Prof. Challis on a Theory of Magnetic Force. 69 
positions N and N! will be destroyed, and the disturbance will 
be in greater degree as the distance between the magnets is less. 
Also the consequences of the disturbance will be different accord- 
ine to the different directions of the currents. First, let B and 
A! be adjacent ends. Then the streams, always flowing towards 
A and A’, will be in the same direction. Hence, by hydrody- 
namics, the density and pressure of the fluid are diminished by 
the junction of the streams, in greatest degree in the space in- 
tervening between B and A’, and in N B and N/A! to a greater 
degree than in N A and N’B!. Thus the increment of density 
from the neutral lines towards the ends is less rapid in the 
adjacent halves, than in the remote halves. Hence the moving 
force of the xther urging the individual atoms towards the 
neutral lines is in excess in the remote parts, causing the mag- 
nets to move towards each other as if they were attracted. The 
same effect would be produced if the adjacent ends were B’ and A, 
because the two currents would still be in the same direction. 
Next, let A and A’ be adjacent. In this case, the streams 
issue from the magnets in contrary directions towards the space 
between A and A’, and by their meeting the ether is condensed 
in such a manner that the decrements of density towards the 
neutral positions are more effective in the nearer halves of the 
magnets than in the more remote. The magnets consequently 
move from each other, or are apparently repelled. Lastly, let B 
and B’ be the adjacent ends. The streams now flowing from 
B towards A and from B! towards A’, a diminution of velocity 
and consequent increment of density, result from their contrary 
tendencies between B and B’. The increase of density in this 
case may be conceived to be produced by the accelerations of the 
ether resolved in directions perpendicular to the common axis of 
the magnets, the resolved parts, in both streams and on both 
sides of the axis, conspiring to produce motion ¢owards that line. 
Thus by the same reasoning as 1m the preceding case, the magnets 
will be repelled. Consequently the known law, that like poles 
mutually repel and unlike poles mutually attract, is accounted for 
on the principles of the hydrodynamical theory. 
I take occasion to add that the above considerations respect- 
ing the mutual influence of opposing and conspiring magnetic 
streams, equally apply to the streams to which in the theory of 
electricity the attractions and repulsions of electrified bodies 
were attributed, and may be regarded as supplementary to the 
explanations given in arts. 18, 19, and 20 of the communication 
to the Number of the ‘ Philosophical Magazine’ for last October. 
8. In a similar manner the mutual action between magnets 
and galvanic currents may be explained. In the theory of gal- 
vanism, reasons were given for concluding that the movement of 
