This has been in my curiosity bin for more than a few years.
It is a ceiling fixture taken from relatively new construction (at the time) and the primary complaint was a burnt out bulb.
The bulbs were small base 25 watt candelabra style and a new replacement bulb also would not light up.
So we detached the fixture from the ceiling and the high resolution image explains why the bulb was kaput.
The picture does not do full justice to the cracked brittle wire that was the source of the scorch marks on the metal base and yellow insulation. This was a relatively new fixture, not something left over from the 19th century.
Of course, there was no solution other than to find a replacement fixture and throw this one into the curiosity bin.
While not an everyday occurrence (not for me at least) this stuff does happen intermittently.