110 Mr. Watkins on Magneto-electric Induction. 



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magnet, should continue to revolve when the latter goes very 

 fast? The only reply I presume to make to the question is, 

 that I suppose, from the needles being very light and deli- 

 cately suspended, when once put into rapid motion they con- 

 tinue for sometime to revolve, by the momentum they have 

 acquired receiving occasionally a fresh impulse by attraction or 

 repulsion from the electro-magnet, according to the conditions 

 in which that magnet may be at the moment. The instanta- 

 neous impulse might not be of a force equal to actuate a large 

 needle through a space sufficiently great so as to bring the 

 other pole of the needle within the sphere of the influence of 

 the changed pole of the electro-magnet, or at least in proper 

 time; therefore vibration or total rest is the consequence. 

 Indeed, I have commonly noticed that when the points of 

 suspension were in a defective state, even with my small and 

 light magnetic needles they would not revolve when the poles 

 of the electro-magnet were changed very rapidly. Another 

 reason may be assumed for the apparent anomaly, viz. that 

 the magnetic needles, when once revolving, keep revolving at 

 the proper velocity by being acted upon by the maximum in- 

 fluence of one particular pole. 



To make my meaning more intelligible, I shall offer, for 

 instance, the magnetic machine now commonly used to ex- 

 hibit electrical phaenomena. We will take decomposition of 

 water for an example: this has been until a recent period 

 generally effected by voltaic electricity, in which it is supposed 

 that a continuous current in one direction is constantly flowing 

 so long as the voltaic battery is in action. The magnetic ma- 

 chine as originally made by Mr. Saxton consists of a revolv- 

 ing soft-iron armature before the poles of a permanent steel 

 magnet, the armature being surrounded by copper wire co- 

 vered with silk. Now it is clear in this arrangement that the 

 steel magnet induces magnetism on the soft iron, that soft 

 iron again inducing magnetism or electricity, if we like to call 

 it so, on the copper wire which is coiled around it, and it is 

 the recomposition or decomposition of the electrical equili- 

 brium in this copper wire which exhibits the electrical phae- 

 nomena so beautifully shown by the magnetic machine. 

 Mr. Faraday, the parent of magneto-electrical science, has 

 shown that when a steel permanent magnet was presented to a 

 metal wire, its electrical equilibrium was disturbed ; and pro- 

 vided the ends of the wire were in connexion with a measure of 

 the disturbance, say a delicate galvanoscope, a sensible effect 

 was produced, and a deflection of the magnetic needle of the 

 galvanoscope took place in one direction ; but this eminent 



