We present 21 cm line observations of two galactic cirrus clouds, the
Polaris Flare and LVC 127, and compare the H I emission with that of C
O and with emission in the IRAS bands at 100 mu m and 60 mu m. The 100
mu m emission per hydrogen nucleus is constant outside, but lower ins
ide the CO emitting volume. We also find an infrared excess emission o
ver and above what can be related to HI or CO emission. We conclude th
at apart from the diffuse atomic hydrogen and the denser molecular hyd
rogen traced by CO emission, there is a third gas component of diffuse
molecular hydrogen. In places the diffuse H-2 has a column density ri
valling that of H I. In general it does not contain a denser CO emitti
ng interior. The fact that the diffuse H-2 is not traced by CO emissio
n is due to the lower gas density, either because CO is not collisiona
lly excited, or because the H-2 is not effective enough in shielding C
O molecules from photodissociation. We find a conversion factor X betw
een CO line integral and H-2 column density similar to other values fr
om cirrus clouds, but lower than values for galactic plane clouds deri
ved from gamma ray studies. If we account for the lower 100 mu m emiss
ion per hydrogen in the CO emitting volume, the difference is reduced,
and our X may be consistent with the lower values found in a recent g
amma ray study.