  We discuss the higher dimensional generalization of gravitational instantons
by using volume-preserving vector fields. We give special attention to the case
of 8-dimensions and present a new construction of the Ricci flat metric with
holonomy in Spin(7). An example of the metric is explicitly given. Further it
is shown that our formulation has a natural interpretation in the Chern-Simons
theory written by the language of superconnections.
