That is way cool! So indeed, the old ones don't need mercury to be viewed??

I've attached a picture from 'Handbook of Photography in Colours'; did it resemble this at all?

I have to admit that I pondered breaking open thermometers and making a mercury holder, BUT then "sense" kicked in, and the mercuric chloride thread, and that seemed to cure that itch. I think it would be a terrible idea...

Something else that confuses me, if mercury is a powerful sensitizing agent, as in astro-photography hyper-sensitization, and also a powerful fogging agent, how come it doesn't adversely affect the Lippmann emulsion?

Sorry, lots of questions, but you've got me excited!