SKETCH OF HE IN RICH HERTZ. 405 



Annalen between the years 1887 and 1890, and in which Hertz 

 showed with ample experimental proof and illustration that elec- 

 tromagnetic actions are propagated with finite velocity through 

 space. These twelve epoch-making papers were afterward repub- 

 lished with an introductory chapter of singular interest and 

 value, and a reprint of some observations on electric discharges 

 made by von Bezold in 1870 under the title Untersuchungen 

 iiber die Ausbreitung der elektrischen Kraft. A translation of 

 this book, entitled Electric Waves, by D. E. Jones, B. Sc., with 

 illustrations and a preface by Lord Kelvin, has just been pub- 

 lished in England. 



In 1889, when laying before the Congress of German Natural- 

 ists at Heidelberg the results of his labors, Prof. Hertz, with the 

 modesty characteristic of the true investigator, the utterly un- 

 assuming disciple of science, gave ready and graceful acknowl- 

 edgment to the efforts made by his predecessors or co-operators 

 in the work, some of whom had all but attained the results which 

 they aimed at and which he achieved. It is pleasant to recollect 

 that when he had gained the end toward which they also had 

 been striving, the English professors, Oliver Lodge and Fitzger- 

 ald, were foremost in announcing his success, and in preparing 

 the English-speaking world to appreciate the importance of his 

 discoveries. A natural bent of mind toward the questions at 

 issue had awakened the young professor's creative powers ; his 

 complete concentration upon the vital point and his intuitive per- 

 ceptions led him to definite results and complete success where 

 so many able minds had searched in vain. In the April number 

 of this magazine Herbert Spencer, speaking of the late Prof. 

 Tyndall, gives a number of traits that apply with singular force 

 and exactness to Prof. Hertz. Of these the first is " the scientific 

 use of the imagination." It may well be said that with this con- 

 structive imagination, as Mr. Spencer terms it, originated Prof. 

 Hertz's rare success as a discoverer and as an instructor. 



To find out the most effective arrangement of electrical con- 

 ductors and to secure the conditions which would produce the 

 strongest vibrations at regular intervals and in quickest succes- 

 sion, we might say the adjustment of his instruments was the 

 first part of his work. Having brought about electric undula- 

 tions up to several hundred millions in one second, Hertz proved 

 through experiment that the waves of electricity are transversal 

 like those of light, and that the transmission requires a certain 

 lapse of time. He ascertained exactly the velocity of electricity ; 

 it is found by multiplying the length of wave, which he measured, 

 by the duration of the vibration, which can be calculated, and he 

 found this velocity to be, as Maxwell had supposed, equal to that 

 of light, and, moreover, equal to the velocity of electric waves in 



