Magnetic Electrepeter and Electrotome. 
T. y I.—Magnetic Electrepeter and Electrotome, to be used 2 
sr a — Pgs ; by Cuartes G. Bam M. D., ‘Weshingaa a 
City, D 
THE figure represents a serie 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 coéperation of ferruginous bodies. The object 
of the instrument, as its name (electrotome) implies, is to bre 
the cireuit ; and as it accomplishes. this by changing the ¢ 
- tion of the galvanic current, it is also a selbanine clectaepaer : 
~~ 
A rotating electro-magnet would effect 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) isa 
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 magriétic bar 
of steel (c) and its axis, the extremity of which plays freely in 
the centre of the cross piece (h.) Between the upright pillars 
are secured two circular pieces of mahogany (a b) (p m) to serve 
a8 supports for the sie cells (dande.) The circular box (@). 
contains two concentric mercury cells, iasaleted from each other, 
