  We introduce a new quantity to probe the glass transition. This quantity is a
linear generalized compressibility which depends solely on the positions of the
particles. We have performed a molecular dynamics simulation on a glass forming
liquid consisting of a two component mixture of soft spheres in three
dimensions. As the temperature is lowered, the generalized compressibility
drops sharply at the glass transition. Our results are consistent with the
kinetic view of the glass transition, but not with an underlying second order
phase transition.
