November i 7, 1923] 



NATURE 



72. 



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by instituting Sub-Committees for some of the 

 important watersheds. But it is difficult to under- 

 stand the attitude of the Ministry of Health and of 

 medical officers. At two recent inquiries relating 

 to new sewers which were designed to discharge 

 sewage untreated into an estuary, the representative 

 of the Ministry of Health admitted that the estuary 

 was already overcharged with sewage, but said that 

 the new sewers would not alter that aspect of the 

 question, that the estuary was so bad now that it 

 would by this addition be very little the worse. 



The medical officer goes further. He says the 

 deaths of the fish in the estuary are caused entirely 

 by trade effluents, and that we should get more 

 powers to deal with such pollution. As for the 

 sewage, he will tell you that no matter how great 

 the quantity it is not unhealthy, it is not in any way 

 related to the destruction of fish, and he will produce 

 statistics to show that the healthiest parts of the 

 county and the city are just where the sewage con- 

 tamination is heaviest. 



Without attempting at present to deny the truth 

 of his extraordinary statements or presuming to 

 explain the reason for his making them, it ought to 

 be pointed out that, even if he is right, he is arguing 

 that it is not necessary in any case to treat sewage, 

 and therefore that authorities everywhere should be 

 freed from the necessity and the expense of doing so. 

 Indeed, we should not lose sight of the fact that if 

 the killing of the fish in the river from whatever 

 cause proceeds to the phase of practical extermina- 

 tion, an important and essential feature of the river 

 will come to an end, nor of the probability that the 

 authorities throughout the watershed will object to 

 being subjected to an expense no longer necessary. 

 The river in such a case would be converted into a 



wer, a condition which is already met with in some 

 of our estuaries and rivers. The river boards, on the 

 other hand, are desirous to preserve the rivers as 

 rivers, and to save them from becoming sewers. 



The experiments which have been made with refer- 

 ence to the estuary of the Tyne have demonstrated 

 plainly (i) that it is over-polluted with sewage ; {2) 

 that it is frequently little better in composition than 

 the liquid outflowing from the sewers ; (3) that the 

 sewage in the region opposite Newcastle is the cause 

 of a serious diminution in the quantity of dissolved 

 oxygen ; (4) that the oxygen frequently descends 

 below the limit necessary' to sustain fish life, and is 

 only restored by freshets from the river ; (5) that in 

 consequence, during dry weather conditions, many 

 deaths occur, either by direct poisoning or by the 

 ck of oxygen. It has been proved by experiment, 



oreover, that the sewage alone will cause death, 



d that it may be directly poisonous to fish. 



It is obvious, therefore, that in the case of the Tyne 

 nd of many other rivers of our country, both the river 

 and the estuary will have to be cleaned. In the case 

 of the river, trade effluents will have to be treated 

 to prevent any poisonous effects. The estuary is far 

 more important, for at present it is liable to provide 

 an impa.ssable barrier to fish. The solution of the 

 problem is not an easy one, but it will have to be 

 faced some time, and, we hope, before the barrier 

 l)ecomes so great that migratory fish will have ceased 

 to enter the river. 



Even with the powers conferred by the new Act, 

 little will be accomplished unless with the sympathetic 

 co-operation of the authorities and the owners of 

 works. Already they have shown a strong disposi- 

 t ion to help in the inquiries and in taking steps to 

 minimise the effects of the effluents. As soon as it 

 IS clearly realised by all concerned that action is 

 necessary, it will not be so difficult to indicate in 

 what direction it should proceed. A. Meek. 



The "J" Phenomena and X-ray Scattering. 



In a number of recent papers. Prof. A. H. Compton 

 brings forward what purports to be a Quantum 

 Theory of the scattering of X-rays. I venture to 

 think that this theory — or more correctly system of 

 rules — has little connexion with the phenomena of 

 X-ray scattering as I observed it nearly twenty years 

 ago, and as I still know it. I do not wish to write 

 of the inconsistency or illogicality of the theoretical 

 assumptions, for they are probably as well known to 

 Prof. Compton as to the most careful reader. Prof. 

 Compton seems to hope that, in spite of this, the truth 

 will emerge. But I am compelled to state a few signifi- 

 cant facts which are not common knowledge. 



Regarding the experimental observations establish- 

 ing a difference between the primary and the second- 

 ary radiations observed (assumed by him to be scattered 

 radiations), I should like to point out that they date 

 from the earliest experiments on the subj ect (see Sagnac ; 

 Barkla, P/«/. Mag^., 1904; Beatty; before those to which 

 he refers) . It is very easy to detect differences in the 

 penetrating powers between the primary and second- 

 ary (scattered) X-radiations as ordinarily measured. 



The greatest difficulty has been experienced by 

 experimenters, not in establishing a difference between 

 the primary and secondary radiations, but in showing 

 that they are at all similar. They have not always 

 realised the conditions essential for this. The necessity 

 of using soft X-radiations in order to obtain evidence 

 of the purest scattering and the almost perfect agree- 

 ment with the classical Thomson theory, I have 

 emphasised again and again. There have been 

 various reasons for this, some obvious, others long 

 since observed but only recently studied. The super- 

 posed radiation excited in tlie scattering substance 

 by the swift electrons constituting the secondary 

 corpuscular radiation and the possible emission of 

 further unknown fluorescent X-radiations are among 

 the obvious. For many years now I have known 

 of a further and more important source of error ; 

 this is connected with what I have called the " J " 

 radiations, discontinuities, or transformations. The 

 important fact, whatever its explanation, is that a 

 beam of X-rays in transmission through matter under 

 certain critical conditions becomes considerably more 

 absorbable both in that and other substances. We 

 have made scores of experiments of various kinds 

 on this abrupt transformation ; more will be said 

 of it elsewhere. What concerns us at present is that 

 this is of such a magnitude as would be accounted 

 for by an absorption and re-emission of the radiation 

 with an increased wave-length of the magnitude 

 required by Compton — about 0-02 A.U. But this is 

 in the direction of propagation of the primary beam ; 

 and experiments do not seem to support this view as 

 to the nature of the change. Absorption in this region 

 evidently depends upon factors other than wave-length 

 and atomic number. This is the J discontinuity which 

 I mentioned in 1916 (Bakerian lecture) and again with 

 Miss White in 1917 [Phil. Mag., Oct. 1917). 



We can now certainly say that these J trans- 

 formations not only might produce, but actually do 

 produce the softening which tve have observed in the 

 scattered radiation in many experiments at any rate. 

 It is not unreasonable to suppose that it is the 

 explanation of the changes observed by others, not 

 only in the region of wave-lengths over which we can 

 make a definite test, but also over the range of shorter 

 wave-lengths, over which we are not at present able 

 to get control. 



It is impossible in the space now at my disposal 

 to give full evidence for this ; but the only rational 

 conclusion is, that this transformation observed is not 

 in the process of scattering but in the subsequent 



NO. 2820, VOL, 112] 



