How happily, said Austerlitz, have I sat over a book in the deepening twilight until I could no longer make out the words and my mind began to wander, and how secure have I felt seated at the desk in my house in the dark night, just watching the tip of my pencil in the lamplight following its shadow, as if of its own accord and with perfect fidelity, while that shadow moved regularly from left to right, line by line, over the ruled paper.