AUGUST 11, 1934 NATURE 215 28 A hollow quartz cylinder possesses, m general, the nucleus forming 14Si (7at), with the emission of three fundamental frequencies. Two of them, high energy y-radiation. Or it may emit a neutron 27 independent of the length of cylinder, are of ordinary leaving 2He• within the new nucleus uSi (6at +D+p) piezo-electric character and correspond respectively and this 'radiosilicon' containing a 'free' nuclear to radial (along the wall thickness) and circular (along protona emits positive electrons transmuting to 27 the wall circumference) vibrations of the hollow uAl • 31 cylinder. These modes of vibration are clearly shown Similarly the emission of 14Si results in the by marking out the actual piezo-electric axes by formation of a diplon within the nucleus, mass defect discharge points in glow pattern or under examina­ energy 5 x 106 e.v. being released. This may be tion with polarised light. The third frequency is emitted in the form of y-radiation when the stable 31 probably of torsional oscillation. Further details will 16P is formed, or the loosely bound neutron may be published shortly elsewhere. be emitted immediately carrying the excess energy. 30 NY Tsi-ZE. As a result, 'radiophosphorus' 11P is formed which 30 TSIEN LING-CHAO, spontaneously emits positrons transmuting to 14Si , Institute of Physics, Thus, on the view of nuclear structure adopted, National Academy of Peiping, the y-radiation of high energy, the neutron and the Peiping, China. positron emission all result from the radio­ March 28. activity of the unstable nuclei produced. It is to be 1 A. Hund and R. B. Wright, J. Res., Bureau of Standards, 4, 383; noticed that spontaneous emission of protons is 28 1930. Proc. Imt. Radio Eng"A 18, 741; 1930. possible from 13Al • 'Ny Tsi-Ze et Tslen Ling-uhao, O.B., 198, 1395; 1934. H. J. WALKE. Department of Physics, Washington Singer Laboratories, Spontaneous Emission of Neutrons from University College, Exeter. 1 Fermi, Ricerca ScwntiJi,ca, 1, 283, 330 ; 1984. Radioactive Isotopes ' Curle, Joliot and Preiswerk, O.R., 198, 2089 ; 1934. IN confirming the pioneer work of Fermi1 on radio­ 1 Goldhaber, NATURE, 134, 25, July 7, 1934. ' Walke, Phil. Mag., 17, 793 ; 1934. activity induced by neutron bombardment, Curie, 6 Walke, Phil. Mag., 18, 129; 1934. Joliot and Preiswerk• have shown that the radio­ 1 Newman and Walke, 134, 64, July 14, 1934. 'Walke, Phil. Mag., 17, 1176; 1934. active isotopes produced when phosphorus and • Oliphant, Harteek and Rutherford, NATURE, 133, 481, Mar. 31, magnesium are bombarded by neutrons emit : 1934. 'Walke, Phil. Mag., 18, 154 ; 1934. (1) negative electrons, (2) high energy y-radiation (,._. 5 X 106 e.v.), (3) positrons (which they tenta­ tively ascribe to pair formation, this explanation being very doubtful as the high en ergy limit of these The Sycamore Maple in A.D. 1300 electrons was ,._. 1·0 X 108 e.v.), ( 4) neutrons. The IN his description of the carvings of the sycamore 31 28 neutron emission they ascribe to 14Si and 18Al , on the shrine of St. Frideswyde in the Oxford unstable isotopes produced by the initial neutron Cathedral, Dr. Burtt Davy1 gives a list of ten species bombardment. of plants that were in all probability growing in or Goldhaber• has shown, however, that these neutrons near Oxford about A.D. 1300, when the shrine was must get into a state of positive energy by some being carved. It is only fair to note that the remark­ primary radioactive process and then be immediately able truth to Nature of the carvings of the fruits emitted. It is the purpose of this note to support and leaves of this tree, and of the nine other species Goldhaber's suggestion and to indicate that the of plants mentioned by Dr. Davy, had already been results observed arise from the radioactivity recognised by Mr. S. A. Warner, with the addition of the two isotopes mentioned. of two more, the water crowfoot, Ranunculus aquatilis, It has been shown'.•, from considering the nuclear and the hogweed, H eracleum sphondylium, to the disintegration experiments which have been per­ list which, with three illustrations, is printed in my formed. that the stable nuclei of the light elements "Early Science in Oxford", vol. 3, p. 198. of even atomic number consist of the maximum R. T. GuNTHER. number of at-particles and neutrons, those of odd The Old Ashmolean, atomic number consisting of the maximum number Oxford. of at-particles, a diplon and a loosely bound neutron. July 14. It has also been shown' that isotopes of the light 1 NATURE, 134, 61, July 14, 1934. elements of even atomic number containing three neutrons and those of the elements of odd atomic number containing a diplon and two neutrons, are THE three illustrations referred to by Dr. Gunther radioactive. In addition it has been demon­ do not include Acer pseudoplatanus, nor do his pub­ strated' that results from the forma­ lished notes make any reference to the fact that the tion of electron pairs within the nucleus with the carving is the earliest known record of the occurrence production of a proton as the positron is captured of the sycamore maple in Britain, antedating previous by a neutron, the negative electron being emitted records by a quarter of a century. I did not mention to form the disintegrating the hogweed and water crowfoot, as their identifica­ 28 Applying these views, the [j-radioactivity of 13Al tion seemed less certain than that of the other species. (6at + D + 2n) results in the formation of a new I owe Dr. Gunther an apology for not having at-particle in the nucleus by the union of the diplon m entioned the notes and reproductions referred to, and the new diplon formed when the positron of the which-! regret to say-1 had not seen. pair unites with the neutrons. This at-particle is J. BURTT DAVY. formed in a state of excess energy as shown by Imperial Forestry Institute, Oliphant, Harteck and Rutherford•. It may then Oxford. transfer to the normal state and be bound within July 21. © 1934 Nature Publishing Group.