Oblique projections of Fig. 6 as seen from a standpoint in the north-eastern and nearer-side to the Sun. Left and right panels show projections rotated by |$30^{\circ }$| around X and |$50^{\circ }$| and |$40^{\circ }$| deg around the Z-axis. So, the two panels are seen from two directions by |$10^{\circ }$| rotated from each other, so that they can be used to obtain a stereo-graphic view of the gas distribution. Magenta dots represent a ring in the galactic plane of radius 120 pc representing the GC Arm I.