Everywhere in Europe, until roughly 1830

The references are everywhere once you look for them, and invisible until you do. Chaucer has a character go back to bed after her firste sleep. A physician recommends conception in the interval, when both parties have rested and have more enjoyment and do it better. A prayer manual supplies devotions specifically for the waking. A court deposition fixes the time of an assault as being after first sleep, and nobody in the room asks what that means.

Sleep came in two. You went down at nightfall, rose around midnight for an hour or two, and went down again until dawn. The interval was not insomnia. It was a room in the night that everybody had furniture in — prayer, sex, tending the fire, visiting a neighbour, interpreting the dream you had just surfaced from, which was still warm.

Then gas, then electricity, and the evening extends, and bedtime slides later, and the eight-hour block is invented by pressure rather than by decision. Within about eighty years the second sleep is gone and the vocabulary for it is gone with it.

It goes so completely that when people continue to wake at two in the morning — which a great many do, in a body that has not been consulted — there is no longer a name for what is happening to them. There is only a disorder, and a prescription, and a sense of personal failure at three a.m.

A tool arrived. A room in the human night was demolished. Nobody voted, nobody mourned, and the people still standing in the demolished room every night are told they are ill.