262 Prof. J. Henry's Contributions 



when helix No. 1 was at the distance of eighteen inches above 

 the coil transmitting the secondary current. 



85. The same screening effects were produced by the in- 

 terposition of plates of metal between the conductors of the 

 different orders, as those which have been described in re- 

 ference to the primary and secondary currents. 



86. Also when the long helix is placed over a secondary 

 current generated in a short coil, and which is therefore, as 

 we have before shown, one of quantity, a tertiary current of 

 intensity is produced. 



87. Again, when the intensity current of the last experi- 

 ment is passed through a second helix, and another coil is 

 placed over this, a quantity current is again produced. There- 

 fore in the case of these currents, as in that of the primary, a 

 quantity current can he induced from one of intensity^ and the 

 converse. By the arrangement of the apparatus as shown in 

 fig. 9, these different results are exhibited at once. The in- 

 duction from coil No. 3 to helix No. 1 produces an intensity 

 current, and from helix No. 2 to coil No. 4 a quantity cur- 

 rent. 



Fig. 9. 



a coil No. 1, b coil No. 2, c coil No. 3, d helix No. 1, e helix 

 No. 2 and 3, / coil No. 4, and g magnetizing spiral. 



88. If the ends of coil No. 2, as in the arrangement of fig. 

 8, be united to helix No. 1 instead of coil No. 3, no shocks 

 can be obtained ; the quantity current of coil No. 2 appears 

 not to be of sufficient intensity to pass through the wire of 

 the long helix. 



89. Also, no shocks can be obtained from the handles at- 

 tached to helix No. 2, in the arrangement exhibited in fig. 10. 

 In this case the quantity of electricity in the current from the 

 helix appears to be too small to produce any effect, unless its 

 power is multiplied by passing it through a conductor of 

 many spires. 



90. The next inquiry was in reference to the direction of 

 these currents, and this appeared important in connexion 

 with the nature of the action. The experiments of Dr. Fa- 

 raday would render it probable, that at the beginning and 



