Tom, Welcome to Lighthousing.net.
For those of you who may be unaware of Tom’s work, please allow me to introduce him to the group.
Tom is without a doubt the foremost authority on the technological history of lighthouse illumination in the US, an active member of the Optical Working Group of the World Lighthouse Society, and serves as Technical Advisor to the United States Lighthouse Society. He has written three insigtful books on the histories of Little Sable Point, Big Sable Point, and the White River lighthouses, along with numerous technical papers. Tom and his wife Phyllis have also researched and colated the premier database of Great Lakes lighthouse keepers, which they have graced me with their permission to incude on my website Seeing The Light.
As he indicated in his posting, we corresponded on this subject of these small lenses over the past 24 hours, and here are Tom's comments from that email:
The 7th and 8th order lenses were used mostly in Scotland and Canada. They were also known as Steamer lenses.
They were used in buoys and in small harbor beacons. They were cut glass - not pressed and were made by Chance
Brothers and others. There were 2 sizes for the 7th order 140 mm focal and 100 mm focal. The 8th order was 75 mm focal.
Below, you will find three of Tom’s photos of such lenses. The first two are 7th order examples, and the third is of the 8th order.
