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PROCEEDINGS OP THE AMERICAN ACADEMY 



to ten cells of grove. Tlie armature was a piece of soft iron, weighing 

 22 grammes. The thickness of the coil, which was equal to the lengths 

 of the iron cores, was 65 mm. The wire of which it was composed was 

 3 mm. in diameter. 



The results of these experiments are given in the following table : — 



Experiments were then made with horseshoe electro-magnets ; but 

 it was speedily found that the phenomenon of the adherence of the 

 armature, after the breaking of the galvanic circuit entered, and the 

 time of release of the armature, was practically infinite. With straight 

 electro-magnets, the above experiments show that the magnetic strength 

 sufficient to maintain an armature of constant weight at the respective 

 poles, had a duration of .091 of a second, and appeared to be not 

 sensibly affected by increase or diminution of the magnetic state of 

 the core, beyond that requisite to barely sustain tho weight of the 

 armature. 



