Maech 11, 1898.] 



SCIENCE. 



327 



eters as well as the fixing of boundary 

 lines between great nations is determined 

 by methods due to slow accumulation of 

 facts, slower development in analysis and 

 calculation and even slower improvement 

 in instruments. 



Galvani's observations that frogs' legs 

 twitch when near a friction machine in oper- 

 ation led him to test the effect of atmospheric 

 electricity upon them. The instant action 

 brought about the discovery that it was due 

 not to atmospheric influence, but to a cur- 

 rent produced by contact of a copper hook 

 with an iron rail. Volta pursued the in- 

 vestigation and constructed the pile which 

 bears his name. With this, modified, Davy, 

 in 1807, decomposed potash and soda, 

 thereby isolating potassium and sodium. 

 This experiment, repeated successfully by 

 other chemists, was the precursor of many 

 independent investigations, which directed 

 to many lines of research, each increasing 

 in interest as it was followed. 



Volta's crown of cups expanded into the 

 clumsy trough batteries which were dis- 

 placed finally in 1836 by Daniel's constant 

 battery, using two fluids, one of which was 

 cupric sulphate. De la Rue observed that, 

 as the sulphate was reduced, the copper was 

 deposited on the surface of the outer vessel 

 and copied accurately all markings on that 

 surface. Within two or three years Jacobi 

 and Spencer made the practical application 

 of this observation by reproducing engrav- 

 ings and medals. Thus was born the sci- 

 ence of electro-metallurgy. A.t first mere 

 curiosities were made, then electro-plating 

 in a wider way, the electrotype, the utiliza- 

 tion of copper to protect more easily de- 

 structible 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 applications in the reduction 

 of metals and to the saving of materials 

 which otherwise would go to waste. 



Oersted, in 1819-1820, 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 the same lines, found that 

 soft iron enclosed in a coil, through which 

 a current passes, becomes magnetic, but 

 loses the power when the current ceases. 

 This opened the way for our own Henry's 

 all-important discovery of the reciprocating 

 electro-magnets and the vibrating arma- 

 ture — 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, dream- 

 ing night and day of the telegraph, was 

 experimenting with Moll's electro- magnet 

 and finding only discouragement. His col- 

 league, Professor Gale, advised him to dis- 

 card 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 

 instrument bearing Morse's name was con- 

 structed. Henry's scientific discoveries 

 Avere transmuted by the inventor's in- 

 genuity into substantial glory for Morse 

 and proved a source of inconceivable ad- 

 vantage to the whole civilized world. Stein- 

 hal's discovery that the earth can be util- 

 ized for the return current completed the 

 series of fundamental discoveries, and since 

 that time everything has been elaboration . 



Oersted's discovery respecting the influ- 

 ence of an electric current, closely followed 

 by that of Arago in the same direction, 

 opened the way for Faraday's complete dis- 

 covery of induction, which underlies the 

 construction of the dynamo. This ascer- 

 tained, the province of the inventor was 

 well defined — to conjure some mechanical 



