402 Dr. Faraday on ihe Diamagnetic conditions 



but the ends were shaped to a form approaching that of a cone, 

 of which the sides have an angle of about 100°, and the axis 

 of which is horizontal and in the upper surface of the pieces 

 of iron. The apex of each end was rounded ; nearly a tenth 

 of an inch of the cone being in this way removed. When 

 these terminations are brought near to each other, they give 

 a powerful effect in the magnetic field, and the axial line of 

 magnetic force is of course horizontal, and on a level nearly 

 with the upper surface of the bars. I have found this form 

 exceedingly advantageous in a great variety of experiments. 



When the flame of a wax taper was held near the axial 

 line, but on one side or the other, about one-third of the flame 

 rising above the level of the upper surface of the poles, as 

 soon as the magnetic force was on, the flame was affected ; 

 and receded from the axial line, moving equatorially, until it 

 took an inclined position, as if a gentle wind was causing its 

 deflection from the upright position ; an effect which ceased 

 the instant the magnetism was removed. 



The effect was not instantaneous, but rose graduallv to a 

 maximum. It ceased very quickly when the magnetism was 

 removed. The progressive increase is due to the gradual pro- 

 duction of currents in the air about the magnetic field, which 

 tend to be, and are, formed on the assumption of the magnetic 

 conditions, in the presence of the flame. 



When the flame was placed so as to rise truly across the 

 magnetic axis, the effect of the magnetism was to compress 

 the flame between the points of the poles, making it recede in 

 the direction of the axial line from the poles towards the middle 

 transverse plane, and also to shorten the top of the flame. At 

 the same time the top and sides of the compressed part burnt 

 more vividly, because of two streams of air which set in from 

 the poles on each side directly against the flame, and then 

 passed out with it in the equatorial direction. But there was 

 at the same time a repulsion or recession of the parts of the 

 flame from the axial line ; for those portions which were below 

 did not ascend so quickly as before, and in ascending they 

 also passed off in an inclined and equatorial direction. 



On raising the flame a little more, the effect of the magnetic 

 force was to increase the intensity of the results just described, 

 and the flame actually became of a fish-tail shape, disposed 

 across the magnetic axis. 



If the flame was raised until about two-thirds of it were 

 above the level of the axial line, and the poles approached so 

 near to each other (about 0*3 of an inch) that they began to 

 cool and cqmpress the part of the flame at the axial line, yet 

 without interfering with its rising freely between them ; then, 



