The above link is a link to “flickr” on their if you scroll down their is a very short video of this item in situ , Is a bit clearer the view of the bottle. I have just checked the book for the trial it claims the mining inspector came out 1879 and said no progress had been made and it doubts it will be unless it Is made deeper . It certainly was not made deeper but it could of been carried in later by some 1 prospecting ?
I agree with TOR about the bottle age - I found a very similar one some years back while helping excavate the fill in a lime kiln, and googling showed it to be early 20th century. I think it's a "potions and lotions" type of bottle (mine was for some herbal concoction called Mason's Elixir), and candle holder is my best guess too.
A candle would get blown out is waved about or in draughts and the bottle doesn't look like a candle would burn inside. Surely it'd need to be some sort of lamp and stick to test for CO2 rather than bottle? (or a stick with a lump on the end for carrying a lamp, like a deputy stick)
Stating the obvious, it looks like a small bottle on a stick (assuming the bottle is supposed to live there).
Why would someone want that?
Collecting a liquid sample from a hard to reach location, maybe collecting seepage from somewhere?
Pouring a small quantity of liquid on a hard to reach location
Pouring a small quantity of powder on a hard to reach location
If it's a prospect, it has to be something to do with sampling?
I am wondering if the bottle contained something that a small 'dab' was required for some operation from time to time. I work on my electronics and use flux that comes in bottles with the H and S politically correct difficult to unscrew top. I have a small bottle stuck down in a small plastic tray with silicone so as not to tip over and keep so much flux in it which I use with a 'stick'. actually a piece of cable tie.
Obviously the rail was for portability combined with stability, so it could be leaned up against the side of a level in a cranny or whatever without being easily upset. I think that if it was for pouring something into a difficult to reach location, then timber would have been better than heavy rail.