. . [ 66 ] 
nine inches of this iron wire j and this fame cartridge 
was eafily fired near the battery, connected with 
ftiorter pieces of the fame brafs wire ; fo that the di- 
minution of force mull have been owing to the length 
of the circuit. 
In the place of this fmall brafs wire, I fubfiltuted 
an iron wire one fifth of an inch thick, when about 
half an inch of the fmall iron wire was exploded ; fo 
that the force was not lelTened fo much in a circuit of 
the thick iron wire, as it had been in one of the fmall 
brafs wires. In order to judge how much of the 
force might be loft by nearer circuits, confifting of 
lefs perfe<fl conducflors, I joined the middle of the 
circuit made by the iron wire with water, in which 
both the wires were immerfed. The effedt was, that 
the fmall iron wire was only made red-hot, but not 
exploded as before. 
Being fenfible how much depended upon avoiding 
lelTer circuits, whereby part of the fire of an explo- 
fion might return to the battery, without reaching the 
extremity of the circuit, where I intended the whole 
of its force to be exerted, in the remaining experi- 
ments, I infulated half the circuit of iron wire. 
There was no occafion for infulating the whole cir- 
cuit j for if there was but one paftage to, or from 
the middle of it, there could be but one from, or to 
it. In this method it was eafy to afcertain what lofs 
of force was occafioned by the length of the circuit, as 
every other circumftance was carefully excluded ; and 
it prefently appeared to be very confiderable; for tho’ 
I could melt nine inches of the fmall iron wire at the 
diftance of fifteen yards from the battery ^ when I tried 
twenty yards, 1 found that I was juft able to make 
fix 
i 
