  We briefly recall a fundamental exterior differential system introduced by
the author and then apply it to the case of three dimensions. Here we find new
global tensors and intrinsic invariants of oriented Riemaniann 3-manifolds. The
system leads to a remarkable Weingarten type equation for surfaces on
hyperbolic 3-space. An independent proof for low dimensions of the structural
equations gives new insight on the intrinsic exterior differential system.
