﻿300 The Philippine Journal of Science lei* 



A watch spring is inserted in the woodwork of an eight-day 

 wall clock, with a pendulum of a half-second period. The 

 arrangement is such that a contact is made each second at the 

 end of the swing between the extremity of the pendulum rod 

 and the spring. Parallel wires lead from the works of the 

 clock and from the spring through binding posts in pairs on 

 the several work benches. Six large dry cells furnish the neces- 

 sary electricity to operate the signal magnets which may be 

 connected to the binding posts on the tables. 



With this apparatus, electricity is not being used up except 

 when the circuit is closed by the insertion of a signal magnet. 

 The timer is always ready when it is necessary to make a record. 

 Two or twelve signal magnets may be used simultaneously, and 

 may be inserted on any bench without reference to connections 

 on other tables. The time in seconds will be represented on the 

 record as a single vertical projection from the base line. 



The apparatus requires no attention except winding the clock 

 once every week. Occasionally the contact point on the pendu- 

 lum should be polished with emery and a little mercury rubbed 

 into the brass. The spring should be kept free from rust. 



