DefcrtpttOM and Invention of the koriztntal Efcopcmettt. 53 



dift'inguifhed by the name of a recoil. Other conCderable objcilions, befides that of the 

 continued a£tion of the maintaining power, have been made againft efcapements with a 

 r£Coil ; but it would lead us too far into the minute departments of this fubje£t to difcuf* 

 them. The efcap«ment of Graham, and all fuch as have no recoil, have been called dead 

 beat efcapements, becaufe the index for feconds falls direclly through its arc, and remains 

 motionlefs on the line of divifion till the next vibration. It may be obferved, that the 

 maintaining power in Graham's efcapement may be applied during a fmall portion only of 

 the vibration ; and that an increafe of the maintaining power tends to enlarge the arc of 

 vibration, but fcarcely interferes with its velocity. 



The effeft of the efcapement which has been called horizontal *, becaufe the laft wheel 

 in watches of this conftruftion has its plane parallel to the reft of the fyftem, is fimilar to 

 that of the dead beat efcapement of Graham. In fig. 3, the horizontal wheel is feen with 

 twelve teeth, upon each of which is fixed a fmall wedge fupported above the plane of the 

 wheel, as may be feen at the letters A and B. On the verge of the balance there is fixed 

 part of a hollow cylinder of fleel or other hard material, the imaginary axis of which pafles 

 through the pivots of the verge. C reprefents this cylindrical piece, into which the wedge 

 D may be fuppofed tohave fallen. While the vibration caufes the cylindrical piece to re« 

 volve in the diredlion which carries its anterior edge towards the axis of the wheel, the 

 point of the wedge will merely rub the internal furfacc, and no otherwife affedl the vibra- 

 tion of the balance than by retarding its motion. But when the return of the vibration 

 clears the cylinder of the point of the wedge D, the wheel will advance, and the flope fur- 

 face of the wedge afting againft the edge of the cylinder will affift the vibration of the ba- 

 lance. When the edge of the cylinder arrives at the outer point of the wedge D, its pofte- 

 rior edge muft arrive at the pofition denoted by the dotted lines of continuation ; immedi- 

 ately after which the wedge or tooth E will arrive at the pofition e, and reft on the outer 

 furface of the cylinder, where it will produce no other efFed than that of retardation from 

 fridlion, as was remarked with regard to the wedge D, until the courfe of the vibration 

 ftiall bring the pofterior edge of the cylinder clear of the point of the wedge. In this laft 

 fituation, the wedge will aft on the edge of the cylinder, and affift the vibration, as in the 

 former cafe, until that edge fliall arrive at the outer or pofterior point of the wedge ; imme- 

 diately after which the leading point will fall on the inner furface of the cylinder in the firfl: 

 pofition, as was fhewn in the wedge D. 



"* In the k\'mt\\voV\me oi Machines et Inventmns approuvec! par I' Acai/emii; RoyaU cles Sciences, I find » 

 p.137, that the Sietr Bavfri, a French clock-maker, fettled in London, contrived ihe horizontal fcapement 

 itt 1704. He applied an hollow portion of a cylinder to the verge of the balance, the edges of which were 

 thick enough to afford the inclined furfaccs of Graham's psllets, and thel'e were aflei upon by two com- 

 mon wheels perfeflly fimilar and fixed on the fame axis, fo that the teeth of one corrcfponded with the hollows 

 oftheother. In the fame work, p. 141, the Regie artificielle du temps of Sully, p. 14? — 2 5 1 , is quoted toi 

 fliew that Sir Ifaac Newton poffeiTed one of thefe watches, marked with the name of Baufrc. Peter le Roy 

 improved this fcapement by fubftituting a portion of a cone inftead of the cylinder (Machines et Inventions, 

 '74i)> ^'"'th a double wheel, the axis of which was at right angles to the verge. And M. Gourdain, in the. 

 fame year (p. 141 of the work laft quoted), made another conftruftion, in which a flat circular piece of metal, 

 out of which a portion of about qo° was cut, was fubftituted in the place of the cylinder, and received the ac- 

 ti»n of a wheel with wtdge-teeth, afting alternately in oppofite dircfticns in the notch, and lefting on the flat 

 furface of the metal during the time of repofe. The fc^cment defcribcd iathe text appears to have been a com- 

 bioat.on of the inventions of Baufrc and Gourdain. 



Horizonta' 



