Book History, vol. 11

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Introduction: The Horologium of 1685

In 1665 Christiaan Huygens, one of the most famous Dutch mathematicians, made an unusual appearance on the docks in Amsterdam. His purpose was to host a seminar on the use of his newly invented pendulum clock, and his audience consisted of sea pilots and sailors who could use the marine timekeeper on their ships. In a small room along the waterfront Huygens detailed the clock’s mechanisms, the proper mounting of the instrument, and the manner in which time could be determined at sea. We can only imagine the scene: the upper-class gentleman with his elegant clock, describing for seasoned sailors how the determination of longitude was now possible; the sailors listening dubiously to the promise of an expensive new instrument that could forever change their navigational techniques. Predictably, the workshop was less than appreciated. The sailors hardly disguised their absence of faith in the instrument, as Huygens explained to his father, the renowned Dutch poet and diplomat Constantijn Huygens: “Being in Amsterdam I conferred with several of our seamen, as well as with . . . those who understand navigation; they cannot deny [the clock’s] utility. However, I have noticed how slow and unwilling our seamen are to acknowledge something new which has such obvious utility.” Huygens quickly realized that personal appearances alone would not make marine sailors accept his clock. But his meeting with a group clearly outside of his normal community of mathematicians and natural philosophers provides an excellent example of his attempts to reach different audiences with his work.

In what follows, I will explore the way Huygens actively cultivated heterogeneous audiences for his published works by tailoring them to particular readers and distributing them in strategic ways. Analyzing his authorial intentions in this manner not only enhances our reading of these important works in the history of science, it also helps us to understand how mechanics permeated cultural boundaries in early modern Europe. Though Huygens published across the spectrum of scientific disciplines, with works on mathematics, mechanics, natural philosophy, astronomy, and optics, I focus here on his three publications related to the pendulum clock: the Horologium of 1658, the Kort Onderwijs (Brief Instructions) of 1665, and the Horologium Oscillatorium of 1673. The first two were written when Huygens was an independent scholar in the Low Countries, the third while he was a member of the French Académie Royale des Sciences, under the patronage of Louis XIV and Jean-Baptiste Colbert. Thus the intellectual and institutional contexts in which the works were composed varied, but they had a common objective.

Huygens’s aim was to produce a pendulum clock that was accurate enough to determine longitude at sea, and he had begun working on the problem in 1656. After developing and testing several prototypes he had a model that he felt would solve the problem, and in 1658 he made his design public in his Horologium. By that time Huygens had already shared diagrams of his new clock with a French correspondent, the councillor to the king of France, Jean Chapelain, but upon realizing that he had a marketable instrument, he asked Chapelain to refrain from sharing the design:

“Not having at present the time to respond as I would like to your obliging letter, I offer here only a few lines in order to ask you not to communicate to anyone the construction of my clock, which, while vague enough, could be understood by someone.” Chapelain promised to keep the information private, agreeing that disclosure might cost Huygens priority. The work was finished in mid-June, and Adriaan Vlacq, a well-known Dutch printer, published it in early September 1658.

The Horologium was a simple quarto, only fifteen pages including the dedication. Its purpose was clearly to make the technology and its inventor known. Huygens sought priority not only for himself but for the Low Countries as well, dedicating the book to “The Most Illustrious and Most Powerful Lords of the State of Holland and of the Western Region,” the governing body of the Netherlands: “I felt myself strongly impelled to ensure to our country the credit for this and for any future discoveries, and so I have followed the way which alone seems proper to this end—to make known the whole idea and construction of the new mechanism, which I, the inventor himself, have undertaken to describe in a few words and to produce to the public in a reasonably brief volume.” Huygens goes on to explain that it is not just the book that is being dedicated to the States-General, but the invention itself. By accepting his dedication, they will recognize the public benefit of his instrument, which he compares to the legendary sundial installed in Rome by the censor Quintus Marcius Philippus. The Romans, having relied on a poorly functioning clock for nearly a century “infinitely appreciated this gift,” Huygens writes, because it improved their lives and brought glory to Rome. His own clock promised to do the same for the Low Countries. Moreover, he claimed that publishing the Horologium would help to forestall other nations that might attempt to steal the idea—a notion that would ultimately prove contentious.

Huygens tailored the Horologium for an educated audience. Like other works of mathematics or mechanics of the period, it is in Latin, but careful examination of the text and images reveals his hope to gain a wider readership interested in the technology. The book’s detailed explanation of the clock asks readers to merge the visual description of a carefully labeled diagram with the written account of its construction, and Huygens’s narrative facilitates this. He describes the weight ∆ (delta), attached to the pulley F, and a series of gears that turn up through the saw-toothed wheel L (figure 1). L turns the vertical arbor MN, which moves the vertically mounted crown wheel P and the crutch QR, and here Huygens’s instrument stands out among others of the day, because the crutch is what keeps the pendulum from swinging wildly. The oscillation impelled by the weight ∆ is kept in check and consistent. Following the description Huygens writes, “These are indeed the details of my mechanism which require precise explanation because the point of the whole invention turns on them.” The account he provides reads like a modern patent request, a “virtual construction” wherein the details are essential for preserving priority. Indeed, Huygens did apply for patents for his clocks in the Low Countries and later in England, but as Mario Biaglioli has shown, legal protection of an invention was typically granted when one could show authorities a working model. Written descriptions of instruments and their inner workings were almost never necessary. Why then publish such precise details of his clock? For Huygens, the issue was about earning credit for his invention—not simply in the legal sense, but credit in terms of a reputation as an authority on pendulum clocks and in terms of priority for developing such a clock before anyone else.

We can then surmise that Huygens intended the Horologium to be read by mechanicians—at least those versed in Latin—who had some understanding of how clocks work. However, his targeted audience went beyond this narrow group of readers. In Huygens’s private workbook, under the heading “Exemplaria Horologij, primum editionis,” he listed fifty-nine individuals to whom he planned to send a copy of the book (figure 2 and Table 1). Huygens drew up such a list of designated recipients for each of his major publications. Buried among his notes, these rosters provide insights into his desired audience for a given work. They are all the more valuable because in many cases we have letters from Huygens to his chosen recipients, as well as the recipients’ responses to presentation copies. No other natural philosopher or mathematician from the period is known to have left such a clear indication of their intended audiences, especially over the course of a lifetime.

In the case of the Horologium of 1658, the names on his recipients list are loosely grouped according to nationality. Topping the list is the States-General, the governing body of the Low Countries that had approved a patent for Huygens’s clock on 16 June 1657. As dedicatees of the work, they were also given a pendulum clock by Huygens, which was hung in the chamber where the representatives met. Following the States-General is the name of Johann de Witt, Councillor Pensionary of Holland and former student alongside Huygens at Leiden. De Witt supported Huygens’s efforts to obtain patent rights for various clock models. A number of scholars from the Low Countries follow De Witt on the list almost immediately: Andreas Colvius, Robert Paget, Caspar Caltoff, Adrian van der Waal, Nicholas Heinsius, and Isaac Vossius. These men—with the exception of Caltoff, who was a mechanist—were poets, ministers, and savants with little mechanical aptitude or technical background. For them, the gift of the Horologium was a symbolic gesture from a fellow countryman—a signal of friendship and respect.

In addition to these men of letters, various astronomers and mathematicians throughout Europe were sent copies, among whom were John Wallis (whose name appears third on the list), Giovanni Battista Hodierna, Ismael Boulliau, Guy Personne de Roberval, and Johannes Hevelius. These men understood the benefits of an accurate timekeeper for taking astronomical observations, and they welcomed Huygens’s new model. Hevelius wrote to thank him for sending the description, noting that the clock was “of significant use to all things astronomical.” Wallis too praised the “exceptional and noble” work. Additionally, the French Royal Geographer and engineer Pierre Petit was sent a copy of the book. Petit had a great interest in mechanics (particularly clocks and automata), and upon receiving the details of Huygens’s design he entered into a lengthy correspondence with him about the construction of various clocks.

Finally, there were members of the nobility and aristocrats to whom Huygens sent the Horologium. Princess Elizabeth of Bohemia, René Descartes’s former correspondent and patron, received a copy, as did Leopold de’ Medici, whose volume was accompanied by an actual clock. Leopold responded reticently to Huygens’s gift, leaving no doubt as to his concerns over Huygens’s claim to priority, which he felt belonged to Galileo. A tension between the Italian prince and Huygens resulted, leaving the latter in a precarious position. Meanwhile, in France Monsieur Du Gast wrote to Huygens to confirm delivery of the Horologium to Blaise Pascal and to Louis Charles d’Albert, the Duc de Luynes, both of whom thanked Huygens for the gift. Du Gast characterized the latter as “very intelligent in all things mathematical, and . . . in particular a great amateur of horology, after having read your work with esteem and praise.” He was so fascinated with Huygens’s technology that he requested four clocks be personally chosen by Huygens (from Huygens’s clockmaker’s available stock) and delivered to him. Huygens’s response, delivered via Du Gast, indicates that he was honored to be asked and would see to it that the Duc de Luynes received his clocks as quickly as possible.

Finally, Huygens sent the Horologium to various instrument makers, including two copies to Solomon Coster, his primary clockmaker in The Hague, and one to an instrument maker in Dordrecht. Though it is unlikely that either of these men read Latin, the book served as a signal of Huygens’s gratitude and his achievement. Moreover, a modern horologer interested in clocks of this period has been able to reproduce Huygens’s 1658 clock from the plate alone, demonstrating its utility without any accompanying explanation. The images in the work, then, could serve as blueprints.

The brief text and its chosen audience make clear that the Horologium was fundamentally a description of the instrument and a justification of Huygens’s priority for its discovery. A young man known more at the time for his mathematical works than his mechanics, Huygens needed to secure credit for his invention. To stake his claim he circulated more than sixty copies of the book in different intellectual, political, and social arenas. Some recipients were capable of delving into the mechanistic details, others less so, but all would relate the name of Huygens to the clock that could—potentially—solve the longitude problem. With this accomplished, he could work on small but important design changes to make the clock seaworthy.

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