Nocturnal

horologium nocturnum

English, unsigned;
in the manner of Elias Allen
Engraved gilt brass, iron index
c. 1610–1640 · 62 mm

Before the clock, the hour was read from the sky. The dial is set to the day; the pole star is sighted through the centre; the arm is laid along the two Pointers of the Plough, which swing about the still star once in a night. Where the arm crosses the hours, the time is told — and the teeth are cut in two sizes, so the hour can be found in the dark, by touch alone.

It keeps no time of its own. It reads the one star that does not move, and the turning of all the others.

nocturne · edition vii · polaris set to tonight; the arm rests where the Pointers stand now, and turns with them — a quarter-degree a minute. By morning the sky will have moved on.