92 CHRONOMETERS. 



stud in pocket-watches, whereon the lower pivot 

 of the verge plays, and in the middle of which 

 one pivot of the balance-wheel plays. The bottom 

 of the potence is called the foot; the middle part, 

 the nose; and the other part, the shoulder. 3. The 

 cock, which is the piece covering the balance* 



4. The regulator or pendulum spring, which is the 

 small spring in watches underneath the balance. 



5. The pendulum (see Plate 5. fig. 8.) whose parts 

 are, the verge; palettes 5, .5; cocks; the rod; the 

 fork; the flat; the bob, or great ball; and the 

 corrector, or regulator, being a contrivance for 

 bringing the pendulum to its nice vibrations. 



6. The wheels, which are the crown-wheel in 

 pocket-pieces, and swing-wheel in pendulums, 

 serving to drive the balance or pendulum. 7- The 

 contrate-wheel, which is that next the crown- 

 wheel, &c. and whose teeth and hoop lie contrary 

 to those of other wheels; whence the name. 

 8. The great or first wheel, which is that which 

 the fusee immediately drives, by means of the 

 chain or string of the spring-box, or barrel ; after 

 which are the second wheel, third wheel, &c. 

 Lastly, between the frame and dial plate, is the 

 pinion of report, which is that fixed on the arbor 

 of the great wheel, and serves to drive the dial- 

 wheel, as that serves to carry the hand. The me- 

 thod of calculation is easily understood; for suppose 

 the great wheel goes round once in twelve hours; 

 then, if it is a royal pendulum clock, swinging se- 

 conds, we have 60x60x12—43200 seconds, or 

 beats, in one turn of the great wheel: but because 

 there are 60 beats, or seconds, in one minute, and 

 the seconds are shown by an index on the end of 

 the arbor of the swing-wheel, which, in those 

 clocks, is an horizontal position ; therefore it is ne- 



