Eilectro-Magnetic Apparatus and Eoperiments. 257 
Experiment 3d.—Bring one extremity of-the magnet used in 
the foregoing experiment in contact with one pole of the magnet 
of a common magneto-electric machine. As this disguises a por- 
tion of the magnetism, the amount of electricity developed by 
the revolution of the armature will of course be diminished. 
While working the machine the magnetic state of the electro- 
magnet will vary with the approximation and recession of the 
armature, and a current of electricity in its wires will be the con- 
sequence. When the current from the armature is broken or not 
- suffered to flow at all, the current from the electro-magnet will be 
much. stronger than when the circuit from the armature is con- 
stantly complete. When the armature is leaving the magnet, 
the flowing current or elosed circuit magnetizes the armature and 
consequently disguises more of the power of the inducing mag- 
net, than when the armature leaves without the closing of the 
circuit. . The consequence is a detraction of magnetic power 
from the electro-magnet. Also, breaking the circuit from the 
armature under oil, increases the current from the electro-mag- 
- het. 
_ Experiment Ath. me the ends of the wire coiled on one leg 
of the curved armature of a common magneto-electric machine, 
and allow the coil fromi the other leg to be connected with the 
break piece, as usual. As long as the circuit of the first coil is 
closed, the second coil will furnish scarcely.any electricity ; but 
when the circuit of the first coil is opened, the second furnishes 
nearly as much electricity as the combined current from both 
coils. This singular fact first called my attention to the great 
advantage of short,, straight armatures, for the magneto-electric 
machine. Obviously, the best arrangement for straight arma- 
tures, would be that wherein they revolved between the. ends of 
the magnetic poles, the axis or shaft being parallel to the legs of | 
the magnets. ‘The points gained by this plan would be, a more 
‘uniform and powerful current, and an exact division by the Uni- 
trep of the semicircular: routes through which the alternating 
currents are developed. In the machine described in Vol. 
xxxiy, p. 164, of this Journal, and in all others where the axis of 
motion is perpendicular to the plane of the magnet, if the two 
routes in which, the opposite currents are developed be represented 
by two ares of a circle drawn through the two neutral points, 
that are towards the bend of the magnet will be much the longer, 
Vou. XXXV.—No. 2. : 
