In 1770 Pierre Le Roy, in his "Memoire sur la meilleure manière de mesurer le temps en mer", stated: "I should add here a few words about my pocket watches to be used alongside the marine chronometers…they are more accurate because of: 1. more accurate isochronism to the balance with the method already explained, 2. employment of compensation for the effects of heat and cold, similar to that used by Monsieur Harrison, 3. dead beat escapement where the friction is much less than in a cylinder, etc… The escapement of Monsieur Sully where the wheel is perpendicular to the plates, having been perfected, seems to me the best… large vessels will no longer require marine chronometers as their place will be taken by officer’s watches" In his "Mémoire sur ne nouvelle montre a l’usage des astronomes et des marins", read to the Royal Academy on July 3, 1771, he continues his arguments in favor of the watch: "I call them seamen’s watches and not marine chronometers because they take the place of an ordinary pocket watch. … I have arranged the escapement in such a way, that in this position, the action of the escape wheel relieves the weight of the balance. This arrangement, together with the iso-chronism, all contribute, without doubt, to make my new watch much more accurate than others. The new feature which is very significant, is the compensation for the effects of heat and cold " He continues, describing the bimetallic blade compensation found in this watch and showing its improvements over Harrison’s: "…Harrison’s (compensation) would be easy to apply to his timekeeper but certainly not to a pocket watch…Besides, these blades may only be very short so how is it possible for them to exert sufficient effect on the balance spring ? I found the solution 1. By making the blades work not directly on the spring itself, but through a lever, which makes the effect five times more sensitive. 2. By arranging the wheels in such a way that there is suf-ficient space to fit the blades. Their length is almost equal to the diameter of the watch, their height is almost that of the frame of the movement. Consequently, the blades have another very important advantage over that of Mr. Harrison, which is to provide simple means of increasing or decreasing the desired effect." His first Seamen’s and Astronomer’s watches did not live up to expectations. Therefore, Le Roy made conside-rable changes. His second generation watches had a number of improvements. He wrote about them in "Suite d’un Mémoire sur une Nouvelle Montre a l’usage des Astronomes et des Marins": "Firstly, the watch of 1771 had no fusee and this one does, and I have used the mechanism described in Mr. Harrison’s memoir to keep the watch going during winding (maintaining power). Secondly, I was unable in 1771 to give the blade the strength and size it required, without placing it between the plates, which caused me to leave out the fusee. In the present watch, I have placed the blades on the back plate. In this arrangement the thermometer (bimetallic blades) is strong enough. Thirdly, in Mr. Harrison’s watch and in all carefully made English watches, the balance pivots and those of the last wheels in the train turn in pierced rubies, and the ability to work similar rubies does not exist in France…In place of pierced rubies I have used pierced holes of cast steel, tempered to maximum hardness and by a special method I have given these holes the desired form and strength….I have made the escape wheel of hardened steel which Mr. Harrison has already done. This form of my escape wheel teeth makes this advantage easy to achieve." Le Roy then decided to omit the sus-pension entirely, even when destined for use on board ship. He was given the opportunity to put these ideas into practice when the Duke de Penthièvre, Grand Amiral de France, ordered a watch from him. Penthièvre wished to encourage Le Roy in his work, after the double prize he was awarded by the Académie des Sciences in 1769. In "Objet du mémoire sur ma petite montre de marins" Le Roy wrote: "Monsieur le Duc de Penthièvre having decided that the watch should be able to cope with various jolts of a carriage, a post-chaise, etc., I felt that the marine chronometers such as have undergone trials could not entirely fulfill his requirements and that there could be no better solution than an improved pocket watch, because in a carriage, chaise, etc., the po-cket of a man slouching in automatic anticipation of the worst jolts, is just about the best suspension a watch could have in such circumstances. Convinced of this truth, I made one that I have the honor here to pre-sent. I call it a Seaman’s watch and not a marine chronometer, because it takes the place of an ordinary pocket watch." It was the final form of a Sea-men’s and Astronomer’s watch and was to be worn only in a pocket or in an upright position. It employed very innovative technical solutions, but above all, it introduced a new idea, an idea which in the future was to be called the Deck Watch. Capitalizing on the feature of Sully’s fric-tional rest escapement, in which "the action of the escape wheel takes the weight of the balance and reduces the friction on the end of the pivot that carries it, which happens in no other watch", as he wrote on several occasions, he placed the balance perpendicular to the plates, which meant that it was vertical when carried upright in the pocket, and thus the bottom pivot of the balance staff was relieved of much of the friction during transportation and use. The advantages of this design for pocket watches had already been propounded by Sully himself in his work "Règle artificielle du temps" and given practical application by Verlinden with a frictional rest escapement in a watch made circa 1770-1775. Le Roy gave the watch a dial on both sides, one for hours and minutes and the other for seconds. He had already envisaged this construction in his "Objet du mémoire sur ma petite montre de marins": "With regard to friction, I have considerably minimized it in the seconds indication which is different from others…I would refer you to my memoir read to the Academy in 1764 on a new way of indicating seconds and to my double-dial watches." This is, to date, the only watch known with this feature. Its movement was completely renovated by H. Laresche in 1804. Laresche fitted a new case and two new dials; the one with hours and minutes is signed "H. Laresche Renovavit, Paris 1804". The other dial, with seconds, is signed "Julien Roy Invenit, Paris 1772", signature which was no doubt copied by Laresche, on the gilt brass rim of one of the original dials. Thus, with the fusee given maintaining power, the escapement placed so that the balance is horizontal when the watch is worn vertically in the pocket, the pivot holes made of tempered steel, the balance endstones made of rubies and the temperature compensation placed on and adjusted from the back plate, this watch represents the ultimate development of watches "for the use of seamen and astronomers". The movement in fact features all the designs foreseen by Pierre Le Roy for his precision pocket watches, as defined in the "Mémoire sur une nouvelle montre à usage des astronomes et des marins", which he read to the Académie Royale des Sciences upon presentation of the first watch of this type. In conclusion, this watch, undoubtedly the one made for the Duc de Penthièvre, Grand Amiral de France, was intended for multiple deck use, such as finding the ship’s speed with the log, or timing observations at various stations on board and in particular acting as a link between the ship’s chronometer and the station where a sight is taken. In fact, it was the ancestor of the deck watch known in France as "montre de torpilleur", used in much the same manner in modern navigation. In fact it can be called the very first deck watch in the world. Henri Laresche, Galerie de Vallois, No. 164 à Paris, was known as a fine chronometer maker. He was succeeded by his son towards 1820. Pierre Le Roy (son of Julien) 1717-1785 Born in Paris on 25 November 1717, Pierre Le Roy carried out his apprenticeship and spent his whole career in the family workshop. He took over its direction at his father's death, in 1759. Not only did he use the same signature, but it seems that he was also known in the trade under his father's name: Julien Le Roy. Thus, on 14 October 1775, during his visit to Paris, Dr. Johnson, wrote in his diary: "Then we went to Julien Le Roy, the King's watchmaker, a man of character in his business, who showed a small clock to find the longitude - A decent man". At this period as Julien Le Roy had been dead for sixteen years, the clockmaker could only have been Pierre. On the other hand, in September 1771, a report to the Royal Academy of Sciences begins thus "Monsieur Le Monnier and I have been asked by the Academy to examine a new watch proposed for the use of astronomers and sailors, and executed by Monsieur Julien Le Roy..." It is obvious that this watch had been made by Pierre Le Roy. Once again, this confusion shows that Pierre used his father's name in his business. As far as watches were concerned, four elements allow us to date them, and to distinguish those made in the workshop after Julien's death. To begin with, there is a considerable quan-tity of watches in their original cases, which can be dated precisely by hallmarks stamped inside the case. For those which have lost their original case, the chronological order of the numbers engraved on the movements allows them to be dated, taking as a basis of comparison, the numbers on the watches whose date of manufacture is known from hallmarks. Then, Pierre Le Roy used for some of his simple watches the "fusée renversée" in-vented by his brother Jean-Baptiste in 1760, and a dead beat frictional escapement derived from that of Sully. The watches including these two last inventions, which bear relatively high numbers, fit chronologically among those produced between 1760 and 1775, and therefore after Julien's death. These three elements for determining the date of manufacture (case marks, chronological order of numbers, and technical characteristics) permit us to ascertain a fourth, which makes it much easier to identify the watches made by Pierre Le Roy after his father's death. Doubtless to render him homage, the gilt metal cock on all those is chased and engraved with the initials "J.L.R.". There is no exception to this rule. The only watch movements without it are those "for the use of astronomers and sailors", whose balance, provided with a device for counteracting the effects of temperature, is held in place with a single bridge. Pierre Le Roy presented many papers to the Academy, concerning both watches and clocks. However, his work in the field of marine clockmaking is so important that it possible to speak of his true genius. In 1748 he conceived a detent escapement whose design, published by Gallon in "Machines et inventions approuvées par l’Académie Royale des Sciences does not entirely explain its way of func-tioning. It does, however, show the first attempt at making an escapement which ensured that the balance have complete freedom of motion, outside the phases of unlocking and impulse. In his "Précis des recherches ...", Pierre Le Roy mentioned in 1768 a work that he had already announced in 1750, called "Essai de physique et de dynamique sur les ressorts des corps", which was never published. The manuscript of this essay, which has just been discovered, shows that from this period, his researches on friction, the elasticity of springs and the phenomena of metal dilatation had led him to conceive a primitive form of equalizing winder and a mechanism to compensate the effects of temperature on the functioning of watches. The sealed envelope, which had been deposited at the Academy on 18 December 1754 and opened at his request on 28 June 1763, already contained the essential principles which allowed him to design the marine clock which he presented to the King in 1766 and with which he won the longitude prize, offered by the Academy. This was the first marine clock ever made, which included the three fundamental discoveries which were responsible for the success of marine clocks and watches and later modern chronometers: a free esca-pement, an isochronic hairspring, and a self-regulating pendulum, the compensation for the effects of temperature taking placed directly on the pendulum, without touching the hairspring, so as not to disturb its iso-chronism. In September 1771, Pierre Le Roy presented to the Academy a "Memoire concernant une montre de nouvelle construction pour l’usage de l’astronomie et de la Marine". This was a precision pocket watch placed in gimbals for use at sea. One of these watches was tried out during the voyage of Verdun de la Crenne in 1771 and 1772, but did not give the hoped-for results. Supplied with a compensation for the effects of temperature, it had a dead beat escapement derived from that of Sully. Because of its shape, Pierre Le Roy gave it the name of "petite ronde". In 1773, as he was ill, Piere Le Roy was obliged to rest at the Château de Moisan, and restrict his activity. He was disappointed to learn that the office of Clockmaker Mechanical Expert to the King and the Navy had been awarded to his rival Ferdinand Bethoud, with the position of General Machinery Inspector for the Navy. He then devoted himself to writing his "Suite du précis sur les montres marines en France avec un supplémént au mémoire sur la meilleure manière de mesurer le tems en mer". In 1780, he retired to Viry-sur-Orge where he spent the last five years of his life.