226 Prof. 0. J. Lodge on the Theory 



To get the frequency these three equations must be treated 

 simultaneously ; and even so the solution is not complete, for 

 n appears also in the true expression for 1^ and K 2 , so that 

 the complete solution for a case of divided-circuit condenser- 

 discharge is by no means simple. 



The experiment with an air-gap as the alternative path is 

 better ; because one may be sure then that none of the dis- 

 charge chooses that path, when it is properly adjusted for its 

 sparks just to fail. 



Liability of Objects to be Struck. 



There are also described in my lecture to the Society of 

 Arts, above mentioned, some experiments on the liability of 

 objects to be struck. A distinction is drawn between two 

 possible cases : — 



(1) Where the air above the object is subjected to a steadily 

 increasing strain till breakdown occurs. 



(2) Where the strain is thrown instantaneously upon air 

 and conductors with a sudden rush. 



In the first case the path is prepared inductively in the air, 

 and the breakdown occurs at the place where the tension first 

 reaches its limiting value ; this is generally on a small knob 

 or surface, and so this is struck and carries off all the discharge 

 independently of its resistance. If its resistance is great the 

 flash may be feeble ; if its resistance is small the flash may be 

 noisy ; but the place of occurrence of the flash is not deter- 

 mined by these considerations. Glow and brush discharges 

 from points and small surfaces may readily prevent any noisy 

 flash from occurring. 



The second case is different. When a sudden rush occurs 

 the discharge shares itself among several conductors in pro- 

 portion to their impedances, quite independently of any consi- 

 derations of maximum tension or prearrangement of path by 

 induction ; so that no distinction is observable between points 

 and large knobs, in this case. Points cease to have any 

 protective virtue ; they can be struck by a noisy spark as 

 readily as can a knob. The highest object will, in general, be 

 struck most easily, provided its impedance is not very great. 

 If it has a very high resistance it is barely struck at all, and it 

 does not then protect the others. 



Experiment of the Recoil Kick. 



Among other experiments described in the lectures above 

 mentioned are some which appear to be of considerable theo- 

 retical interest, wherein a recoil kick is observed at the ends 

 of long wires attached by one end to a discharging condenser- 

 circuit. 



