The high Galactic latitude molecular clouds are generally not located
 near intense sources of far-ultraviolet (FUV) radiation.  Most of these
 objects are translucent clouds: that is, the densities and temperatures
 measured for the cores are typical of diffuse clouds.  Because of the
 former property, molecules are able to form in abundance in translucent
 clouds.  However, since the visual extinction is low (Av < 2 typically),
 the ambient radiation field plays an important role in their chemistry.
 In the cores of translucent clouds the visual extinction is such that
 H2 -> HI and CII -> C -> CO photochemistry is occuring.  These objects
 make ideal laboratories for testing chemical models of regions with low
 FUV field intensities.  However, few observations have been made toward
 intermediate-density molecular clouds with no enhanced FUV flux.
 Observations of a variety of atomic and molecular species can provide
 important constraints for interstellar chemistry. In particular,
 for cloud complexes which are both nearby AND have accurately known
 distances, a multi-species observational program can provide quite
 detailed information about the physical state of the gas. In addition
 to parameters like volume number density and kinetic temperature, an
 accurate measurement of the cooling rate of the gas can be measured.
 Missing from, and vital to, any complete characterization of the
 physical state of the atomic and molecular interstellar medium of these
 objects are direct measurements of ionized carbon.  ISO LWS observations
 of [CII] will be used in conjunction with existing [CI], CO, and HI
 data to study the gas properties of atomic/molecular cores identified
 in a sample of nearby (d<200 pc) high galactic latitude translucent
 molecular clouds. ISO measurements of [CII] emission from a sample of
 translucent clouds with optically determined distances should give the
 cooling rate as a function of density and Av.  They can also provide
 important constraints on models for photodissociation regions (PDRs)
 in translucent clouds near weak FUV radiation fields.