We observed the Galactic [C II] line emission with BICE (the
Balloon-borne Infrared Carbon Explorer). Combining our [C II] data with CO
data, we revealed the Galactic arm-interarm contrast in the [C II] to CO
emissivity ratios,  which measure star-formation efficiency, under the
assumption that the emissivities  in our Galaxy distribute axis-symmetrically
for the Galactic center.
However, the results depend on this assumption, which is necessary
for deriving the emissivities from the edge-on view of our Galaxy; this  edge-
on view prevents us from observing separately the arm and the interarm
components. In order to resolve these two components without the assumption of
galactic arm structure, we propose to observe a face-on spiral galaxy in [C
II] 158 micron line with the ISO LWS. We will reveal the galactic arm-interarm
contrast in [C II] intensity and in star-formation efficiency in the face-on
spiral. For this purpose, we choose NGC300, which is near our Galaxy (1.2 Mpc)
and whose arm structure can be resolved with the LWS resolution (approximately
80 arcseconds).
Combining the present proposal with the previously accepted proposals
(OBSID KMOCHIZU, PROPIDs M31 and M33) and with the BICE observations (our
Galaxy), we can achieve the program revealing far-infrared structure of nearby
galaxies with  ISO and BICE. This makes the present proposal appropriate to be
submitted for the Supplemental Call.