  We show that there is a restriction, or modification of the finite-variable
fragments of First Order Logic in which a weak form of Craig's Interpolation
Theorem holds, but a strong form of this theorem does not hold. Translating
these results into Algebraic Logic we obtain a finitely axiomatizable
subvariety of finite dimensional Representable Cylindric Algebras that has the
Strong Amalgamation Property, but does not have the Superamalgamation Property.
This settles a conjecture of Pigozzi
