ROMEX Cable

I'm trying to do some research for a paper for a local jr. college in the field of building inspection.

I am looking for historical pictures and history on non-metallic sheathed cable or ROMEX cable.

What was used before Romex, Knob and Tube maybe? Romex is a trade name licensed to General Cable Corporation in 1922. Some of the old cables had insulated wire that were wrapped individually in a paper that was impregnated with a black substance, may be tar or wax, to keep out moisture them marked white or black. Two wires, one black and one white, were rapped together in the same kind of paper wrapping. Be on that, I don't have any information and I don't know where to look.

Anything you can add would be helpful.

Warren -- PS. Sure, enjoy your electrical inspection section

I can't add much, but if I saw such a paper, I'd like to see it address these topics:
---When was the change made from tarred cloth to PVC insulation?
---When was a ground wire first included? How were boxes bonded? Did NEC ever ask that boxes be bonded before the advent of 3-prong plugs?
---When was it required to make the ground wire the same size as the conductors?
---Did the advent of Romex, and the various clamps, have anything to do with boxes becoming larger and, well, "boxier?"

About Romex, from the source itself: http://www.generalcable.com/Assets/AboutUs/RomexAnniversary.pdf

Key dates are mentioned here: http://www.generalcable.com/Sections/About_Us/a_GCCdates.html

You'll find some photos of old cable and more here: http://www.tradeslang.com/

Out of print, but should be available at a library or used from Amazon.com:
Old Electrical Wiring Maintenance and Retrofit by David E. Shapiro

Still in print, I'm not sure how much history is covered here:
Your Old Wiring also by David E. Shapiro

Hope that helps.