Does anyone know what this is?

Several weeks ago, my youngest dug the bottom half of it out of the dene. He had retrieved the top half a few years ago. They are a perfect match. We are stumped as to its original purpose. it had been holding the bank up by the stream...
Several members of the RWA Northumberland thought it might be an oil lamp cira the late 1890's. I am inclined to agree.
But any and all suggestions welcome. The glass is about an inch thick and there used to be stripes painted on it. There is a metal screw on...