420 Dr. Faraday on the Physical Character of 



be a function in that medium equivalent to conduction, involving 

 differences of conduction in different cases, that of necessity im- 

 plies also reaction or resistance. The differences could not exist 

 without. The analogous case is presented to us in eveiy part 

 by the electric force. When, therefore, a magnet, in place of 

 being a bar, is made into a horseshoe form, we see at once that 

 the lines of force and the sphondyloids are greatly distorted or 

 removed from their former regularity ; that a line of maximum 

 force from pole to pole grows up as the horseshoe form is more 

 completely given ; that the power gathers in, or accumulates 

 about this line, just because the badly conducting medium, i. e. 

 the space or air between the poles, is shortened. A bent voltaic 

 battery in its surrounding medium (3276.), or a gymnotus curved 

 at the moment of its peculiar action (1785.), present exactly the 

 like result. 



3283. The manner in which the keeper or sub-magnet, when 

 in place, reduces the power of the magnet in the space or air 

 around, is evident. It is the substitution of an excellent conductor 

 for a poor one ; far more of the power of the magnet is trans- 

 mitted through it than through the same space before, and less, 

 therefore, in other places. If a horseshoe magnet be charged 

 to saturation with its keeper on, and its power be then ascer- 

 tained, removing the keeper will cause the power to fall. This 

 will be (according to the hypothesis) because the iron keeper 

 could, by its conduction, sustain higher external conditions of 

 the magnetic force, and therefore the magnet could take up and 

 sustain a higher condition of charge. The case passes into that 

 of a steel ring magnet, which being magnetized, shows no ex- 

 ternal signs of power, because the lines of force of one part are 

 continued on by every other part of the ring; and yet when 

 broken exhibits strong polarity and external action, because then 

 the lines, which, being determined at a given point, were before 

 carried on through the continuous magnet, have now to be carried 

 on and continued through the surrounding space. 



3284. These results, again, pass into the fact, easily verified 

 partially, that if soft iron surround a magnet, being in contact 

 with its poles, that magnet may receive a much higher charge 

 than it can take, being surrounded with a lower paramagnetic 

 substance, as air : also another fact, that when masses of soft 

 iron are at the ends of a magnet, the latter can receive and keep 

 a higher charge than without them ; for these masses carry on 

 the physical lines of force, and deliver them to a body of sur- 

 rounding space ; which is either widened, and therefore increased 

 in the direction across the lines of force, or shortened in that 

 direction parallel to them, or both ; and both are circumstances 

 which facilitate the conduction from pole to pole, and the relation 



