  Cross-correlation of the DIRBE 100 micron survey with previously published
H-alpha maps tests correlations between far-infrared dust and the warm ionized
interstellar medium in different regions of the sky. A 10 x 12 deg patch at
Galactic latitude b = -21 shows a correlation slope a_0 = 0.85 +/- 0.44
Rayleighs / MJy sr significant at 97% confidence. A set of H-alpha images over
the north celestial polar cap yields a weaker correlation slope a_0 = 0.34 +/-
0.33 Rayleighs / MJy sr. Combined with observations from microwave anisotropy
experiments, the data show roughly similar correlations on angular scales 0.7
deg to 90 deg. Microwave experiments may observe more emission per unit dust
emission than are traced by the same structures observed in H-alpha.
