| Abstract
| - Further optical and UV spectral data are presented for four stars in the direction of the Riegel & Crutcher cold cloud. Two of the stars lie close in position to the area covered by our previous optical, UV and radio studies near l = 10°, while the other two stars lie near l = 15°. The stars range in distance from about 140 pc to 1.5 kpc. The RC cold cloud gas is detected (at a velocity of ∼ + 3 km s−1) towards a star at a distance of about 150 pc, in agreement with previous cloud distance estimates. The spectra of the more distant stars contain components at higher velocities; components at +20 and + 40 km s−1 may be identified with peculiar-velocity gas associated with the Sagittarius arm, seen elsewhere in the general field, while a component at − 60 km s−1 may be stellar or interstellar in nature. A component at − 20km s−1 seen towards previously studied stars in the field is not clearly identified in the spectra of the present stars. The atomic column densities of the Riegel & Crutcher cloud component do not vary greatly across the field, although the CH and CH+ column densities are more variable. The CH/CH+ column density ratio remains fairly constant, however, at a value that is consistent with the CH+ being formed in a warm boundary layer. Along the HD 167264 sightline, the cold gas has an electron density of the order of 0.05-0.1 cm−3 and a space density of the order of 100-300 cm−3.
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