330 PROGRESS IN PHYSICS. 



thus the dynamo caiiie into existence. In this brilliant investigation 

 he was almost anticipated by Henry, who was working at Albany along 

 the same lines, but under much less favorable conditions. Indeed, in 

 several of the most important points the American actually did antici- 

 pate the Englishman. 



Nearly half a century elapsed before this most, important discovery 

 was sufficiently developed to become commercially valuable, and it is 

 impossible in this place to trace the steps by which during the last 

 quarter of a century the production and utilization of electricitj^ as 

 existing to-day was accomplished, as a result of which the century 

 closes, as one might say, in a blaze of light; and it is unnecessary, 

 because most people have witnessed the spread of the tire which Faraday 

 and Henry kindled. 



Fai'aday's discovery of induction furnished th(5 basis of that mar- 

 velous improvement upon the telegraph by which actual speech is 

 transmitted over hundreds and even thousands of miles. In connec- 

 tion with the invention of the telephone the names of Philip lieiss, 

 (Jraham Bell, Elisha Gray, and Dolbear will always be mentioned, ea(;h 

 of whom, doubtless independently, hit upon a way of accomplishitig 

 the result with more or less success. To Bell, however, belongs the 

 honor of having first practically solved the problem, and of devising a 

 sj'stem which, with numerous modifications and improvements, has 

 come into extensive use in all parts of the world. No other application 

 of electricity has come into such universal use, and none has contributed 

 more to the comfort of life. 



While it is doubtless true that since Faraday's time no discovery 

 comparable with his in real importance has been made, the past twenty- 

 five years have not lacked in results of scientific research, some of 

 which ma}', in the not distant future, eclipse even that in the value of 

 their practical applications. Among these must be ranked Clerk Max- 

 well's theory of electric waves and its beautiful verification in 1888 by 

 the young German physicist, Hertz. This 'brilliant student of elec- 

 tricity succeeded in actually producing, detecting, and controlling 

 these waves, and out of this discovery has come the ' ' wireless telegra- 

 phy" which has been so rapidly developed within the last few years. 

 Many other discoveries in electricit}^ of great scientific interest and 

 practical promise have been recorded in the closing j^ears of the cen- 

 tury, but the necessary limits of this article forbid their consideration. 



No account of the progress of physical science during the nineteenth 

 century would be even approximately complete without mention of 

 other investigations of profound significance. For instance, the stud}' 

 of the phenomena of sound has yielded results of great scientific and 

 some practical value. The application of the theory of interference 

 by Thomas Young; the publication of Helmholtz's great work, the 

 Tonempfinduugen, in which his theory of harmony was first f uUy pre- 



