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POPULAR SCIENCE MONTHLY. 



rora of the northern sky. After 

 Geissler came Prof. Crookes, and 

 other physicists, who varied their 

 queries in many ingenious ways. 

 They replaced air with other gases, 

 they brought exhaustion to a close 

 approach to perfection, they changed 

 the forms of tubes, the material of 

 the electrode or current carriers, they 

 increased and diminished the inten- 

 sity of the electric discharge. Most 

 significant of all, they placed fluores- 

 cent substances in the tubes, and 

 brought them to vivid radiance. 



Now came the epoch-making ex- 

 periments of Hei'tz, which demon- 

 strated Maxwell's theory that light 

 is an electro-magnetic phenomenon ; 

 that light and electricity move 

 through the same medium and at the 

 same rate. Incidentally, Hertz pro- 

 duced electric waves of new ampli- 

 tudes, which readily took their way 

 through wooden doors and stone 

 walls. In his vacuum tubes, by their 

 capacity to excite fluorescence, he 

 found that cathode rays penetrated 

 thin sheets of gold, copper, aluminum, 

 and other metals, while, strange to 

 say, they were arrested by the glass 

 of the tube itself. Hertz had abun- 

 dant reason to think that, given a 

 concordant ray, any substance what- 

 ever offers it a free and open path. 

 His researches, cut short by his la- 

 mented death, were continued by his 

 assistant. Prof. Paul Lenard, who in- 

 serted in the wall of a vacuum tube a 

 tiny window of aluminum. Through 

 this window he succeeded in bring- 

 ing a cathode ray into the outer air 

 for a distance of some three inches. 

 This ray had all the characteristic 

 tokens of light; it was capable of re- 

 flection, refraction, and polarization ; 

 it excited fluorescence; it had pho- 

 tographic power. 



At this point Prof. Rontgen 

 comes upon the scene, repeats the ex- 

 periments of Prof. Leuard, and, by 

 such a stroke of good fortune as be- 



falls only the man who earns it, he 

 incloses an excited vacuum tube in 

 blackened cardboard treated with 

 barium platinocyanide. To his de- 

 light he discovers that the cathode 

 beam is accompanied by a radiance 

 hitherto unknown, which, although 

 of fluorescent and photographic qual- 

 ity, can scarcely be any form of 

 light. It is not susceptible of refrac- 

 tion or polarization ; indeed, it seems 

 as if it might be a stream of infini- 

 tesimal particles, since its path is less 

 impeded in a light metal, aluminum, 

 than in a dense one, such as plati- 

 num. 



Thus culminate the experiments 

 of two companies of students — those 

 devoted to inquiry regarding phos- 

 phorescence, and fluorescence and 

 those who investigated the conduct 

 of attenuated gases excited by elec- 

 tricity in vacua. It was many a 

 weary day before the explorers came 

 within sight of each other, before 

 they could join hands on the com- 

 mon ground where all research meets 

 at last in Nature's fundamental unity. 

 At every step but the flnal one, the 

 observer intent solely on "results" 

 might well have asked, "What's 

 the good?" And yet results of pro- 

 found import to science and art lay 

 bound up in quests not to be sus- 

 pected of the most averted wooing of 

 utility. The eye and its wonderful 

 supplement, the photographic plate, 

 now find disclosed what had been 

 deemed forever hidden from sight 

 and light. The physician and the 

 surgeon rejoice in new powers of re- 

 lieving pain and saving life. The 

 physicist enlarges his conceptions of 

 both matter and energy ; he explores 

 by a new path the mazes of molecular 

 structure and motion. Once more 

 it is emphasized that Truth is won 

 only by her disinterested lovers, who, 

 nevertheless, ever find her dowered 

 with wealth greater than fortune- 

 hunter ever dared pursue. 



