6 



SCIENCE 



[N. S. \0L. XXV. No. 627 



'sign-manual of the elements.' Riecke and 

 Stark^ have furnished us excellent experi- 

 mental reasons, by observing the motion of 

 luminous lithium vapor towards the cath- 

 ode, for thinking that the radiant source is 

 the positive ion; this, it will be noted, is 

 not at all inconsistent with the evidence of 

 the Zeeman effect, since the positive ion 

 carries with it probably a large number of 

 negative electrons, being itself merely a 

 neutral atom minus one or more negatively 

 charged corpuscles. 



Thomson has recently presented three 

 different lines of argument for thinking 

 that the number of corpuscles in the atom 

 is of the same order as its usual atomic 

 weight, i. e., in terms of hydrogen as unity. 

 But most elements emit a number of spec- 

 tral lines which is enormously greater than 

 their respective atomic weights. 



Thomson is, therefore, driven to conclude 

 that "when an atom of an element is giving 

 out its spectrum either in a flame or in an 

 electric discharge, it is surrounded by a 

 swarm of corpuscles; and combinations 

 not permanent, indeed, but lasting sufS- 

 ciently long for the emission of a large 

 number of vibrations, might be expected 

 to be formed. These systems would give 

 out characteristic spectrum lines; but these 

 lines would be due not to the vibrations of 

 the corpuscles inside the atom, but of cor- 

 puscles vibrating in the field of force out- 

 side the atom."® The immediate cause of 

 luminosity would be the bombardment of 

 this system by free corpuscles, or in the 

 case of flames the disturbing cause would 

 presumably be molecular collapse. 



At another time and place Thomson 

 fortifies his view as to the complexity of 

 the radiating atom, by citing the discovery 

 of Lenard, that the speed with v/hich the 

 corpuscles are expelled from the atom by 



"Riecke & Stark, Physih. Zeitsch., 5, 537, 1904. 

 "Thomson, Phil. Mag., 11, 774, 1906. 



ultra-violet light does not depend upon the 

 intensity of the incident ultra-violet light; 

 thus indicating the necessity of at least two 

 independent vibrating systems within the 

 radiant atom. 



I am not clear as to the proper interpre- 

 tation of the measurements which have been 

 made by Stark^ upon the Doppler effect in 

 hydrogen canal rays ; but in any event they 

 would seem to prove that the luminous 

 source in the vacuum tube is not the simple 

 corpuscle of the cathode rays, but the more 

 complex, positive ion (not necessarily the 

 positive charge) of the canal rays. While 

 the experiments of Hull* during the past 

 year combined with that of Schuster and 

 Hemsalech point to a luminous source of 

 such size and complexity that a condition 

 of luminosity may be 'propagated along' it. 



The upshot of the whole matter, then, 

 is that we are landed with a picture of the 

 radiant atom which is complex quite be- 

 yond description. One is reminded, indeed, 

 of the words which Marie Corelli puts in 

 the mouth of Lionel, the youthful hero of 

 her 'Mighty Atom.' "Oh, dear Atom!" 

 says he, "you must be very much more 

 than I have been taught to believe you 

 are. ' ' 



Let us, however, accept the structure as 

 we have received it and, with apologies for 

 any feature of it which has not been cor- 

 rectly represented to you, let us now ask 

 ourselves, how well it can serve as a foun- 

 dation for our spectroscopic edifice. 



APPLICATION OF CRITERIA 



We may make this test most easily per- 

 haps by asking how this atom will account 

 for the nine fundamental phenomena men- 

 tioned above, and — 



1. Does this Saturnian system give sharp 

 lines? Can one predict from its structure 

 that its radiation will be concentrated in a 



'Stark, Ann. d. Physih., 21, 401, 1906. 

 'Hull, Proc. Roy. 8oo., A, 521, p. 80, 1906. 



