108 PROCEEDINGS OF THE EEGENTS. 



pass in opposite directions, they repel each other. On this fact 

 Ampere founded his ingenious theory of magnetism and electro-mag- 

 netism. According to this thejry, all magnetic phenomena result 

 from the attraction or repulsion of electric currents, supposed to exist 

 in the iron at right angles to the length of the bar ; and that all the 

 phenomena of magnetism and electro magnetism are thus referred to 

 one principle, namely, the action of electrical currents on each other. 



Ampere deduced from this theory many interesting results, which 

 were afterwards verified by experiment. He also proposed to the 

 French Academy a plan for the application of electro-magnetism to 

 the transmission of intelligence to a distance ; this consisted in de- 

 flecting a number of needles at the place of receiving intelligence, by 

 galvanic currents transmitted through long wires. This transmission 

 was to be effected by completing a galvanic circuit. When completed, 

 the needle was deflected. When interrupted, it returned to its ordi- 

 nary position, under the influence of the attraction of the earth. This 

 project of Ampere was never reduced to practice. All these discoveries 

 and results were prior to 1823. 



The next investigations relating to the magnetic telegraph were 

 published in 1825 ; they were by Mr. Barlow, of the Royal Military 

 Academy of Woolwich, England. He found that there was great 

 diminution in the power of the galvanic current to produce effects 

 with an increase of distance; a diminution so great in a distance of 

 two hundred feet was observed, as to convince him of the impractica- 

 bility of the scheme of the electro-magnetic telegraph. His experi- 

 ments led him to conclude that the power was inversely as the 

 square root of the length of the wire. The publication of these 

 results put at rest, for a time, all attempts to construct an electro- 

 magnetic telegraph. 



The next investigations, in the order of time, bearing on the tele- 

 graph, were made by Mr. Sturgeon, of England. He bent a piece of 

 iron wire into the form of a horse-shoe, and put loosely around it a 

 coil of copper wire, with wide intervals between the turns or spires 

 to prevent them touching each other, and through this coil he trans- 

 mitted a current of galvanism. The iron, under the influence of this 

 current, became magnetic, and thus was produced the first electro- 

 magnetic magnet, sometimes called simply the electro-magnet. An 

 account of this experiment was first published in November, 1825, in 

 the Transactions of the Society for the Encouragement of the Arts in 

 England ; and was made known in this country through the Annals 

 of Philosophy for November, 1826. 



Nothing further was done pertaining to the telegraph until my 

 own researches in electro-magnetism, which were commenced in 1828, 

 and continued in 1829, 1830, and subsequently ; Barlow's results, as 

 I before observed, had prevented all attempts to construct a magnetic 

 telegraph on the plan of Ampere, and our own knowledge of the de- 

 velopment' of magnetism in soft iron, as left by Sturgeon, was not 

 such as to be applicable to telegraphic purposes. The electro-magnet 

 of Sturgeon could not be made to act by a current through a long 

 wire, as will be apparent hereafter in this deposition. 



After repeating the experiments of Oersted, Ampere, and others, 

 and publishing an account in IBzS of various modifications of electro- 



