284 Historical Sketch of Electro-magnetism. [Oct. 



and the effect was communicated to needles at a distance of five 

 inches from the wire, even when water, or thick plates of glass 

 or metal intervene. 



By these kinds of experiments it was found that a tube of 

 sulphuric acid, one-fourth of an inch in diameter, did not conduct 

 electricity enough to render steel magnetic ; that an explosion 

 through air made the needle placed transversely to it magnetic, 

 though not so strongly as a wire would have done ; that steel 

 bars in the circuit, or parallel to it, did not become magnets ; 

 that two bars placed together across the wire, passing through 

 the common centre of gravity, showed no magnetism after the 

 discharge before they were separated, but exhibited opposite poles 

 on separation. 



One conclusion drawn by the author from these experiments 

 is, that magnetism is produced whenever concentrated electricity 

 is passed through space. 



On arranging numerous wires in circles, and other directions 

 around and about the discharging wire, it was found after the 

 discharge, that all were magnetic, and the poles exactly as before 

 expressed ; so that the north pole of one needle was towards the 

 south pole of the next, and in a constant relation to the course of 

 the discharge, fig. 11. 



The connecting wire being divided in one part into three, four, 

 or more, by small wires, and the voltaic battery discharged 

 through them, they were all found to be magnetic at once, and 

 took up separate cylinders of filings ; when the opposite side of 

 two of these were" brought together, the filings attracted each 

 other. From this, it was expected that when the simdar sides 

 were brought together, the filings on them would repel each 

 other. This was tried by two batteries arranged parallel, but in 

 opposite directions. The filings on these connecting wires 

 repelled each other; and connecting wires of platinum and fine 

 steel wire without filings exhibit similar phenomena of attraction 

 and repulsion. These experiments, it will be perceived, are 

 similar to those made by M. Ampere on the attraction and repul- 

 sion of two connecting wires, or, as he calls them, two electrical 

 currents, and prove the same thing. On placing straight pieces 

 of platinum, silver, and copper wire, on two knife edges of plati- 

 num connected with the opposite poles of a battery, they were 

 found to be attracted and repelled in directions according to what 

 has before been said. Gold leaf made in the same way to form 

 the connexion was found to be moved by a magnet. 



A simple mode of making magnets is pointed out in this paper; 

 namely, by fixing bars of steel across, or circular pieces of steel 

 fitted for horse-shoe magnets, round the electrical conductors of 

 buildings in elevated and exposed situations. 



M. le Chev. Yelin appears to have discovered by accident that 

 by placing a steel needle in a glass tube surrounded by a spiral 

 of wire, along which either simple electrical sparks or discharges 



