Sully invented this escapement around 1736. As he wrote, it is a "frictional 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". 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 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 used this escapement in his first deck watches, claiming: "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 (with Sully's escapement)."The history of the escapement goes back to 1700 when Pierre Debaufree invented a new verge-like escapement in which the crown escape wheel was abandoned in favor of a double wheel acting on two pallets set on the balance staff. It has been called "flying staff" because the pallets look like wings.In 1704 Sir Isaac Newton showed one of Debaufree's watches to Sully. It appears that Sully appreciated the idea and subsequently improved it. There has been some speculation that the escapement was reinvented by Enderlin, however, there is little to support this. Furthermore, there exists a watch with this escapement engraved under the dial "Enderlin de Bâle, fait en 1724 pour Monsieur de Sully" putting all claims to Enderlin's invention to rest.