262 Electro-Magnetic Apparatus and Experiments, 
arrangement for a reciprocating electro-magnetic engine, there 
being no change of poles, as the motion is effected by an ar- 
rangement shown in the two next figures. This form of en- 
gine will be described in a future article. 
oe Revolving Armature. 
_ Figure 5, represents an instrument invented in February, 1838, 
for exhibiting motion by magnetism without change of poles. 
Figure 5. 
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This instrument was the foundation of a series of experiments, 
made with reference to the mechanical application of magnetism, 
which will be published with drawings in a future communica- 
