  We construct geometrically a gerbe assigned to a connection on a principal
SU(2)-bundle over an oriented closed 1-dimensional manifold. If the connection
is given by the restriction of a connection on a bundle over a compact
2-manifold bounding the 1-manifold, then we have a natural object in the gerbe.
The gerbes and the objects satisfy certain fundamental properties, e.g. gluing
law.
