Supplement to "Nature,'' Atcgust 4, 1923 



191 



to jump from one orbit to another, and thereby 

 give out a certain quantum of energy. But this may 

 be a supplementary and not a contradictory state- 

 ment. What makes the electrons jump ? Which 

 electron jumps out ? Sometimes it is from the K 

 ring, sometimes from the L ring ; and so on. All 

 those things may be known. But still I ask, What 

 started the disturbance .? If an electron is generated 

 by the impact of light, it does not follow that that 

 particular electron is the one ejected. Its entry may 

 1)6 the means of ejecting another. Somehow or other 

 the atom must get another, in order to restore its 

 constitution. There are doubtless many ways in 

 which a strayed electron could be recaptured ; and I 

 venture to suggest that our speculation suggests one 

 of them. 



Possible Utilisation of Waste Radiation. 



There is an immense amount of radiation travelling 

 about space. The whole amount of solar radiation is 

 portentous. The fraction which the earth catches, 

 though terrestrially so important, is but a minute 

 fraction of the whole — less than the two thousand 

 millionth part, — and it seems to have been going 

 on for hundreds of millions of years. The radiation 

 from many of the stars is greater. What becomes 

 of all that radiation ? Is it all waste ? Space 

 is so enormous that though thousands of millions of 

 suns have been pouring out their energy for thousands 

 of millions of years, space is no warmer. The ether 

 is not warmed by it : the ether does not absorb it. 

 The ether is perfectly transparent. Yet our instinct 

 rebels against the idea that all this radiation results 

 in nothing. Sir W. Siemens speculated as to its 

 possible concentration by total reflection at an ether 

 boundary. But I cannot imagine an ether boundary. 

 I can more readily imagine that light results somehow 

 in the generation of matter ; and that there is a 

 reciprocal interaction between matter and ether 

 waves ; so that each is generated by the other, — a 

 sort of constant and perennial interchange. 



Electrons have come into existence somehow. The 

 subject of origins usually lies outside science. The 

 origin of matter is as beyond our ken as the origin 

 of life ; and yet people speculate about the origin 

 of life. Some highly estimated men of science hope 

 at any rate that some day the chemistry and physics 

 of life may be so far understood that a highly complex 

 assemblage of organic molecules may simulate and 

 pcrliaps adopt its functions. I see nothing incon- 

 ceivable in this. Life has originated somehow; and 

 if we can get to understand anything about its origin, 

 the effort is legitimate. It may fail ; but it would 

 be a very superficial view of religion which resented 

 its success. Mind dominates matter ; and the mind 

 of man is not altogether of a different order from the 

 mind of the Creator. But this is a subject on which 

 I could say more on a more suitable occasion, I only 

 say thus much now in order to repel any idea of 

 impiety in speculating on a possible origin for matter. 



IIvi'()tiii;tical Conversion of Radiation. 

 'ihe possibility that a small body may gradually 

 -row in mass under the influence of an etherial trans- 

 formation, does not seem one to be scouted witliout 

 proper examination. The amount of matter scattered 



about in space is by no means inconsiderable, and the 

 problem of its origin has never been attacked. Given 

 matter, the origin of radiation has been more or less 

 solved. But, given radiation, the idea of its con- 

 version into matter has not, so far as I know, been 

 mooted. Possibly the idea is erroneous. But inter- 

 actions in Nature are so frequent, and the inter- 

 relations between ether and matter are so ill understood, 

 that I think we should not shut our eyes to the 

 possibilities of some reciprocal interaction, even of a 

 generative kind.^ 



Sometimes I see the difficulties of the hypothesis ; 

 sometimes I feel impressed with a sort of probability 

 about it. It is easier to see the difficulties than the 

 probabilities. But the relationship between energy 

 and matter — connected as they appear to be with 

 the second power of the characteristic ether velocity, 

 and with the conception of an intimate fine-grained 

 rotational structure for the ether — is not a hint that 

 should be too lightly ignored or neglected. 



Electrons build up * matter. What builds up 

 electrons ? They are somehow intimately connected 

 with the ether ; their motion through it displays to 

 us the phenomenon of magnetism ; and their accelera- 

 tion generates waves. So far, we are on firm ground. 

 When we come to the converse or reciprocal relations, 

 we have but few facts to stand on. But the emission 

 of electrons by means of light is one of them ; and 

 the bearing of this fact, until it is properly understood 

 inevitably justifies speculation. 



Previous Guesses, 

 When I say that the idea of reciprocal conversion 

 has not been mooted, I am going beyond the facts. 

 In Loring's " Atomic Theories," page 80, I find the 

 following sentences : 



" Thus it would seem that the energy phenomena 

 are reversible, so that the radiation is as it were con- 

 vertible into moving electrons and moving electrons 

 are convertible into radiation. It is of course only 

 the energy which is thus convertible. The mechanism 

 of conversion is not, however, known." 



Again, in Millikan's book " The Electron," when 

 speaking of Barkla's discovery of the remarkable 

 absorbing property of matter for X-rays, he says : 



" It will be seen from these photographs that the 

 atoms of each particular substance transmit the general 

 X-radiation up to a certain critical frequency, and 

 then absorb all radiations of higher frequency than 

 this critical value. The extraordinary significance of 

 this discovery lies in the fact that it indicates that 

 there is a type of absorption which is not due either 

 to resonance or to free electrons. But these arc the 

 only types of absorption which are recognised in the 

 structure of modern optics. We have as yet no way 

 of conceiving this new type of absorption in terms of 

 a mechanical model." 



Sir William Bragg, in Nature (1921), vol, 107, 

 p. 79, with reference to the experiments of Duane 

 and Hunt, says : " Exactly how this strange transfer 

 of energy from one form to another takes place we do 

 not know : the question is full of puzzles." He has 

 several times urged the extraordinary character of 

 the fact that a stream of radiation excited by the 



3 Cf. letter in Natukk, May 26, 1923, p. 702, 



