484- Prof. J. Henry's CoiUrihutions 



d action, and its action was therefore supposed to be so feeble 

 as not materially to affect the results 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 Ijeginning of the current 

 would be desirable; and accordingly, on resuming the experi- 

 ments, my attention 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 desired result could be obtained by using 

 a compound galvanic battery, instead of the single one before 

 employed. In reference to this conjecture the constant bat- 

 tery 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 re- 

 membered (III. 7.) consists of a copper riband of about sixty 

 feet long, and coiled on itself Hke the main spring of a watch, 

 was connected with the compound battery, and helix No. 1 

 (III. 8.), formed of one thousand six hundred and sixty yards 

 of fine copper wire, was placed on the coil to receive the in- 

 duction, as is shown in Figure 3, which is again inserted here 

 for the convenience of the reader. 



Fig. 3. 



a represents coil No. 1, b helix No. 1, and c, d, handles for receiving the 

 shock. 



This arrangement being made, currents of increasing in- 

 tensity 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 connexions of the several 

 elements of the battery. With the current from one element, 

 the shock at breaking the circuit was quite severe; but at 

 makinn: the same it was very feeble, and could be perceived in 

 the finoers only or through the tongue. With two elements 

 in the circuit, the shock at beginning was slightly increased ; 



