ABSTRACT
In his famous book on the principles of quantum mechanics Dirac2 formulates (in §26) the following proposition: “. . . for a quantum dynamical system that has a classical analogue, unitary transformations in the quantum theory are the analogue of contact transformations in the classical theory.” No detailed description of this analogy is, however, given in Dirac’s book. In the following we intend to investigate this analogy in more detail.
