ADDBESS. 13 



remind us more of those of the metalloids and of chemical compounds 

 than of the metals. Hence it has been argued that in the white, presum- 

 ably the hottest, stars a celestial dissociation of our terrestrial elements 

 may have taken place, whilst in the cooler stars, probably the red, com- 

 bination even may occur. But even in the white stars we have no direct 

 evidence that a decomposition of any terrestrial atom has taken place ; 

 indeed we learn that the hydrogen atom, as we know it here, can endure 

 unscathed the inconceivably fierce temperature of stars presumably many 

 times more fervent than our sun, as Sirius and Vega. 



Taking all these matters into consideration, we need not be surprised 

 if the earthbound chemist should, in the absence of celestial evidence 

 which is incontestable, continue, for the present at least, and until fresh 

 evidence is forthcoming, to regard the elements as the unalterable founda- 

 tion stones upon which his science is based. 



Pursuing another line of inquiry on this subject, Crookes has added a 

 remarkable contribution to the question of the possibility of decomposing 

 the elements. With his well-known experimental prowess, he has 

 discovered a new and beautiful series of phenomena, and has shown that 

 the phosphorescent lights emitted by certain chemical compounds, espe- 

 cially the rare earths, under an electric discharge in a high vacuum ex- 

 hibit peculiar and characteristic lines. For the purpose of obtaining his 

 material Crookes started from a substance believed by chemists to be 

 homogeneous, such, for example, as the rare earth yttria, and succeeded 

 by a long series of fi-actional precipitations in obtaining products which 

 yield difEerent phosphorescent spectra, although when tested by the 

 ordinary methods of what we may term high temperature spectroscopy, 

 they appear to be the one substance employed at the starting point. The 

 other touchstone by which the identity, or otherwise, of these various pro- 

 ducts might be ascertained, viz., the determination of their atomic weights, 

 has not, as yet, engaged Crookes' attention. In explanation of these sin- 

 gular phenomena, the discoverer suggests two possibilities. First, that 

 the bodies yielding the different phosphorescent spectra are different ele- 

 mentary constituents of the substance which we call yttria. Or, if this 

 be objected to because they all yield the same spark spectrum, he adopts 

 the very reasonable view that the Daltonian atom is probably, as we have 

 seen, a system of chemical complexity ; and adds to this the idea that 

 these complex atoms are not all of exactly the same constitution and 

 weight, the differences, however, being so slight that their detection has 

 hitherto eluded our most delicate tests, with the exception of this one of 

 phosphorescence in a vacuum. To these two explanations, Marignac, in 

 a discussion of Crookes' results, adds a third. It having been shown 

 by Crookes himself that the presence of the minutest traces of foreign 

 bodies produces remarkable alterations in the phosphorescent spectra, 

 Marignac suggests that in the course of the thousands of separations 

 which must be made before these differences become manifest, traces of 

 foreign bodies may have been accidentally introduced, or, being present 



