356 ELECTKICITY DURING THE NINETEENTH CENTURY. 



forward, a])<)iit the middle of the contiirv, the idea that lioht waves 

 were really electrieal waves. Light would, then, l)ccouie one form of 

 the manifesl:ation of electrical force; and the same would be true of 

 radiant heat. I'his theory, however, lacked experimental conlirma- 

 tion until the researches of the late Dr. Hertz, too earl 3' lost to science. 

 We see references to what are called "Hertzian waves." These are 

 waves identical in nature with lii»ht waves, but of much lower pitch or 

 period. Red light consists of about four hundred millions of millions 

 of electrical waves in the ether per second; blue or violet light al)out 

 double that numlier. Hertz showed in his experiments that electric 

 sparks between polished l)alls. under proper conditions, were attended 

 b}' ether waves of the same nature as those of light, but having a pitch 

 represented by some millions of vi))rations per second. These waves, 

 however, could })e reflected, could l)e refracted, could be polarized, and 

 be dealt with as if they w^ere light waves. Ordinary alternating-cur- 

 rent waves are, in fact, closely akin to these waves, onl}' their speed 

 is from 25 to 200 or 800 per second. Their ""frequency" is low. 



When we speak of ''high-frequencv waves" w^e usually mean waves 

 of great rapidity as compared with ordinary alternating-current waves. 

 When a Leyden jar is discharged through a short wir^ . or coil of wnre, 

 there is momentarily generated a set of high-frequency waves. This 

 was shown l>y Henry in the early half of the century. The brilliant 

 effects which have been produced within recent years l)y Mr. Tesla, as 

 well as by the present writer, in the use of high-fre(]uency discharges 

 or waves are Avell known. Electric sparks man}^ feet in length are 

 easily generated. Astonishing luminous effects accompany' high-fre- 

 quency experiments. Conductoi's glow in the dark with a bluish 

 luminosity. Vacuum tubes are caused to give out light many feet 

 away from the apparatus in which the high-frequency discharges are 

 generated. 



Most curious perhaps of all. to the lay mind, is the possibilit}' of 

 passing through the body current enough at high frequency to light 

 lamps in circuit with the body, without producing any harmful efl'ects, 

 and, in fact, without producing any sensation whatever. Spark dis- 

 charges from the apparatus which would seem to have the power to 

 kill instantly are received harmlessly. Indeed, when currents ha\'e a 

 frequency' more than a certain amount — say 10,000 per second — the 

 physiological efl'ects seem to be in abeyance, as if the rapid reversals 

 of the current could not leave any permanent efl'ect. 



Certain forms of moderately high frequenc}" currents give promise 

 of actually producing insensibility to pain without interfering with 

 consciousness, and it is possible that the future may see surgical opera- 

 tions performed with the protection of the subject from painful sensa- 

 tions by the passage of these currents. Up to the present, however, 

 there has been no use actuall}^ made in the practice of high-frequency 



