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Magnetic Electrepetet' and Electrotome. 



Art, VII. — Magnetic Electrepeter and Electrotome^ to he used 

 with flat spirals] by Charles G. Page, M. D., Washington 

 City, D. C. 



The figure represents a simple instrument, designed chiefly to 

 aid the operator in exhibiting the magneto-electric properties of 

 flat spirals. Though the flat spiral as a magnetic electrical in- 

 strument is inferior to the compound electro-magnet, described in 

 the last number of this Journal, yet the phenomena are more in- 

 teresting, as they are strictly magneto-electric, produced without 

 the presence or cooperation of ferruginous bodies. The object 

 of the instrument, as its name (electrotome) implies, is to break 

 the circuit ; and as it accomplishes this by changing the direc- 

 tion of the galvanic current, it is also a self-acting electrepeter. 



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A rotating electro-magnet would efl"ect the same object ; but the 

 introduction of an electro-magnet or a coiled wire, in any part of 

 the circuit, would detract from the value of the spiral, {g) is a 

 thin base board of mahogany, which, when the instrument is in 

 use, is to rest upon the spiral coil or the box containing it. At 

 the centre of the base {g) is a pivot sustaining the magnetic bar 

 of steel (c) and its axis, the extremity of which plays freely in 

 the centre of the cross piece (/t.) Between the upright pillars 

 are secured two circular pieces of mahogany {a h) {p n) to serve 

 as supports for the mercury cells {d and e. ) The circular box {d) 

 contains two concentric mercury cells, insulated from each other. 



