As this story begins, most private homes were lit by candle or oil lamp. It wasn’t until the mid-1880's that incandescent bulbs were commercially available. Even then, only a few large American cities had power grids before the 20th century.
During the nights of 1848, homes were filled with fire light. The corners of each room were filled with dark, flickering shadows. The darkness of those nights was inescapable.
Some argue that candle light plays an important role in the human belief in ghosts. There does, at least, appear to be a correlation between the popular decline of the Spiritualist Movement and the rise of incandescent bulbs, lighting the dark corners of households around the country.