MINT 



351 



anything going wrong in the works of the balance. When the machine is to be set 

 in motion, a kind of cheek is made by screwing to touch the face of the stepped- 

 wheel, and thus, by friction, gives motion to the wheel J. This is an elegant mode of 

 meeting a chance of accident, for in the event of the weight proving to be too heavy, 

 any extra force simply disconnects this cheek from the face, and so stops the machine. 

 The machine having been set in motion, the small wheel J (by communication with the 

 larger wheels, J, all of which are driven by it), causes the cam K a to push forward 

 the lever L, which pushes forward the flattened continuation of Y indicated by dotted 

 lines, until it moves a coin placed in the collar at the bottom of the hopper M, on to the 

 scale-pan F, which, for the sake of clearness, is isolated, and will be seen in fig. 1541. 

 So soon as the coin has been placed on the scale-pan F, the cam p lowers a lever, 

 p, the office of which is to permit the opening of the forceps Q, and thus to release the 

 rod D, dependent from F upon the knife-edge c. The forceps are closed by the cam p, 

 which raises p, and by it compresses an attached spring. The forceps are intended to 

 hold this rod, D, while the coin is placed On F, because the friction caused by the 

 placing of the coin would have a tendency to push F from the knife-edge on which 



1541 



1542 



it is suspended, and thus blunt its delicate edge. While the forceps are opened the 

 cam o, by its partial revolution, lifts the rod N, which is steadied in its motion by a 

 pin rising from it and entering the inverted arch ; its lower extremity working into 

 a socket on the table on which the whole frame of the machine stands. 



Towards its lower extremity the rod N will be seen to branch out right and left, 

 until each end passes through a kind of step in the rods D, E, indicated more dis- 

 tinctly in jig. 1541. The office of this rod is to bring the beam, fr6m which the rods 

 D, E, are dependent, to a dead level, as well as to release both ends of the beam by one 

 action. At the moment that the forceps Q have released the rod D, the cam o, by N, 

 releases both the rods D, E, by rising from the steps, thus permitting the beam to 

 determine the weight of the blank placed on F. A close inspection of the illustration 

 will show that the rods A are suspended from and rest upon the knife-edges, c, of the 

 beam. A, which has a centre knife-edge, T, by which the whole mass is supported and 

 poised. The knife-edges are made to find their own planes or resting-places upon 

 curved or hollow pieces of steel, thus securing the smallest point of contact with a 



