  We derive the radio spectral index of the Barnard Loop (BL) from large-scale
radio surveys at four frequencies and find it to be a thermal source. We use
the radio data together with H-alpha data to determine the electron temperature
in BL, the lambda-Ori HII region, and a high-latitude filament; all of these
regions are somewhat cooler than typical HII regions.
  We perform least squares fits of the DIRBE diffuse IR intensities to the
21-cm line and radio continuum intensities. After the resolution of a
``geometrical conundrum'', this allows us to derive the electron density n_e;
we find n_e ~ 2.0 cm^{-3} and pressure (P/k) ~ 24000 cm^{-3} K.
  Grains within BL are warmer than in HI regions. Trapped L-alpha accounts for
the extra heating that is required. This is a general effect that needs to be
accounted for in all analyses that examine IR emission from H^+ regions. Very
small grains that emit 60 micron radiation are enhanced in BL relative to HI by
a factor of 2-3, while PAH's that emit 12 micron are probably deficient by a
factor ~2.
