234 MODERN VIEWS ON MATTER. 



the positive pole the exit for electrons. Falling on a pliosphore.seent 

 body, yttria, for instance — a collection of Hertz molecular resonators — 

 the electrons excite vibrations of, say, 550 billion times a second, pro- 

 ducing ether waves of the approximate length of 5.75 ten-millionths 

 of a millimeter, and occasioning in the eye the sensation of citron- 

 colored light. If, however, the electrons dash against a heavy metal, 

 they produce ether waves of a far higher frecpienc}^ than light and 

 are not continuous vibrations, l)ut, according to Sir George Stokes, 

 simple shocks or solitary impulses, more like discordant shouts as 

 compared with nuisical notes. 



During that address an experiment was shown which went far to 

 prove the dissociation of silver into electrons and positive atoms. "■ A 

 silver pole was used, and near it in front was a sheet of mica with a 

 hole in its center. The vacuum was very high, and when the poles 

 were connected with the coil, the silver being negative, electrons shot 

 from it in all directions, and passing through the liole in the mica 

 screen formed a bright phosphorescent patch on the opposite side of 

 the bulb. The action of the coil was continued for some hours to 

 volatilize a certain portion of the silver. Silver was seen to be 

 deposited on the mica screen only in the immediate neighborhood of 

 the pole; the far end of the bulb, which had been glowing for hours 

 from the impact of electrons, being free from silver deposit. Here, 

 then, are two sinuiltaneous actions. Electrons or radiant matter shot 

 from the negative pole caused the glass against which the}' struck to 

 glow with phosphorescent light. Simultaneously, the heavy positive 

 ions of silver, freed from negative electrons and under the influence 

 of the electrical stress, likewise flew ofl: and were deposited in the 

 metallic state near the pole. The ions of metal thus deposited in all 

 cases showed positive elect ritication.* 



In the 3"ears 1893-1895 a sudden impulse was given to electric vacuum 

 work b}" the publication in Germany of the remarkable results obtained 

 by Lenard and Rontgen, who showed that the phenomena inside the 

 vacumn tube were surpassed in interest by what took place outside. 

 It is not too much to say that from this date wdiat had been a scientilic 

 conjecture became a sober reality. 



One important advance in theoretic knowledge has heen ol)tained by 

 Dewar, the successor of Faraday in the classic laboratories of the 

 Royal Institution. Soon after Rontgen's discovery Dewar found that 

 the relative opacit}' to the Rontgen rays was in proportion to the 

 atomic weights of bodies, and he was the first to apply this principle 

 to settling a debated point in connection with argon. Argon is rela- 

 tively more opaque to the Rontgen raj^s than either oxygen, nitrogen, 



"In describing the experiment, one of fundamental importance, modern terms are 

 empioyed. 



''Proc. Roy. 8oc.,A'ol. LXIX, p. 421. 



