416 Dr. Faraday on the Physical Character of 



the development of its nature, both as a magnet and also as a 

 source of electricity, that we may become acquainted with the 

 great law under which the apparent anomaly may disappear, and 

 by which all these various phenomena presented to us shall 

 become one. 



3274. The physical lines of force, in passing out of the magnet 

 into space, present a great variety of conditions as to form 

 (3238.) . At times their refraction is very sudden, leaving the 

 magnet at right, or obtuse, or acute angles, as in the case of a 

 hard well-charged bar-magnet, fig. 2 ; in other cases the change 

 of form of the line in passing from the magnet into space is more 

 gradual, as in the circular plate or globe-magnet, tigs. 3, 4, 5. 

 Here the form of the magnet as the source of the lines, has much 

 to do with the result ; but I think the condition and relation of 

 the surrounding medium has an essential and evident influence, 

 in a manner I will endeavour to point out presently. Again, 

 this refraction of the lines is affected by the relative difference of 

 the nature of the magnet and the medium or space around it ; as 

 the difference is greater, and therefore the transition is more 

 sudden, so the line of force is more instantaneously bent. In 

 the case of the earth, both the nature of its substance and also 

 its form, tend to make the refractions of the line of force at its 

 surface very gradual ; and accordingly the line of dip does not 

 sensibly vary under ordinary circumstances at the same place, 

 whether it be observed upon the surface or above or below it. 



3275. Though the physical lines of force of a magnet may, and 

 must be considered as extending to infinite distance around it as 

 long as the magnet is absolutely alone (3110.), yet they may 

 be condensed and compressed into a very small local space, by 

 the influence of other systems of magnetic power. This is indi- 

 cated by fig. 6. I have no doubt, after the experimental results 

 given in Series xxviii., respecting definite magnetic action (3109.), 

 that the sphondyloid representing the total power, which in the 

 experiment that supplied the figure had a sectional area of not 

 two square inches in surface, would have equal power upon the 

 moving wire, with that infinite sphondyloid which would exist if 

 the small magnet were in free space. 



3276. The magnet, with its surrounding sphondyloid of power, 

 may be considered as analogous in its condition to a voltaic 

 battery immersed in water or any other electrolyte ; or to a gyni- 

 notus (1773, 1784.) or torpedo, at the moment when these 

 creatures, at their own will, fill the surrounding fluid with lines 

 of electric force. I think the analogy with the voltaic battery 

 so placed, is closer than with any case of static electric induction, 

 because in the former instance the physical lines of electric force 

 may be traced both through the battery and surrounding me- 



