430 Mr DENISON, ON RECENT IMPROVEMENTS IN CLOCK-ESCAPEMENTS. 



pins on which each arm should rest just when it rests also against the pin of the scape-wheel 

 which is going to lift it. 



In turret-clocks the fly is outside the back frame ; then the scape-wheel with its pins point- 

 ing backwards (or towards the pendulum) ; then the arms with their stops pointing the other 

 way ; and then a large cock to carry the back pivot of the scape-wheel arbor and clear the fly, 

 leaving the arms and fork-pins to come through below the cock. The fly should be about 

 4 or 4l inches long and an inch broad, according to the size of the pendulum, i. e. according 

 to the weight of the arms. The stops had better be made of soft steel, screwed on where it 

 is seen they ought to come, and then either they or the pallets (as the case may be) filed 

 away till you have got the proper depth and inclination for locking safely. The depth of 

 locking may be about -j^ inch for arms 9 inches long, and for others in the same proportion ; 

 and the inclination had better be such as to give what they call a little ' recoil the wrong way,' 

 so as slightly to resist the unlocking, and so make the locking more safe : the resistance is far 

 too little to affect the pendulum, in consequence of the small pressure due to the length of the 

 teeth. When the stops are adjusted, they must be taken off and hardened, and their faces 

 polished. The scape-wheel should be of steel about -f^in. thick for a turret-clock, and about 

 half that thickness for a regulator. Such a scape-wheel, for a turret-clock, will weigh only a 

 quarter of an ounce. The lifting-pins may be of brass wire rivetted in. The lifting-faces 

 of the pallets should be hard and polished ; and the whole of the arms had better be of steel, 

 in order that they might be as light as possible with the requisite stiffness, as the action is 

 steadier if some considerable portion of the weight to be lifted is in the horizontal arms. 



E. B. DENISON. 



42, Queen Anne Street, London. 



