262 Mr. R. Phillips on Volta-Electric Induction. 



quantity but differing in velocity; for if a shock of electricity 

 is sent through the wire of a galvanometer in a given time, 

 imparting motion to the needle, then if a shock of the same 

 quantity of electricity passes through the wire in any less time, 

 it will impart, making up in force what it wants in time, the 

 same motion to the needle, while it would develope a much 

 higher magnetism in the indicator. I thus conclude, that when 

 induced currents are produced by the discharge of a Leyden 

 jar, the magnetized needle principally registers the variable 

 difference of velocity between the two currents. 



It will be convenient to call the current induced in the 

 neighbouring coil by completing the battery circuit, the first 

 induced current', and that generated while the battery current 

 ceases, the second induced current. 



It seemed to me very improbable that the first and second 

 induced currents should travel the copper wires with such 

 unequal velocities, and yet be exactly equal in quantity; as it 

 would involve a strange relation between the electromotive 

 force of the induced currents and metallic electric conduction. 



By proper supports and by bending it, I arranged the wire 

 which dipped into the mercury, so that striking the wire, as 

 one would a key of a piano played staccato, sufficed to close 

 and open the battery quickly whenever I pleased. The gal- 

 vanometer being connected with the coil A as before, the 

 needles were made to vibrate through an arc about T \yth of an 

 inch long ; I then struck the wire with my finger at such times 

 as should tend to increase the motion of the needles, on the 

 supposition that the first induced current is the more powerful; 

 the needles were soon reduced to rest. I again made the 

 needies vibrate, and struck the wire at those times when so 

 doing should add motion to the needles according to the no- 

 tion that the second induced is the more powerful current, 

 and now the needles could be kept oscillating in a small arc 

 as long as I pleased. Therefore the second induced current 

 is the larger quantity. 



The third coil C was placed on B, one end of both A and 

 C were united to the indicator, and the other ends bound 

 together ; A and C were so placed that on causing an electric 

 current to circulate through B, the current induced in A should 

 act against that induced in C; I found they effectually neu- 

 tralized each other. 



I next placed a copper plate 4 - 5 inches square (which was 

 the size of all the plates employed in these experiments) and 

 Xth of an inch thick, between B and C, and made and broke 

 the battery circuit once through B, which rendered the eye 

 end of the needle as the marked magnetic pole. 



