Typically a lot of fixtures like this one had a "radial wave" or "ruffled" reflector (or shade) upon them. This is a somewhat unusual instance of a street lamp utilizing an open-bottomed glass refractor for the lightbulb's optics. I believe its principle/purpose was so that the light would be distributed evenly around this corner/intersection with a minimum of unwanted light trespass into adjacent windows.

This porcelain-bodied fixture was mounted upon a neat double-bend, ornate bracket with a wrought-iron scroll undersupport.