  We study the relative Hilbert scheme of a family of nodal (or smooth) curves,
over a base of arbitrary dimension, via its (birational) cycle map, going to
the relative symmetric product. We show the cycle map is the blowing up of the
discriminant locus, which consists of cycles with multiple points. We determine
the relevant cotangent sheaves and complexes. We determine the structure of
certain projective bundles called node scrolls, which play an important role in
the geometry of Hilbert schemes.
