PROGRESS IN PHYSICS. $27 



ELK("TRI< TT'i AM) MAONETI8M. 



In no other department of physical science have such remarkable 

 developments occurred during the past century as in electricity and 

 magnetism, for in no other department have the practical applications 

 of scientific discovery been so numerous and so far-reaching in their 

 effect upon social conditions. In a brief review of the contributions 

 of the nineteenth century to the evolution of the telegraph, telephone, 

 trolley car, electric lighting, and other means of utilizing electricity, it 

 will be possible to consider only a very few of the fundamental discov- 

 eries upon which the enormous and rather complex superstructure of 

 to-day rests. Happily these are few in number, and their presenta- 

 tion is all the more important because of the fact that in the popular 

 mind they do not receive that signilicance to which the}" are entitled, 

 if, indeed, they are remembered at all. 



The first great step in advance of the electricity of Franklin and his 

 contemporaries (and his predecessors for two thousand years) was taken 

 very near the end of the eighteenth century, but it must be regarded 

 as the beginning of nineteenth century electricity. Two Italian 

 philosophers, Galvani and Volta, contributed to the invention of what 

 is know^n as the galvanic or voltaic battery, the output of which was 

 not at lirst distinctly recognized as the electricit}" of the older schools. 

 By this beautiful discovery electricity was for the first time enslaved 

 to man, who was now able to generate and control it at such times and in 

 such quantities as he desired. Although the voltaic batter}^ is now 

 nearly obsolete as a source of electricity, its invention must alwaj^s be 

 regarded as one of the three epoch-making events in the history of 

 the science during the past one hundred and twenty years. For 

 three-quarters of a century it was practically the only source of elec- 

 tricity, and during this time and by its use nearly all of the most 

 important discoveries were made. Even in the first decade of the 

 century many brilliant results were reached. Among the most not- 

 able were the researches of Sir Humphry Davy, who, by the use of 

 the most powerful battery then constructed, resolved the hitherto 

 unyielding alkalies, discovering sodium and potassivmi, and at the 

 same time exhibited in his lectures in the Royal Institution in London 

 the first electric arc light, the ancestor of the millions that now turn 

 night into day. 



The cost of generating electricity by means of a voltaic battery is 

 relatively very great, and this fact stood in the way of the early devel- 

 opment of its applications, although their feasibility was perfectly 

 well understood. Without any other important invention or discovery 

 than that of the voltaic battery much would have been possible, includ- 

 ing both electric lighting and the electric telegraph. Indeed, electric 

 telegraphy had long been a possibility, even before the time of Gal- 

 vani and Volta, but its actual construction and use were almost neces- 



