Effects of EleBricity in Jftortening Wire. 337 ~ 
I have alfo tried a piece as copper wire, gilt with fil- 
ver, and of the fame dimenfions as the iron wire, and 
find, that the fame charge, difcharged through it, fhortens 
it one twentieth of an inch, viz. two-thirds of what the 
iron wire was fhortened. The fame ftrength of electrical 
charge, as near as could be meafured by an electrometer, 
which paffing through the iron wire, made it vifibly 
red-hot in a bright day, the fun fhining at the fame time, 
did not heat a piece of copper wire of the fame dimen- 
fions fo as to appear of a red heat, though the room was 
made dark. If the battery was but a little more charged, 
the iron wire then would be melted; but it had no fuch 
effect on the copper wire.. 
This feems to point out, that iron wire refills the paf- 
fage of the eleftric fluid much more than copper; and 
alfo, that the culinary fire and eledlrical fire have different 
effedls on iron and copper : for malleable iron, I am in- 
formed, is one of the moll difficult metals to melt by the 
culinary fire, and requires a much greater heat to melt 
than copper; whereas, on the contrary, the iron is melted 
with a much lefs charge of electric fire. 
