854 Memorandum of Experiments, SfC. [[Oct. 



3rd Experiment — Three strands of wire were now employed in 

 each conductor, twisted into a cord. The igniting distance was rather 

 more than trebled. 



My stock of wire was insufficient to carry this curious experiment 

 farther ; but a trial with a weaker battery and shorter conductors as 

 far as six strands in each, led to the inference, that the igniting distance 

 increases in an arithmetical ratio with the mass of the conducting 

 wire. 



A very extraordinary circumstance presented itself in these experi- 

 ments, one which has been previously observed by Davy, but the 

 great importance of which in the present inquiry demands a distinct 

 description. 



If at the distance of 130 feet two inches of platinum wire become 

 a bright red, we find that by shortening the wire to one inch the 

 ignition is not increased, but diminishes remarkably. Shortened to 

 half an inch the wire ceases to be even sensibly warm to the touch ! 

 This curious fact is one deserving all the ingenuity of the theorist to 

 explain its nature, but my business now is with practical matters 

 alone. It leads clearly to the employment of exploding wires of much 

 greater length than we would employ were we ignorant of this very 

 singular and apparently anomalous circumstance. 



Insulation of conductors not essential even in water. 



The preceding observations refer to dry conductors. It is almost 

 needless to say that dividing the wires in any part, and thus interrupt- 

 ing the circuit, at once causes the platinum to return to its natural 

 degree of coldness. 



It might be, and indeed generally is supposed, that were the con- 

 ductors immersed in water, this fluid would carry off the electricity, 

 and nullify all effect on the platinum. Thence it would be inferred 

 that it would be necessary to insulate the wires, that is, to place them 

 within a coating of some resinous, or other non-conducting substance, 

 which would at the same time prove impervious to water and a barrier 

 to the passage of the electric fluid. 



Impressed with the idea that this insulation might be dispensed 

 with, I instituted several experiments with the same battery and plati- 



