0» the Efcdpements of Time Pieeit, tf 



Pray who firft applied the duplex efcapement, in London, to watches ? It is the in- 

 vention of a Dutertre early in the eighteenth century *. How long is it fincc watches with 

 the virgule efcapement were fecn ? and who was he who applied it firft ? 



See Regie Artificielle du Temps, par M. Sully, refpe£ting Debaufre's efcapement ; it is 

 but rather treated of there obfcurely, yet I am quite well aware of its conftru£lion. In the 

 fpelling of efcapement I have ufed an elllGon for the e ; however, you may adopt which 

 way you think beft. We ufe the word 'fcapement in common converfation. 



I wonder much at thofe gentlemen of I'Academie Royale des Sciences fo grofsly mif- 

 taking or mifreprefenting what Sully has written ; nothing fo clear to me as the account 

 Sully gives of Tompion's efcapement being the foundation of the horizontal one. Tompion 

 gave it up for a bad job, and this might be one reafon why it was fo late before it was com- 

 pleted under the hands of Graham. Thofe gentlemen of the academy are equally miftaken in 

 their ideas of improvement given by P. Le Roy to Debaufre's efcapement, which they call 

 the horizontal. What P. Le Roy did was, be took one of the wheels, and fubftituted an- 

 other pallet ; but nothing here all the while but is moft diftant from the horizontal one. 

 It is true that Sir Ifaac Newton had one of Debaufre's watches, which he (howed to Sully 

 in 1704. I do not know who this Gourdain was, who is alfo mentioned. It muft be 

 Gaudron that they mean. He was a man of genius, and watch-maker to the Duke of 

 Orleans, during the Regency f. 



• N. B. Enderlin takes the merit of being the inventor as well as Debaufre, and P. Le Roy claims 

 that of Dutertre. See Lepaute, Thiout, &c. 



f Gourdain was a watch-maker probably of Paris. His communications were made to the academy in 

 1742. 



The commiffion of the academy, in their report on M. Gourdain's improvement of Baufre's efcapement 

 (Recueil des Machines, VIE. 137), defcribe this laft as follow : I tranflate verbally. 



" To remedy this inconvenience (the acceleration in the crown wheel and pallets, when the firft mover is 

 augmented) " the Sieur Baufre, a French watcli-makcr, fettled in London, imagined, in 1704, the 

 " efcapement called dead beat (7a Vn nomme a repos). He fupprefled the two pallets and the crown wheel, 

 *' and fixed on the arbor of the balance a kind of cylinder, rather thick, interrupted in one of its halves, 

 " and which, inftead of its being terminated in its feflion by the plane which would pafs through its axis, 

 " js on the contrary (terminated) by two inclined planes, one on each fide of the axis. 



" Oppofite thefe two inclined planes are two wheels fixed parallel to each other on the fame axis, placed 

 «' fo that the teeth of the one are oppofite the interval formed by the teeth cf the other. By this means, as 

 " fcon as one tooth has Aided along one of the inclined planes and impelled the balance, the other tooth 

 " repofcs on thefuperior bafe of the cylinder which carries the inclined plane ; fo that the balance can.f)bey 

 " the whole impulfe it receives, and run throXigh arcs as large as are neceffary, which gives a facility of 

 " regulating the going of the watch, and taking advantage of all the accuracy which the fpiral fpring at- 

 " tached to it is capable of giving." 



The reader will perceive how I myfelf, and not the academicians, have been miftaken in my note at 

 page 53 of the fecond volume of this Journal, in concluding this to be the horizontal efcapement, to which, 

 indeed, the defcription would apply if we were to overlook the words here put in Italic, as I did, and infer 

 that the places of repofe were on the curved furfaces of the cylinder. 



Gourdain'j efcapement is precifely enough defcribed in the note laft quoted.— N. 



Vol. v.— May 1801. I What 



