Anyone know about these lanterns?

[Franklin]

The German translates roughly as 'the candle burns in a cylinder of horn. To increase brightness it was raised, in a draft it was lowered' and that tells the whole story.

So Mike, I'm still a bit confused. Would the horn have been affixed to the lid itself, so that it traveled up and down with the movement of the middle chain? Or would it have been fixed to the base and only the lid moves up and down independently, like taking the top off a jack-o-lantern. Just by looking at it the latter seems more likely, but I can't see that raising the lid would produce that much more light. Maybe if the inside curve of the lid was polished to reflect downward, but I have to imagine that it'd get blackened by soot the moment you lowered it back down again.

Also, would stripping the horn down into sheets even be necessary? Seems to me that horn tends to come in a cylindrical shape rather naturally.