  The 609u 3P1 -> 3P0 line of neutral atomic carbon has been detected in the
protoplanetary nebulae CRL 618 and CRL 2688. CI appears to be about 7% as
abundant as CO in CRL 2688, and 70% as abundant as CO in CRL 618. CI emission
arises primarily from the slow component of the wind from these objects. The
data presented here indicate that CI gradually becomes more abundant as the
star leaves the AGB, and CI is significantly enhanced relative to CO before the
star develops a large HII region.
