120 Contributions to Electricity and Magnetism. 



or fourth orders from the beginning induction, and its action was 

 therefore supposed to be so feeble as not materially to affect the 

 resuks obtained. 



7. Subsequent reflection, however, led me to conclude, that in 

 order to complete this part of my investigations, a more careful 

 study of the induction at the beginning of the current would be 

 desirable, and accordingly, on resuming the experiments, my at- 

 tention was first directed to the discovery of some means by 

 which the intensity of this induction might be increased. After 

 some preliminary experiments, it appeared probable that the de- 

 sired result could be obtained by using a compound galvanic bat- 

 tery, instead of the single one before employed. In reference to 

 this conjecture the constant battery before mentioned (3) was 

 constructed, and a series of experiments instituted with it, the 

 results of which agreed with my anticipation. 



8. In the first experiment, coil No. 2, which it will be remem- 

 bered (III, 7) consists of a copper riband of about sixty feet long, 

 and coiled on itself like the main spring of a watch, was connec- 

 ted with the compound battery, and helix No, 1, (III. 8,) formed 

 of one thousand six hundred and sixty yards of fine copper wire, 



Fig. 3. 



a represents coil No. 1, 6 helix No. 1, and c, <Z, handles for receiving the shock. 



was placed on the coil to receive the induction, as is shown in 

 figure 3, which is again inserted here for the convenience of the 

 reader. This arrangement being made, currents of increasing 

 intensity were passed through the coil, by constantly retaining 

 one of its ends in the cup of mercury forming one extremity of 

 the battery, and successively plunging the other end into the cups 

 which served to form the connections of the several elements of 

 the battery. With the current from one element, the shock at 

 breaking the circuit was quite severe, but at making the same it 

 was very feeble, and could be perceived in the fingers only or 

 through the tongue. With two elements in the circuit, the shock 



