802 PROCEEDINGS OP THE AMERICAN ACADEMY 



of iron wires alluded to above ought to act, as they did, like the solid 

 bar. Fact and theory agree. I am now prepared to answer a ques- 

 tion, from which, curiously enough, the whole of the present investi- 

 gation sprang. I can answer decidedly that there will be no 

 advantage in substituting a bundle of iron wires or plates for the solid 

 core of the helix of a magnetic engine ; but, as the helix will be 

 farther off from the core, the induced current will not be increased, 

 but diminished. 



