I don't think the lights were electric. They were GAS LAMPS which had been around since the 1840's if not before. These lamps were lit each night by a care taker. I don't remember if they had them back in the 1860's but some of the gas lights had a wire screen that was coated with a substance that glowed white when exposed to a hot flame (sort of like the Colman lanterns used by campers today).
Hack Ace is right, the lights in that scene are probably the gas lamps which were used in that time. Actually, electric lights were patented as early as 1878; about 15 years after the movie takes place, not 80 years.
The incandescent light bulb was patented around 1820. The problem was not the bulb, just the filament. It would burn out after afew seconds of use. Electric lightng and batteries have been around for nearly 2500 years. Obviously, they were confined to pagan temples and used as trickery and novelties.