drum. It might be told by the eye what hour it was by the number of doors that were open, and by the ear by the number of balls that fell. When it was twelve o'clock twelve horsemen in miniature issued forth at the same time and shut all the doors."
Sand-glasses were introduced about 330 A.D. Except for special purposes, such as timing sermons and boiling eggs, they have not been of any practical value.
The clepsydra naturally suggested to the mechanical mind the idea of driving a mechanism for registering time by the force of gravity acting on some body other than water. The invention of the weight-driven clock is attributed, like a good many other things, to Archimedes, the famous Sicilian mathematician of the third century B.C.; but no record exists of any actual clock composed of wheels operated by a weight prior to 1120 A.D. So we may take that year as opening the era of the clock as we know it.
About 1500 Peter Hele of Nuremberg invented the mainspring as a substitute for the weight, and the watch appeared soon afterwards (1525 A.D.). The pendulum was first adopted for controlling the motion of the wheels by Christian Huygens, a distinguished Dutch mechanician, in 1659.
To Thomas Tompion, "the father of English watchmaking," is ascribed the honour of first fitting a hairspring to the escapement of a watch, in or about the year 1660. He also introduced the cylinder escapement now so commonly used in cheap watches. Though many improvements have been made since his time, Tompion manufactured clocks and watches which were excellent timekeepers, and as a reward for the benefits conferred on his fellows during his lifetime, he was, after death, granted the exceptional honour of a resting-place in Westminster Abbey.