INVENTION ©F CHRONOMETERS, icC. OQJ 



ner: A pin, which is placed as the preceding one, but in the 

 under face or plane of the balance, pushing the arm C II, wets 

 the arm, e H, out of the circumference of the wheel, and iatro- 

 duces D H ; so that when the pallet, p, arrives at F, the wheel 

 being free, the radius, F r, gives a new impulse to the balance^ 

 and impels the pallet, p, till it is stopped by the arm, D, of the 

 detent, as in Fig. 6. 



To prevent the detent from beirtg displaced by the effect of 

 external motion, a circular curb, i A, i A (Fig^ 5, 6, and 7), 

 has been adapted to the circumference of the balance, near 

 each pin, vvhich disengages the detent : but, the arms of the de- 

 tent can only touch the corresponding curbs, in consequence of 

 ihe most violent shakes. 



The construction of this escapement principally differs from The improred" 



that of 174S in these three points : 1st.— In the last escape- Je STyTciiffei 



ment, the second vibration, or return, is permitted to be com- from his fir?t. 



pleted, and it is not till the balance comes again to move in the ooni^Siorand 



first direction that a new impulse is given to it, in the middle of "o recoil in un- 



the whole arc of vibration ; while, in the former, the free re- dSent! ^^^ 



turn of the balance proceeds no farther than the place where it 



received the first impulse, where a new action is opposed to it. '2A. — The ac- 



2d. — In the second escapement, the pallet is situated near the tion affects the 



'■ balance pivots 



outer cu-cumierence of the balance, with a view to render the less, because it 



impulse upon it more favourable to circular motion, without a '^ ^iven at the 

 . ' circumterence, 



cousequeot actson on the pivots ; while in the former escape- 

 ment the pallet or edge of the half-cylinder is near the cen- 

 tre. 3d. — The mechanism of the detent in the new escape- 3d.— Thed.c 

 ment, having no springs, is also different from that of the other, *^"* ^f^ ^^ 

 which depended upon that description of power. P. le Roy ^*'"°"' 

 was led t© contrive the new detent, because he wished to avoid 

 the inconveniences arising from the use of the springs for that 

 purpose, inconveniences which are considerable in his opinion, 

 on account of the loss of power which takes place if the springs 

 are strong, and of the uncertainty of their performance if they 

 are weak, 

 ^ From the two preceding escapements of P. le Roy, are de- All the modem 

 rived, without material improvements, (unless the spring de- ♦'scapements, 

 tent or locking spring should be esteemed one), all the detached been mudT 

 eacapements which have been executed, to any considerable "^^'^' ^'"^ ^^^^"" 

 aumber, from that to the present time. ' aftlfoS'oru 



About ^^y'-'- 



