  We review the nature of glass transitions and the glasses arising from a
square-well potential with a narrow and deep well. Our discussion is based on
the Mode Coupling Theory, and the predictions of glasses that we make refer to
the `ideal' glasses predicted by that theory. We believe that the square well
system well represents colloidal particles with attractive interactions
produced by grafted polymers, or depletion interactions. It has been recently
shown that two types of glass, an attractive and a repulsive one, are predicted
by MCT for this model. The former can form at quite low densities. Most of our
attention is directed at the mechanical properties of the glasses predicted by
this theory. In particular we calculate the elastic shear modulus at zero
frequency and the longitudinal stress modulus in the long wavelength limit.
Results for both are presented along the glass-liquid transition curves, and
their interesting behaviour is explained in terms of the underlying physics of
the system.
