Darkness and Sleep

In the comments under Wolf Hall on TV (below), Brit mentions the oppressive darkness - a darkness that has drawn a few complaints (and a little critical birdshot). These are quite unmerited - unlike the 'moody', 'atmospheric' darkness of many a modern police/forensic procedural, Wolf Hall's is not a contrivance but a pretty accurate representation of living by candlelight. The producers went to a lot of trouble, too, to get the 'right kind' of candlelight, eventually opting for church candles with a high beeswax content, giving a relatively strong white light.
Anyway, this reminded me of something I'd read on - of all the unlikely places - the BBC News website, about sleeping patterns in premodern times. A psychiatrist had conducted an experiment in which a group of volunteers were plunged into darkness for 14 hours of every 24 and their sleeping habits observed over a month. What happened was that they settled into a sleep pattern of two four-hour spells of sleep with a waking interval of one or two hours in between. And this, all the evidence suggests, is exactly how people slept (and woke) in the long dark nights before electric light, street lighting and the demands of a clock-timed working life. The 'first sleep' would begin a couple of hours after dusk and last around four hours. Then there would be a waking period of one or two hours, followed by the 'second sleep'. This waking period would be spent in praying, sometimes in reading or writing, often in talking with bedfellows and, of course, having sex (this period was recommended as the best time for it). Then it was back to the Land of Nod for another four hours... This way of sleeping apparently began to die out in the late 17th century among the better-off, and gradually, over the years, in the rest of society.
 All this, and much else, is dealt with in a book by Roger Ekirch, At Day's Close: Night in Times Past. This sounds so interesting that I've ordered it on Abebooks. It's extraordinary how little interest we take in that half of our lives we spend abed, sleeping, dreaming, withdrawing into a timeless world...