374 



NATURE 



[May 19, 192 1 



^ther Waves and Electrons.^ 



By Sir William Bragg, K.B.E., F.R.S. 



NEWTON put forward a corpuscular theory of 

 light, and Huyghens believed that it was essen- 

 tially a wave motion. Each gave wrong reasons for 

 his belief. Newton argued that it ought to be possible 

 to see round a corner, since the passage of waves 

 round a corner was a common effect. Huyghens de- 

 clined the corpuscular theory on the grounds that 

 corpuscles could not go fast enough, and that if two 

 people looked into each other's eyes the corpuscles 

 must hit each other and prevent mutual vision. But 

 the wave theory carried all before it, and, developed 

 by Young, Fresnel, and other workers, proved to be 

 capable of explaining optical phenomena in perfect 

 fashion. 



With the advent of X-rays and radio-activity the 

 process of radiation as a whole is seen to depend in 

 part on the movement of electrons. In the X-ray 

 bulb, to take an example, a stream of electrons, which 

 is truly a corpuscular radiation, strikes a block of 

 metal in the centre of the tube. Energy of radiation 

 is carried outwards through the walls of the tube in 

 the form of X-ravs ; that is to say, of wave motions 

 in the aether. When they strike matter, such as the 

 film of a photographic plate, the wave radiation dis- 

 appears and is replaced by moving electrons which 

 produce all the well-known effects ascribed to X-rays. 

 It is probable that this mutual plane of waves and 

 electrons is carried throughout the whole realm of 

 radiation, and the ultimate explanation of all optical 

 problems must involve the recognition of corpuscular 



1 Summary of the Robert Boyle lecture delivered at Oxford on May 12. 



radiations, at times replacing and being replaced by 

 the waves. Thus once more the corpuscular theory 

 appears again as a working hypothesis. 



But in its relation to the wave theory there is one 

 extraordinary and, at present, iirsoluble problem. It 

 is not known how the energy of the electron in the 

 X-ray bulb is transferred by a wave motion to an 

 electron in the photographic plate or in any other 

 substance on which the X-rays fall. It is as if one 

 dropped a plank into the sea from a height of 100 ft. 

 and found that the spreading ripple was able, after 

 travelling 1000 miles and becoming infinitesimal in 

 comparison with its original amount, to act upon a 

 wooden ship in such a way that a plank of that ship 

 flew out of its place to a height of 100 ft. How 

 does the energy get from one place to the 

 other ? 



Very lately considerable new information has come 

 to hand regarding the way in which atoms play a part 

 in this extraordinary transference of energy. In many 

 ways the transference of energy suggests the return to 

 Newton's corpuscular theory. But the wave theorv is 

 too firmly established to be displaced from the ground 

 that it occupies. We are obliged to use each theory 

 as occasion demands and to wait for further knowledge 

 as to how it may be possible that both should be true 

 at the same time. Toleration of opinions is a recog- 

 nised virtue. The curiosity of the present situation is 

 th^t opposite opinions have to be held and used bv 

 the same individual in the faith that some day their 

 combined truth may be made plain. 



The Natives of the Gilbert Islands. 



AT a meeting of the Royal Anthropological Institute 

 on April 21, Dr. W. H. K. Rivers, president, in 

 the chair, Mr. Arthur Grimble read a paper entitled 

 "From Birth to Death in the Gilbert Islands." The 

 paper, which was of considerable importance, as it 

 dealt with a people about which we possess little 

 information, described in detail the ceremonies used 

 at marriage, birth, and death by the Gilbertese- 

 speaking communities. 



The rules relating to consanguinity among the Gil- 

 bertese are genealogical in character, and evidently 

 allied to the Polynesian systems as typified by the 

 Samoan ; but the concubitant relations which exist 

 between a man and his wife's sisters are of a type 

 generally found in Melanesian communities. An 

 extremely interesting relationship is that of Ttnaba, 

 under which a woman owes both filial and sexual 

 duties to the brothers of her husband's father and a 

 man to his wife's mother's sister. Incest is regarded 

 with horror, and the hatred of the sun for incestuous 

 couples is much stressed in native myth. 



There were several forms of marriage ceremony in 

 vogue. On certain islands marriage by capture was 

 practised. Rather more common was the fishing 

 fiction, in which the suitors seated in a loft let down 

 lines into the room underneath, where the girl made 

 a pretence of being caught by one of them. This 

 act was succeeded by the anointing of the couple with 

 coco-nut oil, and the union was complete. The most 

 usual form of ceremony, however, was that known as 

 te rein, of which the essential motive was to test the 

 virginity of the bride. After birth mother and child 



NO. 2690, VOL. 107] 



remained for three days in the place of confinement, 

 while the infant's soul was encouraged into its body 

 by merrymaking, in which fire played an important 

 part. 



A boy's training was conducted with the view of 

 excluding all sexual interests. The cutting of his hair 

 from time to time was performed with rigid cere- 

 monial, until the climax was reached in the initiation 

 ceremonies (which were chiefly trials by fire) under- 

 gone when his pectoral and axillary hair was well in 

 evidence. After submitting to these ordeals he was 

 isolated until he passed certain tests of strength and 

 endurance. He would then be allowed to marry. 



A girl on reaching the age of puberty was isolated 

 in a darkened room for the purpose of bleaching her 

 skin and thus rendering her like the fair-skinned 

 ancestral gods of the race. On release from the 

 bleaching-house she was ready for marriage. 



Great precautions were taken at death to drive away 

 the soul. The body was usually buried on the fourth 

 day, sometimes on the tenth ; occasionally it was sun- 

 dried and kept for a number of years. The skull was 

 often kept. In the lagoon islands the body lay on its 

 back, fully extended, with toes pointing up ; on 

 Banaba the knees were flexed outwards in a frog-like 

 position. 



The paper closed with a summary of the beliefs con. 

 cerning the destination of the departed spirit and of 

 the possible inferences which may be drawn there- 

 from. The names of the various bournes of the dead 

 have an extraordinary resemblance to certain place- 

 names in Indonesia. 



