560 THE APPLICATIONS OF PHYSICAL FORCES. [BOOK v. 



Figures 359 and 360 represent the manipulator. 



It is a brass dial supported by three metal columns on a horizontal 

 wooden base. Two concentric zones of the surface, divided each into 

 twenty-six sectors are marked one with twenty-five letters of the 

 alphabet (French) and a cross, and the other with the successive 

 numbers from 1 to 10, with a series of signs or special signals. These 

 signs were placed in the original instrument by the numbers 10 25 

 (Fig. 360). On an axis which passes through the centre of the dial a 

 handle is attached which can be moved in the direction of the hands 

 of a watch and stop against any of the letters or figures; for this 



FIG. 360. Breguet's manipulator, old form. 



purpose the handle carries a tooth which catches in one of the notches 

 cut in the circumference of the dial at the middle of each of the 

 twenty-six sectors. 



The movement of the handle involves that of its axis, and of a 

 movable wheel in which is sunk a sinuous groove, seen where part 

 of the dial is supposed to be removed in the figure. The sinuosities 

 of this furrow are as numerous as the sectors, that is, there are thirteen 

 concave and thirteen convex arcs, all corresponding to the letters or the 

 numbers. A bent lever, T, jointed at a (Fig. 360), carries a little rod 

 upon which runs a little roller of tempered steel. The motion of the 

 wheel is thus communicated to the roller in the concave part of the 

 groove, so that the end of the lever is sometimes carried nearer and 



