54' Free Efcapement of modern Time- Pieces, 



Horiaontal watches were greatly efteemed during the laft thirty years, until lately, when 

 they gave place to thofe conftruflions which are known by the name of detached or free 

 efcapements. In the common efcapement, fig. i, an increafe of the maintaining power in- 

 ■creafes the recoil, and accelerates the vibrations; but with the horizontal efcapement there 

 is no recoil ; and an increafe of the maintaining power, though it may enlarge the arc of vi- 

 bration, will not neceflarily diminilh or alter the time. It is accordingly found, that the 

 experiment of altering the maintaining power by the application of the key, does not alter 

 the rate in the fame perceptible manner as in common watches. Exceedingly perfeft time- 

 pieces on the hori2ontal principle, with a compenfation for temperature applied to the 

 fpring, were made about fifteen years ago by Emery, of Charing-crofs, and other artifts ; 

 but I am informed that their performance became fenfibly lefs accurate after a few years 

 wear. Whether the difficulty of execution, or the badnefs of workman fliip in low-priced 

 watches of this kind, or whether the fubfequent great improvements in this ufeful engine, 

 have caufed the horizontal principle to be laid aCde, I know not ; but 1 believe few if any 

 watches of this conftrudlion are at prefent made. 



The dead beat efcapement of Graham, and the horizontal efcapement, both appear to be 

 improvements of the common anchor efcapement, fig. i. which by thefe expedients is 

 deprived of its recoil, but flill retains the wedge adion, which has much friftion, and ne- 

 ceflarily requires oil. The quantity of diredl pufli in the efcapement fig. i, which re- 

 quires no oil on the face of the pallets, appears to be the caufe why it aiSls fo freely, and 

 is fo little liable to injury or diforder. I wifti it were lefs diflicult to afcertain the invent- 

 ors and improvers of ufeful contrivances. But in proportion to the utility and univerfal 

 adoption of any inftrument, it always becomes more eafy to mention it by a fingle term. 

 Definitions, defcriptions, and inventors' names naturally become difcarded ; and from this 

 caufe it feems as if a moderate or a fpeculative invention might carry the name of its in- 

 ventor to remote ages, while the great benefa£lors of fociety are forgotten. I do not 

 know who firft undertook to improve efcapements by pallets refembling thofe of fig. i. in 

 the direfl aftion they receive ; but the earlieft contrivance of this kind I have met with is 

 that of M. Le Roy fils aine,of which the account bears date Sept.6, 1748. As it is in efFeiSl 

 the fame efcapement as is now in the higheft efleem in the time-pieces of our beft artifts, 

 I (hall here dcfcribe the latter, and mention the particulars of that of M. Le Roy in a 

 note. 



Fig. 3. PI- III- reprcfents the free efcapement of our beft portable time-pieces. Fig. 4. 

 exhibits the efcapement on a larger fcale. On the verge of the balance is fixed a circular 

 piece of fapphire, or hard fteel, EL, out of which a fefloral piece is* cut. HG is a ftraight 

 fpring fixed near its extremity H, and having at the other extremity a pin G, againft 

 which one of the teeth of the wheel D refts when the train is at reft. This fpring has a 

 flight tendency towards the centre of the wheel, but is prevented by the ftop K from 

 throwing the pin farther inwards than juft to receive the point of the tooth. I is a very 

 {lender fpring fixed at the end I, and preffing very flightly againft the pin G, in a direflion 

 tending to throw it from the wheel D, but which on account of the greater power of HG 

 it cannot efFeft. It may be obferved that the fpring I proceeds a little beyond the pin G.— 

 F is a lever proceeding from the verge of the balance diredly oppofite the end of the 

 fpring I, and long enough to ftrikc it in its vibration. The adion is as follows : — From 



5 the 



