130 Le Roy’s Memoir 6n the best Method 
forrile of the spirals in such a manner, that the points of the 
wheel, instead of corresponding to the lips. of the cylinder, 
fel] in the middle of the cylindric portion where the dead 
part takes place: I then moved the balance, whose axis was 
vertical, from its point of rest by an arc of about 80°; it only 
remaincd in vibration four seconds and a half; instead of 
which, when it was free on its pivots, it vibrated a minute 
and a half. hy 
To avoid this inconvenience of the best: known escape- 
ments, I have used in the new watch an escapement nearly 
similar in its principle to that with @ detent, which is the 
invention of M. le Roy, and described in the History of the 
Academy for the year 1748 *. , The balance wheel_r (PI. I. 
fiz. 7, and Pl. III.), whose teeth are very wide apart, and very 
slight, and consequently whose strengih is very small, its 
power consisting in the length of the lever on which it acts ; 
the balance wheel, I say, by means of the pallet P adapted to 
the circumference of the balance (Plate HI. fig. 1, 2, and 3.) 
restores to it, every second vibration, the motion which it 
loses; and its action is suspended in these vibrations by an 
obstacle foreign to this regulator, that is to say, by a sort of 
detent D, e,H,C, F, (fig. 2, 3, and 5, Pl: II.)f. / The fol- 
Jowing is the way it 1s bora : 
The halance wheel stopped by the ae at D, as in fig. 2. 
Plate Il}, and the balance turning on its axis from nto A, 
after having surmounted the spiral springs, and consumed its 
force, these springs bring it back, and make it turn from A 
toi. In this return, by means of a pin situated on its upper 
plane at i, the balance pushes the arm of the lever F, H; and 
consequently draws out the arm D Hi of the detent from the 
circumference of the wheel and makes the arm eH enter, 
on which the following radius Kr of the wheel rests; this 
is what I call the preparation, and 1s represented i in fig. 3. 
In the following vibration the balance wheel restores the 
motion to the balance by means of the pallet p, in the fol- 
lowing manner :—A pin situated as the preceding, but on 
the lower plane of the balance, pushing the ar m a4 the lever 
~ 
* This is the first work that ty Pp abl shed. 
+ This detent forms a kind cf escapewent which may be varied at pleasune, 
using indifferently that of Graham, Am: an, Sully, &c. 
cH, 
