COMMON THINGS CLOCKS AND WATCHES. 



the wheel, and have a position intermediate between the spur 

 teeth. Upon the axle of the balance-wheel just above the plane 

 of the escapement- wheel is fixed a claw pallet called the impulse 

 Fig 25. pallet, which by 



the combination 

 of the oscillations 

 of the balance and 

 the progressive 

 motion of the es- 

 capement - wheel 

 falls successively 

 between the 



crown -teeth of the 

 latter, receiving 

 from their reac- 

 tion as they escape 

 from it, the restoring action which maintains the range of the 

 oscillations of the balance-wheel. 



Under the pallet and in the plane of the spur teeth is placed a 

 small roller usually formed of ruby or other hard stone, having a 

 notch on one side of it, into which the spur teeth successively fall. 

 After any crown tooth, a for example passes the pallet, the corre- 

 sponding spur tooth A falls into the notch of the roller, and this 

 alternate action continues so long as the watch goes. It will be 

 perceived therefore that the pallet and roller in the duplex 

 escapement play the same part as the two edges of the semicylinder 

 in the cylindrical escapement, and as the two pallets in the 

 common recoil escapement (fig. 17). 



The chief advantage claimed for this system is that there is but 



one pallet, and that the action 

 does not require as perfect 

 execution of the teeth of the 

 escapement - wheel as other 

 arrangements. 



42. The lever escapement 

 is much used for English 

 pocket watches. A lever A B 

 (fig. 26), with a notch at one 

 end, is attached to the 

 anchor c. A pin at a, on a 

 disc D, on the verge or arbor 

 of the balance, enters this 

 notch at each vibration, and first moves the dead part of the 

 pallet off" the tooth of the scape-wheel E, and then receives an 

 impulse, which restores the force it has lost, leaving another tooth 

 33 



