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round it in the opposite direction to that in which it was 
spinning. 
It might he that the electricity in the inducing body 
would produce an opposite magnetic effect on the top ; but 
even if this were so (and I do not think it has been experi- 
mentally shown that it would be so), its effect, owing to its 
distance, would be much less than that of the electricity on 
the very surface of the top. If we take no account of the 
effect of the inducing body the current round the top would 
be of such strength that it would carry all the electricity 
induced in the top once round every revolution. And if the 
top were spinning from west to east by south it would be 
rendered magnetic with the positive pole uppermost, that 
is, the pole corresponding to the north pole in the earth or 
the south pole of the needle. 
In order to show that such a current might be produced, 
a glass cylinder, twelve inches long and four across, was 
covered with strips of tinfoil, parallel to the axis, with 
very small intervals between them. These strips were about 
six inches long and one half inch wide, and the intervals 
between them the two-hundreth of an inch. In one place 
there was a wider interval, and from the strips adjacent to 
this wires were connected by means of a commutator with 
the wires of a very delicate galvometer. This cylinder 
was mounted so that it could be turned twelve hundred 
revolutions in a minute, and brought near the conductor 
of an electrical machine. This apparatus, after it had been 
thoroughly tested, was found to give very decided results. 
As much as 20° deflection was obtained in the needle, and 
the direction of this deflection depended on the direction in 
which the cylinder was turned, and on the nature of the 
charge in the conductor. When this was negative the 
current was in the opposite direction to that of rotation. 
It may be objected that the measurement was not actualty 
made on the cylinder. It must, however, be remembered 
