  We probe in some depth into the structure of eleven-dimensional,
osp(32|1)-based Chern-Simons supergravity, as put forward by Troncoso and
Zanelli (TZ) in 1997. We find that the TZ Lagrangian may be cast as a
polynomial in 1/l, where l is a length, and compute explicitly the first three
dominant terms. The term proportional to 1/l^9 turns out to be essentially the
Lagrangian of the standard 1978 supergravity theory of Cremmer, Julia and
Scherk, thus establishing a previously unknown relation between the two
theories. The computation is nontrivial because, when written in a sufficiently
explicit way, the TZ Lagrangian has roughly one thousand non-explicitly
Lorentz-covariant terms. Specially designed algebraic techniques are used to
accomplish the results.
