Let E be a barrelled space with dual F # E* . It is shown that F has uncountable codimension in E* . If M is a vector subspace of E* of countable dimension with M n F = {o} , the topology x(E, F+M) is called a countable enlargement of f{E, F) . The results of the two previous papers are extended: it is proved that a non-barrelled countable enlargement always exists, and sufficient conditions for the existence of a barrelled countable enlargement are established, to include cases where the bounded sets may all be finite dimensional. An example of this case is given, derived from Amemiya and Komura; some specific and general classes of spaces containing a dense barrelled vector subspace of codimension greater than or equal to a are discussed.
Completeness, codimension in E* and non-barrelled countable enlargementsWe use the notation and terminology of [7]