I had worried that once Brox's story got to the invention of the electric light bulb, things would become rather more plain sailing, and the story a little boring. But no. When we consider the electric light bulb, romantic notions we might have had about candles or lamps will be tested. I had once, in a mood of wistful primitivism, entertained the idea of using an oil lamp to read by, but now I know how dangerous they are, and how much of an immense faff it is to clean them, I have dropped the notion for ever. And candles aren't what they used to be: they're much, much better, and for most of their life most were difficult to make, and stank. The upside was that if, like the builders of the first Eddystone lighthouse, you got trapped for days in a storm, you could eat them.