Glass jewels in a precision regulator?

[TJ Cornish]

I purchased a bucket list clock - an astronomical regulator. This clock is interesting in that it is jeweled throughout the movement, not just pallet jewels.

I’m just getting into the movement, and several of the jewels have been replaced with brass bushings over the years. I’m sure the clock is fine as is, and I could replace the non-original bushings with Butter bearings which would far exceed the performance of jewels, but I’m exploring trying to bring the movement back to as close to original condition as I can.

Thanks to some kind people in the original thread, this clock dates to somewhere around 1830. The jewels in this clock range in outside diameter from slightly less than 1/2” to a full inch in diameter, and they’re about .200” thick. I’m in the process of getting an estimate for these jewels to be manufactured, but I’m expecting to fall off my chair at the price, especially considering I need 6 jewels.

A couple questions- these jewels are huge. They are also clear. I don’t have a good way to gauge hardness. Could these possibly have been glass? Could a small maker in France in 1830 have sourced sapphires this big? Would I be a horrible human being if I re-retrofitted the previously retrofitted brass jewel replacements with Butterbearings?

Thanks in advance!

 

[tok-tokkie]

Here is a description of how to make your own jewels (except he uses agate):

Making your own clock jewel - SNClocks

Putting on my thinking cap, I quickly guessed that someone probably did not insert the jewel into the original brass plug, instead someone probably replaced the other jewel at some point when it was broken. Of course this is just a theory. Perhaps there was a rather bored jeweler somewhere that...

www.snclocks.com