  It is shown that the physical states of a source free gauge field form
pre-Hilbert spaces already on the classical level. These spaces may be closed
in such a way that the determining characteristics remain. One type of free
fields has a continuous mass spectrum with no mass gap. One type is massless.
Dark matter may consist of (otherwise) free gauge fields. Second quantisation
of free gauge fields yield G{\aa}rding-Wightman fields identifying the massless
and the massive fields as different manifestations of the same field.
