We have found many consistent relationships between the grain and gas
phase diagnostics of the interstellar medium of the Cha I cloud. The
warmer interstellar material, based on the IRAS colour index R(60,100)
has more molecular CH, while CH
shows up toward sight lines at
cloud edges with enhanced values of R(12,100) and strong Ca II
absorption. The large column densities of CH and the high values of
N(CH)/
for the stars in our sample suggest a possible
additional production mechanism of CH which outpaces the
photodissociation of CH at cloud edges. The Ca II line profiles
toward Cha I show a consistent velocity structure, where a single
strong component at 
km s
is seen along all
sight lines. Several sight lines exhibit a weak component of Ca II at
km s
. Our observations suggest that the Ca II
absorption lines trace a single dense cloud and an additional warmer
cloudlet with a different velocity. The detections of the strongest
CH
absorptions appear in sight lines which have the additional
Ca II component, suggesting that a possible kinematic disruption of
the Cha I cloud plays an important role in CH
production.
Additionally, we observed that the polarization of the stars was less
efficient at higher extinctions with 
, which we
attribute to either more spherical dust grains or increased
de-alignment of the grains in the cores of the dense, high extinction
sight lines. The IR diagnostics of R(12,100) and R(60,100) were
consistent with our observations of polarization and molecular
absorption. We found a strong anticorrelation between R(12,100) and
the maximum percentage of polarization 
, suggesting that the
processes responsible for the production of the small grain population
with strong 
m emission is also responsible for disrupting the
alignment of the grains in the clouds.
A lack of correlation between R(12,100) and 
suggests
that if small grains are responsible for the enhanced values of
R(12,100), they are a population which is separate from those
responsible for most of the polarization of starlight. If the small
grains do arise from the larger grains of the Cha I sight lines as
Boulanger & Gry (1994) have suggested, they must evaporate or split
from the larger polarizing grains non-destructively in order to
maintain the size distributions which indicate large average grain
sizes.
Acknowledgments We wish to thank the European Southern Observatory for the allocation of time for this project. B.E.P. wishes to thank Pomona College for research grants which enabled trips to Europe to collect and analyze data. B.E.P. and E.P. would like to thank the Osservatorio Astronomico di Capodimonte for their hospitality. This research made use of the SIMBAD database, operated at CDS, Strasbourg, France.