Page:Popular Science Monthly Volume 45.djvu/421

 Annalen between the years 1887 and 1890, and in which Hertz showed with ample experimental proof and illustration that electromagnetic actions are propagated with finite velocity through space. These twelve epoch-making papers were afterward republished—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 über 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 published in England.

In 1889, when laying before the Congress of German Naturalists at Heidelberg the results of his labors, Prof. Hertz, with the modesty characteristic of the true investigator, the utterly unassuming disciple of science, gave ready and graceful acknowledgment 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 Fitzgerald, 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 perceptions 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 constructive 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 conductors and to secure the conditions which would produce the strongest vibrations at regular intervals and in quickest succession, we might say the adjustment of his instruments was the first part of his work. Having brought about electric undulations 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