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XXIX. Farther 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 Humphry Davy, Bart. P. R. S. 
Read July 5, 1821. 
I. In my letter to Dr. Wollaston on the new facts dis- 
covered 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 dis- 
charge 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 metallic wire ; and I attributed 
the first circumstance to the sulphuric acid being too bad a 
conductor to transmit a sufficient quantity of electricity for 
the effect ; and the second, to the electricity passing through 
air in a more diffused state than through metals. 
To gain some distinct knowledge on the relations of the 
different conductors to the magnetism produced by electricity, 
I instituted a series of experiments, which led to very decisive 
results, and confirmed my first views. 
II. I found that the magnetic phamomena 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 
