﻿4 o Prof. E. Taylor Jones on the most 



is unity in each of the adjustments specified in Table I. if the 

 resistances of the circuits are negligible. But it is easy 

 to see that of these adjustments the first (i. e., n 2 jni = 'd, 

 L 1 C 1 = *429 L 2 C 2 ) is the one which gives the longest spark 

 for a given primary current. For let us suppose that an 

 induction-coil is so constructed, and the primary condenser 

 so chosen, that X.'=*914 and L 1 Ci = , 164L 2 C 2 . This is the 

 second adjustment of Table I., and it allows the whole of 

 the primary energy JL^'q 2 to be converted at a certain 

 moment after the interruption into electrostatic energy in 

 the secondary circuit. Now by inserting coils of suitable 

 self-inductance, say l u in the primary circuit (coils which do 

 not act inductively on the induction-coil) we can reduce the 

 coupling coefficient to "756 ; and if the primary condenser is 

 chosen so that (L 1 + Z 1 )C 1 = *429L 2 C 2 , we then have the first 

 adjustment, with n 2 /n 1 =3. The system has again unit 

 efficiency, but the maximum electrostatic energy in the 

 secondary is now i(L 1 + / 1 )? 2 , and is greater than the 

 former value in the ratio of L1 + /1 to L x . The capacity C 2 

 of the secondary coil being unaltered, the secondary 

 potential is increased in the ratio s^L^lx to */ h t . The 

 3/1 adjustment is thus more effective (though not more 

 efficient) than the others because it allows a greater quantity 

 of initial energy to be converted into electrostatic energy 

 in the secondary circuit, in which therefore the charge and 

 potential developed are greater than in the other cases. 



There are other ways in which the coupling coefficient 

 could be reduced (e. g., from *914 to '756), but none of 

 them are so effective as the plan of introducing external 

 inductance into the primary circuit. For instance*, 

 external inductance may be introduced in the secondary 

 circuit. This increases C 2 , and to some extent L 12 , without 

 altering Lx and L 21 , and therefore, by (3 b) , lowers the 

 secondary potential. Again, k may be reduced by re- 

 moving a part of the iron core. This diminishes Lx 

 without causing any increase in L 21 /L 12 , or any change 

 in C 2 , and therefore, by (3 b), reduces V 2m . The reduction 

 of the coupling may also be effected by withdrawing the 

 primary coil with the core to a suitable distance along 

 the axis of the secondary. This process reduces L 12 , L 21 , 

 and L 2 , without changing Lj, and should cause no change 

 in the secondary potential except such as may be due to a 

 slight diminution of C 2 or of the ratio L 21 /L 12 . 



It should be clearly understood that these reductions 

 of the coupling are supposed to bring the system from 



* In each of these supposed modifications the primary capacity is to 

 be adjusted so that L 1 Ci = (l-^' 2 )L 2 C 2 . 



