1715: Meeting of Henry Sully and Julien Le Roy

Last updated on August 5, 2022

Left: Henry Sully, Right: Julien Le Roy

One of my activities during the pandemic year of 2020 was to research and write an article that was submitted to the Antiquarian Horological Society in London, for publication in its journal Antiquarian Horology in June 2021.

The article (see below) deals with the meeting in Paris of English horologist Henry Sully (1679-1728), with French horloger Julien Le Roy (1686-1759). They collaborated on a “watch of a new construction” presented by Sully to the Académie royale des sciences in Paris in 1716. The two men remained friends and occasional collaborators until Sully’s untimely death in 1728.

Règle artificielle du temps by the English watch/clockmaker Henry Sully, first written and printed in Vienna in 1714, and in a revised form in Paris, in 1717, is a significant book on horology. It touched on many aspects of watch construction and more importantly, for watch owners to whom the book is also addressed, it offered practical advice on selecting a good watch and taking care of it. The language is clear, articulate, easy to understand, which is even more remarkable in that Sully was writing in French, and not his native English. 

In the 1737 edition is featured the story of a particular watch, which resulted from the collaboration of Sully and the famous Parisian watchmaker [horloger] Julien Le Roy. The story of how the watch came to be, how it was designed and constructed, and what it led to, is told from two relevant and interesting perspectives, written many years apart by the two main protagonists.

Firstly, Sully himself devoted a chapter of his book to the watch and to the presentation he gave on its merits to the Académie Royale des Sciences, in June 1716. This chapter is found after page 192 in Règles Règle, preceded by a revealing preface, which leads into the actual description of the watch on page 201. The chapter ends, on pages 236–238, with a report of members of the Académie pronouncing themselves favourably on the qualities of the watch.

Secondly, in the memoirs that Julien Le Roy added to Sully’s book when he participated in its revision for a new edition in 1737, is one entitled Historical memoir on Mr. Sully’s watch, starting on page 275. In the following seventeen pages, Le Roy told the story of the watch and of his participation in its design and construction, the conversations he had had with Sully about it, and his later opinions on aspects of the watch, reflections stemming from twenty additional years of watchmaking experience he had at the time of the new edition. Le Roy also briefly discussed the history surrounding the watch, in the part of the book entitled Memoir to serve for the history of horology, from 1715 to 1729. This memoir, from pages 381 to 413, essentially consists of a biographical overview of Sully’s life and work, from Le Roy’s firsthand perspective. 

It is interesting to read in Sully’s memoir the detailed descriptions of the various aspects of his ‘new watch’, and the way that these innovations (not all successful as it turned out) came about through discussions between the two watchmakers, both in their prime at the time. Prior to this, horological books and treatises did not quite go to this level of detail in describing the components of a watch and their relationships, and doing so in such exquisite details and flowing literary style. Sully wrote very clearly in an engaging manner, which demonstrates how formidable a communicator he must have been, both verbally and in writing. This skill allowed him to impress and befriend many important people over the years, talking to them about his ideas and plans, horological or otherwise. 

It should be noted, as Sully himself will be quoted as saying later in this article, that this ‘new watch’ was not a radical departure from the typical verge escapement and mainspring-fusee powered watch design that had prevailed in Europe almost unchanged since the sixteenth century. These ‘verge-fusee’ watches had been reliable, long-lived, though not always very accurate. The introduction of the balance spring around 1675 had greatly increased the accuracy of these watches, but Sully felt that there remained opportunities for improving certain aspects of watch construction to reduce friction and wear, with the aim of the watch remaining a reliable timepiece for longer times between service. His attention focused particularly on watch components where friction was more likely to occur: the mainspring and its barrel, the fusee pivots, the other key pivots in the watch train, especially those of the balance wheel and verge. He offered a novel way of maintaining oil at the crucial interface between the watch pivots and the holes in the watch plates. Finally, he suggested a different location of the crown wheel and its pivots, to make the watch more consistently accurate in both vertical and horizontal positions.

Not all aspects of Sully’s ‘new watch’ significantly changed watchmaking practices overall, or remained in use for a long time, but they did stimulate thinking by watchmakers about ‘doing things in a better way’, which at least indirectly led to some of the great innovations in watch design that came about in France in the decades that followed, some of which coming from the mind and the hand of Sully’s collaborator in the ‘new watch’, Julien Le Roy.


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