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ON TIME The Quest for Precision

An Exhibition of Rare Books from the Linda Hall Library Held at the Grolier Club 14 September 2016 – 19 November 2016

by Bruce Bradley, History of Science Librarian Emeritus Historical clocks, watches, and artifacts selected by Fortunat Mueller-Maerki, Grolier Club member The Linda Hall Library of Science, Engineering & Technology for the Grolier Club Kansas City, Missouri 2016

Copyright 2016 The Linda Hall Library Trusts 5109 Cherry Street Kansas City, MO 64110-2498 ISBN 978-0-9763590-6-7 Catalog by Bruce Bradley Digital photography by Jon Rollins, Digital Services Unit, Linda Hall Library Catalog design by Melissa Dehner, Graphic Designer, Linda Hall Library Cover A repeater watch by English clock and watchmaker, George Graham. From Thomas Reid. A Treatise on Clock and Watch Making. Philadelphia, 1832 (item 82).

Exhibition and catalog supported by a generous grant from the Ascher Family Foundation and by the Linda Hall Library Foundation.


This exhibition represents a selection of books held by the Linda Hall

Library of Science, Engineering and Technology. They document the development of ever greater precision in timekeepers – a story of how improvements in clocks and watches have made them increasingly accurate, with less and less need for weekly or even daily adjustment. The story begins with books from the fifteenth century and continues to the present, drawing upon the comprehensive twentieth- and twenty-firstcentury collections of the Linda Hall Library to tell it. Beginning in the fifteenth century, books on science and technology were published to describe techniques of timekeeping, to announce new inventions and discoveries, and to instruct others in the construction and use of timekeeping instruments. Many of these books are part of the Linda Hall Library’s History of Science Collection of rare books, and others are found in the Library’s general collections. They have been collected in pursuit of the Library’s goal to establish a research collection in the history of science and engineering, representing all disciplines within those general parameters except clinical and surgical medicine. The books that illustrate the techniques, discoveries, and innovations in timekeeping are a fascinating subset of the much larger collection to which they belong. The exhibition has been complemented with selected horological objects, chosen by Grolier Club member Fortunat Mueller-Maerki from his personal collection. His passions include both bibliography and horology, allowing him to devote his energy toward the preservation and dissemination of knowledge on the art and science of timekeepers, timekeeping, and time.

ABOUT THE LINDA HALL LIBRARY he Linda Hall Library is one of the world’s foremost independent T research libraries devoted to science, engineering, and technology. A notfor-profit, privately funded institution, the Library is open to the public free of charge. The Library was established by the wills of Herbert and Linda Hall and opened in 1946. Since then, scholars, students, researchers, academic institutions and businesses throughout the Kansas City region, across


the nation, and around the world have used the Linda Hall Library’s collections to learn, investigate, invent, explore and increase knowledge. Hundreds of people of all ages attend the Library’s public programs each year to expand their awareness and understanding of science and technology. Herbert and Linda Hall built a home located in an area that has become the cultural center of Kansas City, Missouri. Through his grain business, Herbert Hall amassed a sizable estate, and with no direct heirs, he and Linda chose to leave their wealth as a bequest to create a free public library on the site where they had lived. The library was to be named in honor of Linda who died in 1938. Herbert died in 1941.

COLLECTIONS HISTORY he foundation for the Library’s collections was determined by the T Board of Trustees who defined the Library’s area of specialization as “covering the fields of basic science and technology.” Clinical medicine, dentistry, and business were excluded since other local and regional libraries collect these subjects. The collection policy emphasizes the acquisition of journals and other serial publications. Monographs, conference proceedings, indexes and abstracts, documents, technical reports, and other reference materials are also acquired to support the journal collection. Although the Library has regularly acquired material since 1946, several acquisitions are specifically worth noting. The Library’s first major purchase was the library collection of the American Academy of Arts and Sciences in 1946. This acquisition provided a strong foundation for the Library’s collections including journals, rare books, and the exchange program that supports the interchange of material with foreign academies and societies. A second significant acquisition occurred in 1985 when part of the library of the Franklin Institute was transferred from Philadelphia. Nearly 600 serial titles were added to the Linda Hall Library, increasing or completing runs of serials titles, and adding new titles.


In 1995, the Engineering Societies Library (ESL) was transferred to Linda Hall, an acquisition equal in significance to the Academy collection, and greater in the number of volumes received. The ESL collection added depth to both the journal and monograph collections, especially with material published before 1950. Today, the Linda Hall Library remains devoted to its goal of remaining one of the world’s pre-eminent collections of materials devoted to science, engineering, technology, and their histories by continuing to acquire contemporary and historical materials of intellectual significance.

LINDA HALL LIBRARY BOARD OF TRUSTEES Marilyn Bartlett Hebenstreit, Chairman John A. MacDonald Charles A. Spaulding III Terry Bassham Nicholas K. Powell Stephen D. Dunn Charles S. Sosland Lisa M. Browar, President

Clock face for a pendulum clock made in Paris. From G. J. de Marinoni. De astronomica specula. Vienna, 1745 (item 49).


INTRODUCTION: ACCURACY AND PRECISION rom sundials to atomic clocks, the story of precision in timekeeping F is documented in rare books and journals from the Linda Hall Library that are displayed in this exhibition. Many of the books are recognized as landmarks in the history of science and technology, such as John Harrison’s Principles (London, 1767) describing his marine chronometer. Others announced a major invention, such as a contribution to the Philosophical Transactions of the Royal Society of London describing Christiaan Huygens’s spring balance for a watch in 1675. Together, these publications show how clock and watchmakers have, with different methods and techniques, met the challenge of creating ever more precise timekeepers. The accuracy of those timekeepers, once set to the correct time, depends on the precision of their clockworks. A clock is said to be accurate when it is set to the correct time, according to the prevailing standard. An accurate sundial, for example, is set to show when the time is noon at a particular location. A precise clock, on the other hand, is one that shows the passage of time consistently. Once a clock is set to the accurate time, its precision depends on how well it measures the hours, minutes, and seconds without deviation from the accurate time, and thus without having to be reset. Without precision, a clock that is set to the standard time becomes inaccurate, as it no longer shows the correct time. Measuring time with increasing precision, as documented in scientific books and journals, is the thread that weaves together the various themes of this exhibition.

Sundial and an early mechanical clock, both showing the hours in a clockwise direction. From Robert Fludd. Utriusque cosmi maioris. Oppenheim, 1617 1618 (item 37).

Early mechanical clocks offered several advantages over sundials, such as portability and the ability to show the time during cloudy weather and at night. They lacked precision, however, and had to be readjusted periodically to synchronize them with local solar time. After the


appearance of mechanical clocks, books about sundials and how to make them remained popular. Demand for them continued throughout the sixteenth century and into the seventeenth. Nighttime hours could be measured with water clocks, often called clepsydra in ancient texts. Illustrated editions and translations of the Roman engineer Vitruvius, which included discussion of ancient clepsydra in Alexandria, began to appear in the sixteenth century. Water clocks were no more precise than sundials, but they offered a means for round-the-clock timekeeping. The first mechanical clocks in the thirteenth century may have been crude, imprecise, unreliable instruments. Yet by introducing a mechanical means of generating and counting a repeating beat, they marked a revolution in timekeeping. Their use of oscillating motion to divide time into countable beats, first illustrated in an encyclopedic-like book by Robert Fludd in 1617, was the basis for all subsequent improvements in precision timekeeping.

Woodcut with details of the mechanism regulated by oscillation of a simple pendulum. From Christiaan Huygens. Horologium oscillatorium. Paris, 1673 (item 44).

Pendulum clocks were an invention of the seventeenth century, and that is a story with which both Galileo and the Dutch scientist Christiaan Huygens are associated. Because of their precision, clocks regulated by pendulums brought the accuracy long sought for scientific observations, particularly astronomical ones. Spring balances, another seventeenth-century invention attributed to Huygens, also added precision to timekeepers, many of which became wonders of mechanical complexity, portability, and, in the case of watches, miniaturization.


In the twentieth century, further precision in timekeeping came from clever use of the vibrations of a miniature tuning fork, and from the vibrations of electrically activated quartz crystals. Since 1955, atomic clocks have continued to set new standards of accuracy. In 1967, the General Conference on Weights and Measures redefined the second. As published in the conference proceedings, a second is no longer a fraction of the mean solar day, but is now measured by transitions of the cesium 133 atom. Clocks have become more constant, and thus more precise, than the Earth’s rotation.

1. SUNDIALS books on sundials were filled with practical geometry Sandixteenth-century introductory astronomy. Understanding the daily movement of the Sun across the sky provided a convenient way to measure time, as it is regular and repetitive. The shadow of a vertical stick rising from any horizontal surface is the simplest kind of sundial. As the shadow rotates around the stick in a clockwise direction, its position can be geometrically plotted and used to mark the time. Woodcuts of sundials in early books showed how to construct them so that the shadow of the vertical pointer, called the “gnomon,” would indicate noon. This gave a precise measurement of local apparent time, and it is the same for every point on a meridian, an imaginary half circle that runs from the North Pole to the South Pole. Any point east or west of a particular meridian will have its own local apparent time. A fifteenth-century instrument, the nocturnal, relied on the apparent rotations of the stars to determine the hour at night. By the sixteenth century, books on instruments and

A variety of different sundials, horizontal, vertical, and inclined. From Sebastian Münster. Horologiographia. Basel, 1533 (item 1).


horology often described a common version of the nocturnal, with instructions on how to make and use one. Sixteenth-century books also began to describe mechanical clocks, and as those clocks became more precise, sundials began to assume importance as ornaments in parks and gardens as much as timekeepers. Endless variations of sundials were described and built, depending on the skill, knowledge, and imagination of the maker.

A nocturnal, with instructions. From Peter Apian. Cosmographia. Antwerp, 1587 (item 5).

1. Mßnster, Sebastian, 1489-1552. Horologiographia. Basel: excubebat Henricus Petrus, 1533. Mßnster’s Horologiographia is the first book exclusively on sundials and it is still considered a comprehensive treatise on the subject. The first edition was issued as Compositio horologiorum in 1531, but it was popular enough to warrant this second enlarged edition just two years later. Both editions illustrate all manner and variety of sundials with beautiful woodcuts, some of which are attributed to Hans Holbein the Younger. 2. Clavius, Christoph, 1538-1612. Gnomonices. Rome: Apud Franciscum Zanettum, 1581. In an era when mathematicians were interested in the theory and design of sundials, no one produced a more complete book on the subject than Clavius, the Jesuit professor of mathematics in Rome. Geometrical diagrams illustrate portable and fixed sundials, showing many details for construction. A diagram at the bottom of the engraved title page hints at the geometrical approach to determining time by solar reckoning that readers would find inside the book.


3. Apian, Peter, 1495-1552. Introductio geographica. Ingolstadt: [Peter Apian], 1533. The torquetum was a complex instrument for making astronomical observations, including determining the hours of the day or night. Peter Apian’s account of the instrument is one of the best known, due in part to the splendid woodcut illustration. The account includes complete instructions for making the instrument, but curiously does not give any dimensions. The book was printed on Apian’s own press in Ingolstadt, and the instrument was later described in Apian’s Astronomica Caesareum (1540). A sundial for sounding the hours. From Athanasius Kircher. Ars magna lucis et umbrae. Rome, 1646 (item 7).

4. Apian, Peter, 1495-1552. Instrument Buch. Ingolstadt: [Peter Apian], 1533.

Peter Apian’s Instrument Buch describes a variety of instruments for taking measurements and explains how to use them. Some of these are shown in use on the title page of the book, such as a quadrant on the left, a cross staff in the middle, and a nocturnal on the far right, for measuring time at night by using the stars as a clock. 5. Apian, Peter, 1495-1552. Cosmographia. Antwerp: Gregorio Bontio, 1550. Peter Apian’s books were noted for showing how to construct and use astronomical and surveying instruments. The nocturnal is one, used for finding the local time at night. With the handle perpendicular to the ground, the user sights the North Star through the hole in the center. By aligning the index pointer with the first two stars in the Big Dipper, it serves the function of an hour hand by pointing out the hour. 6. Caus, Salomon de, d. 1626. La pratique et demonstration des horloges solaires. Paris: Hyerosme Droüart, 1624. Salomon de Caus, a French engineer and scientist, developed a strong interest in mechanical devices, particularly hydraulic devices to power ingenious fountains, musical instruments, and various automata. In 1624, after moving to Paris the previous year to work as a hydraulic engineer,


he published this practical book on sundials. It was the first such book written in French. Christoph Clavius, he noted, had earlier written a very learned treatise on the subject, but it was difficult to understand without long study. This book, he declared in the dedication to Cardinal de Richelieu, would be easier to understand and made even more accessible with pop-up models of sundials made of thick paper. 7. Kircher, Athanasius, 1602-1680. Ars magna lucis et vmbrae in decem libros digesta. Rome: Sumptibus Hermanni Scheus, 1646. Sundials retained their attraction in the seventeenth century, even as the popularity of mechanical clocks grew. Kircher’s encyclopedic work on optics illustrated many optical toys and inventions, with several intriguing engravings of sundials. One is a sundial in the shape of a bowl that would show the time and sound the hours. The Sun’s rays are focused by a glass sphere, casting a point of light to show the hour and ignite small gunpowder charges, which trigger hammers on bells at each hour of daylight.

Garden sundial with 20 gnomons to show time around the world. From Richard Hobson. Charles Waterton: His Home, Habits, and Handiwork. London, 1867 (item 9).


8. Scheuchzer, Johann Jacob, 1672-1733. Physica sacra. Augsburg & Ulm: Christoph Ulrich Wagner, 1731-1735. With almost 2,000 pages of folio text and over 750 full-page engravings noted for their elaborate baroque borders, the Physica sacra became known as the “Copper Bible,� using selected biblical verses to discuss and illustrate scientific concepts. In the second Book of Kings, a reference to a sundial on the staircase of King Ahaz allowed Scheuchzer to show how such a sundial could be built, with each step representing half an hour, and then to discuss common sundials shown at the top of the engraving. 9. Hobson, Richard, 1795-1868. Charles Waterton: His Home, Habits, and Handiwork. London: Whittaker & Co., 1867. This biography of Waterton, a British traveler and naturalist, describes his estate in Yorkshire, where visitors flocked to see the exotic animals he collected. An ornamental sundial on the grounds, built by George Boulby in 1813, showed those visitors the solar time in cities all over the globe. Each of its 20 equilateral triangles is an individual sundial, positioned in accordance with the different degrees of longitude for the various cities.

2. CALENDARS alendars help societies keep track of the days of the year and know C when to plant crops and observe religious holidays. These very practical concerns made books on calendars popular, as demonstrated by the many editions of the calendar of Regiomontanus by Erhard Ratdolt, a successful printer and publisher of beautiful fifteenth-century scientific books. Instructional explanations in other books showed how the calendar is determined by the annual position of the Earth relative to the Sun. The summer solstice, the day with the longest amount of sunlight, is a convenient annual marker of the solar cycle, as is the equinox in spring and fall when the day is divided into equal halves of daylight and darkness. Precise measurement of the cycle is crucial. One way to mark the dates in the yearly calendar is by use of a meridian line, which is a special kind of sundial, positioned exactly north and south on the floor of a large building. Scientists in the seventeenth century documented the meridian lines they designed and built in books illustrated with elaborate engravings. A long fold-out frontispiece shows


The solar year, defined by the Earth’s orbit around the Sun. From Andreas Cellarius. Harmonia macrocosmica. Amsterdam, 1661 (item 10).

how the astronomer Giovanni Domenico Cassini laid out the meridian line in the church of San Petronio in Bologna, plotting it at an angle to the walls and squeezing it past the massive pillars supporting the roof. A beam of sunlight from a hole in the ceiling crosses the meridian line at noon each day, moving south along the line in summer and then north after the summer solstice. Since the Sun determines the calendar year, the seasons, and days, it might seem logical to use the Moon’s cycle to determine the months. But the lunar cycle is a calendar all to itself, calculated by mathematicians and astronomers and included in both annual calendars and texts that predicted future lunar positions. The lunar calendar had special significance to Christendom for determining the date of Easter. That date became problematic using the Julian calendar, which lacked precision and gained about three days every four centuries after its introduction by Julius Caesar. Attempts to revise and correct the calendar were published long before Pope Gregory XIII issued a papal bull in 1582, removing 10 days in October that year and creating the new Gregorian calendar that we still use. Reformers in the twentieth century wanted to replace it and created the World Calendar Association to promote a new perpetual calendar, but were unsuccessful in securing its adoption through their periodical publications and colorful printed almanacs.


10. Cellarius, Andreas, c. 1595-1665. Harmonia macrocosmica. Amsterdam: Apud Joannem Janssonium, 1661. One of the hand-colored plates of the Copernican system in Cellarius’s sumptuous atlas and astronomical textbook shows the Earth four times to illustrate the seasons of a solar year. A solar year is the length of time the Sun takes to return to the same position in the cycle of seasons. This may seem a simple concept, but the original engraving mislabeled the two equinoxes, spring (left) and autumn (right), which were later corrected. 11. Regiomontanus, Joannes, 1436-1476. [Calendarium.] In laudem operis calendarij. Venice: Erhard Ratdolt, 1485. A poem in praise of the calendar. From Joannes Regiomontanus. Calendarium. Venice, 1485 (item 11).

Erhard Ratdolt began his printing career in Venice in 1476, with an edition of Regiomontanus’s popular calendar. More editions followed, each with charts linking days of the month to feast days, tables for moon phases and solar paths, and, in this 1485 edition, illustrations of predicted lunar eclipses printed in two colors. The book concludes with working paper instruments – a volvelle for lunar positions and instruments for telling time. It begins with a poem in praise of the calendar surrounded by an enticing border, encouraging buyers. 12. Stoeffler, Johannes, 1452-1531. Calendarium romanum magnum. Oppenheim: Per Jacobum Köbel, 1518. The Julian calendar, introduced in 46 BCE with 365 days and a leap day every four years, gained about three days over the solar year every four centuries. By the 1500s, it was annoyingly out of agreement with astronomical events. Stoeffler, invited to come up with a solution, made suggestions in his Calendarium, exquisitely printed by Oppenheim’s first printer, Jacob Köbel, who produced his first publication there in 1499. Better solutions for the calendar came several decades later, with reforms of the Gregorian calendar in 1582.


13. Clavius, Christoph, 1538-1612. Operum mathematicorum. Mainz: sumptibus Antonii Hierat, 1612. Clavius wrote extensively to defend and explain the new calendar announced by Pope Gregory XIII in 1582. His writings were collected into the final thick volume of his mathematical works, beginning with a reprint of Inter gravissimas, the papal bull issued to announce the reforms. Known as the Gregorian calendar ever since, it corrected a problem in the Julian calendar that caused the first day of spring to gradually shift, so that by the 1580s it was occurring about 10 days too early. 14. Cassini, Giovanni Domenico, 1625-1712. La meridiana del tempio di S. Petronio. Bologna: Per l’erede di Vittorio Benacci, 1695. This book’s six-foot folded frontispiece, made of three sheets pasted together, illustrates the brass meridian line on the floor of a church in Bologna that is over 200 feet long. Sunshine from a hole in the ceiling crosses the meridian at noon. Each day the noon mark moves along the line, north in winter and south in summer. The meridian line is a calendar and a clock, indicating the day of the year by the point on the line crossed by the sunspot.

The church of San Petronio in Bologna, with the meridian line installed by G. D. Cassini in the mid-seventeenth century. From G. D. Cassini. La meridiana del tempio di S. Petronio. Bologna, 1695 (item 14).


15. Gabbrielli, Pirro Maria, 1643-1705. L’ heliometro fisiocritico, o vero, La meridiana Sanese. Siena: Appresso il Bonetti nella Stamparia del Pub., 1705.

An elaborate diagram to show lunar phases. From Athanasius Kircher. Ars magna lucis et umbrae. Rome, 1646 (item 16).

Gabbrielli built a meridian line about 45 feet long of iron in the meeting room of the scientific academy in Siena and finished writing this detailed description shortly before he died. The building and instrument were destroyed in an earthquake in 1798, making the book the only record of the achievement. As shown in the engraving of the room, a hole for stellar observations in the ceiling’s north side (in addition to the one for a sunbeam on the south) made the meridian an astronomical instrument as well as a clock and calendar.

16. Kircher, Athanasius, 1602-1680. Ars magna lucis et vmbrae in decem libros digesta. Rome: Sumptibus Hermanni Scheus, 1646. In Ars magna lucis et vmbrae, Kircher discussed everything that gives or receives light, including the Moon. One elaborate diagram, engraved by Pierre Miotte, shows 28 phases of a lunar month in the oval border. Two spiral mirror images show the waxing Moon expanding from the center, while the waning Moon shrinks to the center. Since the lunar cycle is regular and predictable, it would be a convenient way to define a calendar month. But it never matches the 12 months of a solar year, and is a calendar all to itself.


17. Evelyn, John, 1620-1706. Sylva … Kalendarium hortense. London: Royal Society, 1664. John Evelyn’s practical book on arboriculture, Sylva, is the first publication of the Royal Society of London. It concludes with practical appendices for gardeners, including a gardener’s calendar, or Kalendarium hortense. Common gardeners, Evelyn thought, needed only enough precision in their calendar to show the required gardening activities for the twelve monthly divisions of the year. It would be less confusing and distracting, Evelyn wrote, for the “ordinary sort of Gard’ners.” 18. Wilson, P.W., World Calendar Almanac. New York: The World Calendar Association, [c. 1934-39]. The World Calendar captured interest in America in the 1930s. It was a perpetual calendar that would be the same every year, with January 1 always falling on Sunday. The bibliographic service Engineering Index reviewed it in 1941, as indicated by stamps on the cover of this copy of the almanac. In spite of enthusiastic promotion through the 1950s and 1960s, calls to adopt the World Calendar repeatedly failed passage in the United Nations.

3. WATER CLOCKS water clock, or clepsydra (water thief), is any kind of a clock that A uses water as the driving source of power. The simplest ones work by the constant dropping or running of water from one vessel into another. The concept is ancient, perhaps as old as or even older than sundials, and many sixteenth- and seventeenth-century books described water clocks. Some were ancient devices, such as the Clepsydra of Ctesibius of Alexandria. The Roman engineer Vitruvius described it in his Ten Books on Architecture, which saw many early editions and translations. In Ctesibius’s Egypt, the day was divided into 12 hours of daylight and 12 hours of nighttime, which meant that the length of an hour varied every day, and that day and night hours were never equal except on two days of the year, the spring and autumnal equinoxes. With inspiration perhaps stemming from the concepts of Ctesibius, Salomon de Caus invented two hydraulic mechanical clocks in the early seventeenth century. He described them in a beautifully illustrated book


on machines powered by water. His two water clocks were powered by a continuous stream of water – an alternative to having continually to rewind mechanical clocks powered with springs or weights. Claude Perrault was a founding member of the Académie des Sciences in Paris, which published his work on animal anatomy. He also worked on problems of mechanical engineering, and a posthumously published collection of his inventions included his design for a water-powered clock that he invented around 1669. Perrault’s plans for the clock incorporated the ancient ideas of control by water with the new concept of the pendulum clock. It was a hybrid, the best of old and new technology, even if it was impractical.

Water clock for a military camp. From Roberto Valturio. De re militari. Paris, 1534 (item 19).

19. Roberto Valturio, 1413-1483. De re militari libris XII. Paris: Apud Christianum Wechelum, 1534. Valturio’s De re militari is noted for early depictions of technical military equipment. It was first printed in Verona in 1472, and for the first time in France in this edition of 1534. The woodcuts of catapults, battering rams,


cannon, scaling ladders, pontoon bridges, and something resembling a tank were all copied in reverse from the second edition of 1483. A curious water clock marked with 17 hours on the dial is included in the section on setting up and regulating a military camp. The heavier of two weights would sink slowly in the tub, turning the crossbar that turns the pointer on the clock face. 20. Marcus Vitruvius Pollio, first century BCE. De architectura libri decem. Venice: Apud Franciscum Franciscium Senensem, 1567. In his book De architectura, the Roman engineer Vitruvius described some of the accomplishments of the Egyptian engineer Ctesibius of Alexandria. An Italian translation of Vitruvius with commentary by Daniele Barbaro appeared in 1556, and his commentary was translated into Latin for this new edition of 1567. Among the many woodcuts is an artist’s conception of the Clepsydra of Ctesibius, a water clock with gears to turn a dial that showed the hour of the day and night. 21. Besson, Jacques, 1540-1573. Theatrum instrumentorum et machinarum. Lyon: Apud Barth. Vincentium, 1578. This was Besson’s last work, published in multiple editions and several languages. In it, the mathematician from Orléans described and illustrated instruments, tools, pumping plants, military devices, and a decorative water clock. Since it was continuously powered by water from a natural stream, the clock would run accurately without having to be wound, or so Besson claimed. He omitted the details, however, promising that, “God willing, I shall write about [them] another time.” 22. Fine, Oronce, 1494-1555. Opere. Venice: Presso Francesco Franceschi Senese, 1587.

Water clock controlled by a float and siphon. From Oronce Fine. Opere. Venice, 1587 (item 22).

Oronce Fine was a mathematician in Paris, and this is the first Italian translation of his works. The part on horology includes an ingenious


design for a simple water clock that utilizes a ship for a float and its mast for a siphon. The water siphons into an open tub at the bottom, and as the tank empties and the ship slowly falls, an hour hand rotates around the clock’s dial. 23. Caus, Salomon de, 1576-1626. Les raisons des forces mouuantes auec diuerses machines. Frankfurt: En la boutique de I. Norton, 1615. Among the ingenious water-powered machines of Salomon de Caus illustrated in this folio volume are mechanical birds, a lathe, music boxes, a fire engine, and a hydraulic clock that would run perpetually. A constant and regulated water supply would fill a bucket with water once a minute, causing a lever to rise and push gears that turn the clock dials. When full, the bucket would tip to dump the water and begin the process anew. The full-page engraving shows a cutaway view, exposing the mechanical gears and bucket of water behind the clock face.

Water-powered mechanical clock, with a bucket that fills and dumps once a minute to control the mechanism. From Salomon de Caus. Les raisons des forces mouvantes avec diverses machines. Frankfurt, 1615 (item 23).


24. Schott, Gaspar, 1608-1666. Mechanica hydraulico-pneumatica. Frankfurt: sumptu heredum J. G. Schönwetteri, excudebat H. Pigrin typographus, Herbipoli, 1657. The Jesuit scientist Gaspar Schott published books on mechanics, natural magic, and cosmology. His Mechanica hydraulico-pneumatica describes mechanical devices powered by water or wind, some of which are perpetual motion machines. One plate illustrates a perpetually-powered water clock, in which a constant drip of water moves the dial hands. The source of water is continually replenished by a siphon. On the same plate, an Archimedean screw keeps turning without additional power. 25. Perrault, Claude, 1613-1688. Recueil de plusieurs machines, de nouvelle invention. Paris: Chez Jean Baptiste Coignard, 1700. Claude Perrault was a founding member of the Académie des Sciences in Paris. His posthumous Recueil de plusieurs machines includes a design for a water-powered pendulum clock that dates to about 1669. Perrault sent plans for the clock to Christiaan Huygens, who apparently never replied. The clock could have worked but it would have served no practical purpose, given the comparative portability and other advantages of mechanical clocks driven by weights and springs. 26. Bion, Nicolas, 1652-1733. The Construction and Principal Uses of Mathematical Instruments. London: Printed by H.W. for J. Senex and W. Taylor, 1723.

Hypothetical design for a water-powered pendulum clock. From Claude Perrault. Recueil de plusieurs machines. Paris, 1700 (item 25).

Bion was a Paris instrument maker with a shop located in the Quai de l’Horloge, the Clock Wharf. Edmund Stone prepared this first English translation of Bion’s comprehensive work on scientific instruments. Among them is a water clock, illustrated to show how water drains from a drum, which slowly descends to indicate hours as it falls. Other illustrations on the same plate depict a variety of sundials that were convenient, accurate, and inexpensive alternatives to portable spring-driven mechanical clocks.


4. CLOCK MAKING he “Clock maker,” a famous woodcut by Jost Amman, shows a T tradesman at work with an assistant in his sixteenth-century shop, discussing his clocks with a prospective customer. The occupation was by this time wellestablished, although its origins in the thirteenth century are obscure. A forge, as shown in Amman’s woodcut, was an integral tool of the early trade, but refined tools specific to clock and watch making soon were invented. Many of these resembled familiar tools of the metal working industry, but in miniature form. Refined but typical versions of them were illustrated in the pages of the Encyclopédie, which provided a virtual catalog of clock making tools. The first practical manual on clock making was written by William Derham, a clergyman who later wrote books on natural theology and compared the ordered universe of the creator to the clockwork machinery of a clock maker. His The Artificial Clock-Maker includes the only documentation of a claim by Robert Hooke to have invented the anchor escapement, which is usually credited to William Clement.

The Clock maker. From Hartmann Schopper. [Panoplia] omnium illiberalium mechanicarum. Frankfurt, 1568 (item 27).

It was not Robert Hooke’s only foray into the design of clock mechanisms and tools. One of his contributions was an early machine shop tool that automated the process of cutting clock gears. Although he did not publish any description of it, variations of the machine were soon included in books on clock making and machine tools. Knowing the tools of the trade and how to use them was as important to a clock maker as an understanding of the mechanical workings of a clock.


27. Schopper, Hartmann, b. 1542. [Panoplia] omnium illiberalium mechanicarum. Frankfurt: Sigismundus Feyerabent, 1568. Clock making was a well-established line of work by the mid-sixteenth century. The famous woodcuts by Jost Amman in this book were an attempt to portray all the professions, both spiritual and worldly, and especially the arts, crafts, and trades. The “Clock maker” (Uhrmacher) shown in one of the illustrations works with an assistant while discussing his clocks with a prospective customer. A forge to fashion the metal parts in the background was an integral tool of the trade. 28. Derham, William, 1657-1735. The Artificial Clock-Maker. London: Printed for James Knapton, 1696. The Artificial Clock-Maker was Derham’s first book, a practical manual on clock making without precedent. It treats the subject so plainly, Derham wrote, “as to be understood by a vulgar workman.” The word “artificial” refers to mechanical clocks in contrast to sundials and water clocks. Derham was a clergyman and in his later book, Astro-Theology, he compared the ordered universe of the creator to the clockwork machinery of a clock maker. 29. Derham, William, 1657-1735. The Artificial Clock-Maker. The Second Edition Enlarged. London: Printed for James Knapton, 1700. The first edition of Derham’s practical Title page of the first practical book on clock making. From William Derham, The Artificial manual on making mechanical clocks Clock-Maker. London, 1696 (item 28). was well received and several editions followed. In addition to practical help for the working clock maker, Derham gave one of the first attempts at a history of horology. Added to this second edition was a folded plate to instruct the reader on basic parts of a pendulum clock.


Complex cutting machine for making gear wheels and pinions. From Antoine Thiout. Traité de l’horologerie, méchanique et pratique. Paris, 1741 (item 32).

30. Derham, William, 1657-1735. The Artificial Clock-Maker. The Third Ed. London: Printed for James Knapton, 1714. Invention of the anchor escapement is often credited to the London clockmaker, William Clement, who began selling clocks with the anchor escapement around 1680. In The Artificial Clock-Maker, Derham reported that the scientist Robert Hooke claimed it was his invention, which he showed to the Royal Society around 1665. There is no mention of the invention in any of Hooke’s papers, however, and Derham’s mention of it in the several editions of his book is the only evidence for Hooke’s claim. 31. Leupold, Jacob, 1674-1727. Theatrum machinarum generale. Leipzig: druckts Christoph Zunkel, 1724. This book by the German scientist and mathematician Jacob Leupold was both important and popular for its detailed descriptions of machine tools. The process of cutting clock gears benefitted from the invention of early machine shop tools, and Leupold described one he designed that was powered by an easy-to-use foot treadle. With such a machine, Leupold claimed, an artisan could do more in an hour, and more accurately, than had been possible in a day by hand.


32. Thiout, Antoine, the elder, 1692-1767. Traité de l’horologerie, méchanique et pratique. Paris: Chez Charles Moette, 1741. The 91 folded engraved plates in the two volumes of this work describe clock and watch tools and mechanisms popular in the eighteenth century, such as a complex cutting machine for making gear wheels and pinions. Robert Hooke, a founding member of the Royal Society of London, invented such a gear-cutting machine around 1672. Instead of filing gear teeth by hand on a blank metal disk, this machine cut them with automatic precision. 33. Encyclopédie. Recueil de planches, sur les sciences, les arts libéraux, et les arts méchaniques, avec leur explication. Troisieme livraison. Paris: Chez Briasson, David, Le Breton, 1765. Many clock- and watch-making tools are smaller versions of typical metal-working tools, such as anvils, vises, hack saws, files, pliers, and hammers. A full complement of clockmaking tools was illustrated in the plates for the Encyclopédie, which had a long section on horology with many articles on various aspects of the subject. The illustrated tools were those that would have been available from toolmakers that specialized in supplying the clock- and watch-making trade.

Special tools for the clock- and watch-making trade. From Encyclopédie. Recueil de planches. Paris, 1765 (item 33).


5. ENERGY, ESCAPEMENT, AND EARLY CLOCKS heoretical and practical aspects of mechanical clocks and clock-making T began to appear as parts of large scientific treatises published in the sixteenth and seventeenth centuries, often with graphics to explain how the parts functioned to drive and regulate a clock mechanism. One of the earliest illustrations of a weight-driven clock appeared in an encyclopedic book by Girolamo Cardano, as part of Cardano’s general discussion on the use of one kind of force, that is, a falling weight. No woodcut was available for the first edition in 1550, however, and the space where it would have gone was simply left blank. Readers of the French translation were luckier in 1566, when a small woodcut was supplied to clearly show the weights hanging from a mechanical clock, albeit without revealing the rest of the mechanism. The energy from a coiled spring, released as it unwinds, is another way to drive the movement in a clock. The spring is usually enclosed in a drum, with one end attached to a fixed center axle and the other end attached to the wall of the drum. The first printed illustration of such a mechanism appeared in 1557, in another book by Cardano. The woodcut shows only the mechanism and not the face, hands, or case, and is hard to recognize as a clock. It detailed an important conical-shaped part, the fusee, used in many clocks to compensate for the diminishing power of the unwinding spring. The first printed illustration with details of a mechanical clock’s escapement appeared in 1617, in a book by Robert Fludd. The escapement is essential for any mechanical clock and is discussed in every treatise on clock and watch making. Its function

Weight-driven mechanical clock, from Girolamo Cardano. Les livres ... intitulez De la subtilité, & subtiles inuentions. Paris, 1566 (item 35).


is to control the fall of clock weights or the unwinding of a clock spring to drive the clock at a constant rate. Fludd’s illustration shows a verge escapement, typical of many early clocks. As the verge, a vertical rod with two tabs or pallets, rotates back and forth, the pallets alternately engage and release the escape wheel. A crossbar or foliot at the top of the verge, also shown in Fludd’s book, controls the oscillating motion that is necessary for accurate timekeeping. New concepts for escapements were announced in scientific and technical publications, and celebrated for being as important as any other new technology. Precision mattered. Some books, without focusing on the clock’s mechanism at all, simply showed how to use the best available clocks to get the most accurate readings for scientific purposes, especially astronomical observations.

First printed illustration of a clock mechanism. From Girolamo Cardanao. De rerum varietate libri XVII. Basel, 1557 (item 34).


34. Cardano, Girolamo, 1501-1576. De rerum varietate libri XVII. Basel: Henrichum Petri, 1557. The first printed illustration of a clock mechanism appeared in this folio encyclopedia as part of Cardano’s discussion of motion. The clock uses a spring to drive the mechanism and compensates for the diminishing power of the unwinding spring with a conical fusee. The fusee was a standard part of many later spring-driven clocks and watches that gave the spring a nearly constant driving force. An octavo edition appeared the same year and used the same woodcut. 35. Cardano, Girolamo, 1501-1576. Les livres ... intitulez De la subtilité, & subtiles inuentions. Paris: Per Claude Micard, 1566. An early illustration of a weight-driven clock appeared in another encyclopedic book by Cardano. Curiously, the space for the woodcut was left blank in the original Latin edition published by Johann Petreius in 1550. This French translation added a small woodcut, recognized as one of the earliest printed illustrations of a mechanical clock. It shows little of the mechanism other than the weights, dial hand, and a bell to sound the hour. The text describes the falling weight as a type of force. Later in the book, spring-driven clocks are discussed as a new invention, but not illustrated. 36. Brahe, Tycho, 1546-1601. Astronomiae instauratae mechanica. Nuremberg: Apud Levinum Hulsium, 1602. Tycho Brahe owned some of the best astronomical instruments of the sixteenth century, which he described and illustrated in this book. He made observations of star positions with the mural quadrant and used two clocks to reduce error and record the exact moment of observation. Brahe mentioned that there were four clocks in the observatory, and the largest must have been huge. One of the three wheels was cast from solid brass, had 1,200 teeth, and a diameter of two cubits – about three feet.


37. Fludd, Robert, 1574-1637. Utriusque cosmi maioris scilicet et minoris metaphysica, physica atque technica historia in duo volumina. Oppenheim: Aere Johan Theodori de Bry, 1617-1618. The key invention that made all mechanical clocks possible was the escapement, and Robert Fludd’s illustration of a mechanical clock’s escapement is the first one to appear in print. His book, The History of the Macrocosm and Microcosm, is an immense encyclopedia, famous for many elaborate engravings that illustrate an interconnected universe. The escapement image is more didactic, demonstrating how a crown wheel, driven by a weight or spring, is allowed to “escape” as two pallets on a vertical shaft alternately catch and release it. An oscillating bar regulates the motion that ultimately moves the hands of the clock. 38. Martinelli, Domenico, 17th century. Horologi elementari divisi in qvattro parti. Venice: Per Bortolo Tramontino, 1669.

Verge and foliot escapement. From Robert Fludd. Utriusque cosmi maioris. Oppenheim, 1617-1618 (item 37).

Martinelli described mechanical timekeepers powered by one of the four elements -- earth, water, air, or fire. One of the 16 plates shows a clock driven by a weight (representing the element earth) that is an imitation of the tower clock on St. Mark’s Square in Venice. Two figures, the Moors, strike a bell to sound the hours, while the three Magi, led by an angel, periodically visit the Virgin and Child. Below them are the dials to show hours, minutes, and phases of the Moon.


Dead beat escapement. From Alexander Cumming. The Elements of Clock and Watch Work. London, 1766 (item 41).

39. Horrebow, Peder, 1679-1764. Basis astronomiae; sive, Astronomiae pars mechanica. Copenhagen: Apud viduam beati Hieron. Chr. Paulli, 1735. Copenhagen’s great fire of 1728 destroyed the papers and instruments of the astronomer Ole Rømer, who died in 1710. His assistant, Peder Horrebow, published this account of Rømer’s methods and discoveries, and it is still a principal source about Rømer’s work. One of the plates shows Rømer working at his meridian telescope, observing star positions. A Huygens-style pendulum clock, probably more accurate than the two clocks built into the wall, hung by the window where the astronomer could easily read the time of an observation.


40. Le Roy, Julien, 1686-1759. “Échappement de pendule de M. Sully, perfectionné.” In: Machines et inventions approuvées par l’Académie Royale des Sciences, vol. 6 (1732-34). Paris: Chez A. Boudet, 1735. Clockmaker Henry Sully designed an escapement that was included in the multi-volume set of descriptions of machines examined and approved by the Académie des Sciences in Paris. The well-illustrated collection, compiled by the engineer Jean Gaffin Gallon, documents scientific instruments and technical achievements in eighteenth-century France. These included textile and paper-making machines, hydraulic engineering devices, umbrellas, calculating machines, and clocks. Sully worked in both London and Paris, and this particular design that utilized a spring balance was perfected by another Paris clockmaker, Julien Le Roy. 41. Cumming, Alexander, 1733-1814. The Elements of Clock and Watch-Work, Adapted to Practice. London: Printed for the author; by J. Hughs, 1766. Cumming’s book, the second work in English on clock making, received a long and critical review in the Gentleman’s Magazine when published, but today is considered a definitive professional textbook. It provides details of general clock-making issues, showing for example, George Graham’s 1715 improvement of the anchor escapement. Known as the deadbeat escapement, Cumming’s illustration shows how the pallets are designed to fall clean on the escape wheel, producing no recoil or backward motion. 42. Reid, Thomas, 1746-1831. A Treatise on Clock and Watch Making. Second ed. Glasgow: Blackie & Son, 1844. Clockmaker Thomas Reid was 80 when this book first appeared in 1826. It was quickly acclaimed the best treatise on the subject, and many editions and reprints followed. Its 33 chapters gave details about things such as the anchor escapement, which allowed the pendulum to swing in a very small arc. The name derives from the shape of the pallets, the two angled pieces that catch the escape wheel and which resemble the flukes of an anchor. William Clement, regarded as the inventor, was in fact originally an anchor-smith.


6. PENDULUM CLOCKS cientific reports in the seventeenth and eighteenth centuries were Simportant ways of publishing information about discoveries and inventions related to pendulum clocks. The Accademia del Cimento in Florence published an influential set of research reports in 1667, which included a report on experiments with pendulums. It pointed out that Galileo was the first to observe that a pendulum would be an ideal timekeeper, and that he had described a clock mechanism regulated by the swing of a pendulum to his son, Vincenzo. The academy apparently did not know that Vincenzo made a drawing, and illustrated the 800 copies of the report instead with a fanciful clock that represented the concept only. In contrast, the pendulum clock illustrated in Christiaan Huygens’s landmark book of 1673, Horologium oscillatorium, was anything but fanciful. Huygens designed the clock in 1656, and contracted with the clockmaker Salomon Coster in The Hague to build one the next year. It was the first successful pendulum clock, but Huygens improved its precision by altering the pendulum’s swing with two curved metal pieces at the top, changing the swing to the arc of a cycloid. The mathematical proof that a cycloid was the perfect curve to produce constant oscillation for a pendulum is what he presented in his book in 1673.

A view of Huygens’s pendulum clock. From Christiaan Huygens. Horologium oscillatorium. Paris, 1673 (item 44).

An unexpected conclusion about the length of a pendulum appeared in an important collection of nine scientific reports, published under the auspices of the Académie des Sciences 20 years later. Jean Richer had taken two Huygens-style pendulum clocks on an astronomical expedition to South America in 1672, and discovered that one of them, set to beat once per second in Paris, ran slower in Cayenne. Beyond the practical result that the length of a one-second pendulum is not universal, his report had implications about the varying strength of gravity and, ultimately, about the shape of the Earth.


A change in temperature was another problem that affected the accuracy of early pendulum clocks. Cold weather would shorten a rod and cause it to swing faster, while warm weather caused it to expand and lengthen, slowing the swing. The Ellicott Pendulum offered a solution with a design that would compensate for errors caused by temperature changes. John Ellicott announced it to the Royal Society of London in 1752, and a report was subsequently published in the Society’s Philosophical Transactions. 43. Accademia del Cimento, Florence. Saggi di naturali esperienze. Florence: Giuseppe Cocchini, 1667. Galileo observed that a pendulum would be perfect for regulating a clock, but he never made one and left only a sketchy design, drawn by his son, Vincenzo. The Accademia del Cimento in Florence published an illustration of the “Galileo clock” to honor Galileo in this collection of research reports, written by the Academy’s secretary, Lorenzo Magalotti. Vincenzo’s drawing was either not known or not available, as the engraving is an imaginary clock. Printing began in 1664 and was not completed until 1667. Copies were distributed by gift to friends and colleagues and not sold through bookshops. 44. Huygens, Christiaan, 1629-1695. Horologium oscillatorium. Paris: Apud F. Muguet, 1673. Huygens, who designed the first successful pendulum clock in 1656, enclosed the pendulum string with two curved metal strips that made the swing slightly steeper at the ends. In the Horologium oscillatorium of 1673, he presented a mathematical proof that the curve required for a pendulum to keep perfect time was a cycloid. The book’s famous woodcut shows the clock, its mechanism, and the “cycloid cheeks” that changed the swing from a circle to a cycloid.


Design to illustrate Galileo’s early concept of the pendulum as a regulator for a clock, from Accademia del Cimento. Saggi di naturali esperienze. Florence, 1667 (item 43).

45. Schott, Gaspar, 1608-1666. Technica curiosa, sive mirabilia artis. Nuremberg: sumptibus Johannis Andreae Endteri, 1664. Gaspar Schott published an account of pendulum clocks in his Technica curiosa, seven years after the inventor, Christiaan Huygens, collaborated with Salomon Coster to build one and patent it. Huygens’s own book, Horologium oscillatorium, did not appear until 1673, although he did publish a short description in a now very scarce pamphlet in 1658. Schott’s account is that of a scientific reporter, explaining to readers a variety of methods for converting older clocks with mechanisms that couple the new oscillator, a pendulum, to the escapement. 46. Richer, Jean, 1630-1696. “Observations astronomiques et physiques.” In: Recueil d’observations faites en plusieurs voyages. Paris: De l’imprimerie royale, 1693. The astronomer Jean Richer discovered that gravity varies at different points on Earth when he took a pendulum clock, set to beat once per second in Paris, to Cayenne near the equator in 1672. The clock lost time and the length of the pendulum had to be shortened. It was, Richer stated, “one of the most considerable observations I made.” His report, one of nine from various expeditions published at royal expense by the Académie des Sciences in Paris, was illustrated by Sébastien Le Clerc. His engraving at the head of the report shows one of Richer’s two clocks and other instruments. 47. Bion, Nicolas, 1652-1733. Traité de la construction et des principaux usages des instrumens de mathematique. The Hague: Chez P. Husson, 1723.

“Cycloid cheeks,” for controlling the swing of the pendulum in Huygens’s clock. From Nicolas Bion. Traité de la construction et des principaux usages des instrumens de mathematique. The Hague, 1723 (item 47).

Bion was an instrument maker in Paris whose catalog of instruments went through several editions and translations. This second edition in French appeared the same year as an English translation by Edward Stone. It was more about the use of instruments than constructing them. Bion advised readers that a pendulum clock was necessary for an astronomer to accurately time


observations. The pendulum clock he illustrated is a nicely engraved copy of the woodcut from Huygens’s Horologium oscillatorium of 1673. 48. Cassini, Jacques, 1677-1756. “Moyens de construire un pendule qui ne puisse point s’allonger par la chaleur, ni se raccourcir par le froid.” In: Histoire de l’Académie Royale des Sciences. Avec les mémoires de mathematique & de physique, [for the year 1741]. Paris: Imprimerie Royale, 1744. Cassini took over as head of the Paris Observatory from his father around 1709. For him and other astronomers, pendulums that changed length in cold and hot weather due to expansion and contraction were a problem, making their clocks imprecise. His solution, published in the Academy of Science’s Mémoires, was a pendulum made of iron and copper rods. Theoretically their different rates of expansion would keep the pendulum’s overall length constant.

The Ellicott pendulum, designed to compensate for changes in temperature. From John Ellicott. “A Description of Two Methods…” In: Philosophical Transactions, vol. 47. London, 1753 (item 50).

49. Marinoni, Giovanni Jacopo de, 1676-1755. De astronomica specula domestica et organico apparatu astronomico. Vienna: Leopoldus Joannes Kaliwoda, 1745. Marinoni established a finely equipped observatory in Vienna, where he was the Imperial Court Mathematician. This account describes his instruments, which are well-illustrated with 43 folded plates. One of them was a tall-case pendulum clock from France, called the “Paris Equation Clock.” An equation clock includes a mechanism to simulate the equation


of time, so that the clock will show solar time, as would be shown on a sundial. A finely engraved folded plate shows the complicated dials on the clock’s face, or “frontispicium.” 50. Ellicott, John, 1706-1772. “A Description of Two Methods, by Which the Irregularity of the Motion of a Clock … May Be Prevented.” In: Philosophical Transactions of the Royal Society of London, vol. 47. London, 1753. Ellicott is remembered for his work on temperature-compensated pendulums, but during his lifetime his superior clock-making skills led to his appointment as Clockmaker to King George III. The “Ellicott Pendulum” used iron and brass rods, cleverly connected to keep the overall length constant and compensate for errors otherwise caused by changes in the temperature. His design was announced in 1752, and published in the Royal Society of London’s Philosophical Transactions with a large folded plate.

Engraved headpiece by Sébastien Le Clerc of seventeenth-century scientific instruments. From Recueil d’observations faites en plusieurs voyages par ordre de sa Majesté. Paris, 1693 (item 46).

51. Gallonde, Louis Charles. “Pendule inventée par M. Gallonde, Me. Horloger.” In: Machines et inventions approuvées par l’Académie Royale des Sciences, vol. 7 (1734-54). Paris: Chez A. Boudet, 1777. The engineer Jean Gallon received a commission in 1729 to edit all the descriptions of machines approved by the Académie des Sciences. The result was this seven-volume record of the history of inventions in France in the late seventeenth and early eighteenth centuries, including many clocks. One of them was a mechanism for a pendulum clock by Louis Charles Gallonde, first published in the Academy’s Mémoires for 1740. The noteworthy design reduced friction, allowing a one-pound weight to power the clock.



he artistic, symbolic, and decorative features of a clock may sometimes T be more important than its precision. For many people, a clock not only has to accurately tell the time, it needs also to be an interesting object, and plenty of them were described in scientific and technical books. What could be more interesting than a clock powered by the mysterious force of magnetism? After William Gilbert’s De magnete (1600) put a spotlight on the study of magnetic phenomena, an age of magnetism followed that was characterized by scientific publications that attempted to understand it. None was more comprehensive than the work of Athanasius Kircher, which analyzed every form of attraction as a kind of magnetism, including the power of the Sun to attract a flower and make it function as a kind of vegetable sundial. Kircher also described ways to secretly use magnets to mysteriously drive a clock, except that the real force was some other kind of mechanical drive powered by water or falling weights. His illustrations revealed the secret sources Sunflower clock. From Athanasius Kircher. Magnes siue de arte magnetica opus of power, but other authors did not feel the tripartitum. Rome, 1641 (item 52). same obligation to disclose how their perpetual motion clocks could actually work. Clocks that seemed to run without any source of power were not uncommon in seventeenth-century technical books. These were for the reader to contemplate as provocative ideas, no more preposterous than a lighter-than-air ship, held aloft by copper spheres evacuated with an air pump and described in Francesco Lana Terzi’s Prodromo (1670), along with a perpetual motion clock. Electricity was another mysterious force studied in the seventeenth and eighteenth centuries. Electrical experimenters could point to very few practical applications of their static generators, but they could delight viewers with plenty of novel demonstrations. A clock escapement powered by static repulsion, as described in James Ferguson’s textbook on electricity, probably was not a great timekeeper, but it would have been great fun to watch the wheels turn by an unseen electrical force.


After all, how many of us really need precision to the microsecond? A clock that is accurate to within a few minutes per day might serve one’s practical needs perfectly well, especially if it is an interesting object, entertaining to watch, and provocative regarding ideas about universal forces in nature. 52. Kircher, Athanasius, 1602-1680. Magnes siue de arte magnetica opus tripartitum. Rome: Sumptibus Hermanni Scheus, 1641. Kircher wrote a short dissertation on magnetism in 1631, and 10 years later produced this huge scholarly encyclopedia on the subject, with 31 engraved plates. One of them shows the curious sunflower clock, floating on a piece of cork with roots in the water. Vegetable magnetism supposedly caused the flower to follow the Sun, so that a pointer fixed in the center would indicate the hour on a clock dial. Its function may have been as much symbolic as practical. 53. Kircher, Athanasius, 1602-1680. Magnes sive de arte magnetica opus tripartitum. Cologne: Apud Iodocum Kalcouen, 1643.

A magnetic clock. From Athanasius Kircher. Magnes sive de arte magnetica opus tripartitum. Cologne, 1643 (item 53).


A second corrected edition of Kircher’s encyclopedia on magnetism appeared only two years after the first. Both editions present a variety of designs for magnetic clocks, as much to showcase the qualities of magnets as to present accurate timekeepers. One of them used a small Earth-shaped magnet called a terrella, mysteriously turning inside a liquid-filled glass globe while a fish pointed to the hour. Hidden below, a mechanism controlled by a water clock rotated a strong magnet, causing the magnetic terrella to rotate sympathetically.

54. Lana Terzi, Francesco, 1631-1687. Prodomo ouero saggio di alcune inuentioni nuoue premesso all’arte maestra. Brescia: Per li Rizzardi, 1670. Lana Terzi, a Jesuit and an associate of Kircher, was professor of physics at Brescia. His book of marvels is best known for a concept of an airship, held aloft by four evacuated copper spheres. The other 19 copperplates show more inventions and instruments, including a perpetualmotion clock. The pendulum and crown wheel escapement are driven by a ball rolling down an inclined plane. An Archimedean screw raises the ball in a perpetual cycle, except there is no source of power to turn the screw. 55. Wheeler, Maurice. “A Letter ... Concerning a Movement that Measures Time after a Peculiar Manner.” In: Philosophical Transactions of the Royal Society of London, vol. 14 (1684). Oxford: 1684. Although there were earlier descriptions of an inclined-plane clock, Wheeler’s account Inclined-plane clock, descending on a spiral in the Philosophical Transactions was the first track. From Nicolas Grollier de Servières. clear explanation, and he claimed to be the Recueil d’ouvrages curieux de mathématique inventor. The cylindrical clock itself was three et de mécanique.Lyon, 1719 (item 56). and one-half inches in diameter and revolved once a day, for seven days, rolling down a board that was six feet long. The engraved illustration had room to show only a foreshortened plank. A cutaway view exposed the tiny gears and pendulum of the clock’s mechanism. 56. Grollier de Servières, Nicolas, comte, 1677-1745. Recueil d’ouvrages curieux de mathématique et de mécanique. Lyon: D. Forey, 1719. The designs for clocks and other mechanical curiosities in this book were all created by Nicolas Grollier de Servières, a cousin of the bibliophile, Jean Grolier. Some of his inclined-plane clocks seem much influenced by Wheeler’s design in the Philosophical Transactions. The weight of the clock itself provided the driving force for these clocks. One design twisted the inclined plane into a spiral track, and made the clock an attractive feature for a table top. Grollier de Servière displayed models of his work in Lyon where many distinguished visitors came to see them, including Louis XIV.


In addition to clocks, his designs included a version of the book wheel, designed by Agostino Ramelli, which allowed many books to be consulted by rotating it. 57. Grollier de Servières, Nicolas, comte, 1677-1745. Recueil d’ouvrages curieux de mathématique et de mécanique. Seconde ed. Paris: Chez Ant. Jombert, 1751. A second edition of this catalog of curious inventions appeared in Lyon in 1733, and was reissued in Paris, as here, with a new title page in 1751. After his death, Grollier de Servière’s son and grandson continued to display his models in Lyon. The grandson compiled the account of them for this book, but he may not have known many working details. In one attractive clock, an Archimedean screw continually raised a ball to roll down a spiral track. Two dials in the base showed hours and minutes, but the source of power was not revealed.

Inclined-plane clock, with details of the weighted internal pendulum and gears on the right. From Maurice Wheeler. “A Letter ... Concerning a Movement that Measures Time after a Peculiar Manner.” In: Philosophical Transactions, vol. 14 (1684) (item 55).

58. Schott, Gaspar, 1608-1666. Magia universalis naturae et artis. Würzburg: sumptibus haeredum Joannis G. Schönwetteri ..., excudebat Henricus Pigrin, 1657-1659. Gaspar Schott’s encyclopedic-like survey of natural and artificial wonders included a lengthy section on magnetism, with reports of scientific and technological achievements of his contemporaries. These included


A clock powered by static electricity and other electrical machines. From James Ferguson. Introduzione alla elettricità. Florence, 1778 (item 59).

accounts of Athanasius Kircher’s curious magnetic clocks. In one, a magnetic bird appeared to chase a magnetic lizard on a column marked with hours. In another, a column of glass spheres used floating magnetic figures to point the hours. Schott, a Jesuit, was transferred to Würzburg in 1655, where he wrote many books on mechanics, natural magic, and cosmology. Magia universalis naturae et artis was one of his earliest. 59. Ferguson, James, 1710-1776. Introduzione alla elettricità. Florence: Per Gaetano Cambiagi, 1778. In the eighteenth century, books on electrical experiments and theories were popular in all languages and in every country. Experiments with electrostatic generators, Leyden jars, and even lightning gave practitioners much to think and write about. Electrical demonstrations were popular, and Ferguson’s textbook (An Introduction to Electricity. London, 1770) provided clear descriptions of the experiments he could demonstrate. This rare Italian edition is evidence of its broad appeal. Among his several electrical devices was a clock, designed to show daily movements of the Sun and Moon. A static charge drove the fins on a great wheel to power the clock.


8. STANDARD TIME he ancient text of Ptolemy’s Geography discussed the concept of T longitude, or the distance east or west from a prime meridian. Maps of the whole world, as Ptolemy would have known it, were included in early printed editions of the Geography in the sixteenth century. They showed Ptolemy’s prime meridian of zero degrees longitude somewhere near the present-day Canary Islands. This was the western-most part of the known habitable world, and the map stretched to the east for 180 degrees of longitude, representing a 12-hour difference in time. The correspondence between time and longitude is inseparable, and textbooks on astronomy could clearly make the point by showing how the Earth’s circumference of 360 degrees can be divided into 24 equal parts. Every segment of 15 degrees of longitude represents a one-hour difference in time, so the longitude of any location can be calculated by knowing the difference in the local time from that of the time at the prime meridian.

Map of the whole inhabited world known in Ptolemy’s era, with 0 degrees longitude at the Fortunate Islands on the western edge. From Ptolemy. Geographicae enarrationis libro octo. Strassburg, 1525 (item 60).


The Meridian of London, with meridian lines marked every 15 degrees distance from the prime meridian. From James Ferguson. The Young Gentlemen and Lady’s Astronomy. London, 1768 (item 62).

Greenwich, or the Meridian of London as it was called in some texts, was not officially adopted as the prime meridian until October 1884, at an international conference in Washington, DC. The printed proceedings of the conference are a permanent record of the resolutions that established an internationally recognized prime meridian and universal day. After that, everyone set their clocks by the master clock at Greenwich. Although the prime meridian was originally an important maritime standard for determining longitude at sea, it was the needs of the railroads for synchronized clocks that brought about standard or universal time. In North America a scientific society, the American Metrological Society, published a report on the confusing mass of time standards used by railroads, with recommendations for reform with standard time zones that we use today. Standard time is still based on the time at zero degrees longitude at Greenwich, and is known as Coordinated Universal Time (UTC). Publications from the National Institute of Standards and Technology (NIST) provide standards that allow consumer clocks to be synchronized with UTC, and nearly as accurate as the world’s best atomic clocks.


60. Ptolemy, second century. Geographicae enarrationis libro octo. Strassburg: Iohannes Grieningerus, communibus Iohannis Koberger impensis excudebat, 1525. The location for the prime meridian at zero degrees longitude is arbitrary. Ptolemy chose the westernmost point of land known in his time, the Fortunate Islands, often identified as the present-day Canary Islands. The world map in this fourth Strassburg edition of Ptolemy’s Geographicae shows the whole inhabited world known in his era and spans 180 degrees. It represents a time span of 12 hours, from noon at the Fortunate Islands to midnight at the eastern edge. The woodcut was printed from the same block used in the 1522 edition. 61. Kircher, Athanasius, 1602-1680. Ars magna lucis et umbrae, in X. libros digesta. Amsterdam: Apud Joannem Janssonium à Waesberge, & Haerdes Elizaei Weyerstraet, 1671. Kircher’s Ars magna lucis et umbrae originally appeared in 1646, with an elaborate diagram in the form of an olive tree graphically displaying the time in far-flung Jesuit outposts around the world. Rome, at the tree’s base, represents standard time while Quebec, a leaf on a high branch, is six hours behind. When this second edition appeared in 1671, the original engraving was replaced by a completely new and even larger one, challenging a reader to safely unfold and examine it. Keeping track of multiple local times may have had significant practical importance for railway passengers and crews in the nineteenth century but, as Kircher’s Jesuit time tree demonstrates, it was not an entirely new practice. 62. Ferguson, James, 1710-1776. The Young Gentlemen and Lady’s Astronomy. London: Printed for A. Millar and T. Cadell, 1768. Before the international agreement of 1884, countries tended to use their own national observatory as the prime meridian. Astronomer James Ferguson used the Meridian of London, which passed through the Greenwich observatory. This first edition of one of his popular works is based on a set of lectures given to a teenage girl. She would have learned from Ferguson that each 15 degrees distance from the prime meridian represents exactly one hour’s difference in time from the standard time at Greenwich.


Time Ball for regulating marine chronometers. From R. Wauchope. “Description of the Apparatus or Signal-Post for Regulating Chronometers.” In: The Edinburgh New Philosophical Journal, vol. 8, 1830 (item 63).

63. Wauchope, R. “Description of the Apparatus or Signal-Post for Regulating Chronometers.” In: The Edinburgh New Philosophical Journal, vol. 8. Edinburgh, 1830. Even the most precise nineteenth-century chronometers needed to be regulated against a standard time device or signal. One widely used signal was a time ball dropping at noon. This article described one in Portsmouth, England, large enough to give a visual signal for setting chronometers on all the ships in port. It appeared in The Edinburgh New Philosophical Journal, which ran from 1826 until 1864, when it was absorbed by the Quarterly Journal of Science. It began as the Edinburgh


Philosophical Journal in 1819. The Linda Hall Library owns complete runs of all three titles of the periodical. 64. Fisher, R.S. American Railway Guide. New York: Curran Dinsmore & Co., 1853.

Title page of a mid-nineteenth century railroad guide, an essential pocket timetable for passengers. From The American Railway Guide, June 1853 (item 64).

Growing railroad networks in the nineteenth century highlighted the need for precise and standard timekeeping. Before standard railway time took effect in the United States, there were about 50 regional times. Monthly railway guides tried to make sense of it all for the average traveler. This pocketsized one from the 1850s was sold by subscription, so that it could be discarded and replaced with a later version the next month. A complete railway map was promised on the title page, but it is missing and may have been separately issued with the subscription and not with each monthly guide.

65. Abbe, Cleveland, 1838-1916. “Report of Committee on Standard Time. May 1879.” In: American Metrological Society Proceedings, vol. 2. New York, 1880. This unassuming committee report, buried in the proceedings of a technical society, provided the outline to establish uniform timekeeping with five time zones across the United States and Canada. A map issued with the report shows the 75 time standards used by railroads in North America in 1879. Instead of this confusing multiplicity of time standards, the committee recommended five time zones an hour apart, designated Eastern, Atlantic, Valley, Mountain, and Pacific Time. The areas designated by “Eastern” and “Atlantic” time were switched, and the “Valley” zone became “Central” when the recommendations were adopted.


66. Fleming, Sandford, 1827-1915. Buffalo Convention: Report / Standard Time Committee, American Society of Civil Engineers. [Buffalo?]: American Society of Civil Engineers, 1884. The Standard Time Committee of the ASCE recommended adoption of a standard 24-hour clock. To help people convert their watches from 12 - 24-hour dials, the Committee’s report included a separate sheet, printed with multiple clock dials showing hours 13-24. One of these paper dials, cut and pasted on a conventional pocket watch, would instantly create a 24-hour dial. Unlike the Committee’s recommendation for reform of railway time into five standard time zones that took effect the previous year, the 24-hour standard for clock dials was largely ignored. 67. International Meridian Conference (1884). International Conference Held at Washington for the Purpose of Fixing a Prime Meridian and a Universal Day. October, 1884. Protocols of the Proceedings. Washington, DC: Gibson Bros., 1884. In practice, most nations and seamen already used Greenwich as the prime meridian, but this international conference in October 1884 made it official. The Protocols of the Proceedings gave a permanent record of the intelligent and civil debate. It concludes with delegates voting to adopt the line “passing through the centre of the transit instrument at the Observatory of Greenwich” as the prime meridian for navigation and timekeeping purposes. The delegation from San Domingo cast the only negative vote. The French delegation, preferring Paris but knowing it would not win, simply did not vote. 68. Lombardi, Michael A. [et al.]. WWVB Radio Controlled Clocks: Recommended Practices. [Gaithersburg, Md.]: National Institute of Standards and Technology (NIST), 2009. The National Institute of Standards and Technology (NIST) publishes recommended practices for manufacturers of radio-controlled clocks and watches. These devices receive a radio signal from NIST, broadcasting the Coordinated Universal Time (UTC) kept at the prime meridian in Greenwich. If a radio-controlled clock is working properly and follows the NIST standards, it corrects for the local time zone and is a reliable source of official standard time, accurate to within one second or less. The Recommend Practices are available online as a PDF document, or free upon request as a printed government document SP960-14.


9. CLOCKS AT SEA or the maritime powers of Europe in the eighteenth century, F determining longitude at sea was an enormous problem. A pamphlet by the mathematician and astronomer William Whiston called attention to the problem by proposing an implausible scheme of synchronized time signals. Whether anyone took seriously the plan to set up a network of floating cannons or not, the tract did highlight the basic challenge, which was for mariners to have a reliable way to set their clocks. With no accurate way to determine how far east or west they were from a known geographical location, ships at sea were subject to delays in transit, to becoming lost, and to shipwreck. Two promising approaches emerged for determining longitude at sea. One, the lunar distance method, used the Moon’s apparent motion relative to stars as a clock. It required accurate lunar tables for the Moon’s position and a precise instrument for making observations from the deck of a ship.

Triangular pendulum clock proposed by Christiaan Huygens for use on board a moving ship. From Christiaan Huygens. Opera varia. Leiden, 1724 (item 70).


Details of John Harrison’s successful marine chronometer, H-4. From The Principles of Mr. Harrison’s Time-Keeper. London, 1767 (item 74).

The other method, the use of a mechanical clock that was reliable at sea, seemed nearly impossible. Pendulum clocks provided the needed accuracy and, on paper, the design published by Huygens for a maritime version of his pendulum clock looked ideal. Sea trials proved otherwise, as the clock did not perform well on a moving ship. A new invention, a spiral spring attached to an oscillating balance wheel, immediately was recognized for its potential use in a sea-going watch or clock. Huygens rushed to publish the idea and establish priority for the invention, unlike Robert Hooke who had the same idea years earlier but failed to get anything into print that documented it. There was a huge gap, however, between the published concept of a balance spring and the design and construction of a watch that would be reliable at sea. When John Harrison finally built one, the accurate working model was not enough to win the longitude prize offered by the British government. It also had to be practical, and that meant publishing the design so others could emulate it. Exacting care was taken to print engravings of the mechanism, along with a technical description.


As a result, Captain James Cook was able to take an exact copy of Harrison’s chronometer on his second voyage to the Pacific Ocean in 1772, and he wrote about it in his popular narrative of the voyage that was published when he returned. It performed so well that readers frequently came upon Cook’s enthusiastic references to the watch, “our trusty friend.” 69. Whiston, William, 1667-1752; and Ditton, Humphrey, 1675-1715. A New Method for Discovering the Longitude Both at Sea and Land. London: Printed for John Phillips, 1714. This pamphlet of less than 100 pages by two respected mathematicians helped unite the shipping interests to petition the government to support research and offer a prize for solving the problem of finding longitude at sea. Whiston’s and Ditton’s grand and impractical scheme envisioned a fleet of stationary ships firing cannon at regular intervals. Sailors would see and hear the shots exploding a mile in the air, giving them a time signal to use in calculating their own longitude. 70. Huygens, Christiaan, 1629-1695. Opera varia. Leiden: Apud Janssonios Vander Aa, 1724. This first collected edition of Huygens’s works includes four volumes and begins with a reprint of Huygens’s book on pendulum clocks, Horologium oscillatorium, from 1673. The first part of that work described the new clock and how to build it, and ends by describing an adaptation for use at sea that Huygens hoped would keep accurate time for calculating longitude. The clock used a triangular pendulum and was suspended below deck. A 50-pound weight at the bottom helped prevent excessive movement, while pivots allowed the clock to rotate and remain vertical as the ship rocked. Though innovative, the clock’s performance was erratic and the accuracy unreliable. 71. Huygens, Christiaan, 1629-1695. “An Extract ... Concerning a New Invention of Monsieur Christian Hugens..., of Very Exact and Portative Watches.” In: Philosophical Transactions of the Royal Society of London, vol. 10. London, 1675. Scientific periodicals did not exist before the late seventeenth century, and the Philosophical Transactions of the Royal Society of London, which began in 1665, was one of the first. It allowed quick dissemination of new discoveries and results. Details of Huygens’s balance-spring watch appeared in Paris only a few weeks before its announcement and explanation in the Philosophical Transactions in March 1675. The spiral spring keeps the


balance wheel rotating back and forth regularly, like a pendulum. The invention was vital in providing portable watches with the same degree of accuracy as pendulum clocks, but it was not without controversy. Robert Hooke immediately proclaimed that he had invented the balance spring years earlier, without publishing the design.

Details of Pierre Le Roy’s marine chronometer. From “A Memoir on the Best Method of Measuring Time at Sea.” In: Philosophical Magazine, vol. 26, 1806 (item 77).

72. Hooke, Robert, 1635-1703. Lectiones cutlerianae, or A Collection of Lectures: Physical, Mechanical, Geographical, & Astronomical. London: Printed for John Martyn, 1679. The invention of a balance spring to regulate watches was immediately recognized for its potential use in a watch at sea. Robert Hooke claimed he came up with the idea years before Christiaan Huygens announced the invention in 1675. Hooke published his claim as part of the Cutlerian Lectures, an endowed lectureship he gave at Gresham College. Six of the lectures were printed from 1674-1678, and issued together with a collective title page in 1679. In the lecture dated 1676, Hooke claimed it was 17 years since he first had the idea. The last lecture, on the force of springs and dated 1678, pointedly illustrates one of the experiments with an engraving of a spiral watch spring.


73. Huygens, Christiaan, 1629-1695. Opuscula postuma. Leiden: Apud Cornelium Boutesteyn, 1703.

Christiaan Huygens, engraved portrait, From his Opera varia. Leiden, 1724 (item 70).

The spring balance, Huygens realized, could regulate clockwork mechanisms other than ones designed for use at sea. He designed a planetarium with a spring balance, and wrote a detailed description. His manuscript on the “automaton” was one of six edited for publication after his death and published in this collection for the first time in 1703. Large folded plates show details of the machine, including the complex clockwork mechanism and spring balance. Clockmaker Johannes van Ceulen built the planetarium in 1682 for Huygens, who was unable to sell it. The machine remained in his estate, along with the unpublished manuscript describing it, and is currently in the Boerhaave Museum in Leiden.

74. Harrison, John, 1693-1776. The Principles of Mr. Harrison’s Time-Keeper. London: Published by order of the Commissioners of Longitude, 1767. John Harrison, a clockmaker recognized for uncanny ingenuity, perfected a chronometer accurate enough to find longitude at sea. H-4 was his fourth marine chronometer. On a trip to the West Indies it lost only five seconds, eventually earning Harrison the coveted longitude prize. The Board of Longitude insisted that details of H-4 be published so that other watchmakers could duplicate the work. The Preface is by Nevil Maskelyne, Astronomer Royal, who also wrote the “Notes” taken when Harrison dismantled H-4 in the presence of experts. Harrison’s own technical description is keyed to the plates of the mechanism, which reproduce his original drawings and were engraved under Maskelyne’s personal supervision.


75. Cook, James, 1728-1779. A Voyage Towards the South Pole, and Round the World. London: W. Strahan and T. Cadell, 1784. This narrative of Captain Cook’s second voyage (1772-1775) to the Pacific has many references to a marine chronometer, made by Larcum Kendall, that Cook called “our trusty friend the Watch.” It was an exact copy of John Harrison’s chronometer H-4, which stayed on land. With its help, Cook made the first highly accurate charts of the South Sea Islands, and demonstrated the accuracy of marine watches for finding longitude at sea. He wrote the narrative while preparing to leave on his third voyage, from which he did not return, and entrusted others to see the first edition through the press. 76. Berthoud, Ferdinand, 1727-1807. Essai sur l’horlogerie. Paris: J.G. Merigot le jeune, 1786. Ferdinand Berthoud, a noted French clockmaker, first published this comprehensive treatise on clock making in 1763, the same year he made an official visit to London to learn secrets about John Harrison’s marine chronometer, H-4. The secrets remained in England, as Harrison refused to let him examine it, and Berthoud was left to design marine clocks based on his own ingenuity. He had plenty of ideas and produced about 70 marine chronometers. This second edition of his work, unchanged from the first, shows some of them. 77. Le Roy, Pierre, 1717-1785. “A Memoir on the Best Method of Measuring Time at Sea.” In: Philosophical Magazine, vol. 26. London, 1806. The Philosophical Magazine began in 1798 and, with some variations in its title, has been published continuously ever since. In 1806, it published this translation from French of a memoir on Pierre Le Roy’s marine clock. Le Roy built his first marine clock in 1756, and presented this improved version to the French king 10 years later. The clock was given sea trials in 1767 and was reported to have done as well as Harrison’s chronometer. The complex mechanism may have been difficult to reproduce quickly or cheaply. Some of the features nevertheless became standard elements in modern marine chronometers.


10. WATCHES, TUNING FORKS, AND ATOMIC CLOCKS mall portable clocks meant to be worn or carried in a pocket were Sknown in the sixteenth century. In the seventeenth century, watchmakers sometimes published their designs in scientific journals as a way of claiming priority for an innovative concept. In Leipzig, the Acta eruditorum provided a forum for disclosing new ideas, such as a watch mechanism that relied on a magnet to make a balance oscillate. Technical encyclopedias became a source of detailed information on watches in the eighteenth century, with Diderot’s Encyclopédie leading the way in both text and illustrations. The fine engraved plates illustrated many types of watches that utilized a balance spring regulator as part of the typical mechanism. The fullpage folio plates showed several internal views of a watch on the same page, exposing different layers and demonstrating how all the hand-made precision parts would fit together inside the case. Editors of nineteenth-century technical encyclopedias recruited experts to write comprehensive articles on horology. Their contributions on watches could almost serve as an introductory textbook, with examples illustrating some of the finest work of watchmakers.

Exploded view of an eighteenth-century pocket watch. From Encyclopédie. Recueil de planches. Paris, 1765 (item 79).


From the elaborate decorated cases to the tiniest pins that held hairsprings in place, the watches described in the technical literature were all handmade. In America beginning in the 1850s, things changed with the introduction of machine-made parts that were interchangeable.

The original Elgin watch factory north of Chicago. From Henry Abbott. The Watch Factories of America. Chicago, 1888 (item 83).

A writer in the 1880s could marvel at the changes in watch-making technique and output that had occurred within living memory. Mass-produced watches of high quality were available from Elgin and other manufactures in quantities that would have seemed unbelievable earlier in the nineteenth century. All were still mechanically controlled, however, until the 1960s. Bulova’s electronic Accutron watch heralded a new era of design and precision in watch engineering, so it is not surprising that details of the watch’s tuning fork mechanism were published in a paper at an engineering conference in 1963. Atomic clocks had even greater precision than the Accutron, but they were never intended to be portable or for the consumer market. They were the work of physicists, and the first one was described in Nature, a distinguished scientific journal known for publishing important new advances and original research. Because of the precision in timekeeping realized by atomic clocks, the international body responsible for standard weights and measures redefined the concept of a second in 1967, publishing the result in the proceedings of their scientific meeting.


78. Kochanski, Adam Adamandus, 1631-1700. “Novum genus perpendiculi pro horologiis rotatis portatilibus.” In: Acta eruditorum. Leipzig: Apud J. Grossium, 1685. The mathematician Gottfried Leibniz was one of the editors of the Acta eruditorum, an early scientific journal published in Leipzig beginning in 1682. Its monthly issues included reports of new inventions, such as a portable watch invented in 1659 and described in this article. Two views of the watch on an engraved plate showed the internal mechanism, with a strong magnet causing a balance to pivot on an axis and oscillate, much like a pendulum. A diagram of an elaborate air pressure experiment filled the space on the plate above the watch figures. 79. Encyclopédie. Recueil de planches, sur les sciences, les arts libéraux, et les arts méchaniques, avec leur explication. Troisieme livraison. Paris: Chez Briasson, David, Le Breton, 1765.

A repeater watch by English clock and watchmaker, George Graham. From Thomas Reid. A Treatise on Clock and Watch Making. Philadelphia, 1832 (item 82).


The text of Diderot’s Encyclopédie included many articles on aspects of horology, while the separately published volumes of plates had an entire section. In one engraving, an exploded view of an eighteenth-century watch exposed the internal parts, laid out on the page as if the watch were disassembled on a table. It displayed the tiny chain connecting the drum and conical fusee, the coiled spring that powered the watch and the delicate hairspring and balance that regulated it. 80. Rees, Abraham, 1743-1825. The Cyclopaedia. First American Edition. Philadelphia: Published by Samuel F. Bradford, [1805-1825]. The article on watches in Rees’s Cyclopaedia had little about their history, mentioning only that portable watches were common by 1544, but much about the technical details of nineteenth-century watches. The American edition appeared by subscription in Philadelphia from 1805 to 1825, with 41 text volumes referencing the six volumes of plates. Detailed engravings for the horology section were minutely copied from those of the English edition. The common watch for consumers could have features that might slow or affect the accuracy of a precision marine chronometer, such as an alarm, chimes, or repeater mechanism. 81. The Edinburgh Encyclopaedia. Edinburgh: W. Blackwood, 1830. David Brewster, physicist, mathematician, and inventor, edited and also wrote many of the articles for the 18 volumes of this encyclopedia. Contributions from other scientists, including Charles Babbage and John Herschel, gave the work a strong emphasis on science and technology. Noted clock maker and author Thomas Reid wrote the article on horology, which detailed the fundamentals of clocks and watches. One of the instructional illustrations demonstrated the typical assemblage of wheels and pinions in the movement of a watch or small clock, with a coiled spring as a source of power and an oscillating balance wheel to regulate the watch. 82. Reid, Thomas. A Treatise on Clock and Watch Making. Philadelphia: Carey and Lea, 1832. In horology, a “complication” is a feature beyond the simple display of time. Thomas Reid’s acclaimed treatise on clock and watch making used examples from Europe’s best practitioners. To illustrate a watch with one complication, the example is a repeater watch by the celebrated English clock and watch maker George Graham (1673-1751). A repeater will strike the hour, quarters, and sometimes minutes at the press of a button. One


movement controls the timekeeping and another, the complication, is for the repeater. 83. Abbott, Henry G. (pseud. of George H.A. Hazlitt), 1858-1905. The Watch Factories of America, Past and Present. Chicago: Geo. K. Hazlitt & Co., 1888. This slim volume documented a revolution in American watch making, resulting from the introduction of machine-made, standardized, and interchangeable parts. The agent of that change was Aaron Dennison, whose innovations in 1850 caused, in the author’s view, “one of the most marvelous growths of mechanical genius of this wonder-working nineteenth century.” Typical factory output went from two watches per week to thousands per day at the Waltham and Elgin factories. The original Elgin factory described by Abbot produced half the watches in America from its founding north of Chicago in 1864 until it closed in 1964. 84. Bennett, William O. “Accutron : a Chronometric Micro-Powerplant.” SAE Preprint 711C, International Summer Meeting. New York: Society of Automotive Engineers, 1963. William Bennett helped turn Bulova’s Accutron wristwatch into a commercial success in the 1960s. He presented a paper with technical details of the watch, its tuning fork, and its transistorized electronic circuit at a 1963 summer meeting of the Society of Automotive Engineers, a division of which is concerned with aerospace engineering. The watch’s electronically activated micro-tuning fork oscillator made it more precise than the best mechanical watches, and its mechanism, Bennett argued, had great potential for use as a timing device in satellites. The scarce paper was published as a preprint only, and never appeared in any other published journal or proceedings of the conference. 85. Essen, Louis, and J. V. L. Parry. “An Atomic Standard of Frequency and Time Interval: A Caesium Resonator.” In: Nature, vol. 176. London, 1955. Louis Essen designed and built the first atomic clock, known as Caesium 1, in 1955. He worked with Jack Parry at the National Physical Laboratory in Teddington, England, and together they published an article in Nature to announce and describe the clock. It was accurate to within .0001 second per day, or about one second in 30 years. A photograph in Nature of the original atomic clock shows the initial installation at the National


Physical Laboratory. The clock has since been moved to the Science Museum in London for preservation and display. 86. International Bureau of Weights and Measures. Conférence générale des poids et mesures (Thirteenth: 1967). Paris: Gauthier-Villars, 1969. The second, previously defined as a fraction of the solar day, was redefined in Paris at this thirteenth General Conference on Weights and Measures. Atomic clocks are more accurate than the Earth’s rotation, and delegates knew that astronomical timekeeping was doomed. Their new definition was in terms of the frequency of light. As published in this report, a second is now “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.”

Weight-driven clock mechanism. From Robert Fludd. Utriusque cosmi maioris, 1617-1618 (item 37).


INDEX Index of names. Numbers refer to catalog entry numbers.

Abbe, Cleveland: 65 Abbott, Henry G. (pseud. of George H.A. Hazlitt): 83 Accademia del cimento: 43 Amman, Jost: 27 Apian, Peter: 3-5 Barbaro, Daniele: 20 Bennett, Wiliam O.: 84 Berthoud, Ferdinand: 76 Besson, Jacques: 21 Bion, Nicolas: 26, 47 Boulby, George: 9 Brahe, Tycho: 36 Brewster, David: 81 Cardano, Girolamo: 34-35 Cassini, Giovanni Domenico: 14 Cassini, Jacques: 48 Caus, Salomon de: 6, 23 Cellarius, Andreas: 10 Clavius, Christoph: 2, 6, 13 Clement, William: 42 Cook, James: 75 Coster, Salomon: 45 Ctesibius: 20 Cumming, Alexander: 41 Dennison, Aaron: 83 Derham, William: 28-30 Diderot, Denis: 79 Ditton, Humphrey: 69 Ellicott, John: 50 Encyclopédie: 33, 79 Essen, Louis: 85 Evelyn, John: 17 Ferguson, James: 59, 62 Fine, Oronce: 22

Fisher, R.S.: 64 Fleming, Sandford: 66 Fludd, Robert: 37 Gabbrielli, Pirro Maria: 15 Galilei, Galileo: 43 Galilei, Vincenzo: 43 Gallon, Jean Gaffin: 40, 51 Gallonde, Louis Charles: 51 Graham, George: 41, 82 Gregory XIII, Pope: 13 Grollier de Servières, Nicolas: 56-57 Harrison, John: 74, 76 Hazlitt, George H.A.: 83 Hobson, Richard: 9 Hooke, Robert: 30, 32, 71-72 Horrebow, Peder: 39 Huygens, Christiaan: 25, 44- 45, 47, 70-73 International Bureau of Weights and Measures: 86 International Meridian Conference (1884): 67 Kendall, Larcum: 75 Kircher, Athanasius: 7, 16, 52-53, 58, 61 Kochanski, Adam Adamandus: 78 Köbel, Jacob, 12 Lana Terzi, Francesco: 54 Le Clerc, Sébastien: 46 Leibniz, Gottfried Wilhelm: 78 Le Roy, Julien: 40 Le Roy, Pierre: 77 Leupold, Jacob: 31 Lombardi, Michael A.: 68


Magalotti, Lorenzo: 43 Marinoni, Giovanni Jacopo de: 49 Martinelli, Domenico: 38 Maskelyne, Nevil: 74 Miotte, Pierre: 16 Münster, Sebastian: 1 Parry, J. V. L.: 85 Perrault, Claude: 25 Petreius, Johann: 35 Ptolemy: 60 Rees, Abraham: 80 Regiomontanus, Joannes: 11 Reid, Thomas: 42, 81-82 Richer, Jean: 46 Rømer, Ole: 39 Scheuchzer, Johann Jacob: 8 Schopper, Hartmann: 27 Schott, Gaspar: 24, 45, 58 Stoeffler, Johannes: 12 Stone, Edward: 47 Sully, Henry: 40 Thiout, Antoine: 32 Valturio, Roberto: 19 Van Ceulen, Johannes: 73 Vitruvius Pollio, Marcus: 20 Waterton, Charles: 9 Wauchope, R.: 63 Wheeler, Maurice, 55 Whiston, William: 69 Wilson, P.W.: 18 World Calendar Association: 18

On Time: The Quest for Precision