UNSUSPECTED RADIATIONS. 383 



chemic-ally from their nearest of kin—bismuth, harimu. and titanium— 

 their existence nuist still remain (loul>tf ul. But the spectrum of radium 

 has ah-eady been examined by Demaryay ' and hy Dr. C. Runge under 

 a vei-y o-reat dispersion; and the great German specialist in spectra 

 found that radium really gives three distinct lines which belong to no 

 other element.' 



The radio-activity of these new metals is realh^ striking. For polo- 

 nium it is four hundred times, and for radium nine hundred times, 

 greater than for metallic uranium. Radium illuminates a phosphores- 

 cent screen indefinitely, and its salts glow without requiring for that 

 a preliminary excitement l)y light, F. Giesel, who, almost siuuiltane- 

 ously with the Curies, obtained a substance that must be radium, saw 

 the chloride and bromide of this substance, although chemically iden- 

 ticid \\ith the same compounds of barium, sending such strong rays 

 that the shadow of a hand appeared on a phosphorescent screen at a 

 distance of 18 inches and the raj^s pierced metallic plates four-tenths 

 and eight-tenths of an inch thick. Salts containing an admixture of 

 the new su})stance were so phosphorescent that one could read in their 

 })]w light. As to polonium, although a pure specimen of it Avas as 

 phosphorescent as pure radium, its invisible rays had, however, a much 

 smaller penetrating power; even cardboard would weaken them.^ 



The inain interest of these researches is, however, in the problematic 

 nature of the Becquerel radiations. Are the}' not a general property 

 of matter, only varying in degree in different substances? This is the 

 (juestion which is now asked. Some thirty or thirty-five years ago it 

 was mentioned in some scientific reviews that various objects — a printed 

 page or a piece of metal — left their impressions on a white sheet of 

 paper if the two had been kept for some time at a small distance from 

 each other. These experiments, which seemed to prove the existence 

 of some sort of radiation of matter, interested me then a great deal 

 becaus<^ they gave support to a very ingenious theory, developed by 

 Seguin, concerning the existence of infinitely small particles of matter 

 dashing in all directions through space and penetrating matter. With 

 th(^ aid of these particles Seguin endeavored to explain gravitation, 

 heat, light, and electricity. Now W. J. Russell, continuing the experi- 

 ments of Colson on zinc and other metals,' laid before the Royal Society 

 in the autumn of 1807, and later on with more details, in a Rakerian 

 lecture, experiments having very much the same purport. He found 

 that certain metals (magnesium, cadmium, zinc, nickel, etc.) and ceilam 



1 llevue Generale .len Sciences, the 'AOth of September, 1900, -rives :i plioto-rapli of 

 tliis Hpectruni. 



' Annalen der Pl.ysik, 1900, 4tl. series, Vol. II, p. 742. I'ol..nium -uve .... <'l.a.-ac- 



te.'istic li..'\s. 



n^hysikalische Zeitschrift, Vol. I, 1900, p. 10. 

 *Conii)tes Rendns, 1S9H, Vol. CXXIll, p. 49. 



