  Lema\^{i}tre-Tolman-Bondi (LTB) solutions have traditionally been confined to
systems with no pressure in which the gravity is due to massive dust, but the
solutions are little changed in form if, as in cosmology, the pressure is
uniform in space at each comoving time. This allows the equations of cosmology
to be deduced in a manner that more closely resembles classical mechanics. It
also gives some inhomogeneous solutions with growing condensations and black
holes. We give criteria by which the sizes of different closed models of the
universe can be compared and discuss conditions for self-closure of
inhomogeneous cosmologies with a $\Lambda$-term.
