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LXXXIII. Further Researches on the magnetic Phenomena 
produced by Electricity ; with some new Experiments on the 
Properties of electrified Bodies in their Relations to conducting 
Powers and Temperature. By Sir Humpury Davy, Bart. 
P RiS.* 
Ti Ix my letter to Dr. Wollaston on the new facts discovered 
by M. Oersted, which the Society has done me the honour to 
publish, I mentioned, that I was not able to render a bar of steel 
magnetic by transmitting the electrical discharge across it through 
a tube filled with sulphuric acid; and I have likewise mentioned, 
that the electrical discharge passed across a piece of steel through 
air, rendered it less magnetic than when passed through a me- 
tallic wire; and I attributed the first circumstance to the sul- 
phuric acid being too bad a conductor to transmit a sufficient 
quantity of electricity for the effect; and the second, to the elec- 
tricity passing through air in a more diffused state than through 
metals. 
To gain some distinct knowledge on the relations of the dif- 
ferent conductors to the magnetism produced by electricity, I in- 
stituted a series of experiments, which led to very decisive results, 
and confirmed my first views. 
II. I found that the magnetic phenomena were precisely the 
same, whether the electricity was small in quantity, and passing 
through good conductors of considerable magnitude ; or, whether 
the conductors were so imperfect as to convey only a small quan- 
tity of electricity ; and in both cases they were neither attractive 
of each other, nor of iron filings, and not affected by the magnet ; 
and the only proof of their being magnetic, was their occasioning 
a certain small deviation of the magnetized needle. 
Thus, a large piece of charcoal placed in the circuit of a very 
powerful battery, being a very bad conductor compared with the 
metals, would not affect the compass needle at all, unless it had 
a very Jarge contact with the metallic part of the circuit ; and if 
a small wire was made to touch it in the circuit only in a few 
points, that wire did not gain the power of attracting iron filings ; 
though, when it was made to touch a surface of platinum foil 
coiled round the end of the charcoal, a slight effect of this kind 
was produced. And in a similar manner fused hydrate of pe- 
tassa, one of the best of the imperfect conductors, could never 
be made to exert any attractive force on iron filings, nor could 
the smallest filaments of cotton moistened by solution of hy- 
drate of potassa, placed in the circuit, be made to move by the 
magnet; nor did steel needles floating on cork on an electrized 
* From the Transactions of the Royal Society for 182], Part II. 
solution 
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