HISTORY AND PROGRESS. 61 



lever engages with one of the pallets of the escapement h ti, 

 and governs the motion of the axis i. When a current 

 traverses the coils of the electro-magnet the armature and 

 lever are depressed, the click is put in gear, and the pallet 

 h of the escapement, released, turns with the axis i. At the 

 moment when the pallet h' passes under the lever, it relifts 



Fig. 32. 



it, and depresses the screw d', returning thereby the armature 

 to the poles of the electro-magnet, and, at the same time, 

 throwing the click out of gear. 



The magnet B is of novel construction. It consists of a 

 permanent horse-shoe magnet, with soft iron cylindrical con- 

 tinuations on the poles. These continuations are each en- 

 circled by a coil of wire. When no current passes through 

 the coils, the armature is attracted to the poles by the 

 magnetism distributed in the iron. This force is opposed 

 by the adjusting spring, which is so regulated that, the 

 armature being in contact, a very weak current is able to 

 neutralise the attraction. 



The printing shaft has also the duty of correcting the move- 

 ments of the type- wheel, and of insuring always that, at the 

 moment of printing a letter, the type is in its proper position. 

 This is effected by means of a curved cam, h 2) on the axis i. 

 The instant the cam 1i lifts the arm b of the frame carrying 

 the printing roller, the projection h 2 locks into the teeth of 

 the wheel H', and adjusts, if it be necessary, its position. If, 

 on entering the teeth of H', the cam has to push the wheel 

 forwards, or, to accelerate the motion of the axis c tf, the 

 click m is pushed onwards, passing over one or more of the 



