  The FUSE far-ultraviolet interstellar spectra toward seven targets in NGC
6231 show that the molecules H_2, HD, and CO as well as various atomic species
are distributed in several clouds. The main absorption component found on the
sight lines lies in the Lupus cloud region at a distance of about 150 pc, and
there is a weaker second one, presumably in the Sco OB1 shell surrounding NGC
6231 (d~1.8 kpc). H_2 excitation modelling is used to constrain the radiation
field and the density in the gas; HD is used to estimate the abundance of H+.
The small angular separation of the target stars allows column density
variations to be probed over the field of view, on scales of 0.05 pc in the
case of the Lupus cloud distance. They are 40% for H_2 and 60% for H I. A
rather strong radiation field inside the molecular clouds suggests a separation
of the gas into smaller cloudlets also along the line of sight.
