On the magnetic phenomena produced by electricity. In a letter from Sir Humphry Davy, Bart. F. R. S. to W. H. Wollaston, M. D. P. R. S

• Published in: Abstracts of the Papers Printed in the Philosophical Transactions of the Royal Society of London
• Format: Article in Journal/Newspaper
• Language: English
• Published: The Royal Society 1833
• Subjects: South Pole; Wollaston; South pole
• Online Access: http://dx.doi.org/10.1098/rspl.1815.0139; https://royalsocietypublishing.org/doi/pdf/10.1098/rspl.1815.0139

In repeating the experiments of Oersted, Sir Humphry found that with a voltaic battery of 100 pair of 4-inch plates, the south pole of a magnetic needle placed under the communicating wire of platinum, (the positive end of the apparatus being on the right) was strongly attracted by the wire, which was shown to be itself magnetic, by its power of attracting steel filings, and of communicating permanent magnetism to steel bars attached to it transversely, while similar bars placed parallel to the wire were only magnetic during its connection with the voltaic apparatus. The actual contact, however, of the steel wire with that of platinum, or other metal forming the voltaic conductor, is not necessary, for magnetism was communicated to a needle placed transversely to it, but at some distance. Sir Humphry Davy next details some experiments, showing that the magnetic power is proportionate to the quantity of electricity passing through a given space, without any relation to the transmitting metal; and that the finer the wires, the stronger their magnetism. He found an analogous effect produced by the discharge of a Leyden phial through a wire; and by passing the discharge of a Leyden battery of 17 square feet through a silver wire, with a steel bar transversely attached to it of two inches in length, the latter became powerfully and permanently magnetic. The same effect was produced at a distance of five inches through air, water, and even through thick plates of glass.