cker-moving pendulum than an ordinary
clock.

Ordinary civil time thus depends on the apparent revolution of the sun
round the earth. As, however, this is not uniform, it is needful for
practical convenience to give it an artificial uniformity. For this
purpose an imaginary sun, moving round the earth with the average
velocity of the real sun, and called the "mean" sun, is taken as the
measure of civil time. The day is divided into 24 hours, each hour into
60 minutes, and each minute into 60 seconds. After that the sexagesimal
division system is abandoned, and fractions of seconds are estimated in
decimals.

A clock consists of a train of wheels, actuated by a spring or weight,
and provided with a governing device which so regulates the speed as to
render it uniform. It also has a mechanism by which it strikes the hours
on a bell or gong (cp. Fr. _cloche_, Ger. _Glocke_, a bell; Dutch
_klok_, bell, clock), whereas, strictly, a _timepiece_ does not strike,
but simply shows the time.

The earliest clocks seem to have come into use in Europe during the 13th
century. For although there is evidence that they may have been invented
some centuries sooner, yet until that date they were probably only
curiosities. The first form they took was that of the balance clock, the
invention of which is ascribed, but on very insufficient grounds, to
Pope Silvester II. in A.D. 996. A clock was put up in a former clock
tower at Westminster with some great bells in 1288, out of a fine
imposed on a chief-justice who had offended the government, and the
motto _Discite justitiam, moniti_, inscribed upon it. The bells were
sold, or rather, it is said, gambled away, by Henry VIII. In 1292 a
clock in Canterbury cathedral is mentioned as costing L30, and another
at St Albans, by R. Wallingford, the abbot in 1326, is said to have been
such as there was not in all Europe, showing various astronomical
phenomena. A description of one in Dover Castle with the date 1348 on it
was published by Admiral W.H. Smyth (1788-1865) in 1851, and the clock
itself was exhibited going, in the Scientific Exhibition of 1876. A very
similar one, made by Henry de Vick for the French king Charles V. in
1379 was much like the common clocks of the 18th century, except that it
had a vibrating balance instead of a pendulum. The works of one of these
old clocks still exist in a going condition at the Victoria and Albert
Museum. It came from Wells cathedral, having previousl