128 Magneto-Electridty, and Eledro-niagnetical Machines. 



ducing deflection by magneto-electricity, for it sent the currents 

 all in one direction, instead of producing the alternate or vibrating 

 motion occasioned by the common magneto-electrical machine. 

 It is curious to observe that electro-magnetical engines, moving 

 by the reaction of an electrq-magnet and a permanent one, are 

 also magneto-electrical engines. When electricity is supplied 

 to them from a battery, they revolve ,■ and if they be made to re- 

 volve by hand or otherwise, they give out electricity ; electricity 

 and motion producing each other reciprocally. 



The problem proposed in the first part of this paper, solved hy 

 the Dipping-needle used as a Magneto- Electrical Machine. — 

 Does a magneto-electric helix, or coil, act more powerfully by pass- 

 ing the poles of the exciting permanent magnet abruptly, by mov- 

 ing in a plane perpendicular to that in which the magnet lies, or 

 by approaching the pole of the magnet from the middle or neutral 

 point, keeping constantly close to the magnet itself? I restored 

 the semicircular magnet to its place, still keeping the galvanom- 

 eter connected with the instrument. Here, as the coil-bound 

 iron needle revolved in the plane of the magnet, and close to it, 

 I had one of the conditions proposed in the question. I adjusted 

 the torsion index so that it required sixty revolutions of the iron 

 needle per minute, to keep the galvanometric needle constantly 

 at the point of strongest deflection, viz., parallel to the coils of the 

 galvanometer ; then letting it return freely to its place, I found 

 the torsion to have been 62 J°. Taking out the semicircular 

 magnet and placing it in a plane, at right angles to that in which 

 the coil-bound iron needle revolved, so that its convex bend pre- 

 sented to the west, and its poles only were presented to the iron 

 needle at the points of the dip, I obtained the other condition of 

 the question, the abrupt production of polarity. I then proceeded 

 as before, to adjust the torsion index until sixty revolutions per 

 minute would evolve electricity enough to hold the galvano- 

 metric needle constantly to the point of strongest deflection, and 

 letting it return freely to its place found the torsion to have been 

 41°. From these experiments, it appears that the deflecting 

 power, by abruptly passing the poles, is only about two thirds as 

 much as when continuous proximity is preserved. In order to 

 determine whether electricity, produced by inversion of polarity, 

 is in the simple ratio of the number of inversions in a given time, 

 or increases in some higher power, I varied the above experi- 



