The most valuable new information on galactic magnetic fields is derived from the study of Faraday effects in extragalactic radio sources and pulsars. The rotation of the plane of polarization of an electromagnetic wave with a wavelength of 1 m – the so called Rotation Measure RM – which traverses a medium with electron density ne (cm−3) and magnetic field intensity H (in μG) is given by where dl is the element of length along the line of sight expressed in pc. In the case of the pulsars, the delayed arrival of the pulses at the longer wavelengths immediately yields the integrated electron density along the line of sight, that is

A model of a quasi-steady circulation of gas near the galactic center is considered to explain the outward motion of the 3-kpc arm. A hydromagnetic wind from the galactic nucleus reaches the 3-kpc arm, where a shock is formed; then the gas moves out of the plane and eventually returns to the nucleus. The secular behavior of the model is discussed.

A circular arm with elliptical cross-section is used as a model of the spiral arm. It is demonstrated magnetohydrodynamically that interstellar gas may flow in a helical path along the axis of the arm and interstellar helical magnetic lines of force can spiral around it. It is pointed out that though the rolling motions of gas do not always indicate the existence of the helical magnetic field, the latter cannot be in a stationary state without the former. Some observational supports to the present model are given.

No paper was submitted.

The polarization data of 1421 southern OB-stars of the Heidelberg catalogue have been measured and plotted in a galactic lII, bII-diagram. For some longitude intervals the relationship of the standard deviation of the electric vector alignment and the galactic longitude was computed.

Some observable features of our Galaxy are explained in terms of a theory of the origin of spiral structure, whose basic feature is a gradually contracting gaseous subsystem with a magnetic dipole of which the axis is very close to the galactic plane.

Our Symposium has truly been held in the spirit of IAU Commission 33. This Commission has traditionally provided the opportunity for optical and radio astronomers to meet with theorists interested in the dynamics of stellar systems. Our good relations with Commission 34 assure us that in our deliberations we shall not lose sight of the physical implications of our theoretical and observational developments. The past and present Presidents of Commission 33 are proud of the fact that they – and their Organizing Committees – took the initiative for holding this Symposium in Basel. We need not hide the fact that the plan to go to Basel came because many of us wished to honor Wilhelm Becker and his associates for the beautiful and basic researches they have done relating to the spiral structure of our Galaxy.