ADDRESS OF PROF. A. GRAY. 59 



For the telegraph, and for electro-magnetic machines, what was 

 now wanted was not discovery, l>ut invention, nut the ascertainment 

 of principles, but the devising <>f methods. These, tin; proper 

 subjects of patent, have been supplied in various ways and, as to 

 the telegraph, with wonderful efficiency; — in Europe, by the trans- 

 mission "f si^ns through the motion of a magnetic needle; in 

 America, by the production of sounds or records by the electro- 

 magnet. MORSE was among the first to undertake the enterprise, 

 and, when directed to the right way through Professor Gale's 

 acquaintance with IIkxry's published researches, he carried the 



1820. Aiot.uk discovered that two win's through which currents are passing in the 

 same direction attract, and in opposite directions repel, each other; am! thence 

 he inferred thai magnetism consists in the attraction of electrical currents 

 revoU ing at righl angles to the line joining the two poles of the magnet, and 

 is produced in a bar of steel or iron by induction from a series •'! electrical 

 currents revolving in the same direction at right angles to tin' axis of I lie bar. 



1820. Schweigger in the same year produced the galvanometer. 



1825. Sturgeon ma.li' the electro-magnet by bending the bar, or rather a piece 

 of iron wire, into the form of a horse-shoe, covering il with varnish to insulate 

 it. ami surrounding it with a helix of wire the turns of which were at a dis- 

 tance. 



1829- 1830. Henry, in a rdance witli tin- theory of Ampere, produced the intensity 



or spool-wound magnet, insulating the wire instead of the rod or liar, ami 

 covering the whole surface of the iron with a series of coils in close contact. 



lie extended the principle to the full by winding an ssi\e strata of insulated 



wire over each ol her, thus producing a compound helix formed of a hue' wire 

 of many c.ils. ,\| the same time he developed the relation of tin- intensity 

 magnet to the intensity battery, ami their relations i.. the magnet of quantity. 

 He thus made the electro-magnet capable of transmitting power t.. a long 

 distance, demonstrated the principle and perfected the magnet applicable to 



the purpose, was the first actually to magnetize a piei f iron at a distance, 



ami lo demonstrate ami declare tin- applicability ol ih" electro-magnet to 

 telegraphy at a distance. i'shm the terminal short-circuit magnet of quantity, 

 and the armature as the signaling device, he was the first to make by if 

 acoustic signals, sounding a hell at a distance by means .,i the eleetro-magnet. 



is:;. Wi beb discovered thai tin- conducting-wires of an electric telegraph could 

 he hit without insulati ixcept at the points of support. 



1833. Gauss ingeniously arranged the application ..i a dual sign in such manner 

 as to produce a true alphabet lor telegraphy. 



1836. Daniell invented ami brought Into use a constant galvanic battery. 



1s:;t. Steinheil discovered that the earth may form the returning half of the 

 circuit, so that a singh nducting wire suffices lor telegraphy. 



1837. Morse adopted, through the agency of Dr. Leonard Gale, the principle of 

 the Henry electro-magnet, ami made of the armature a recording instrument. 



ls:;s. morse devised his "dot and dash" alphabet, a great improvement upon the 



Gauss and sri iniif.il alphabets. 

 1844. Morse suggested ami brought into use the system of relay-magnets, 



relay-circuits, to reinforce the current. 



