Comment by ipcress_file

My house once had knob and tube wiring. Over the past 15 years I have replaced most of what I assume is the second-generation cloth-covered wiring (which dates back to the 40s, 50s, and 60s). Every once in a while, I come across the insulators from an older electrical system, but most of the wire that went with those insulators was pulled out long ago. The only remains are short bits of wire that were wrapped around the insulators.