This is a method for the generic function rescale.  The spatial coordinates in the window X
  (and its window) will be re-expressed
  in terms of a new unit of length that is s times the current
  unit of length given in X.
  (Thus, the coordinate values are divided by s,
  while the unit value is multiplied by s).
  The result is a window representing the same region of space,
  but re-expressed in a different unit.