5§ 



NATURE 



[March 20, 19 13 



essential difference between the two types. Besides 

 it can be stated definitely that for any one kind of 

 instability, or for any one radio-active change, the 

 past exercises absolutely no influence upon the events 

 of the future. The period of average life of an atom 

 depends neither upon how long it has already been in 

 existence nor upon any other known condition. It is 

 independent of concentration or the environment in 

 which the atom disintegrates. These features of 

 radio-active change are against the view that any- 

 thing of the nature of atomic synthesis is going on 

 concurrently with the disintegration, or that dis- 

 integration is conditioned by the drain of energy from 

 the atom by radiation, as is so often affirmed. 



The mass of evidence that has been accumulated 

 that different elements have identical chemical nature 

 is not accurately described as purely negative in char- 

 acter. The statement that A is non-separable from B 

 is negative in form only. It contains explicitly an 

 infinite number of definite positive statements that A 

 is separable from C or D, or any other of the 

 hundred or more known elements, or any conceivable 

 mixture of them, by chemical methods, which are 

 exactly indicated by the statement. It is not neces- 

 sary that A and B should in every case coexist, though 

 in certain cases — the two uraniums is a good example 

 — they have never been obtained apart. Mesothorium- 

 II. ordinarily occurs free from actinium, and the 

 putting in of the latter substance is a voluntary ex- 

 perimental device to show that once mixed these two 

 elements are chemically non-separable. The complete 

 chemical nature of either, or of any other of the radio- 

 elements, could be described in detail ab initio, but 

 the negative form is brief and complete. 



I do not think there are weaknesses in this part of 

 the argument. It has been a slowly growing theo- 

 retical development, and I do claim for it something 

 approaching experimental proot. 



As regards the view that chemically identical groups 

 of elements have the same spectrum, this admittedly 

 I put forward on a single case, that of ionium and 

 thorium. It rests entirely on the validity and 

 generality of the a and /3 ray change rules, but, if 

 these are true, ionium must be the direct product of 

 uranium-II. ; its period cannot be less than 100,000 

 years, and its proportion in the preparations spectro- 

 scopically examined less than 16 per cent, and 10 per 

 cent, respectively. Any other view requires the 

 assumption that one or more a ray and twice as many 

 B ray changes remain to be discovered in the series, 

 and it can be stated with some certainty that no such 

 changes remain unknown. 



Frankly, I do not expect Prof. Schuster or anyone 

 else to accept a view of this kind, put forward on a 

 single thread of evidence. The value of the view is 

 merely that it suggests definite new lines of work, 

 difficult and costly, but still experimentally feasible. 



Prof. Schuster points out that the members of the 

 thallium group, for example, ought to give the thal- 

 lium spectrum in absence of thallium in the material. 

 The latter condition is easy to ensure. But the case 

 is not a very favourable one on the radio-active side, 

 as thorium-D, the best example of the group to select, 

 has a period of average life of only 4-5 minutes. The 

 case, however, might be within the resources of some 

 radium institute. 



Since Prof. Schuster made this suggestion, I hav 

 S'one into the experimental feasibility of getting 

 evidence of this kind, and have decided to concentrate 

 in the case of thorium-X, the spectrum of which 

 should be identical with that of radium. It is a par- 

 ticularly crucial case. The spectrum reaction of I 

 radium is excessively delicate, and the amount of this | 

 element can be easily evaluated in quantities I 

 NO. 2264, VOL. 91] 



thousand:, of times less than can be spectroscopically 

 detected. The chemical work is complicated, but 

 really exceptionally favourable and elegant. 



Mesothorium-I. is non-separable from radium, and 

 radiothorium from ionium, the parent of radium, so 

 that if radiothorium is grown from ionium-free meso- 

 thorium it can be purified from radium to any extent 

 and left to produce thorium-X. Naturally, however, 

 the work will require some years, but it should be 

 within the resources of the individual investigator. 

 At the same time, it will be possible to try during- 

 the course of the work a large number of similar 

 cases, if a sufficient supply of the primary material, 

 mesothorium-I. can be obtained. This inference as 

 to the spectra is purely a personal view, and is to be 

 taken merely as a suggestion until further evidence is 

 forthcoming. But I would not have made it if I 

 thought it inconsistent with any known evidence. 



Frederick Soddy. 



Physical Chemical Laboratory, Glasgow University . 

 March is. 





1 .•'' .*!'?•- 



An Unknown Assyrian Antelope. 



My attention has been directed by the Rev. A. 

 Paterson to a plate in a portfolio of photographs from 

 Assyrian bas-reliefs published at Haarlem, but now 

 out of print. This plate represents a bas-relief in the 

 great hall of Sinnacherib's palace at Nineveh, and 

 consists of an upper and a lower portion. The latter 

 depicts the monarch in his chariot, while the upper 

 shows a reed swamp with wild animals. This swamp 

 is believed to be part of a pleasure-ground made by 

 Sinnacherib in the neighbourhood of the palace, into 

 which wild animals were turned. It is divided in the 

 bas-relief into an upper and a lower portion. In the 

 left-hand corner of the lower half is shown a wild 

 sow with a litter of young, as they might appear at 

 the present day in 

 the reed-brakes of 

 the Euphrates. 

 The other animals 

 are three rumi- 

 nants, about half 

 as big again as 

 the sow, but with 

 longer legs. The 

 two in the 

 upper half of 

 the scene — of 

 which one is lying 

 down — are horn- 

 less, and therefore 

 females, but the 

 third, in the right- 

 hand corner of 

 the lower half, 

 carries spirally 



twisted horns, re- 

 calling those of 

 the African kudu. The raale antelopein the bas-relief of Sinna- 

 nyala, and situ- c erl s wampa - ,neve 



tunga, although not corresponding exactly in 

 curvature with any of them. The tail is rela- 

 tively short, as in the nyala. The buck is 

 represented with its head down, nibbling the stem 

 of a reed; on its body, in addition to parallel lines 

 representing the ribs, are certain patches, which may 

 be intended for broken pieces of reeds. These animals 

 have been regarded as deer, but the buck carries 

 horns, and not antlers, and antlered deer are not 

 inhabitants of reed-brakes. On the other hand, such 

 situations are the resort of several African antelopes, 

 notably the situtunga, and it therefore seems prac- 









