  The XA region of the Cygnus Loop is a complex zone of radiative and
nonradiative shocks interacting with interstellar clouds. We combine five far
ultraviolet spectral observations from the Hopkins Ultraviolet Telescope (HUT),
a grid of 24 IUE spectra and a high-resolution longslit Halpha spectrum to
study the spatial emission line variations across the region. These spectral
data are placed in context using ground-based, optical emission line images of
the region and a far-UV image obtained by the Ultraviolet Imaging Telescope
(UIT). The presence of high-ionization ions (OVI, NV, CIV) indicates a shock
velocity near 170 km/s while other diagnostics indicate v_shock=140 km/s. It is
likely that a large range of shock velocities may exist at a spatial scale
smaller than we are able to resolve. By comparing CIV 1550, CIII 977 and CIII]
1909, we explore resonance scattering across the region. We find that a
significant column depth is present at all positions, including those not near
bright optical/UV filaments. Analysis of the OVI doublet ratio suggests an
average optical depth of about unity in that ion while flux measurements of
[SiVIII] 1443 suggest a hot component in the region at just below 10^6K. Given
the brightness of the OVI emission and the age of the interaction, we rule out
the mixing layer interpretation of the UV emission. Furthermore, we formulate a
picture of the XA region as the encounter of the blast wave with a finger of
dense gas protruding inward from the pre-SN cavity.
