AS early as it as of was ft physicists decay, already suggested by several different groups of physicists that the different weak processes such as ß decay, μ decay, and  μ capture may be characterized by a single universal form of interaction. However, at that time because of the lack of detailed and accurate knowledge of these reactions it was difficult to subject this attractive idea to quantitative tests.

Since the establishment of nonconservation of parity, the discovery that in a decay process the neutrino carries away not only energy and momentum but also a definite (longitudinal) angular momentum gives a new possibility of investigating the dynamics of weak interactions by measuring angular momenta. These new measurements on angular momenta together with other already existing experiments lead now to a much simpler phenomenological description of the weak interactions. 41 Indeed, it was found 42 quantitatively that a certain coupling constant in the beta decay appears to be exactly the same as that which occurs in the ju, decay in spite of the difference that nucleons have strong interactions but juT and e ± have only electromagnetic and weak interactions. Such identity and other universal characters of these interactions may lead to a deeper and unifying principle underlying all different weak reactions.

It was realized in the 192O's that by analyzing the energy spectrum of the electron in beta decay there was an apparent nonconservation of energy. Pauli 10 resolved this difficulty by postulating the existence of a neutral particle with spin = \ h and zero (or very small) mass. Subsequently, Fermi l l developed the theory of beta decay. This neutral particle was called the neutrino v and its antiparticle the antineutrino.

Further experimental confirmations of this particle came later from the measurement of the recoil of the final nucleus, from the capture experiment of the antineutrinos and from the over-all verifications of Fermi's beta-decay theory.

The conference opened with a reception and dinner given by the Weizmann Institute and the Municipality of Rehovoth, at which the Israel Prime Minister Mr. David Ben Gurion welcomed the participants on behalf of the Government of Israel. Prof. G. Racah was in the chair and the Chairman of the Institute's Executive Council, Mr. Meyer W. Weisgal, joined in the welcome to the delegates. The sessions began the following morning and lasted from 9:15 A.M. to 6:00 P.M. for four full days, with an additional evening session on the first day. These were held at the Weizmann Institute in the Michael and Anna Wix Auditorium. Coffee and tea were conveniently served in the auditorium lobby during the short breaks in the sessions, and lunch was obtained at the cafeteria in the Faculty Club Building. The air conditioning in both the auditorium and the faculty club gave welcome relief from the warm Israel September weather, although a number of participants, particularly those from northern Europe, expressed their pleasure at being in a place where the sun shone all the time. Every evening cocktails were served informally at the pleasant seaside hotel where most of the participants were staying, the Sharon Hotel near Tel Aviv. Discussions continued until all hours, after which some of the more energetic scientists took a midnight swim in the Mediterranean from the beach just outside the hotel. Evening entertainment possibilities also included performances by theater and dance groups in nearby Tel Aviv. In the middle of the conference, the Hebrew University invited the delegates to a tour of Jerusalem, ending with a reception given by the President of Israel, Mr. I. Ben Zvi. The last session was followed by a garden party given by Mr. Weisgal at his home in the Institute compound. The following day there was a sightseeing excursion to the region just south of Rehovoth including the town of Ashkelon with its ruins and antiquities from the times of the Philistines, Romans, and Crusaders, and also a border collective settlement overlooking the Gaza Strip. In the evening the conference was officially closed at the Conference Dinner with Professor Pauli as toastmaster.

THE two parity sessions were considerably less turbulent than had been expected a few weeks before, when different laboratories had obtained contradictory results for parity experiments, particularly the measurement of beta-ray polarization. The parity experimentalists succeeded in settling their differences among themselves just before the conference and presented a "united front", to the great disappointment of certain theorists who had hoped to see a big scrap. It was now admitted by all concerned that all reliable results obtained thus far for beta-ray polarization were consistent with full polarization in all cases, left-handed for negatons and right-handed for positons. Only the recoil experiments measuring electron-neutrino angular correla-tion still presented a confused picture of mutually inconsistent experimental results.

These sessions began with a series of lectures presenting an excellent survey of the present state of beta decay. E. J. Konopinski presented a summary of the conclusions regarding the nature of the beta-decay interaction which were obtainable from "classical" (before parity) experiments. He stressed the revisions necessary in these conclusions in view of the nonconservation of parity, particularly those drawn from the absence of Fierz interference. The weakening of these conclusions left accurate recoil experiments as the only method for determining the beta interaction. T. D. Lee then presented the theoretical aspects of parity nonconservation in beta decay, treating a four-component neutrino, introducing the concept of helicity, and pointing out the simplifications possible if lepton conservation and twocomponent theory were valid. C. S. Wu presented the experimental aspects of parity conservation, including a description of the different types of new parity experiments and a summary of the present state of experimental data.

The session concluded with report on the recent controversial recoil experiments by Allen et al. on A³⁵ (presented by H. Frauenfelder) and Ridley et al. on Ne²³ (presented by P. E. Cavanagh), after which Chairman 0. Kofoed-Hansen concluded that since it had taken two years of careful work in these difficult recoil experiments to reach the present confused state, it would probably take another two years to clear it up.

Dr. Allen's treatment retains the physics of the many aspects of beta decay; the shape of the continuous spectrum (especially near its end point), angular correlations in the three-body breakup, double beta decay, decay of polarized nuclei, meson decay, helicity experiments, the nature of the basic interactions, and the universal Fermi interaction all receive discussion.

There is sufficient theory to give unity and a feeling for the objectives sought by all of the investigations, but the text is at its best when it deals with the experiments. As one reads successively about the various measurements that have informed us about the neutrino, one cannot avoid being struck by the ingenuity that has been shown. The account is in a way an incidental history of the development of laboratory skills, exemplified in the progressively increasing specificity of the experiments.

The latter have been notoriously difficult, for sundry reasons: the measurements of the upper end of the tritium spectrum were difficult because of the low energy of the particles and the fact that they vanish in intensity in the region of interest, and yet they have told us that the rest mass is less than a thousandth of that of an electron; the experiments on nuclear recoil from electron capture have been difficult because of the low energy of the recoils, with the consequence that "vacuum" sources have to be used, and yet they have been forced to such detail as a revelation of the recoil line shapes; the experiments on beta particle-recoil nucleus angular correlations have been difficult for similar reasons, and yet they have informed us about the nature of the basic interactions; the experiments on double beta decay have been difficult because of the tantalizing infrequency of the events; the radiochemical experiments have demanded the application of the finest of technique, sometimes almost on a chemical engineering scale; and (most of all) the experiments on the detection of the free neutrino have been difficult because they demanded the measurement of interaction cross sections about 10 12 times smaller than those that had previously been considered small.

It is therefore fitting that the emphasis be experimental, as it is also fitting that the story be told by one who has contributed substantially to it.

A major seat of pure research is the Weizmann Institute of Science, located in Rehovoth, 15 miles from Tel-Aviv. No formal teaching is done here and one is reminded immediately of the Princeton Institute for Advanced Study. The obvious difference is that the Weizmann Institute is for research in the natural sci- ences only (including applied mathematics). As with the preceding institutions the setting is new and beauti- ful—and physics again finds itself in a building honoring the name of Albert Einstein. The Weizmann Institute seems truly a scientist's heaven, with no students to contend with and apparently little or no politicking to distract one. The only difficulty which may exist is social isolation of members of the Institute community, who live significantly far from Tel-Aviv. The Weizmann Institute has some fairly large and elaborate research equipment, including a heavy-water plant, a 3-Mev Van de Graaff generator, a 30-ft-long vacuum Ebert spectrometer, and doubtless much more that I didn't see in my brief visit. The high-resolution Ebert is used in near infrared studies of dispersion in gases and liquids. Nuclear resonance research is in progress on chemical kinetics, solid-state electronics work is on ferrites, magnetism, and applied electronics. Nuclear physics research includes theoretical work on the shell model and experimental work with the Van de Graaff, cosmic rays (plates), and the beta-ray spectrometer.