An interesting article on sleep. There is a reference to second sleep in one of the Bronte sister's books. I, of course, do not remember which one. ETA: I was tired when I got home this evening, so I had something to eat and laid down to 'rest a bit' at 10pm. I didn't wake up until 12:30 am. Now I am still up, which is longer than the tradition period between first and second sleep.