  We present neutral hydrogen observations of the nearby edge-on spiral galaxy
NGC891 which show extended extra-planar emission up to distances of 15 kpc from
the plane. 3D modeling of the galaxy shows that this emission comes from halo
gas rotating more slowly than the gas in the disk.We derive the rotation curves
of the gas above the plane and find a gradient in rotation velocity of -15
km/s/kpc. We also present preliminary results of a galactic fountain model
applied to NGC891.
