  We describe far infrared observations of early-type galaxies selected from
the ISO archive. This rather inhomogeneous sample includes 39 giant elliptical
galaxies and 14 S0 (or later) galaxies. These galaxies were observed using a
variety of different observing modes, each of which requires different and
often rather elaborate photometric reduction procedures. The ISO background
data agrees well with COBE-DIRBE results to which we have renormalized our
calibrations. As a further check, the ISO fluxes from galaxies at 60 and 100
microns agree very well with those previously observed with IRAS at these
wavelengths. The spatial resolution of ISO is several times greater than that
of IRAS and the ISO observations extend out to 200 microns which views a
significantly greater mass of colder dust not assessable to IRAS. Most of the
galaxies are essentially point sources at ISO resolution, but a few are clearly
extended at FIR wavelengths with image sizes that increase with FIR wavelength.
The integrated far infrared luminosities do not correlate with optical
luminosities, suggesting that the dust may have an external, merger-related
origin. In general the far infrared spectral energy distributions can be
modeled with dust at two temperatures, ~ 43 K and ~ 20 K, which probably
represent limits of a continuous range of temperatures. The colder dust
component dominates the total mass of dust, which is typically more than ten
times larger than the dust masses previously estimated for the same galaxies
using IRAS observations. For S0 galaxies we find that the optically normalized
far-infrared luminosity $L_{FIR} / L_B$ correlates strongly with the
mid-infrared luminosity $L_{15\mu\rm{m}} / L_B$, but that correlation is weaker
for elliptical galaxies.
