Theory of Magnetism. 253 
coil of 10 millim., we obtain the numbers 1°25, 1°25, 1°32, 1:4, 
14. The ratio of the magnetic moments of points of the rod 
equidistant from each other is therefore not constant, as in the 
case of the endless rod, but increases as we approach the end 
of the rod, as indeed was to be expected. 
Van Rees found that in a homogeneous prismatic magnet 
the magnetic moments of the sections decrease parabolically, 
as with the uniformly magnetized iron bar. This, however, 
holds good only for those magnetic bars to which, in the 
process of magnetization, a uniform moment has been com- 
municated through the entire length. As soon as the magne- 
tizing force has ceased to act, all the molecular magnets have 
the same tendency to return again to the unmagnetized con- 
dition, whence at last the same condition of magnetic equili- 
brium results, as with the uniformly magnetized iron bar. 
Lastly, I should like to make a few further remarks on a 
previous communication of mine *. 
I proposed the theory at that time, that the molecular mag- 
nets assumed in the Ampére-Weber theory must consist each 
of two elementary magnets or solenoids close together with 
opposed poles, capable of free rotation together in any direc- 
tion without meeting with resistance, but directed by external 
magnetizing forces, and separately rotated, as would be the case 
with astatic pairs of needles capable of free and independent 
rotation. I did not then know that Stephan had already ex- 
pressed the same view, and accompanied it by important 
mathematical considerations. Now, in accordance with the 
theory explained above, the Amperian theory must be extended 
as already mentioned, by supposing all space to be filled with 
paired molecular solenoids, or, if we adopt Hdlund’s view 
that the electric current consists in ether in forward motion, 
filled with ether vortices, and that these are present in magnetic 
material in greater numbers than in nonmagnetic material. 
Since, now, a magnetizing force acting upon the mole- 
cular magnets only exerts a perceptible influence on the rota- 
tion apart from each other of the paired elementary magnets 
when all the neighbours in the magnetic circuit follow the 
motion,and so are able to produce a closedsystem of equilibrium 
capable of mutual attraction, it follows that the rotation di- 
rectly produced by the magnetizing force must be very small 
in comparison with the mutual strengthening of the rotation 
in the closed magnetic circuit. The magnetic moment pro- 
duced must thus be essentially the product of the mutual 
strengthening of rotation of which the magnetizing force is 
the cause. Here the difficulty is presented that the rotation 
* Loe. cit. p. 703. 
Phil. Mag. 8. 5. Vol. 19. No. 119. April 1885. fi 
