90 DR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. (SERIES XXVII.) 
of the needle. In every other position it affected it ; so that these two planes divided 
the sphere of action into four segments, as before. 
2987. As the helix passes from one quadrant to another, the direction in which the 
needle is deflected changes as before (2982.). If the helix is in the upper north seg- 
ment or the lower south segment, the upper or south end of the needle is deflected 
towards the south ; if the helix be in the upper south or lower north segments, the 
upper or south end of the needle is deflected towards the north. If the helix be 
carried round the needle in tlie direction of the plane of motion, which in this case 
is that of the magnetic meridian, tlie end of the needle starting from a mean or un- 
affected position wall move first one way, as for instance, north and then south ; 
north again and south again, and finally north to regain its place of rest: so that 
there are two extreme deflections of the end in each direction, as before, in the case 
of the declination magnet (2982.). 
2988. In other words, when the helix was anywhere below the magnetic equator, 
the lower or norti) end of the needle tendetl to point outwards from it or outside of 
it, being as it were repelled by the axis of the helix, but drawn by the outer curved 
lines of force, fig. 20 (2992.). Or if the helix were above the equator, then the upper 
or south end of the needle went outwards from the helix, moving exactly in the same 
direction in relation to the helix as the lower pole did before. 
2989. The support of the needle was turned round 90°, which therefore removed 
the plane in wliich the needle could move 90° from the magnetic meridian. This 
carried the plane of no action on the needle 90° round, so that it now coincided with 
the magnetic meridian ; and the plane, which, standing east and west, was before 
neutral, was no longer a plane of indifference, but in fact passed at the middle of the 
segments through the places of strongest action. 
2990. Here, with incUnation, as before with declination, it is not the direction in 
which the needle stands that determines what action the helix may have upon it ; 
for it may be loaded or otherwise restiained, as all horizontal needles are; but it is 
the direction of the lines of force at the needle which, with the helix, governs all. 
The helix may be above or below the prolongation of the needle indifferently ; for if 
it still continues on the same side of the line of force, under the influence of which 
the needle acts, then the end of the needle moves in the satne direction, though it 
may travel towards the helix in one instance and from it in another. 
2991. I suspended a needle so that it was free to move in every direction, and 
now I obtained the simple natural effect of the helix, or a diamagnetic globe (2877-) 
on a given line of force, and it is well to have it in mind. For, though we are 
obliged for the sake of practical observation to divide the position into two parts, 
declination and inclination, yet the results in each case are much better compared 
and remembered when the simple law of change in the whole line of force is ready in 
the mind for reference. The equatorial plane and the magnetic axis are now the 
only parts in which the lielix can be without affecting the position of the needle; 
