One day as I turned away from here I noticed that sunlight was picking out the pebbles in the white-painted pebbledash wall. The light happened to be glancing exactly along the plane of the wall, and in a matter of seconds the pebbles would be in shadow like the hollows around them. The time was eleven, or just a few minutes past. Aha! The real sun time was twelve noon, which in summer, by the astronomically stupid system called "daylight-saving time", we change to clock time eleven. So this was an interesting moment, showing that the wall must be aligned due south, toward the noonday sun. (And the date was July 6, not far past the June 21 solstice, so the sun was at about its highest in the sky.) That's why I decided to sketch the situation.

But does this wall actually point south? I hadn't thought so, and on looking at a map I confirmed my fear that it points southeast. What had I figured wrong? It took me a while to calculate the explanation for the discrepancy—involving the "equation of time" (the sun on July 7 goes over the meridian not at 12:00 but at 12:05), longitude (Lyme is nearly three degrees west of Greenwich), azimuth (the middle hours of the day are when the sun moves most rapidly in azimuth, that is, around the horizon). On Aug. 20 the pebble-picking light occurred at 10:30 by the clock.