INVENTION OF OIIRONOMIiTERS, &C. 293 



place; and the action of the escapement proceeds successively, 

 as explained before. 



The detached escapement used by jMr. Earnshaw is reprc- Earnshaw'a 

 sented in Fig. 13, which istalcen from his statement, presented ^^^'^^I*^'^"""** 

 to the Board of Longitude. This escapement is similar to that— is in effect 

 of Arnold's, already described, except in small variations, which j„ j-Q^m nearly 

 will be easily perceived, on a comparison of the two figures. It the same as 

 is besides asserted, and it appears probable from every circum- 

 stance relative to these constructions, that the late Mr, Ar- —choused it 

 nold had made use of this form of escapement long before 

 ^Ir. Earnshaw, but that he laid it aside, in order to adopt the 

 escapement with cycloidal teeth, which he esteemed far prefer- 

 able. In the escapement we are now considering, the escape 

 wheel is shaped as appears in the figure ; and, on the inspection 

 of this representation, it will be easily observed, that the teeth 

 presenting a right line, and escaping by a sharp point, their ac- 

 tion cannot be so smooth, and the wear of the whole must be — it is more 

 greater, than in the construction with protuberant cycloidal 

 teeth. The detent is of the same kind as the other, and only 

 differs from it, in being stopped by the inside of the head of the 

 adjusting screw, instead of the extremity of the screvv itself, 

 and unlocking outwards, and not towards the centre. 



The two constructions, which may be considered as the The escape- 

 fcame, differ from the French detached escapements, such as b*y Anioid^and 

 those of F. Berthoud, which we have already explained, in the Earnshaw are 

 detent. In the new detent, the pivots are abolished, and the "j!^^^ ^I^q^J^'^^^I- 

 centre of motion is established in the locking piece itself ; the French, 

 which, for that purpose, is made flexible near the extremity sp,.jjj^"^jj^^^q|- 

 by which it is fixed. The elasticity of the detent, or locking the rJetent in- 

 piece, supplies also the office of the auxiliary spring placed at ^^^ ^"*^ 

 a or u (Fig. 9 and 10), or the spiral spring, which has been 

 sometimes applied to the axis of the pivots, to keep the detent 

 in the proper situation. 



The pivots of the old detent are so slender, that its perform- Probability 



ance cannot be supposed subject to any considerable degree V^^^ *^!^^ ^f^""^ 



of friction ; and watches, with that kind of detent, have been superior to that 



known to go very well. Some able artists, upon that account, ^,eap^es"s'^'^' "^ 



think, that the new detent is only preferable to the other, only ; 



because it saves v/ork, and is less expensive ; but while the 



spring detent is allowed to perform as well, if not better, than —but it is as 



,ho good, if not 

 "'^ hetter, and 



