chance Brothers works after seeing a letter linked to the subject by Alan Taylor, creator of the lighthouse website, in issue 67 (Spring 2004) of The Glass Cone (newsletter of the Glass Association).
[In 2003/ 2004, I had attended an auction in South Wales, in order to buy a very interesting and likely Vasart paperweight. While I was there I visited a nature reserve with a lighthouse in situ and, as I do every so often, I hatched a crazy plan. I intended to start a project of photographing as many UK lighthouses as I could - just for the fun of it :!: :!: But my bird-watching interest eventually displaced that idea since it provided me with plenty of fresh air and exercise without having to travel quite so far or to get caught out by dangerous tides, cliffs and so forth.]