No hostile weather at time. This is the 3rd time in ten years that it has happend, same fixture subject to vibrations from adjacent stairs. Re: current, the filament does show signs of physical distortion that would indicate high current considering the properties of tungsten. It doesn't make sence but I'm sure the flash seen is from an arc. And Nigel, unless there was a third page in the original discusion, It has not been answered. (If someone wants to talk lead acid stationary batteries, I'm the guy. Charging, step loads, short circuit currents, heat, testing, longevity, etc.)