  We study a class of generalized fifth order Korteweg-de Vries (KdV) equations
which are derivable from a Lagrangian L(p,m,n,l) which has variable powers of
the first and second derivatives of the field with powers given by the
parameters p,m,n,l. The resulting field equation has solitary wave solutions of
both the usual (non-compact) and compact variety ("compactons"). For the
particular case that p=m=n+l, the solitary wave solutions have compact support
and the feature that their width is independent of the amplitude. We discuss
the Hamiltonian structure of these theories and find that mass, momentum, and
energy are conserved. We find in general that these are not completely
integrable systems. Numerical simulations show that an arbitrary compact
initial wave packet whose width is wider than that of a compacton breaks up
into several compactons all having the same width. The scattering of two
compactons is almost elastic, with the left over wake eventually turning into
compacton-anticompacton pairs. When there are two different compacton solutions
for a single set of parameters the wider solution is stable, and this solution
is a minimum of the Hamiltonian.
