  We use Hubble Space Telescope/Space Telescope Imaging Spectrograph (HST/STIS)
longslit low-resolution spectroscopy from 1150A to 10,300A to study the
physical conditions in the narrow-line region (NLR) of the Seyfert 2 galaxy
Markarian 3. We find from the HeII 1640/4686 line ratio and the Balmer
decrement that the extinction within Markarian 3 along the line-of-sight to the
NLR is best characterized by a Large Magellanic Cloud (LMC) type extinction
curve. We observe an extinction gradient increasing from west to east along the
STIS slit in both line and continuum emission. We infer from this gradient that
the host galaxy disk is tilted towards the observer in the east: the
line-of-sight to the eastern emission-line cone intersects more dust in the
plane of the galaxy than that to the western cone. We model the observed
continuum as a combination of reddened host galaxy light from an old stellar
population, reddened H+ and He++ recombination continua, and less reddened
scattered light from the central engine with spectral index alpha=1 (L(nu)
proportional to nu^(-alpha)). The host galaxy to scattered-light ratio is
estimated to be 3:1 at 8125 A in 0.1 X 1.8 square-arcsecond aperture. We
estimate that the amount of intrinsic non-ionizing UV continuum scattered into
our line-of-sight is 0.04%. This is consistent with our estimate of the
scattering fraction for broad CIV 1548,1551 emission.
