1881.] The Source of Electric Energy . 517 
the same extent that their own movement is hindered. In 
like manner the movement of the negative poles of the first 
is hindered, and causes a like movement in the positive poles 
of the second. This adtion is followed by eledtric neutral- 
isation in both wires, and must cause in the second an eledtric 
current in an opposite direction to that proceeding in the 
first. To the exadt extent that motive energy is taken from 
the first it is given to the second, and the eledtric current in 
the second is the exadt equivalent of that hindered in the 
first. The chemical energy has a greater sum of resistances 
to overcome, and must be more vigorous ere the current can 
pass. Yet this effedt is only momentary. When the eledtric 
current of the first has become fully established, the hindrance 
of the second becomes ineffective. The condition of the first 
has been changed, and the second has entered into new 
relations with it. And a reversal of these new relations is 
resisted as vigorously as was the change in the primary rela- 
tions. The cessation of the current experiences a hindrance 
from the second wire equal to that of the formation of the 
current. As the cessation of the current is equivalent to a 
backward flow of eledtricity, its resistance by the second 
wire produces a forward flow in this. Thus a return to the 
original relations of the two wires is accompanied by an 
adtion in the second equal and opposite to that caused in the 
loss of the original relations. Any partial change in the 
strength of the current necessarily produces similar effedts 
to those of the complete formation or cessation of current, 
for each increment of current adts upon the conducting wire 
as though it were otherwise unaffected. And also any vari- 
ation of distance between the wires strengthens and weakens 
their relations of mutual influence, with the accordant cur- 
rent effects. 
If there be no second wire this principle of resistance to 
change manifests itself between the molecules of the primary 
wire. For these molecules are really independent, except 
so far as their mutual influence goes, this influence differing 
from that between the molecules of two separate wires of 
the same substance only in being more vigorous and less 
exposed to exterior substance. There is, therefore, a resist- 
ance to change of these molecular relations, possibly between 
the interior and surface molecules, since these surface 
molecules are to a certain extent affedted by exterior influ- 
ences. Thus, if there be no second wire, all the effedts of 
indudtion are displayed in the first, through a principle of 
resistance to change exadtly analogous to that of the former 
case. 
