296 



NA TURE 



[January 25. 1900 



THE METHODS OF INORGANIC EVOLUTION} 



II. 

 T HAVE already said that I think most chemists would 

 ■■■ consider that the formation of larger masses by poly- 

 merisation is more probable than by the coming 

 together of dissimilar atoms ; but if we consider chemical 

 compounds, certainly the analogy is all in favour of the 

 latter view if the principle of continuity be taken into 

 account, for we are ignorant of the point at which one 

 evolutionary process resigns in favour of another. The 

 present separation of compound from simple bodies is, 

 indeed, simply a measure of our ignorance arising from 

 the feebleness of our laboratory resources in relation to 

 the temperature required to produce more and more 

 simplifications. 



I discussed this question in my "Chemistry of the 

 Sun "2 in 1887, and showed that the analogy of the com- 

 pletely studied hydrocarbon series beginning with CHj 

 suggested a hypothetical elemental sequence. 



a b 



a + b 



a + ((^ + (5) written by chemists ab^ 



a + {b^){b^) ,, ,, ab^ 



and so on. 



In the concrete hydrocarbon series we have continuous 

 additions of CH.^ to CH4 until we reach a molecule de- 

 fined by C1UH34, and as the building up of this molecule 

 can be traced without difficulty, so we can imagine it 

 simplified by successive sheddings of its constituent 

 CH2 ; we pass from a simplification which we can bring 

 about by simple halving to one which provides us with 

 relatively large and small masses. 



The next question which arises then is whether there 

 is any way open to us of getting still more light on this 

 matter beyond that furnished by orthodox chemistry. 



Let us consider the regions of thought from which we 

 may expect it. To do this, I must go back to my original 

 conclusion derived in 1873 from the spectroscopic facts 

 then accumulated in the work on the sun and stars, and 

 the laboratory observations made to attempt to under- 

 stand them. 



I then wrote : — 



" I have asked myself whether all the above facts can- 

 not be grouped together in a working hypothesis which 

 assumes that in the reversing layers of the sun and stars 

 various degrees of ' celestial dissociation ' are at work, 

 which dissociation prevents the coming together of the 

 atoms which, at the temperature of the earth and at all 

 artificial temperatures yet attained here, compose the 

 metals, the metalloids and compounds." ^ 



With the progress of science the idea of "atoms" has 

 considerably changed, and this change of view enables 

 us to study the question of dissociation in a more rigid 

 way than was previously possible. 



Formerly " atoms " were regarded as merely chemically 

 different from element to element ; the recent investiga- 

 tions have introduced a new conception. It is now no 

 longer chemically different matter merely, but matter, 

 whether chemically different or not, carrying an electric 

 charge. In the first work along this new line physicists, in 

 order to grapple with the phenomena of electrolysis and 

 solutions, imagined sub-molecules or sub-atoms carrying 

 an electric charge in an electrolyte from the anode to the 

 kathode ; this was called an ion (Gr. a goer). This con- 

 ception has been more recently used to explain those 

 movements of particles of matter which produce light, 

 and therefore spectral lines. The sub-particle, this ion^ 

 with its electric charge e and its mass ;«, is supposed to 

 move in an elliptic orbit under the attraction of a centre. 

 At first the theory stipposed the ions to be electrified par- 



1 Continued from p. 131. 2 p. 263 et seq. 



3 Bakerian Lecture, \%Ti(^Phil. Trans. y dxiv. Part 2, p. 491). 



NO. 1578, VOL. 61] 



tides, but a recent extension considers them to be complex 

 dynamical systems the motions of which are registered 

 by spectral phenomena. 



It will be gathered from what I have already said re- 

 lating to the various questions connected with the study 

 of "series" of spectral lines how the idea of "complex 

 dynamical systems " is also demanded to explain the 

 phenomena presented by them. 



Thus I have shown it to be probable that the hydrogen 

 atom which the chemist weighs may be built up of 

 hundreds of the things, call them what you will, a few 

 of which in the hottest stars produce the vibrations which 

 we take as demonstrating the existence of hydrogen in 

 the celestial spaces. 



Both these lines of modern evidence tend to justify 

 the view that the different spectra are not produced by 

 different material, but by different conditionings of the 

 same material. 



These different conditionings may refer either to the 

 electric charge or to the mass of the ion, or of the mole- 

 cule round which the ion circulates. The units of matter 

 present in the ion or in the central molecule may vary 

 in number, or their arrangement may vary. 



Imagine a series of substances "chemically" dif- 

 ferent, the intrinsic difference of which really consists 

 merely of their being built up of dijferent numbers oj 

 units, from A the simplest to Z the most complex. 

 When Z is simplified by heat, its complex system of 

 centre of force and ion with their electric charges will 

 undergo changes which we may expect to result in 

 the formation of less complex systems doubtless built 

 on a like pattern, and therefore capable of pro- 

 ducing spectra ; hence we are bound to see the 

 spectra of some of the intermediate forms which, when 

 they are stable and go about in company, it may well 

 be that physicists have already recognised. These we 

 may call B or C, or R or S, or X or Y, as representa- 

 tives of various complexities. 



The more complex the form experimented on and the 

 higher the temperature employed in the laboratory, the 

 more spectral lines indicating different chemical " ele- 

 ments " in intermediate stages may we see. 



I say in the laboratory because in the stars the result 

 will be different. There, in consequence of the long con- 

 tinued action of heat and the shielding of the reversing 

 layer from the effects of lower temperature, we may only 

 see at the highest temperature the spectra of the forms 

 A and near A. We now know what these are. 



To take another case, let us assume that the electric 

 charges or arrangement as well as the number of the 

 units of matter may vary. Under these conditions, 

 when we dissociate Z, not all, but only some, of 

 possible intermediate forms may be expected to afford 

 spectral evidence. Say, to take an example, those in 

 the vertical columns of Mendeleef's table, and I 

 am led to make this suggestion because Kayser has 

 shown that in "series" the duplicity or triplicity 

 of lines is associated with the position of the ele- 

 ments producing them in these columns. A concrete 

 case would be afforded by contrasting the behaviour of 

 sodium and caesium, representing relatively simple and 

 complex substances. We might observe the lines of 

 sodium when caesium is dissociated ; we should not 

 expect to see the lines of caesium when sodium is dis- 

 sociated. 



The two cases taken it is possible may illustrate the 

 difference between related and not related groups of 

 " elements." 



The apparently constant appearance of representative 

 lines of the spectrum of one substance of a group in that 

 of the other member of the same group may be thus 

 explained, although it has generally been attributed to 

 the presence of impurities, as in the case of all common 

 long lines seen in spectra ; and this in spite of the pro- 



