82 Sir Humphry Davy on [Aug. 



trical phenomena exhibited by the wonderful combination of 

 Volta, at that time almost entirely absorbed the attention of 

 scientific men ; and the discovery of the fact of the true con- 

 nexion between electricity and magnetism, seems to have been 

 reserved for M. Oersted, and for the present year. 



This discovery, from its importance and unexpected nature, 

 cannot fail to awaken a strong interest in the scientific world ; 

 a,nd it opens a new field of inquiry, into which many experi- 

 menters will undoubtedly enter : and where there are so many 

 objects of research obvious, it is scarcely possible that similar 

 facts should not be observed by different persons. The progress 

 of science is, however, always promoted by a speedy publication 

 of experiments ; hence, though it is probable that the pheno- 

 mena which I have observed may have been discovered before, 

 or at the same time in other parts of Europe, yet I shall not 

 hesitate to communicate them to you, and through you to the 

 Royal Society. 



I found, in repeating the experiments of M. Oersted with a 

 voltaic apparatus of one hundred pair of plates of four inches, 

 that the south pole of a common magnetic needle (suspended in 

 the usual way) placed under the communicating wire of plati- 

 num (the positive end of the apparatus being on the right hand), 

 was strongly attracted by the wire, and remained in contact 

 with it, so as entirely to alter the direction of the needle, and 

 to overcome the magnetism of the earth. This I could only 

 explain by supposing that the wire itself became magnetic dur- 

 ing the passoge of the electricity through it, and direct experi- 

 ments, which I immediately made, proved that this was the 

 case. I threw some iron filings on a paper, and brought them 

 near the communicating wire, when immediately they were 

 attracted by the wire, and adhered to it in considerable quanti- 

 ties, forming a mass round it 10 or 12 times the thickness of 

 the wire : on breaking the communication, they instantly fell 

 off, proving that the magnetic effect depended entirely on the 

 passage of the electricity through the wire. I tried the same 

 experiment on different parts of the wire, which was seven or 

 eight feet in length, and about the twentieth of an inch in 

 diameter, and I found that the iron filings were every where 

 attracted by it ; and making the communication with wires 

 between different parts of the battery, I found that iron filings 

 were attracted, and the magnetic needle affected in every part 

 of the circuit. 



It was easy to imagine that such magnetic effects could not 

 be exhibited by the electrified wire without being capable of 

 permanent communication to steel. I fastened several steel 

 needles, in different directions, by fine silver wire to a wire of 

 the same metal, of about the thirtieth of an inch in thickness 

 and 11 inches long, some parallel, others transverse, above and 

 below in different directions ; and I placed them in the electrical 



