December 7, 1899] 



NATURE 



129 



THE METHODS OF INORGANIC EVOLUTION. 

 T N the study of the facts of inorganic evolution pre- 

 '■ sented to us by stellar spectra, there is one point of 

 paramount importance to be inquired into. In the 

 problems of inorganic evolution which we have now to 

 face, it is sufficiently obvious that we have to deal with a 

 continuously increasing complexity of chemical forms, 

 precisely as in organic evolution the biologist has had to 

 deal, and has dealt successfully with, a like increase of 

 complexity of organic forms. 



How has this inorganic complexity been brought 

 about? In the case of known compound bodies an easy 

 answer is given by analysis. Chloride of sodium, for 

 instance, is formed by the combination of chlorine and 

 sodium. But when we wish to deal with the formation 

 of the so-called "elements" themselves, no such easy 

 solution of the problem is open to us. 



If in order to investigate this problem we take the 

 analogy furnished by compound bodies as our guide, we 

 should say that the molecules of the elements themselves 

 were produced by the combination of unlike forms. 



But as a matter of fact, this method of producing com- 

 plexity is not the only one known to chemists. There 

 are bodies of the same percentage composition which 

 differ in molecular weight ; the methane series of hydro- 

 carbons is a case in point ; the higher molecular weights 

 or greater complexes are produced by additions of the 

 unit C.H2, so that these higher complexes are produced 

 by the combination of similar lower complexes. This 

 process is termed polymerisation. 



We are then familiar with two methods of increasing 

 complexity, which we may represent by a-\- a (poly- 

 merisation) and X +y (combination), producing a 

 form A. 



This, then, is the problem from the purely chemical 

 side. On which of these methods have the elements them- 

 selves been formed, now that we are justified in consider- 

 ing them as compound bodies } I suppose that chemists 

 when hypothetically considering the possible dissociation 

 of the chemical elements would favour the view of de- 

 polymerisation ; that is, the breaking up of a substance 

 A into finer forms (a) weighed by A/2 (or A/3), rather 

 than a simplification of A into x and j. 



The method of attacking this problem from the 

 chemical point of view in the first instance, must be a 

 somewhat indirect one. 



T/ie Stars and the Periodic Law. 



In a recent lecture I referred to the hypothesis put 

 forward by Newlands, Mendel^ef and others in re- 

 lation to the so-called " periodic law," which law in- 

 dicates that certain chemical characteristics of the 

 elements are related ttf their atomic weights. I further 

 showed that the order of the appearance of the various 

 chemical substances in the stars of decreasing temper- 

 atures did not appear to be on all-fours with the require- 

 ments of the periodic law. 



It will be well to study this question with a view 

 of discussing it more fully in the light of all the facts 

 known to us, among which the stellar evidence and that 

 afforded by the study of series are, I think, of especial 

 importance, since it may be said that we are now 

 absolutely justified in holding the view that of the lines 

 which make their appearance in the spectra of chemical 

 substances when exposed to relatively high temperatures, 

 a varying proportion is produced by the constituents of 

 the substance., whether it be a compound like the chloride 

 of magnesium, to take an instance, or of magnesium 

 itself. 



Now the periodic law based upon atomic weights deals 

 with each *' element " as it exists at a temperature at 

 which the chemist can handle it ; that is, if it be a 



NO. 



571, VOL. 61] 



question, say of magnesium, the chloride or some other 

 compound of the metal must have been broken up, and 

 the chlorme entirely got rid of before the pure mag- 

 nesium IS there to handle, and of this pure magnesium 

 the atomic weight is found and, having also regard to 

 Its chemical characteristics, its position in the periodic 

 system determined. 



But if the magnesium be itself compound, the positioi> 

 thus assigned for the element is certain not to tally with 

 the stellar evidence if the temperature of the star from 

 which information relating to it is obtained is high 

 enough to continue the work of dissociation ; that is to 

 break up magnesium itself into its constituents as cer- 

 tainly as the chloride of magnesium was broken up in 

 the laboratory in the first instance. 



It is now known that dealing with this very substance 

 magnesium, high electric tension brings us in presence 

 of a spectrum which consists of at least two sets of lines, 

 numerous ones seen also at the temperature of the arc,, 

 and a very restricted number which make their appear- 

 ance in the spark. 



If this be the work of dissociation— and, as I have 

 shown elsewhere, the proofs are overwhelming— the 

 " atomic weight " of the particle, molecule or mass, call 

 it what you will, which produces the restricted number 

 of lines— the enhanced lines— must be less than that of 

 the magnesium by the breaking up of which it is brought 

 into a separate existence. 



And now comes the chief point in relation to the 

 periodic law. Seeing that the smaller masses which pro- 

 duce the enhanced lines have not been yet isolated, their 

 " atomic " weiohts and their chemical characteristics have 

 not been determined, and so of course their places in the 

 periodic table cannot be indicated as it at present exists. 



My contention, therefore, is that some, at all events, of 

 the apparent discrepancies between the stellar evidence 

 and the "periodic" hypothesis arise from this cause. 



The magnesium, and I will now add calcium, which 

 the chemist studies at relatively low temperatures have 

 atomic weights of 24 and 40 respectively, and the stellar 

 evidence would be in harmony with the periodic law if 

 magnesium (24) made its appearance after sodium (23),. 

 and calcium (40) after chlorine (39), and generally each 

 substance should make its appearance after all other 

 substances of lower atomic weight than itself. 



But, and again for the sake of simplicity I shall con- 

 fine myself to magnesium and calcium for the moment, 

 in the stars we find lines in the high temperature 

 spectrurn of magnesium and calcium appearing before 

 known lines in the spectrum of oxygen which has an 

 atomic weight of 16. 



How are these results to be reconciled? I suggest 

 that the explanation is that the substances revealed by 

 the enhanced lines of magnesium and calcium and notec 

 in the hottest stars have lower atomic weights (smaller 

 masses) than the oxygen of the periodic table. 



Let us next, then, see what these atomic weights may 

 possibly be. Assuming A/2 the atomic weight of protn- 

 magnesium would be 24/2=12; of proto-calcium 

 40/2 = 20, supposing only one depolymerisation has 

 taken place. If we assume two, we get 6 and 10 as the 

 " atomic " weights of the simpler forms of magnesium 

 and calcium which make their appearance in the hottest 

 stars. 



In this way we can explain the appearance of those 

 finer forms of magnesium and calcium before oxygen, 

 with a small numberof depolymerisations, and the stellar 

 record of the order of atomic weights would be the 

 same : 



Hydrogen ... 

 Proto-calcium 

 Proto-magnesium 

 Oxygen 



