244 THE DISCOVERY OF NEW ELEMENTS. 



On our planet it appears, on tLe contrary, to be very rare, aud may 

 be ranked among the rarest of elements. Still, it bad been nearly dis- 

 covered several times; in 1882 Palraieri' actually observed the line of 

 helium in the ' ourse of his researches upon the lava of Vesuvius, but 

 he pursued the matter no further; it was the same with Hillebrand,^ 

 who, in 1891, obtained, in the spectrum of the gas obtained from uran- 

 ite, lines which were probably those of helium. 



Since then helium has been found in a great number of ores, gener- 

 ally associated with uranium, yttrium, and thorium; in mineral waters, 

 and in very small quantities in atmospheric air. Helium is the lightest 

 of all the gases except hydrogen; Stoney" deduces from this fact an 

 explanation of the existence of these two elements in but very small 

 quantities in a free state upon the face of the earth, while they are dis- 

 tributed in enormous masses throughout the universe. The compara- 

 tively small force of the earth's gravitation does not form a sufficient 

 counterpoise to the velocity of their molecules, which therefore escape 

 from the terrestrial atmosphere unless restrained by chemical combi- 

 nation. They then proceed to reunite around great centers of attrac- 

 tion, such as the fixed stars, in whose atmospheres these elements exist 

 in large quantities. 



The study of the spectrum of helium is of the greatest importance, 

 because it gives us information concerning the nature of distant celes- 

 tial bodies. It also, as is shown by the researches of Eunge and 

 Pascheu,* suggests doubts as to the elementary character of the new 

 body. However that may be, if we admit that helium is composed of 

 two gases (Mr. Lockyer has already proposed the name of asterium for 

 the second), one of these gases ought to have a boiling point nearly as 

 low as the absolute zero, and in any case below 264° C, for the master 

 in liquefaction of gases, Mons. K. Olszfewsky,-^ has not, so far, succeeded 

 in producing a change of state in helium; so that he proposes to use 

 this gas for filling gas thermometers to be used for measuring very low 

 temperatures. 



Up to the present time helium has shown itself as refractory as argon 

 to chemical combination, and there is such an uncertainty as to the 

 position to which it ought to be assigned that I will not discuss the 

 hypotheses that have been put forward with regard to it. 



It is not impossible that the discovery of these two new elements, 

 argon and helmm, may give rise to a remodeling if not a transforma- 

 tion of the periodic system; a remodeling which will cause the disap- 

 pearance of some uncertainties, or even contradictions, which now exist. 

 Thus, for example, the atomic weight of tellurium, recently determined 



' Palmieri, Rend. Ace. di Napoli, 20. 

 "Hillebrand, Sill. Am. Journ., 38 et 40, 



''J. Stouey, Chem. News, 71. (See also Martin Mugdon: Argon et li61ium, denx 

 <5I(?ments gazeux nouveux; Stuttgart, 1896.) 

 •^Sitznugsber. d. Akad. d. Wisseusch. Berlin, 1895. 

 * K. Olszewski, Anzeiger der Akad. d. Wissenschaft in Krakau (Cracow), June 1896. 



