Lydney Harbour Light
Since the lantern of the light was completely symmetrical, the reason for the rotating mechanism was not immediately clear but I surmised that it might have acted as a form of warning light with the lantern head shuttered and rotating like those in conventional lighthouses. Thanks to a lead provided by my friend Mike Peet, I have since discovered that this was indeed the case.
The light appears to have been manufactured by William Sugg Ltd. of Westminster who provided gas lighting for many of the most famous locations in London and whose columns can still be seen today. On the excellent site dedicated to the history of theWilliam Sugg Co. there is a section related to the Lydney Harbour light.
Lydney Harbour Light, William Sugg archive image
This image, taken from the their web site, shows the light partially blacked out. I presume, from the location of the ladder that this was the landwards section and that the light flashed out to sea.
Lydney Harbour Light archive image
In this more modern image from the William Sugg & Co. site, the lantern is quite different. It appears from the close up (below) to have been converted to electricity using overhead conductors; risky for the those climbing the ladder!. Also, at this unknown date, the column does not have a rotating lantern and is not blacked out.
Lydney Harbour Light close up archive image
This section of the Severn Estuary can be difficult to navigate with very strong tides and shifting sand banks. Although narrowboats do pass this way with the aid of a pilot, this section of the estuary has had disastrous accidents, most notably the accident that destroyed the Severn Railway Bridge just a few miles upstream. That disaster occurred on the night of October 25th 1960, in thick fog, as two petrol barges made their way upstream towards Sharpness Docks. They failed to see the entrance to the docks and collided together as one barge turned to go back. Together they hit the Severn Bridge and exploded destroying the bridge and killing five people. It is chilling to think that the crews would have passed close by the Lydney Harbour light, then working on gas and presumably flashing, as they made their way upstream; the navigation channel is close to the "Welsh" shore. I presume the reported manual gong was also in use since that fateful night several of the boats that left Avonmouth were bound for Lydney Harbour carrying wood and would have required guidance to enter the harbour.
The site of the Severn Railway Bridge in 2011
Taken from the Gloucester & Sharpness Canal showing a model of the swing section over the canal