William Clement

"William Clement, of Wissingsett, Norfolkshire, to whom in the reign of Queen Elizabeth, in the year 1563, the Family Arms were granted by the visitation of Norfolk, made by William Harvey Clarencieux King of Arms, South of Trent, and Confirmed by John Raven, Richmond Herald, in the year 1613."

Source: THE VISITATIONS OF NORFOLK, 1563, 1589, and 1613

pg. 73

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Accurate Mechanical Clocks

In 1656, Christian Huygens, a Dutch scientist, made the first pendulum clock, regulated by a mechanism with a "natural" period of oscillation. Although Galileo Galilei, sometimes credited with inventing the pendulum, studied its motion as early as 1582, Galileo's design for a clock was not built before his death. Huygens' pendulum clock had an error of less than 1 minute a day, the first time such accuracy had been achieved. His later refinements reduced his clock's errors to less than 10 seconds a day.

Around 1675, Huygens developed the balance wheel and spring assembly, still found in some of today's wrist watches. This improvement allowed 17th century watches to keep time to 10 minutes a day. And in London in 1671 William Clement began building clocks with the new "anchor" or "recoil" escapement, a substantial improvement over the verge because it interferes less with the motion of the pendulum.

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The mechanical clock was probably invented in medieval Europe. Clever arrangements of gears and wheels were devised that turned by weights attached to them. As the weights were pulled downward by the force of gravity, the wheels were forced to turn in a slow, regular manner. A pointer, properly attached to the wheels, marked the hours.

These clocks became common in churches and monasteries and could be relied upon to tell when to toll the bells for regular prayers or church attendance. (The very word "clock" is from the French cloche, meaning "bell.")

Eventually, mechanical clocks were designed to strike the hour and even to chime the quarter-hour. However, they had only an hour hand and were not enclosed. Even the best such clocks would gain or lose up to half an hour a day.

A technological advance came with the invention of the “spring-powered clock” around 1500-1510, credited to Peter Henlein of Nuremberg, Germany. Because these clocks could fit on a mantle or shelf they became very popular among the rich. They did have some time-keeping problems, though, as the clock slowed down as the mainspring unwound. The development of the spring-powered clock was the precursor to accurate timekeeping.

In 1582, Italian scientist Galileo, then a teenager, had noticed the swaying chandeliers in a cathedral. It seemed to him that the movement back and forth was always the same whether the swing was a large one or a small one. He timed the swaying with his pulse and then began experimented with swinging weights. He found that the "pendulum" was a way of marking off small intervals of time accurately.

Once Galileo had made the discovery, the regular beat of the pendulum became the most accurate source used to regulate the movement of the wheels and gears of a clock.

It wasn't a perfect system, though, as a pendulum swings through the arc of a circle, and when that is so, the time of the swing varies slightly with its size. To make the pendulum keep truly accurate time, it must be made to swing through a curve known as a "cycloid."

In 1656, Dutch astronomer Christian Huygens first devised a successful pendulum clock. He used short pendulums that beat several times a second, encased the works in wood, and hung the clock on the wall. It had an error of less than one minute a day. This was a huge improvement on earlier mechanical clocks, and subsequent refinements reduced the margin of error to less than 10 seconds per day.

In 1670, English clockmaker William Clement made use of a pendulum about a yard long that took a full second to move back and forth, allowing greater accuracy than ever before. He encased the pendulum and weights in wood in order to diminish the effect of air currents, thus was born the "grandfather's clock." For the first time, it made sense to add a minute hand to the dial, since it was now possible to measure time to the nearest second.

In 1721, George Graham improved the pendulum clock’s accuracy to within a second a day by compensating for changes in the pendulum's length caused by temperature variations. The mechanical clock continued to develop until it achieved an accuracy of a hundredth of a second a day and it became the accepted standard in most astronomical observatories.