CHRONOMETERS. 97 



the seconds are seen on a flat moveable ring, at the 

 extremity of a fleur-de-lis engraved on the dial- 

 plate. A, in Fig. 6. is the great wheel of this 

 clock, containing 120 teeth, turning round in 

 twelve hours. The axis of this wheel bears the 

 plate of hours, which may be moved by a pin 

 passing through small holes drilled in the plate, 

 without affecting the wheel-work. The great 

 wheel A turns a pinion B, of ten leaves, round in 

 an hour, and carries the minute hand, B, on its 

 axis round the dial-plate in the same time. On 

 this axis is a wheel C, of 120 teeth, turning round 

 a pinion D, of six leaves, in three minutes ; on the 

 axis of which there is a wheel E, of 90 teeth, that 

 keeps a pendulum in motion, vibrating seconds by 

 palettes, as in a common clock, when the pen- 

 dulum-wheel has only SO teeth, and goes round in 

 a minute. In order to show the seconds by this 

 clock, a thin plate must be divided into three 

 times 60, or 180 equal parts, and numbered 10, 

 20, 30, 40, 50, 60, three times successively, and 

 fixed on the same axis with the wheel of 90 teeth, 

 so as to turn round near the back of the dial-plate ; 

 and these divisions will show the seconds through 

 the opening e f g h, Fig. 5. This clock will go a 

 week without winding. 



VOL. 1. h 



