MODERN VIEWS ON MATTER. 235 



or sodiimi, and from this Dewar inferred that the atomic weight of 

 argon was twice its density relative to hydrogen. In the light of 

 to-day's researches on the constitution of atoms it is impossible to 

 overestimate the importance of this discovery. * 



In 1896 Becquerel, pui'suing the masterly work on phosphorescence 

 inaugurated by his illustrious father, showed that the salts of uranium 

 constantl}" emit emanations, which have the power of penetrating 

 opaque substances and of affecting a photographic plate in total dark- 

 ness, and of discharging an electrometer. In some respects these 

 emanations, known as "Becquerel rays," behave like rays of light, but 

 they also resemble Rontgen rays. Their real character has onh^ recentl}^ 

 been ascertained, and even now there is much that is obscure and pro- 

 visional in the explanation of their constitution and action. 



Following closel}" upon BecquereVs work came the l)rilliant researches 

 of M. and Mme. Curie on the radio-activity of bodies accompanying 

 uranium. 



Hitherto I have been recounting isolated instances of scientific specu- 

 lation with apparently little relation to one another. The existence 

 of matter in an ultra gaseous state; material particles smaller than 

 atoms; the existence of electrical atoms or electrons; the constitution 

 of Kontgen rays and their passage through opaque bodies: the emana- 

 tions from uranium; the dissociation of the elements — all these isolated 

 hypotheses are now focussed and welded into one harmonious theory 

 by the discover}^ of radium. 



Often do the spirits 



Of great events stride on before the events, 



And in to-day already walks to-morrow. 



No new discovery is ever made without its influence ramifying in 

 all directions and explaining much that before had been m3^stifying. 

 Certainly no discovery of modern times has had such wide-embracing 

 consequences and thrown such a flood of light on broad regions of 

 hitherto inexplicable phenomena as this discovery of M, and Mme, 

 Curie and M. Bemont, who patiently and laboriouslv plodded along a 

 road bristling with difficulties almost insuperable to others who, like 

 myself, have toiled in similar labyrinths of research. The crowning 

 point of these labors is radium. 



Let me briefly recount some of the properties of radium and show 

 how it reduces speculations and dreams, apparently impossible of 

 proof, to a conci'ete form. 



Radium is a metal of the calcium, strontium, and barium group. 

 Its atomic weight, according to C. Runge and J. Precht, is probably 

 about 2.58. In this case it occupies the third place below barium in 

 my lenmiscate spiral scheme of the elements," two unoccupied gaps 

 intervening. 



"Proc. Roy. So.-., Vol. LXITT, p. 409,. 



