160 The Evolution of Electric and Magnetic Physics. 



galvanic current, however, was much, more amenable to con- 

 trol in this respect, and telegraphy, with the aid of the mag- 

 netic needle, in 1833 became a successful experiment. Morse 

 succeeded in making his electro-magnetic system practicable 

 in 1837. 



The stimulus that electricity gave to the study of magnet- 

 ism, immediately following Oersted's discovery, reacted by 

 reflection upon electrical progress also, and an electro-mag- 

 netic era was entered that has gone on with ever-increasing 

 impetus since that time. The telegraph, fairly in operation 

 by 1840, spread from city to city, and in 1850 first crossed 

 the sea. Electroplating as an art sprang into existence 

 about the same time, the first practical experiment being 

 performed about the year 1832. The debt that commerce 

 and civilization owed to science for these arts has since 

 been richly repaid by the aid that commerce has given in 

 the direction of pure science ; for, in order to foster and in- 

 vigorate these arts, commerce has defrayed the expense of 

 many scientific investigations intermediately necessary, and 

 this community of object is continually strengthening and 

 enriching each at the present time. 



From 1830 to 1859 Faraday made his masterly re- 

 searches. He discovered among other things the electro- 

 chemical law that now bears his name, and the influence 

 of magnetism upon light ; but his crowning discovery was 

 that of electro-magnetic induction, which has paved the 

 way for the dynamo-electric machinery of the present 

 time. 



The scientific development of the subject was also active 

 during this period. In 1840 Ohm published his well- 

 known law that reduced the elements of the galvanic cir- 

 cuit to simplicity. There was still, however, a difficulty in 

 measuring electricity quantitatively,- owing to the absence 

 of any common system of units. Each observer measured 

 and recorded his results in arbitrary units of his own selec- 

 tion, and great confusion existed when attempts were made 

 to compare the results so obtained. Nor was the deficiency 

 confined to science only, for practical telegraphy sorely 

 labored under the same disadvantages. To meet the grow- 

 ing need for a universal system of measurements, the 

 British Association for the Advancement of Science ap- 

 pointed a committee to consider the matter in 1861, and 

 this committee succeeded in establishing within four years 

 the celebrated centimetre, gramme, and second system that 



