We present GHRS observations of interstellar C I and CO toward three stars
located in the direction of the Perseus region near the B5 molecular cloud
and discuss these together with published results from a fourth sight line.
The column densities of the three fine-structure levels of C I are used to
gether with ground-based optical data and published ultraviolet data to yie
ld several properties of the gas along the stellar sight lines. The selecte
d stars probe gas located in the neutral envelope surrounding the dense mol
ecular cloud. The gas pressure is tightly constrained by our observations,
yielding a value of approximate to 2200 K cm(-3) in the vicinity of B5, som
ewhat higher than in the surrounding interstellar medium. We also present e
stimates of the kinetic temperature, based on observations of H-2 and C-2,
yielding 20-60 K in the vicinity of B5. Together with the pressure determin
ation, this implies a local gas density of 35-100 cm(-3), very close to tha
t which would be implied by the observed H-2 column density assuming a fill
ing factor of unity. This result provides additional support to the notion
that the gas is part of an extensive, uniform gaseous halo surrounding the
B5 cloud. The combination of temperature and pressure suggests that the dif
fuse gas may be part of a general outflow from the dense molecular cloud.