284 lNVE>iTlON OF CHROiJOMETERS, &C, 



English patent by Mr. Harrison. Jt would be hard, indeed, to find a similar 



instance of an invention, the first author of which may be so 



clearly ascertained, and from which a second inventor, if 



Arnold can be allowed as such, has dei'ived so much credit. 



Concerning the We have not yet taken any notice of the improvements made 



escapement. jj^ jj^g escapement ; because, after all the plans proposed for 



this most essential part of chronometers, the principle of what 



is called the detached escapement, is the only one now used ; 



and, being established upon long experience, seems to merit 



the preference given to it over all the constructions proposed 



till now. We shall content ourselves with stating in a general 



manner the beginning and progress of that escapement. 



Explanation ©f In all the escapements known till the middle of the last 



of the main- * century, the escape wheel was in continual contact with the 



taining power pallets belonging to the axis of the balance wheel; and the 



ed constantly' fr'Ction, proceeding from this circumstance, may be considered 



with the legu- as a principal source of irregularity in the going of the watches. 



Suppose, that a regulator should be made so perfect as to be 



A balance, tho' exactly isochronal, while vibrating in a free situation: that 



would not ' advantage would be diminished or lost as soon as it was placed 



iTieasure time if in connection with a train of wheels ; and the errors would be 

 so connected. . , . , , . - . . . 



more or less, aceordmg to the nature and quantity of friction 



in the escapement. It would be, therefore, extremely useful 



to secure to the regulator a perfect liberty of vibration, except 



during the short intervals of time which may be necessary for 



the action of the escape wheel, to give it a new impulse. This 



Peter le Roy ingenious idea was also started by P. le Roy, and carried into 

 also contrived .,, .. ,ii-ii , 



the first de- execution by the same artist, m a model which he presented 



tached escape- jn 1/48 to the Academv of Sciences of Paris, and is described 

 ment m 1748. . , ,, • ^ " , . i , i ■ r 



in the collection or machines approved by that society for 



the same year.* 



Description of That escapement is represented in Fig. 4, Pl.VII. ; O H is tlie 



eapenientr" escape wheel, the profile of which is shewn at gk, and TV the 



balance. The curved pallet, AE, is affixed to the axis under 



the balance ; and on the same axis, but above the balance, 



and under the spiral spring, is attached the half-cylinder, C I, 



the end, C, of which is round, and placed in such a manner, that 



* Vol. vii. No, 481, p. 385, intituled, Echappement a detente, 

 invente par M. le Roy, Fils aine, Horloger. 



a line 



