In the part where Rhett and Ashley come home from the KKK meeting and Ashley is wounded, Melanie lifts a lamp to examine the wound. The lamp has an electrical cord on it! The crew obviously knew about this and planned to edit it out, but obviously someone forgot to. Oops!
I have heard of portable natural gas appliances. A lamp would use a rubber hose and connect to the wall on a stepped fitting similar to those gas valves used for supplying the Bunsen burners in science labs. In this case, however, the cord is clearly electrical and an oversight. It really stands out like a sore thumb in the scene.