January 29, 1915] 



SCIENCE 



161 



vances have been made — while much light has 

 been thrown on the ultimate structure of 

 matter. Tears ago, during the persistent and 

 systematic fractionation of yttrium, I ex- 

 plained that I had succeeded in separating 

 the atoms of the so-called elements into 

 groups; these groups undoubtedly exhibited 

 different phosphorescent spectra and presum- 

 ably had different atomic weights — although 

 from the chemical point of view all the groups 

 behaved similarly. I concluded that, of the 

 lines and bands of the compound spectrum 

 of an element, some are furnished by certain 

 atoms and some by others. I pointed out that 

 this was not likely to be an isolated case; that 

 probably in all so-called elements the whole 

 spectrum, does not come from, all the atoms — 

 that different spectral rays come from differ- 

 ent atoms, which may be interpreted to mean 

 that there are definite differences in the inter- 

 nal motions of the several groups of which the 

 atoms of a chemical element consist. I ven- 

 tured to suggest a possible explanation of these 

 facts, based on the assumption that acting on 

 the original protyle were two forces — one of 

 the character of time, accompanied by a lower- 

 ing of temperature, while the other, swinging 

 to and fro like a pendulum, and having periodic 

 cycles of ebb and flow, rest and activity, would 

 be intimately connected with the force of elec- 

 tricity. I arrived at a presentation of the ele- 

 ments on a lemniscate path which seemed to 

 me to throw some light on the question of their 

 genesis. My researches seemed to show that 

 the persistence of the ultimate character, the 

 eternal self-existence, the fortuitous origin of 

 the chemical elements, could no longer be re- 

 garded merely as probable. 



Apparently bodies exist which possess close 

 upon the same atomic weights and combine in 

 definite proportions with other substances and 

 yet exhibit certain minute differences. For 

 these substances, which are capable of being 

 isolated and identified, I suggested the name 

 " meta-elements." Thus there appears to me 

 to be a gradation of molecules of different 

 ranks between the atom and the compound — 

 and these aggregations of atoms in certain 

 circumstances might well pass for simple ele- 

 mentary bodies. 



In recent years the old idea of the ultimate 

 atom as a solid particle, spherical or otherwise, 

 has slowly, almost imperceptibly, given way 

 to the more rational conception of a minute 

 planetary or " Saturnian " system of dazzling 

 complexity; the conception is many-minded, 

 aided here and there by facts that failed to 

 fall in with the old lines of thought. Among 

 the most prominent men through which the 

 new conception has come to light, we have 

 Kelvin, Stoney, Thomson, and, more recently, 

 headed by Sir Ernest Eutherford, a host of 

 vigorous workers in the new science of radio- 

 activity, who have built up a conception of 

 atomic physics often " hard to be understood," 

 but that probably is a move in the right direc- 

 tion. Sir Ernest Eutherford supposes the atom 

 to be composed of a nuclear positive charge, 

 exceedingly small compared with the sphere 

 of action of the atom, and consisting of a 

 number of unit charges. Surrounding this 

 nucleus is an external shell in which a num- 

 ber of separate negative electrons are dis- 

 tributed. Professor Soddy — whose name is 

 closely associated with that of Sir Ernest 

 Eutherford — is one of the earliest workers 

 in radioactivity, and has developed a theory of 

 the chemistry of the radio-elements based upon 

 the periodic law and a modified form of lem- 

 niscate spiral where the existence of pseudo~ 

 elements having slightly different atomic 

 weight but identical chemical properties are 

 set out. These " isotopic " elements occupy 

 the same place in the periodic table. He has 

 thus arrived, by a totally different path from 

 the one I traveled, at the conception of an ele- 

 ment having atoms of different weight though 

 chemically identical. The theory has recently 

 received some confirmation by the analyses of 

 the lead that is found in the minerals pitch- 

 blende, thorianite, etc. In my own laboratory 

 a spectroscopic examination of the lead from 

 Cornwall pitchblende has shown traces of 

 thallium not found in pure assay lead; the 

 unexpected presence of this element may have 

 some bearing on the slightly different atomic 

 weight values recorded for the lead extracted 

 from the radio-minerals. 



Without risking a charge of being unduly 

 optimistic I think I may believe we are on the 



