180 STEVENSON. 



la Rue observed that as the sulphate was reduced, the copper 

 was deposited on the surface of the outer vessel and copied ac- 

 curately all markings on that surface. Within two or three 

 years Jacobi and Spencer made the practical application of this 

 observation by reproducing engravings and medals. Thus was 

 born the science of electro-metallurgy. At first mere curiosities 

 were made, then electro-plating in a wider way, the electrotype, 

 the utilization of copper to protect more easily destructible 

 metals, the preparation of articles for ornament and utility by 

 covering baser metals with copper or silver or gold ; while now 

 the development of electro-generators has led to wide applica- 

 tions in the reduction of metals and to the saving of materials 

 which otherwise would go to waste. 



Oersted in 1819-20, puzzling over the possible relations of 

 voltaic electricity to magnetism, noticed that a conductor carry- 

 ing an electrical current becomes itself a magnet and deflects 

 the needle. Sturgeon, working along these lines, found that 

 soft iron enclosed in a coil, through which a current passes be- 

 comes magnetic, but loses the power when the current ceases. 

 This opened the way for our own Henry's all-important dis- 

 covery of the reciprocating electro-magnets and the vibrating 

 armature — the essential parts of the magnetic telegraph. Henry 

 actually constructed a telegraph in 1832, winding the wires 

 around his class-room in Albany and using a bell to record the 

 making and breaking signals. Here, as he fully recognized, 

 was everything but a simple device for receiving signals. 



Several years later, Professor Morse, dreaming night and day 

 of the telegraph, was experimenting with Moll's electro-magnet 

 and finding only discouragement. His colleague. Professor Gale, 

 advised him to discard the even then antiquated apparatus and 

 to utilize the results given in Henry's discussion. At once the 

 condition was changed and soon the ingenious recording instru- 

 ment bearing Morse's name was constructed. Henry's scien- 

 tific discoveries were transmuted by the inventor's ingenuity into 

 substantial glory for Morse, and proved a source of inconceiv- 

 able advantage to the whole civilized world. Steinhal's dis- 

 covery that the earth can be utilized for the return current com- 



