This one is for the lens experts.

Ok, we know that there is the order of the lenses, from 1st to 6th. Then there are the various styles of lenses. Some styles come in more than one order, i.e. a photo posted recently by Gary Martin of Bodie Island's first order lens looks very much like the HL 4th order lens. Perhaps only the higer order lenses came in diferent styles? So...my question is how many different combinations of lenses are/were there?

Wow, there's a tough question...

I'm not sure that anyone could answer that. Tom Tag or Jim Dunlap or Tom Taylor might be able to come up with some sort of number, but we'd have to get into more specifics.

There's the "classical" lens, the "clamshell" type, and various combinations thereof (e.g., Race Rock's old fourth order half classical/half clamshell)...

Within the classical, there are fixed, flashing, and combinations thereof (e.g., the extremely odd fourth order lens on display at Fire Island)...

And then there are the various manufacturers and countries of origin (mostly, France, Britain, and the US)...

And different types of glass and frame materials...

And the different numbers of panels within the orders...

All within the framework of the seven common orders (don't forget the 3 1/2) and even the hyperradial.

Some of the combo lenses were done post-manufacture (again, the Fire Island display lens, which combines French BBT fixed panels with American MacBeth-Evans flashing panels), so they may not have even been recorded.

Now that I think about it, I'm not even sure that Tom Tag could venture a number (do I lose my Tom Tag Fan Club membership, complete with "Tom is God" T-shirt, for that?).

If anyone does find a verifiable number, I will throw myself shamelessly at their feet. :-)

Dang, I love Fresnel lenses. It truly is a sickness.

Bob is right...impossible to count...

Wow, I guess I really didn't mean to be quite that specific! If we discount the more or less one of a kind lenses and didn't get picky about glass color, panel numbers or materials and such it would probably be easier. Was there much difference in similar lenses made by more than one manufacturer? As far as flashing or fixed, isn't that mostly a function of the light rather than the lens?

So I guess if we started with 7 for the number of orders and counted only the more common, mostly similar styles it might be easier to come up with a number?

Flashing could possibly account for the most variations in lenses - a non flashing light (a fixed display) would be the traditional beehive design. A flashing light would incorporate one or more bullseyes into the lens. The number of flashes might be determined by the number of bullseyes and/or the speed with which the light revolved.

The HL 4th order lens is modeled after one at the USCG's ANT school at Yorktown, VA.



There are 12 bullseyes. If the lens makes one full rotation per minute, there would be 12 flashes per minute or 1 flash every 5 seconds. If it look 2 minutes to make a full revolution, there would be 12 flashes every 2 minutes, or 1 flash every 10 seconds. If there is one, or two, or however many bulseyes, there would be a flash each time the bullseye passed a given point and focused the light to appear as a "flash" to someone observing the light.

This could get real confusing and real deep before it is done!

Dave

Did these fresnel makers every put out 'catalogs' of their offerings? Or was each lens made to order by the appropriate government agency?

In my various readings, I seem to recall that lights were ordered by size and flash. Those two parameters would have been set by the appropriate lighthouse authority, making each light made to order. Another point of trivia that has stuck with me comes from a visit to Ken Black's museum in Maine: not only were the lenses all made to order, each one was so unique that each screw was hand tapped. You have to put the screw back into the exact hole that it came from for the threads to match. Talk about a potential nightmare if you managed to mix 'em up!

So maybe we should just forget trying to answer my question. Just reading the replies is quite educational!

No, Sue, this is the kind of question that needs to be asked, as every one of us will learn some fom the discussions and answers. I was hoping a few more folks might weigh in on the topic.

Nice additions to the conversation, Dave.

I believe the screw threads were specific to each manufacturer. When the old Little Gull Island 2nd order lens (the rarest imported order) was reassembled, the volunteers found that the threads were not standard. The solution? They drilled them out and replaced them with phillips head hardware. The phillips head design, BTW, was not invented until the 1930s by an Oregon man. So their presence on a 19th century French lens is, if I may use the term, blasphemous. This sort of thing underscores the need for the public to watch nonprofits and the projects they undertake. This rare artifact was irreversibly damaged. But I have digressed...

To answer John's question, I am aware of a catalog made by the Chance Brothers (British lens manufacturers). I have a reproduction of it, with some pricing, in my files somewhere. I believe they may sell these reproduction catalogs at the Horton Point lighthouse.

Also, regarding flash frequency: In addition to the lens construction, the rotation rate of the clockworks could be varied. A lens with any number of panels could be rotated at different speeds, depending upon the needed characteristic. That still applies. A couple of years ago, Horton Point's FA251 optic's rotating mechanism burned out. The local CG ATON guys did not have the same mechanism, but did have one that rotated twice as fast. So they replaced half the flashing panels with black panels, giving the same characteristic as the old mechanism with all the panels. Follow me?

This is fun stuff. :-)

And VERY EDUCATIONAL!

I've done some research on the web and through the USLHS. There's an article in the MAY edition of HARBOUR NEWS, the bimonthly newsletter of the North Georgia Beacon Brigade - here's a link to the website
http://www.ngbb.org/

Go to the NEWSLETTER page and the May edition. There are some pictures showing a few variations, including a Portuguese lens with a special panel used as an aerobeacon.
Anne

I believe that Ken Black of the Shore Village Musuem in Maine could probably "shed some light" on this topic.