4 6 



MEASUREMENT OF OSCILLATIONS. 



Elongations and 4 give 42-20* as the approximate value of the 

 time of oscillation ; dividing this time by the interval between the 

 fourth elongation and the first of the following series, we get the 

 number 142-98; this latter elongation, which is of the odd order, 

 will have the number 147. We proceed in the same way for the 

 following series : 



