COMMON THINGS CLOCKS AND WATCHES. 



construction the regulator may be made so as to oscillate nearly 

 at the required rate, it cannot be made to do so exactly. Besides, 

 even though it should vibrate exactly at the required rate, it will 

 be subject, from time to time, to lose that degree of precision, and 

 to vibrate too fast or too slowly from the operation of various 

 disturbing causes. 



It has been already shown, that the rate of vibration of the 

 pendulum is rendered more or less rapid by transferring the centre 

 of gravity nearer to, or farther from, the point of suspension. 

 Upon this principle, therefore, the adjustment of the rate of 

 vibration depends. The heavy disc v, fig. 19, is made to slide 

 upon the rod RE, and can be moved upon it, upwards or down- 

 wards, by a fine screw attached to it, which works in a thread cut 

 in the rod. In this manner the centre of gravity of the disc v 

 may be transferred nearer to the suspension ss, so as to shorten 

 the time of its vibrations, or removed farther from ss, so as 

 to lengthen the time. If the clock is found to lose or go too 

 slowly, it is screwed up, and if it gain or go too fast, it is screwed 

 down. 



In chimney and table time-pieces, the pendulum is regulated in 

 a different manner. It is usually suspended upon a loop of silken 

 thread, which can be drawn up or let down through a certain 

 limited space, by means of a rod, upon which one end of the 

 thread which forms the loop is coiled. This rod, passing through 

 the dial-plate, has a square end, upon which a key can be applied, 

 by turning which in the one direction or the other, the loop is 

 drawn up or let down. 



