CORRECTION OF OBSERVATIONS. 277 



With a sinusoidal swing we should have similarly by equation (49) 



In the method of recoil (887) the deflection b' for the small 

 impulse is still equal to aq ; but to obtain the extent a of the 

 retarded swing we should replace z' in equation (48) by a', 

 z/ by -b'g, and v by a ; we have then 



which gives 



or 



For a sinusoidal impulse we should replace in this formula 



* i 6* 



by 

 6 4 



The mixed method (888) would give rise to analogous cor- 



f" G 2 



rections; but unless the ratios ^ and cannot be altogether 



neglected, it seems difficult to arrange experiments in so perfect 

 a manner that these corrections can be made with any cer- 

 tainty. 



894. DISCHARGE OF A CONDENSER. When a condenser of 

 capacity C is put in connection with the earth, or the two 

 armatures are connected with each other by a conductor of re- 

 sistance R, and whose coefficient of self-induction is L, the 

 charge Q and the intensity of the current I at the period / are 

 given by expressions 



1= - 



