Salisbury Cathedral

The Cathedral Church of the Blessed Virgin Mary, also known as Salisbury Cathedral, is noted for having the tallest church spire in England, but it has other notable qualities: the largest cloister, one of the oldest working clocks in the world, and one of four original copies of the Magna Carta.

There was already a gothic cathedral in Salisbury at Old Sarum, but a decision was made to construct a new church and move the cathedra, or bishop's seat, to Salisbury town. The bishop at the time was Richard Poore (died 15 April 1237), who lived almost to see the new building finished. Fees for construction came from canons and vicars of the diocese annually until the building was completed. (Legend that Bishop Poore shot an arrow that hit a deer, and where the deer died was chosen as the new site, cannot be substantiated.)

The first of its 70,000 tons of stone were laid down on 28 April 1220 by the 3rd Earl of Salisbury William Longespée, an  illegitimate son of King Henry II, and his wife. Remarkably for a structure of it size, it was completed in 38 years, which led to a consistency of design sometimes lacking in cathedrals that took generations and had multiple architects over time. It also took 3000 tons of timber and 450 tons of lead. The spire (a later addition, in 1320) and tower alone used 6400 tons of stone and would have collapsed like many other spires if not for the addition of buttresses and anchor plates (iron braces holding stones together). Sir Christopher Wren in 1668 added tie beams above the crossing (where the nave and apse intersect, above which stood the tower), which also helped.

The copy of the Magna Carta—incidentally the best preserved of the four surviving originals—came to Salisbury because one of the men given the task of distributing copies of the document, Elias of Dereham, was also a stonemason who oversaw the cathedral's construction and became a canon of Salisbury.

The famous clock, thought to be the oldest working clock in the world, has no face. Early clocks did not have hands; rather they noted the hour by ringing a bell. It was used regularly until 1884, when it was placed in storage and forgotten. Found again in 1928, it was restored in 1956 and works to this day.

I mentioned Bishop Richard Poore who oversaw most of the building of the cathedral. There is a statue of him in one of the many niches in the cathedral. He did arguably much more important work at Salisbury than building a new cathedral, which I'll tell you about tomorrow.

Let's Talk Clocks

What constitutes a "clock"? The Latin horologium could refer to a clock or a timepiece of a sundial or the building or structure designed to support any of those.

Modern horology, the study of the measurement of time, distinguishes clocks which mark time by striking something (the word "clock" comes from French cloche, "bell"), whereas a timepiece does not. So a timepiece can mean a watch, a sundial, a clepsydra, or an hourglass, etc.

The sundial was likely the earliest way to measure time: a shadow on a flat surface displays the progression of the sun.

The clepsydra (Greek κλεψύδρα, literally "water thief"), was used in Babylonb, Persia, and Egypt as far back as the 16th century BCE. The simplest form is a bowl or other vessel with a hole from which the water drains, and markings to match drainage levels with the passage of time. The Greco-Roman world devised an in-flow (rather than out-flow) method which, as water filled a container, would trigger a sound, creating an "alarm clock." Water clocks evolved that used gears and escapement mechanisms to produce greater accuracy.

An escapement is a gear mechanism that ticks forward and back to cause another piece to advance. The illustration shows how this works in a pendulum clock, advancing the hands. The use of the escapement was crucial to the development of mechanical clocks, which started to appear in the 14th century in Europe. (Not in the 10th, built by Gerbert d'Aurillac.)

Let's not neglect candle clocks. A Chinese poem written in 520CE by You Joanfu mentions a clock marked so that it could be used while burning to measure the passage of night time. The Anglo-Saxons credit Alfred the Great with creating the candle clock. He used squat candles (<5" high) marked at 1" intervals to mark time.

The hourglass was also a common method of measuring time, the earliest depiction of which is in a 1338 painting by Ambrogio Lorenzetti.

The earliest mechanical clock, a clock that did not use water or sand or candles, that used a predictable motion due to the escapement and a pendulum, did not appear until the early 1300s. Norwich Cathedral had a tower clock constructed in the early 1320s. The first known municipal clock that struck on the hours was in Milan in 1336. Over the next few decades, mechanical clocks appeared all over: Old St. Paul's Cathedral, Salisbury Cathedral (still has many original parts!), Wells Cathedral (still with its original face), etc. Detailed descriptions of clock designs by Richard of Wallingford (1292 - 1336) and Giovanni de Dondi (c.1330 - 1338) still exist, though the many clocks they built are long gone.

A king who developed his own timepieces made from candles? He sounds like someone worth looking into.

Who Invented the Mechanical Clock?

In researching the previous post, I came across a reference to Pope Sylvester II (formerly Gerbert d'Aurillac, c.946 - 1003) inventing the mechanical clock. The source of this was the William Godwin's final book, Lives of the Necromancers, An Account of the Most Eminent Persons in Successive Ages Who Have Claimed for Themselves, or to Whom Has Been Imputed by Others, The Exercise of Magical Powers [1834]:

This generous adventurer, prompted by an insatiable thirst for information, is said to have secretly withdrawn himself from his monastery of Fleury in Burgundy, and to have spent several years among the Saracens of Cordova. Here be acquired a knowledge of the language and learning of the Arabians, particularly of their astronomy, geometry and arithmetic; and he is understood to have been the first that imparted to the north and west of Europe a knowledge of the Arabic numerals, a science which at first sight might be despised for its simplicity, but which in its consequences is no inconsiderable instrument in subtilising the powers of human intellect. He likewise introduced the use of clocks. He is also represented to have made an extraordinary proficiency in the art of magic; and among other things...

The italics are mine. A little further along, Godwin adds a footnote that tells us his information comes from William of Malmesbury. William (c.1095 - c.1143) was the foremost English historian of the 12th century. Not exactly a contemporary, but maybe near enough that the memories and stories were still fresh? It would be difficult to determine the accuracy of this report, especially in the context of a brief blog post. Fortunately, I don't have to.

As it turns out, Marek Otisk of the University of Ostrava (Czechoslovakia) published an article on this very topic in September 2020, Gerbert of Aurillac (Pope Sylvester II) as a Clockmaker. He examines the reports from William of Malmesbury, the Chronicle of Thietmar of Merseburg (died c.1018), and a much later record (someone who died in 1610). Among his detailed examination of these and other historical records we learn that although William claims Gerbert built a clock in Reims, a friend of Gerbert's (Richest of Reims), writes about Gerbert's stay in Reims in detail and never mentions a clock. Otisk concludes that William's ascribing of the creation of a clock to Gerbert cannot be trusted.

The later report by the Benedictine monk Arnold Wion, who died about 1610, claims Gerbert built a clepsydra, a water clock, in Ravenna. What we know of Gerber's time in Ravenna, however, is that it was very short; again, no contemporary accounts support this story.

Thietmar of Merseburg tells a different story, that Gerbert created a clock in Magdeburg. Thietmar was a bishop and close friend of Holy Roman Emperor Henry II, who succeeded Otto III, credited with making Gerbert into Pope Sylvester II. Thietmar's Chronicle includes a specific detail about Gerbert creating, in Magdeburg, "created clocks (horologium) which he correctly calibrated according to the Polar star (stella, dux nautarum) which he observed through an observation tube (fistula)." [Otisk, p.32] Otisk likes this account because both Thietmar and Gerbert were in Magdeburg in the late 990s, and very likely crossed paths several times.

The use of the word horologium is misleading, however. We use it for the word "clock," but it is more likely that Gerbert was creating a calibrated armillary, or possible even an astrolabe, which he knew about from his exposure to science being done by Islamic philosophers.

So I can't tell you who created the first mechanical clock. But the question of horologium remains: when long-ago writers refer to "clocks," what exactly did they mean? What constituted a clock? There were several ways to measure time without staring at the sun and judging, and I'll talk about those devices tomorrow.

Armillary Spheres

The "wooden terrestrial spheres" mentioned here are what we now call "armillary spheres." An armillary is a spherical arrangement of rings designed to mimic the orbits of the sun and planets around the Earth—or around the Sun, depending on the prevailing theory at the time. If the Earth is the center, it is a Ptolemaic sphere; if the Sun is at the center, it is a Copernican sphere. China and Greece each invented them BCE. Hipparchus credited Eratosthenes (276 - 194BCE) as the inventor.

An early Christian philosopher, John Philoponus, wrote the earliest extant treatise on the armillary sphere and the astrolabe. The oldest example of one we have today dates to the 11th century.

Gerbert d'Aurillac (946 - 1003), who became Pope Sylvester II in 999, had brought the armillary sphere to Western Europe. He was also responsible for introducing Western Europe to the abacus, the Hindu-Arabic numeral system we use today, and (possibly) the mechanical clock.

Sylvester used the armillary sphere and sighting tubes to determine the definitive position of the pole star and to record measurements for the tropics and the equator. His work was improved upon in the Renaissance by Tycho Brahe (1546 - 1601). Public figures would have an armillary sphere incorporated into their portraits to indicate their wisdom and knowledge.

I've written about clocks before, but I don't recall learning that Gerbert d'Aurillac invented it. I want to check that out; I'll let you know what I find.

The Birth of Tick-Tock

A city without bells is like a blind man without a stick. —Rabelais

Rabelais (c.1494-1553) was a little late for this blog, but his statement in Chapter XIX of Gargantua indicates a reliance on time-keeping that the modern world can understand. It was not always thus, however, for the Middle Ages.

I discussed yesterday how early concepts of time by their nature might have made it difficult to think of time as something measurable. I mentioned a mid-1200s definition of time that came from Franco of Cologne, the mathematically-minded music theorist who created what is the basis for modern musical notation. Franco's most diligent biographer places him as chapelmaster at Notre Dame in Paris.

Johannes de Sacrobosco (c.1195-c.1256) taught at the University of Paris, probably contemporaneously with Franco. Johannes was an astronomer who, among other things, declared that there was a flaw in the Julian calendar: it was 10 days off. (That error wouldn't be corrected until long after.) He also wrote of an attempt he knew to construct a wheel that would make a complete rotation in one day. Robertus Anglicus wrote a commentary in 1270 on Sacrobosco's treatise, mentioning the device and further spreading the idea. In that same decade, a clock is described by someone writing in Spain that runs by the flow of mercury from chamber to chamber in a wheel.

It only took a generation for this idea to catch on. By 1300, clocks were becoming widely known (if not widely owned), but the early ones only measured hours—they rang bells, but had no faces with markings around a dial, no minutes or seconds were counted, that we know of.

The device described by Sacrobosco and Anglicus used a weight hanging from a line around a wheel or cylinder. The Middle Ages understood wheels, gears, levers and pulleys, but how could these be used to guarantee a steady revolution of the weighted wheel? Sometime around 1300, or not long after, some early mechanical "Eureka" moment took place. Someone designed what we call the "escapement," which rocked back and forth on a toothed gear, allowing the wheel to turn at a steady, measurable, predictable speed. It also had a side-effect: a steady sound that we have been listening to ever since.

The escapement.

Within a generation after 1300, Dante Alighieri (c.1265-1321) considers his audience familiar enough with clocks and their mechanism to use gears as a metaphor:

As the wheels within a clockwork synchronize
       So that the innermost, when looked at closely
       Seems to be standing, while the outermost flies. (Canto xxiv, Paradiso)

Humans could now mark time in sequences of ticks and tocks. Minutes and seconds could be distinguished. Hours could be regulated. Six hours before noon became the same, whether it were dark in winter or already light in summer. (That's right: the 12 hours from sunrise until sunset used to be extended or shortened depending upon the season.) This was a change from the canonical hours described by the Rule of St. Benedict, for whom prayers at Matins were supposed to end as the sun rose, and therefore had to be started at different times depending on the season. In 1370, Charles V of France installed a clock in his palace, and decreed that all clocks in Paris be set according to his. Punctuality, crucial feature of our modern world, was born.

What is Time?

What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not: yet I say boldly that I know, that if nothing passed away, time past were not; and if nothing were coming, a time to come were not; and if nothing were, time present were not. Those two times then, past and to come, how are they, seeing the past now is not, and that to come is not yet? But the present, should it always be present, and never pass into time past, verily it should not be time, but eternity.

With this passage, found halfway through Book XI of his Confessions, St. Augustine of Hippo (13 November 354-28 August 430) discussed the difference between Time and Eternity. He knows that he is not aware of time that is yet to come, or time that is past; only time that is present; but he still doesn't know how to define what time is.

A medieval 24-hour clock.

Measurement of time was imprecise. There were "hours" of the day: the Vigil took place between 2:30 and 3:00 a.m., Matins came at Dawn, et cetera. These hours designated times of worship and work for monks and were extended to general use, but they were not exactly a way to quantify time. The hour of Sext was at noon, for instance, which was recognized when the sun was highest, but Matins/Dawn came more or fewer hours before Sext, depending on the time of year. They were segments of the day that altered with the seasons; they did not measure a span of time.

St. Benedict of Nursia (c.480-543), in his Rule for monks, intends them to worship at specific times, and finds a way to measure a span of time. Monks were not to slack at getting up for Matins, and so:

If anyone shall come to matins after the Gloria of the 94th Psalm, which on this account we wish to be said slowly and leisurely, he shall not take his place in the choir, but go last of all, or to some place apart which the abbot may appoint for those who so fail in his sight.

Time could be measured, therefore, by comparison to a known duration.* But even durations could be tricky. Augustine had pondered thinking of a long syllable as equivalent to two short ones, "But when two syllables sound one after the other—the first short, the second long—how shall I keep hold of the short one?" Augustine seemed to be caught up in the idea that time was a continuum, and that he was living in a constant present and could not treat the past and future in the same conceptual way, since he could not live in them. The Middle Ages couldn't grab time and measure it, like water or distance or even acceleration. It was insubstantial, and belonged to God.

The concept of time had to change ... and eventually it did. There was no clear turning point; there had to be some conceptual change, planned or otherwise, to see time not as a line but as a series of points, as separate moments that could be thought of without being linked to a past or future moment.

Sometime in the mid-13th century, we find Franco of Cologne. He was a music theorist who gave us the idea that a mark on a page should distinguish how long a note should be. This was the logical extension of Franco's definition of time: "Time is the measure of actual sound as well as of the opposite, its omission."

Was this the moment? Was it music, with its attention to and reverence for mathematics that accidentally inspired the thinking of time as separate units that could be measured and counted? We might be able to believe that, if there were some evidence that the world began to measure and quantify time; for instance, if the development of mechanical clocks were to start around this time.

Well, guess what happened next?

*This method of measuring spans of time without a clock is used even today.