170 MR. FARADAY’S EXPERIMENTAL RESEARCHES IN ELECTRICITY. 
city should therefore be from north above to south, and below back to north, 
in a metal ball revolving from east above to west in these latitudes. Now 
these currents are exactly those required to give the directions of the needle 
in the experiments just described ; so that the coincidence of the theory from 
which the experiments were deduced with the experiments themselves, is 
perfect. 
167- Upon inclining the axis of rotation considerably, the revolving ball was 
found to affect the magnetic needle ; and it was not until the angle which it 
formed with the magnetic dip was rendered small, that its effects, even upon 
this apparatus, were lost (153.). When revolving with its axis parallel to the 
dip, it is evident that the globe becomes analogous to the copper plate ; elec- 
tricity of one kind might be collected at its equator, and of the other kind at 
its poles. 
168. A current in the ball, such as that described above (161.), although it 
ought to deflect a needle the same way whether it be to the right or the left 
of the ball and of the axis of rotation, ought to deflect it the contrary way 
when above or below the ball ; for then the needle is, or ought to be, acted 
upon in a contrary direction by the current. This expectation was fulfilled 
by revolving the ball beneath the magnetic needle, the latter being still in- 
closed in its jar. When the ball was revolved from east over to west, the 
marked pole of the needle, instead of passing eastward, went westward; and 
when revolved from west over to east, the marked pole went eastward. 
169. The deflections of the magnetic needle thus obtained with a brass ball 
are exactly in the same direction as those observed by Mr. Barlow in the revo- 
lution of the iron shell ; and from the manner in which iron exhibits the phe- 
nomena of magneto-electric induction like any other metal, and distinct from 
its peculiar magnetic phenomena (132.), it is impossible but that electric cur- 
rents must have been excited, and become active in those experiments. What 
proportion of the whole effect obtained is due to this cause, must be decided 
by a more mature investigation of all the phenomena. 
170. These results, in conjunction with the general law before described, 
suggested an experiment of extreme simplicity, which yet, on trial, was found 
to answer perfectly. The exclusion of all extraneous circumstances and all 
complexity of arrangement, and the distinct character of the indications 
