The stars looked down on the old monk as he shuffled along, the frozen snow biting his bare toes in his well worn sandals as he made his way to the little open hut that housed the bell.
This day had been his turn to ring the Offices and now, with Compline, he was finished. As his stiff old fingers grasped the frost-encrusted rope of the bell, he couldn’t help himself wishing that there was some way of making this job a mechanical task and not one that relied on humans. But since this was the year 1130, it would be fully two hundred years before such men as he would see such a marvel.
Water clocks, or clepsydrae, had been known in Babylon and Egypt since 1500 B.C., but were used mainly for astrological purposes. They were set to time against sundials and proved useful for their purpose. India and China saw them too, but for the purpose of this article, we’ll stick to clocks as we know them. It’s such a vast subject, that we may allow ourselves only an overview.
The oldest surviving mechanical clock is the one in Salisbury Cathedral, in England. It’s a large, iron framed mechanism that would strike a bell every hour. There was no strike work, nor was there a dial. By strike work, I mean the locking wheel or rack and snail for counting the hours. However, it does have a strike train and also a time train.
At the end of the 17th. century, the escapement was changed from verge and foliot to anchor escapement and pendulum. Further adventures awaited the dear old clock, however, but finally, in 1956, it was fully restored, even to having a new verge and foliot made for it so that now it’s as close to its original condition as may be imagined.
It sits in its ancient glory in the aisle of Salisbury Cathedral, still running, but no longer striking. The clock’s powered by two large stones as the weights. The framework is held together by metal dowels and pegs. Nuts and bolts had yet to be invented.
Earlier than this, however, was a clock made by Richard of Wallingford for the abbey at St Albans. Regrettably, the clock’s no longer extant, but it seems he made a number of them.
From Richard, we skip forward two hundred years, to a gentleman named Taqi-al-Din, an Ottoman engineer. He wrote a book on clocks, describing one in particular that would strike the hours, had three dials; hours, minutes and seconds, an alarm and moon phase. Again, though, the old verge and foliot was in use. The book was published in 1559.
Twenty five years later, a man named Jost Burgi invented what became known as the crossbeat escapement as well as the remontoire. This latter was a remarkable achievement for his day. It’s a mechanism that supplies constant power to the escapement, thus negating any backlash in the gear train. This, apparently, reduced timekeeping errors to about one minute per day.
The next milestone was in 1656, when Galileo invented the pendulum. Unfortunately, the poor old boy died before he was able to do anything with his invention and the task fell to the great Dutch clockmaker, Christiaan Huygens, to develop the mathematical calculation which coupled the length of the pendulum to the count, or number of teeth, in the gear train.
At about this time, 1670, William Clement invented the anchor escapement. Before we go any further, I think a quick word of clarification is necessary regarding escapements.
An escapement is the method used in mechanical clocks and watches to allow the power of the weight or the mainspring, the motive force, to escape in a controlled manner. Without it, the clock or watch would be completely under the control of the motive force and would simply run down at a very high speed. Nothing would be attained, save a few broken teeth!
The other point to bear in mind is that the pendulum must control the clock and not the other way around. In other words, the pendulum needs to be relatively heavy. The one used for the old verge and foliot was very light, giving an amplitude of about 100 degrees. William Clement, with his anchor escapement, so called because it had the shape of an anchor, cut this wild swing right down to between four and six degrees. This meant that not only was the timekeeping vastly improved. It meant also that a minute hand could be successfully fitted and even a seconds hand.
Mr. Clement is also credited with designing the longcase, or grandfather, clock in 1671. Although spring driven clocks had appeared in the 1400’s, the difficulty was to equalize the power of the spring. This was attempted in a number of ways, the stackfreed and the fusee being two. The fusee was the only one that lasted.
In 1675, a Mr. Robert Towneley invented the deadbeat escapement which improved timekeeping still further. However, it was first used by the great English clockmaker, Thomas Tompion in 1675.
The other great horologist, John Harrison, although he made a number of longcase clocks with wooden works, spent most of his life on the question of Longitude, upon which a book has been written.
In all, he designed five chronometers, made to keep accurate time at sea. The story of Harrison and his efforts to satisfy the Board of Longitude and so claim the 20,000 pound sterling prize is a long, and often bitter one. There was much jealousy from other people against him, and even when he produced phenomenal results with his instruments, when these same results stared people in the face, the Board still refused to grant him the prize.
It wasn’t until he and his son, John, took the matter to the King himself, George the Third, was any action finally taken. After the King’s intervention, a new Longitude act was was passed in 1765. In the autumn of that same year, Harrison finally received another 10,000 pounds. This still wasn’t the total, but history has remembered him as one of the giants. He died in 1776.
From Harrison, too, came the gridiron pendulum, which is of a type that compensates for temperature, and his famous grasshopper escapement.
The marine chronometer was improved upon yet again, when Thomas Earnshaw invented the spring detent escapement. One great advantage of this type is that it doesn’t require any lubrication. These days, this isn’t quite so important because of the high grade of oil now available, but in Earnshaw’s day, the oil was of decidedly poor quality.
No clock history would be complete without mentioning Big Ben. It was built at the north end of the Palace of Westminster. The job of actually making the clock was given to Edward John Dent, one of the leading clockmakers of the day. Unfortunately, he died, and his stepson, Frederick Dent, completed the work in 1854.
The clock tower took another five years to build and was designed by Mr. Augustus Pugin. This poor man had the misfortune to lose his sanity immediately upon completing his task, and died shortly thereafter.
The Westminster chimes that Big Ben rings out every quarter of an hour evolved from Handel’s ‘Messiah, the fifth bar of ‘I know that my Redeemer liveth.’
I think it’s worth reflecting on the fact that Thomas Earnshaw invented and used the spring detent escapement for marine chronometers in 1783. The famous firm of Thomas Mercer was still producing these amazing instruments well into the 1970’s, almost exactly as Earnshaw had designed them. They would time to about 1/10 of a second per day.
The other fact is the deadbeat escapement and pendulum. Since 1675, it was never improved upon until the 1930’s.
