^226 IMPROVEMENTS IN CHRONOMETERS. 



the greater expansion of the stud will in some measure 

 counteract the alterations of the springs by heat and cold. 

 N N is the potance. 

 Its manner of The action of the escapement is thus. The wheel being 

 aauig. propelled by the main spring in the direction of the arrow 



J V, and prevented from revolving by the detent of the pal- 

 let H, the balance by its vibration knocks out the detent at 

 d, and at the same time the tooth E raises the pallet G, 

 till it comes to its detent. In the n)ean time the balance 

 carries the pallet H through its semivibration, and h fol- 

 lowed back by the pallet as far as the rim of the wheels 

 between the teeth d e, this gives the balance force sufficient 

 to knock out the detent of the pallet G, and the same ac- 

 tion and reaction will continue so long as the moving power 

 acts. 



To prevent any possibility of the wheel tripping, I put two 

 banking pins as at g on the arm of each ])allet, which pre- 

 vent the pallet from going farther back than is necessary to 

 allow the tooth to raise up the pallet to its detent, by means 

 of the catches p p, the end of which is a fine tender spring ; 

 and I make a circular piece to project oiit from the catch, 

 so that the crank in its vibration first raises up this catch, 

 and keeps it up while it knocks out the detent. 



AcUantages of Having explained the action of mv scapement, I will now 

 th s scai)ement. „ n , , ,^^ 



state a tew of the advantages, which appear to me to arise 



from these alterations. 1st. By making use of a double 

 wheel, I not only reduce the wear of the teeth, but I can 

 in this way place niy detent pallets and back springs so as 

 not to interfere with one another, and I can have the pallets 

 to turn upon the same centre. 2d. Straight springs are al- 

 ways preferable to a spiral one, wiiere they can be used, 

 because they are not so difficult to make, and their strength 

 can be altered by adjusting screws, which cannot be done 

 when spiral springs are used. Another advantage gained by 

 using straight springs is, that the compensation may be put 

 ,to the springs themselves, which is preferable to a corapen- 

 tjation on the balance. 

 Objections an- In using a gun lock spring, the pressure of the tuoth 

 fcwcre . against the inclined plane is equal, and will therefore wear 



the fate of the pallet equally. I am awiire, that many 



objections 



