626 



NATURE 



{Oct 10, 1878 



in the great natural laboratories of the sun or stars ? And 

 facts recently observed by Lockyer give some countenance 

 to those who would answer this question in the affirmative. 

 The spectra of compounds are as a rule more complex than 

 those of elements. The former bodies, speaking broadly, 

 yield channelled or band spectra, the latter line spectra. 

 The non-metallic elements, also, yield spectra which may 

 be generally described as channelled or band spectra, 

 while the spectra of the metals are more to be described 

 as line spectra. Again, with increase of temperature band 

 tend to change into line spectra ; with increase of tempe- 

 rature compounds tend to be decomposed into their con- 

 stituent elements. But the solar spectrum is a line spec- 

 trum, the spectra of certain stars — Sirius, &c., — are line 

 spectra, but simpler in their character than that of the 

 sun ; the hydrogen line is predominant in the Sirian 

 spectrum. The spectra of certain other stars — e.g.., the red 

 stars — are very complicated, and consist for the most part 

 of bands and channelled spaces. 



Putting these facts together, the hypothesis has sug- 

 gested itself to Lockyer that the atmosphere of the red 

 stars contains certain compounds and many non-metallic 

 elements, that the atmosphere of the sun is characterised 

 by the presence of metals, there the non-metals are de- 

 composed into simpler forms, that those elementary bodies 

 which are not found in the hotter part of the sun's atmo- 

 sphere are being formed in the upper and cooler portions, 

 but as they descend they are again dissociated, and 

 lastly, that in the very hot stars our elements are for the 

 most part resolved into simpler forms. Hydrogen, how- 

 ever, appears to exist there in the form in which it is 

 known on this earth. This hypothesis is put forward ten- 

 tatively by its author, and must only be accepted as a 

 working hypothesis. It is most interesting to the chemist ; 

 in some of its bearings it also tends to throw light upon 

 the physical conditions of the existence of stars and suns. 

 Yet it is only an hypothesis, we must beware of accepting 

 it as a dogma. 



There is one point as bearing on Lockyer' s hypothesis 

 to which I should wish to direct attention. Non-metals 

 show more variations in their spectra than are exhi- 

 bited by the spectra of the metals. Metals yield, 

 as a rule, only line spectra, non-metals channelled, then 

 line spectra, as the temperature increases. Analogous 

 with these changes in the spectra of non-metals is the 

 well-known " plasticity " of these bodies. The instances 

 of allotropy about which we have any accurate know- 

 ledge are instances among the non-metallic elements ; 

 probably, then, these bodies will be more readily decom- 

 posed than the metallic elements. 



Putting together all that is known on the subject, the 

 balance of probability appears to me to be in favour of 

 the hypothesis that the elements are not really elementary. 

 But if one is asked to put forward a positive hypothesis, 

 not merely to favour a negative one, the task becomes 

 much harder. 



In a short, but exceedingly suggestive paper (" Specu- 

 lative Ideas respecting the Constitution of Matter," 

 Phil. Mag,, February, 1864), Graham tentatively put 

 forward the hypothesis of original matter having a 

 molecular or atomic structure, ail the molecules being 

 uniform in size and in shape, but not all possessed of the 

 same amount of motion. In the differences in the 

 motions of the parts of this original matter Graham sees 

 the origin of all differences in the properties of our 

 various elements. The gaseous molecules which we are 

 accustomed to measure are not, says Graham, to be re- 

 garded as the ultimate molecules of the original matter, 

 but as composed of a "group or system " of these. This 

 hypothesis of Graham appears to me to be one of great 

 merit. But if we start with one matter, whose molecules 

 are of equal mass, may we not imagine these molecules 

 originally possessed of equal amounts of motion ? Having 

 got these molecules, it is not, I think, beyond the powers 



of the scientific imagination to regard some of them as 

 coming within the sphere of each others' action, and as 

 coalescing to form new compound molecules, the mass of 

 such new molecules being of course different from that of 

 the original molecules. After such an encounter the new 

 molecule will possess an amount of energy different from 

 that possessed by the original molecules ; hence it will 

 exhibit new properties. The original matter has thus 

 become differentiated ; we have now more than a grained 

 structure, the grains vary in mass, and in the amounts of 

 energy which they possess. This process of evolution 

 of higher and higher orders of molecules may proceed 

 (may be now proceeding) until we arrive at those 

 systems which are at present generally regarded by 

 chemists as the molecules of distinct forms of matter, as 

 the elementary bodies of to-day. These elementary 

 bodies are again ready, under proper conditions, to form 

 yet higher orders of molecules ; these are our compounds, 

 but these higher orders are less stable, under average 

 conditions, than the lower (elementary) orders of mole- 

 cules. If by any means a very large amount of energy 

 be added to our elementary molecules they would tend 

 to dissociate and to reform the simpler orders or groups 

 from whence they have been derived. Such addition of 

 energy appears to be given in the intensely hot atmo- 

 sphere of the sun, where metallic bodies may seemingly 

 remain in company with heated oxygen, yet unoxidised. 

 If, however, a small amount of energy only be given to 

 an element, then that element becomes ready to unite 

 with another, or with others, to form a compound body. 

 The bodies which we call elements would, on this 

 hypothesis, be but intermediate stages in the evolu- 

 tion of complicated compounds from one original form 

 of matter. At certain stages in this process points of 

 comparative rest are reached; one of these points 

 marks the existence of our so-called elements. Bodies 

 which are elementary in our laboratories are compounds 

 in the more energetic laboratories of the sun and hot 

 stars. Many of our compounds, again, are elementary in 

 the cold, listless atmosphere of the moon. Just as it is 

 very difficult, if not impossible, to define a chemical com- 

 pound, to say where the mere mechanical mixture or 

 aggregation ends and the true chemical compound begins, 

 so, in this view, would it be impossible to define a 

 chemical element. Whether a substance is compound or 

 elementary depends upon the point of time at which the 

 investigation is made and upon the conditions of the envi- 

 ronment. Graham has pointed out that the " colloidal 

 state" seems to intervene between the liquid and crys- 

 talline states ; the experiments of Faraday, of Caignard 

 de la Tour, of Andrews, and more recently of Pictet and 

 Cailletet, have taught us that between the gaseous and 

 liquid states there is no hard hne of demarcation ; many 

 facts in chemistry and in chemical physics appear to be 

 exphcable only on the supposition that the passage from 

 mechanical mixture to chemical union is a gradual and 

 continuous, not an abrupt and discontinuous one. Why, 

 then, should not the passage from the one original ele- 

 ment to the one final compound be also a gradual 

 passage ? 



And as in animate nature we know that the (com- 

 parative) permanence of a species is in no way contra- 

 dictory to the general law of gradual development, so in 

 the history of molecular arrangements it may be that the 

 present permanence of our so-called elements only marks 

 a resting point in the slow but sure process of formation 

 of more and more complicated compounds. The ave- 

 rage conditions of our present surroundings may not 

 allow of the existence of any less complicated molecular 

 aggregations than those which we call elementary, just as 

 they do not appear to allow of the existence of any ex- 

 tremely complicated aggregations of chemically united 

 molecules. 



There is another aspect of the question upon which one 



