  An intriguingly natural generalization, using complex octonions, of general
relativity is pointed out. The starting point is the vierbein-based double dual
formulation of the Einstein-Hilbert action. In terms of two natural structures
on the (complex) quaternions and (complex) octonions, the inner product and the
cross products, respectively, this action is linked with the complex
quaternionic structure constants, and subsequently generalized to an
achtbein-based 'double chi-dual' action in terms of the complex octonionic
structure constants.
