88 WRITINGS OF JOSEPH HENRY. [1835 



5. The effect is increased, by using a longer and wider 

 ribbon, to an extent not yet determined. The greatest effect 

 has been produced by a coil ninety -six feet long and weigh- 

 ing 15 lbs. ; a larger conductor has not been received. 



6. A ribbon of copper, first doubled into two strands and 

 then coiled into a flat spiral, gives no spark, or a very feeble 

 one. 



7. Large copper handles, soldered to the ends of a coil of 

 ninety-six feet, and these both grasped, one by each hand^ 

 a shock is felt at the elbows, when the contact is broken in 

 a battery of a single pair with one and a half feet of zinc 

 surface. 



8. A shock is also felt when the copper of the batter}^ is 

 grasped with one hand and one of the handles with the 

 other ; the intensity however is not as great as in the last 

 case. This method of receiving the shock may be called 

 the direct method; the other, the lateral one. 



9. The decomposition of a liquid is effected by the use of 

 the coil with a battery of a single pair, by interrupting the 

 current and introducing a pair of decomposing wires. 



10. A mixture of oxygen and hydrogen is also exploded 

 by means of the coil, and breaking the contact, in a bladder 

 containing the mixture. 



11. The property of producing an intense spark is induced, 

 on a short wire, by introducing at any point of a compound 

 galvanic current a large flat spiral, and joining the poles by 

 the short wire. 



12. A spark is produced when the plates of a single bat- 

 tery are separated by a foot or more of diluted acid. 



13. Little or no increase in the effect is produced by in- 

 serting a piece of soft iron into the centre of a flat spiral. 



14. The effect produced by an electro-magnet, in giving 

 the shock, is due principallj' to the coiling of the long wire 

 which surrounds the soft iron. 



[The foregoing article was re-printed in Silliman's American Journal of 

 Science, July, 1835, vol. xxviii, pp. 327-329.] 



