Henry Sully- Éclaircissements (Clarifications) 1726

Last updated on August 5, 2022

(Translation and commentary by Robert St-Louis, 2020)

Henry Sully’s Marine Clock

In 1726, Henry Sully wrote and published the following book in Paris:

Description abrégée d’une horloge de nouvelle invention pour la juste mesure du temps en mer avec le jugement de l’Académie des Sciences sur cette invention et une dissertation sur la nature des tentatives pour la découverte des Longitudes dans la navigation et sur l’usage des horloges pour la mesure du temps en mer. 

English translation of the title: Summary description of a newly invented clock to accurately measure time at sea, with judgment from the Science Academy on this invention, and an essay on the nature of attempts to discover longitude in navigation and the use of clocks to measure time at sea.

The book is 290 pages long and a collection of various documents, letters, and other information related to Sully’s personal attempts to develop and demonstrate a pendulum clock to be used at sea. The first part of the book had been published in Paris in January 1726, and is combined here with the second part, originally printed in Bordeaux in December 1726. Bordeaux is where Sully had taken his clock (and marine watch) for sea trials; these resulted in some positive but ultimately inconclusive results, and suggested that more work was required to improve his clock, make it more accurate and reliable during a long voyage at sea in all kinds of weather and sea conditions. The Paris edition (published by Briasson) brings together both parts of the story.

Starting on page 254 of the book, in a section entitled “ECLAIRCISSEMENS” [Clarifications], Sully provides insights on the invention of his “lever pendulum clock”, in which he names, in chronological and almost autobiographical form, the many people (some quite famous scholars or well-known personalities) with whom he had discussed his ideas of developing a marine clock over more than twenty years.

In this lengthy text, Sully appears sensitive toward some opinions offered by others [Graham, for one] about his clock, in which it was directly or indirectly suggested that he had used aspects of clocks from other makers, and passed them off as his own inventions. The section starts with an introduction in which Sully speaks in a rather philosophical tone:

Men create nothing; they gather ideas by using their senses and their mind; of themselves there is only the arrangement of these that they know to put in their works, and this arrangement, when it is particular and distinguished from others, is called invention.

An invention consists of knowing how to equally choose, reject, combine, separate, elevate and destroy; it only has merit from the utility of the object, or from the knowledge and skill that the invention requires, and that the inventor can bring to bear.

At the root of all talents is a certain aptitude which is constantly a gift of nature; the one who possesses these talents only adds the manner in which they are utilized, cultivated, enhanced: perhaps in this there is little that is actually ours; self-esteem enlarges the object.  But if enough remains to encourage men to do well, little remains to inspire their humility.

Based on these principles, there is nothing that men can legitimately draw from vanity; it follows that one should be quite indifferent as to the property of those goods that we call inventions; goods very prone to appropriation, that one never possesses without exciting envy, and that one can hardly preserve without very good titles.

However, we see little of this philosophical indifference, when it comes time to dispute one’s titles against those who have stolen them, or to defend them against all that tends to rob them from the legitimate owner.  Sometimes the interest that one has of being recognized as the inventor of useful things, is joined to the honour of being such; this circumstance change the thing’s nature: it becomes a treasure that one finds while searching through one’s lands, and it is permitted to push away those who come to take it away.

All honest people agree that plagiarism, even of the dead, is loathsome; and to want to appropriate the fruits, genius, and works of contemporaries, is insolent and odious.  One is more tolerant of certain passe-droits of little consequence, and one prefers sometimes to endure small thefts, than to dispute with one’s friends.

Since I oppose these indignant practices, and would be mortified to just be suspected of such, I take the liberty to declare that I don’t wish to rob the goods of anyone, nor to beautify myself with their feathers; that I will preserve as best I can what remains of mine, and what I could lose in the future, and that I will take back what belongs to me, wherever I find it.

It’s not that I am so eager to have the name inventor, I don’t dwell on it as long as the thing invented has some utility; and in order not to err I expose my ideas to wise experts so they can offer their judgment; they can criticize or condemn these things: I defend them only when I feel that truth is on my side; and I am the first to get back up from my errors, as soon as I realize them.

Following this approach, I could not appropriate what does not belong to me: it would be telling those who have the right to claim them back, and not allow me to keep it from them.  If I wish to preserve what remains of mine, it’s that I believe that what came from me, could belong to me as much as to someone else who would want to take it.  And if I want to take back something of this kind that has been taken from me, I would produce such good titles, and behave so honestly that that people I would oblige to give back my property, would find nothing to criticize about my actions.

On page 261 of the ECLAIRCISSEMENS, Sully goes on to say about his clock:

To prove without a doubt that I am the author of this clock, and that it is different from any other, I don’t feel I need any better title than the pages of the registers of the Académie Royale des Sciences de Paris.  In all the works that appeared there, either in physics, or mathematics, or mechanics, nothing indicates, even in the remotest manner, a clock construction that would have the least resemblance to this one, or that suggests that someone had tried to do something similar.  If I needed other proof, it would be very easy for me to produce some.  I have for witnesses (b) many of the most illustrious persons in England, Holland, Germany, and France, and who know about the beginning of this endeavour, and of the progress that I have made from time to time, since the year 1703.  That this design had been suggested to me by the late Sir Wren (able mathematician and great architect) whose name and merit are known in the entire learned world.

In the footnote (b), Sully launches into an interesting and detailed chronological overview of his work in the areas of marine clocks, and the many people that he met and discussed the subject with along his lengthy project, culminating in the clock he was describing in the book written in 1726.  This chronological, almost biographical note [which starts on page 261 and completes on page 264], is worthy of translation since it has not been available in English before, to the knowledge of this writer, and will assist in his project to write a fulsome work on Henry Sully.

(b) I wouldn’t have intended to bring forward these proofs, were it not that some people have tried in many ways to do me harm and to deprive me, if they could have, of all the fruits of my applied work during so many years.  I therefore felt that I needed to demonstrate their imposture, make them ashamed of their arrogance, and silence them forever.

In the year 1703, the late Sir [Christopher] Wren, judging me worthy of making a useful attempt toward the measurement of time at sea, gave me a fine recommendation to this effect.  I asked to see the Duke of Somerset [Charles Seymour, the 6th Duke][1], who received me very graciously, and instructed me to address myself on his behalf to Sir Newton[2], to explain my views to him, which gave me the great honour of being known by this great man, who gave me insights that I needed, being at the time just a young man of 23 years; he encouraged me in my plan [to develop a marine clock], and gave me a favourable testimony.  Following this, the Duke of Somerset tried to engage Lords Sommers[3] and Hallifax and others to join him, to create a fund, which would engage me to apply myself entirely to this research, which was at that time my one and only goal, but this attempt did not succeed.  I nevertheless applied myself to it using my own resources, which became known in London among ingenious persons: the late Mr. Flamsted[4] and Mr. Hudson, who assisted the wise astronomer in his observations, and who is presently Professor of Mathematics in the School of Christ [Christ College] in London, and of the Royal Society, were among those people.

The learned and famous Professor Dr. Boerhave[5] will well remember the discussions I had the honour of having with him on this subject when I was in Leyde [Leiden, Holland] during the years 1708, 1709 and 1710, and with several magistrates of that city.

Being in Franckfort on Meyhe [Frankfurt on Main] in the year 1711, I published a small brochure in French, entitled “Méthode pour régler les montres” [Method to regulate watches], with a dissertation on “l’excellence de l’horlogerie” [the excellence of horology]; in which I insinuated what could be expected of this Art for use in navigation; one can still find copies of it among the learned people of that country.  The Reverend Jesuit Father Des Bosses[6], then living in Cologne, communicated this brochure to the journalists of Trévoux[7]; they speak of it in one of their journals in October 1712 or 1713, as I recall; I’ve seen this little brochure translated into German.

But no one has been more informed, either of my goals or of the progress I had accomplished, than my illustrious benefactor my lord the Duke of Aremberg[8], who gave me the honour of keeping me at his side, solely to better allow me to carry out my views on how to perfect my Art.  It was under the guise of this generous Prince that I enjoyed all the advantages that I could hope for during the years 1714 and 1715, that I had the honour of following him in his travels to Vienna and Paris.  In this way I met and adopted the ways of the learned elite of the countries where I found myself.  While in Vienna I knew the famous Mister Leibnitz[9]: he perfectly understood my views, continually urged me to pursue them and provided me with news; and he honoured me with his friendship and his correspondence by his letters until his death.  If the mention of my name, that he gave me the honour of including in his letters that were printed, and in the hands of learned people, was not sufficient to prove it, I have as witnesses that I dare name, my lord the Prince Eugene of Savoye[10], my lord the Duke of Arenberg, my lord the Count of Koningseck [Koenigsegg][11], then ambassador in France and now in Spain, my lord the Count of Mattuof, ambassador in Moscovie [Moscow], the Baron of Huldenberg, envoy of Hannover, Mr. Brunix, envoy of Holland, Mr. Clement, resident of the late Queen of Great Britain, and many other persons of the utmost distinction that I had the honour of knowing at the Court in Vienna in 1714, who also knew about my work.

As early as 1716, being in Paris, I declared to the learned members of the Académie Royale des Sciences, by whom I had the honour of being known, how far ahead I was in this work, and that I anticipated the way to overcome difficulties, that were well known to me:  I can claim here the testimonies of the illustrious Abbé Bignon[12], Mr. de Fontenelle[13], Mr. Saurin[14], and many other fellows of the Académie; and since I had reason to believe that almost the entire Académie had a general notion of what I was working on, I concluded in these terms a memoir that I had the honour to read in this illustrious assembly that same year. “The indulgence that you will show for this little essay may incite me to one day produce some fruit of my work which will be more worthy of your attention”.  And it was this very work [i.e. marine clock] that I was designating in these terms.

It was only in the year 1720 that I discovered, almost at the same time, the curve (Courbe) which I use; the compensation for the action of weight, which I only before saw the possibility, and which had stopped me during 12 years; and the use of rollers (rouleaux) and the lever (levier).

In the year 1721, in London[15], I found myself with the leisure to execute everything I had been mulling over previously; I started with the escapement.  A diamond watch that Sir Newton had shown me in 1704, and of which I will speak later, gave me the first idea[16]: as early as 1712, I had imagined the necessary changes to be made, without having completed their execution.  I built a watch with this escapement, and showed its construction to Lord Parker[17], at the time Chancellor of Great Britain, and Lord Islay[18], and demonstrated its workings in the Academic assembly of Mrs. Watts and Worster, and many other knowledgeable and interested people of London, and among other able craftsmen [artistes], to Mr. Vick, watchmaker to the King.

I also showed my “pendule à levier” [lever clock], and I announced its properties to all my friends, but showing its construction to only one London clockmaker, who was Mr. Reith[19].  I then wrote about it to Mr. Le Roy[20], watchmaker of Paris, whose ability is now deservedly well known by the public. 

Having arrived in Paris in 1722, I showed my lever clock uncovered, first of all to Mr. Saurin, and then in 1723 at Versailles to the Duke of Chaulnes, his Eminency l’Abbé de Livri, now ambassador for the King in Poland; Mr. le Chevalier de Luines [Luynes][21] and Mr. le Chevalier de Bethune[22]; then to the late Mylord Duke of Orleans, at the Académie, and to the King, Mylord the Cardinal of Fleury, then bishop of Frejus, being present, and many of the principal noblemen of the Court; and from that time to all the interested people who came to see it at my home, among whom were found most of the ministers of foreign Courts.

It’s not strange that people seeking applause that they have not worked to deserve, have tried to make a name for themselves at my expense; an attempt that has however not met with success: but it would be very surprising if someone in the future tried to do the same, after all the proof that I have just presented.


[1] It is interesting that after seeing Wren, Sully went to see the Duke of the county of his birth, Somerset.  Sully was born from parents who resided in Bicknoller Somerset.

[2] Sir Isaac Newton (1643-1727) English mathematician, physicist, astronomer, theologian, and author, was President of the Royal Society of London in 1703.  He became a Commissioner of Longitude under the Act of 1714, and corresponded widely on proposals for finding longitude at sea. (Wikipedia)

[3] Lord John Somers (1651-1716) was Lord High Chancellor of England under King William III and was a chief architect of the union between England and Scotland achieved in 1707 and the Protestant succession achieved in 1714. He was President of the Royal Society from 1698 to 1703. (W)

[4] John Flamsteed (1646-1719) was an English astronomer and the first Astronomer Royal, at the newly created Greenwich Observatory.  He spent almost 40 years observing stars and producing a catalogue of almost 3,000, published after his death.  (W)

[5] Dr. Hermann Boerhaave (1668-1738) was a Dutch botanist, chemist, Christian humanist, and physician of European fame, who taught at the University of Leiden.  He introduced the quantitative approach to medicine and was the first physician to use thermometer measurements in clinical practice.  His motto was Simplex sigillum veri: ‘Simplicity is the sign of the truth’. He is often hailed as the “Dutch Hippocrates”. (W)

[6] Barthélemy Des Bosses (1668-1738) was a Jesuit priest who taught philosophy and mathematics in Germany.  He translated a work by Leibniz into latin, and the two exchanged a voluminous correspondence from 1705 until Leibniz’s death in 1716. (W)

[7] The Journal de Trévoux, often called the Mémoires de Trévoux, was an influential academic journal that appeared monthly in France between January 1701 and December 1782. It published critical reviews of contemporary books and papers on a broad range of subjects, mostly non-fiction, and most of the authors were members of the Society of Jesus (Jesuits). (W)

[8] Leopold Philippe of Arenberg (1690-1754) was the 4th Duke of Arenberg, an aristocrat and military officer.  He fought in the War of Spanish Succession in 1706, and was a field commander on several other European conflicts. He moved to Paris in 1716, and Sully followed him there.

[9] Gottfried Wilhelm Leibniz (1646-1716) was a prominent German polymath and one of the most important logicians, mathematicians and natural philosophers of the Enlightenment.  He made major contributions to physics and technology, and anticipated notions that surfaced much later in philosophy, probability theory, biology, medicine, geology, psychology, linguistics, and computer science. (W)

[10] Prince Eugene Francis of Savoy–Carignano (1663-1736) was a Paris-born field marshal in the army of the Holy Roman Empire and of the Austrian Habsburg dynasty during the 17th and 18th centuries. He was one of the most successful military commanders of his time, and rose to the highest offices of state at the Imperial court in Vienna. (W)

[11] Count Koenigsegg, an Imperialist ambassador, became ambassador to France and later, to Spain.

[12] The Abbé Jean-Paul Bignon (1662-1743) was a French ecclesiastic, statesman, writer and preacher and librarian to Louis XIV of France.  From 1706 to 1714, he presided over the committee of men of letters who edited the Journal des sçavans, which position he took again in 1724.  (W)

[13] Bernard Le Bovier de Fontenelle (1657-1757) was a French author and an influential member of three of the academies of the Institut de France, noted especially for his accessible treatment of scientific topics during the unfolding of the Age of Enlightenment. He is noted for the accessibility of his work – particularly its novelistic style. This allowed non-scientists to appreciate scientific development in a time where this was unusual, and scientists to benefit from the thoughts of the greater society. (W)

[14] Joseph Saurin (1659-1737) was a French mathematician and a converted Protestant minister. He was the first to show how the tangents at the multiple points of curves could be determined by mathematical analysis. (W)

[15] After the unsuccessful attempts to maintain watch-making factories that he had created in Versailles (under John Law) and later in Saint Germain (under the Duke of Noailles), Sully had been forced to return to London, along with most of the English workers he had convinced to go to France to work with him.  The lack of income caused Sully to ponder on his next venture, and he found the time to devote efforts to his interrupted marine clock project.

[16] This watch had an escapement made by DeBaufre. (expand)

[17] Thomas Parker, 1st Earl of Macclesfield (1666-1732) was an English Whig politician who was Lord Chief Justice from 1710 to 1718 and acted briefly as one of the regents before the arrival of King George I in Britain. (W)

[18] Archibald Campbell, 3rd Duke of Argyll, 1st Earl of Ilay (1682-1761) was a Scottish nobleman, politician, lawyer, businessman, and soldier. He was known as the Earl of Ilay from 1706 until 1743, when he succeeded to the dukedom. He was the dominant political leader in Scotland in his day, and was involved in many civic projects. (W)

[19] ?? Reith was the assistant director under Sully of the Versailles watchmaking factory.  When Sully was removed by John Law, Reith became the director until the factory closed down.  Both later returned to London along with the other English watchmakers who had been enticed to go work in those factories, accompanied by their families.

[20] Julien Le Roy (1686-1759) was a major early-mid-18th-century Parisian clockmaker and watchmaker.  He and Sully knew each other and often exchanged horological ideas while the latter lived in Paris.  They were also founding members of the Société des Arts.  In 1737, LeRoy worked with the publisher to edit and augment Sully’s 1717 book, in a revised and final edition.

[21] Charles-Hercule d’Albert de Luynes, entitled Chevalier de Luynes (1674-1734) was a marine officer and French aristocrat descendant from two noble families.  He served in the Royal Marine under Louis XIV and XV.

[22] François-Annibal de Béthune (1642-1732) was also a French aristocrat and marine officer.

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