  We argue that the narrow line regions of Seyfert galaxies are powered by the
transport of energy and momentum by the radio-emitting jets and consequently
that the ratio of the radio power to jet energy flux is much smaller than is
usually assumed for radio galaxies. This can be partially attributed to the
smaller ages ($\sim 10^6 yrs$) of Seyferts compared to radio galaxies but one
also requires that either the magnetic energy density is more than an order of
magnitude below the equipartition value, or more likely, that the internal
energy densities of Seyfert jets are dominated by thermal plasma. If Seyfert
jets are initially dominated by relativistic plasma, then an analysis of the
data on jets in five Seyfert galaxies shows that all but one of these would
have mildly relativistic jet velocities near 100 pc in order to power the
respective narrow-line regions. However, observations of jet-cloud interactions
in the NLR provide additional information on jet velocities and composition via
the momentum budget. Our analysis of a jet-cloud interaction in NGC 1068,
implies a shocked jet pressure much larger than the minimum pressure of the
radio knot, a velocity $\sim 0.06 c$ and a jet temperature $\sim 10^9 K$
implying mildly relativistic electrons but thermal protons. The jet mass flux
at this point $\sim 0.5 M_\odot yr^{-1}$, is an order of magnitude higher than
the mass accretion rate into the black hole, strongly indicating entrainment.
The initial jet mass flux $\sim 0.02 M_\odot yr^{-1}$, comparable to the mass
accretion rate and is consistent with the densities inferred for accretion disc
coronae from high energy observations, together with an initially mildly
relativistic velocity and an initial jet radius of order 10 gravitational
radii.
