TRANSACTIONS OF SECTION B. 569 



In the original genesis the longer the time occupied in that portion of the 

 cooling down during -which the hardening of the iirotyle into atoms took place, 

 the more sharply defined would be the resulting elements ; and, on the other hand, 

 ■with more irregularity in the original cooling, we should have a nearer approach 

 to the state of the elemental family such as we know it at present. 



In this way it is conceivable tbat the succession of events which gave us such 

 groups as platinum, osmium, and iridium — palladium, ruthenium, and rhodium — 

 iron, nickel, and cobalt, if the operation of genesis had been greatly more prolonged, 

 would have resulted in the birth of only one element of these groups. It is also 

 probable that by a much more rapid rate of cooling, elements would originate even 

 more closely related than are nickel and cobalt, and thus we should have formed 

 the nearly allied elements of the cerium, yttrium, and similar groups ; in f^ct the 

 minerals of tlie class of samarskite and gadolinite may be regarded as the cosmical 

 lumber-room where the elements in a state of arrested development — the uncon- 

 nected missing links of inorganic Darwinism — are finally aggregated. 



I have said that the original protyle contained within itself the potentiality of 

 all possible atomic weights. It may well be questioned whether there is an abso- 

 lute uniformity in the mass of every ultimate atom of the same chemical element. 

 Probably our atomic weights merely represent a mean value around which the 

 actual atomic weights of the atoms vary within certain narrow limits. 



Each well-detined element represents a platform of stability connected by 

 ladders of unstable bodies. In the first accreting together of the primitive stuif 

 the smallest atoms would form, then these would join together to form larger 

 groups, the gulf across from one stage to another would be gradually bridged over, 

 and the stable element appropriate to that stage would absorb, as it were, the un- 

 stable rungs of the ladder which led up to it. I conceive, therefore, that when we 

 say the atomic weight of, for instance, calcium is 40, we really express the fact that, 

 while the majority of calcium atoms have an actual atomic weight of 40, there 

 are not a few which are represented by 39 or 41, a less number by 38 or 42, and 

 so on. We are here reminded of Newton's ' old worn particles.' 



Is it not possible, or even feasible, that these heavier and lighter atoms may 

 have been in some cases subsequently sorted out by a process resembling chemical 

 fractionation ? This sorting out may have taken place in part while atomic matter 

 was condensing from the primal state of intense ignition, but also it may have 

 been partly efiected in geological ages by successive solutions and reprecipitations 

 of the various earths. 



This may seem an audacious speculation, but I do not think it is beyond the 

 power of chemistry to test its feasibility. An investigation on which I have been 

 occupied for several years has yielded results which to me appear apposite to the 

 question, and I therefore beg permission here to allude briefly to some of the 

 results, reserving details to a subsequent communication to the Section. 



My work has been with the earths present in samarskite and gadolinite, separat- 

 ing them by systematic fractionation. Chemical fractionation, on which I hope to 

 say more on another occasion, is very similar to the formation of a spectrum with a 

 wide slit and a succession of shallow prisms. The centre portion remains un- 

 changed for a long time, and the only approach to purity at first is at the two ends, 

 while a considerable series of operations is needed to produce an appreciable change 

 in the centre. The groups of didymium and yttrium earths are those which have 

 chiefly occupied my attention. On comparing these rare earths we are at once 

 struck with the close mutual similarity, verging almost into identity, of the mem- 

 bers of the same group. 



The phosphorescent spectra of these earths when their anhydrous sulphates are 

 submitted to the induction discharge in vacuo are extremely complicated, and change 

 in their details in a puzzling manner. For many years I have been persistently 

 groping on in almost hopeless endeavour to get a clue to the meaning I felt con- 

 vinced was locked up in these systems of bands and lines. It was impossible to 

 divest myself of the conviction that I was looking at a series of autograph inscrip- 

 tions from the molecular world, evidently of intense interest, but written in a strange 



