188 MR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 
selves are reversed (fig. 41.), and the induced current is therefore (114.) still 
in the same direction as before. It is also, for equally sufficient and evident 
reasons, in the same direction, if produced by the influence of the curves de¬ 
pendent upon the wire. 
23/. When the second wire is retained at rest in the vicinity of the principal 
wire, no current is induced through it, for it is intersecting no magnetic curves. 
When it is removed from the principal wire, it intersects the curves in the 
opposite direction to what it did before (235.) ; and a current in the opposite 
direction is induced, which therefore corresponds with the direction of the 
principal current (19.). The same effect would take place if by inverting the 
direction of motion of the wire in passing between either set of poles (fig. 41.), 
it were made to intersect the curves there existing in the opposite direction to 
what it did before. 
238. In the first experiments (10. 13.), the inducing wire and that under 
induction were arranged at a fixed distance from each other, and then an 
electric current sent through the former. In such cases the magnetic curves 
themselves must be considered as moving (if I may use the expression) across 
the wire under induction, from the moment at which they begin to be de¬ 
veloped until the magnetic force of the current is at its utmost; expanding as 
it were from the wire outwards, and consequently being in the same relation 
to the fixed wire under induction as if it had moved in the opposite direction 
across them, or towards the wire carrying the current. Hence the first cur¬ 
rent induced in such cases was in the contrary direction to the principal cur¬ 
rent (17- 235.). On breaking the battery contact, the magnetic curves (which 
are mere expressions for arranged magnetic forces) may be conceived as con¬ 
tracting upon and returning towards the failing electrical current, and there¬ 
fore move in the opposite direction across the wire, and cause an opposite in¬ 
duced current to the first. 
239. When, in experiments with ordinary magnets, the latter, in place of 
being moved past the wires, were actually made near them (27- 36.), then a 
similar progressive development of the magnetic curves may be considered as 
having taken place, producing the effects which would have occurred by motion 
of the wires in one direction; the destruction of the magnetic power corre¬ 
sponds to the motion of the wire in the opposite direction. 
