CAOperator:

I saw one of those fixtures you mention mouted SIDEWAYS on a sidewalk shed once (the sidewalk shed is used to protect passersby from falling material when the walls of a building are being worked on.

Anyway, I saw the lightbulb was turned on, and it was half submerged in a pool of WATER!!!

The water had filled that glass jar - probably as it trickled down the side of the fixture and seeped in between the edge of the glass and the gasket.

The top of the water was like 1/2 inch away from the edge of the lampholder!!!! [Linked Image]