290 INVENTION OF CimOIfOMETEIlS, Si.€. 



--aiKl even kpcpcrs * with an article entitled, De fa mdf'trence que Von dvii 

 then prcfrn-ed ,;„. ^ ?'/ ? , v . ^ 



the dead-beat ^^^^"'^^ '^ ^ echappement a repos a palettes de rubis, sur celui d 

 with ruby pal- 'vibrations libres ; constatk par des experiences dicisives : while 

 lets to the free t r> r .1 ■ ,. , 



escapement. ^^ ^"3'' "'O'^^ ^^e conviction of the accuracy wf his construc- 

 tion, ventured to assert (in his Precis de$ differentes Recherches, 

 &c. p. 37), that chronometers would, in future, be made, accord- 

 ing to those principles, without material variations. Long expe- 

 Tssertid th? ''^^"^^ ^'"^^ already j ustified M. Le Roy's ideas, and established, 

 snj»eriority of beyond doubt, the great advantages of the detached escape- 

 Berthoud' fn'"^ ^ent ; and F. Berthoud, in his history, published in 1802, has, 

 1802, admits at last, done something like justice to that great watchmaker. 



Ins claim, but g^^j hjg construction ; but, at the same time, has associated 



demands to . ' ' 



share it. himself to the honour of the invention of the detached escape- 



- ment, in terms, which, so far from appearing well established, 



are rather in contradiction to the evidence afforded by an 



attentive comparison of his preceding works. 



Of the different constructions of the detached escapement 



The construe- published by F. Berthoud, which indeed diflfer from one ano- 



tion of the de- ^ •' , 



tached escape- ther merely in the contrivance of the detent, and are all made 



ment of Ber- jq act with springs, we shall only notice the kind which has been 

 thoud, which r o - j 



has been most the most generally used both in Great Britain and France. 



uS"""''^ Fig. 1 0, Plate IX. represents this escapement, as copied from the 



Description Traite des Horloges Marines., 1773, Fig. 5, Plate XIX. The 



Tife*d?tS^has escape wheel, A, is stopped by the arm, B d, of the detent,/B d, 



a back spring, whilethc balance vibrates in two directions : the detent moves 



recoi/^'^*^ '^ "^ on pivots, and is pressed by the spring, a. Cis a circle, or wheel, 



attached to the axis of the balance, but of smaller dimensions, 



and has a pallet, c ; which, when it turns from c towards e, acts 



on the arm, f, and disengages the escape wheel. At the same 



moment the pallet, g, which is placed within the thickness of 



the circle, C, and stands as high as tlie escape wheel, receives an 



impulse from the tooth, i. During this action, the pallet, c, quits 



the arm,/ ; and the detent, pressed by its spring, drops into the 



escape wheel, to meet the succeeding tooth, and keeps it at rest, 



after the communication of power is completed. The tooth, i, 



is, at this time of stopping, disengaged out of the pallet ; and the 



balance, being free, finishes its vibration. When the balance 



returns in the direction from e to C, the pallet, c, acts on the 



back of the arm, /; but this part is flexible, and forms an in- 



* Traite des Horloges Marines, p. 576. 



clined 



