  We have carried out a statistical study of the average orientation of the
magnetic field in solar filaments with respect to their axes for more than 400
samples, based on data taken with daily full-Sun, full-Stokes
spectropolarimetric observations using the He I 1083.0 nm line. The major part
of the samples are the filaments in the quiet areas, but those in the active
areas are included as well. The average orientation of the magnetic field in
filaments shows a systematic property depending on the hemisphere; the
direction of the magnetic field in filaments in the northern (southern)
hemisphere mostly deviates clockwise (counterclockwise) from their axes, which
run along the magnetic polarity inversion line. The deviation angles of the
magnetic field from the axes, are concentrated between 10--30 deg. This
hemispheric pattern is consistent with that revealed for chirality of filament
barbs, filament channels and for other solar features found to possess
chirality. For some filaments it was confirmed that their magnetic field
direction is locally parallel to their structure seen in Halpha images. Our
results for the first time confirmed this hemispheric pattern with the direct
observation of the magnetic field in filaments. Interestingly, the filaments
which show the opposite magnetic field deviation to the hemispheric pattern,
are in many cases found above the polarity inversion line whose ambient
photospheric magnetic field has the polarity alignment being opposite to that
of active regions following the Hale-Nicholson law.
