Observations of the outer spiral structure of the Milky Way andits relation to the high velocity clouds
New observations have been made of the neutral hydrogen emission from the outer spiral structure of the Milky Way. A number of new arms with densities about I per cent of the well-known spiral arms have been discovered at distances of 15-20 kpc from the galactic centre. The bands of high velocity clouds (HVCs) appear to fan upwards from these outermost spiral arms in a trailing sense. It is suggested that the tilt in the galactic plane and the asymmetrical distribution of the HVCs is produced by a close passage of the Large Magellanic Cloud. A few HVCs having velocities incompatible with galactic rotation are also believed to be a consequence of this interaction.