  We demonstrate that there are systematic scale errors in the [Fe/H] values
determined by the Hamburg/ESO Survey (and by the HK Survey by inference) for
certain extremely metal poor (EMP) highly C-enhanced giants. The consequences
of these scale errors are that a) the fraction of carbon stars at extremely low
metallicities has been substantially overestimated in several papers in the
recent literature b) the number of EMP stars known is somewhat lower than has
been quoted in the recent literature c) the yield for EMP stars by the HK and
the HES Survey is somewhat lower than is stated in the recent literature. A
preliminary estimate for the frequency of Carbon stars among the giants in the
HES sample with -4 < [Fe/H] < -2.0 dex is 7.4 \pm 2.9%, and for C-rich giants
with [C/Fe] > +1.0 dex is 14.4 \pm 4%.
  Here we present the key results of detailed abundance analyses of 14 C-stars
selected from the HES as candidate EMP stars, of ~50 such stars analyzed. About
80% of such C-stars show highly enhanced Ba as well, with C enhanced by a
factor of about 100, and [Ba/C] roughly Solar. These stars often show prominent
lead lines, The remaining 20% of the C-stars do not show an enhancemement of
the s-process neutron capture elements around the Ba peak. They tend to be the
most metal-poor stars studied. We suggest that all these EMP C-stars are the
remnants of the secondary in a mass transfer binary system where the former
primary was an AGB star, which transferred substantial mass at that
evolutionary stage. (published abstract will be shorter due to space
limitations)
