  We present moderate resolution spectroscopy of extraplanar diffuse ionized
gas (EDIG) emission in the edge-on spiral galaxy NGC 4302. The spectra were
obtained with the SparsePak integral field unit (IFU) at the WIYN Observatory.
The spectra are used to construct position-velocity (PV) diagrams at several
ranges of heights above the midplane. Azimuthal velocities are directly
extracted from the PV diagrams using the envelope tracing method, and indicate
an extremely steep dropoff in rotational velocity with increasing height, with
magnitude ~30 km/s/kpc. We find evidence for a radial variation in the velocity
gradient on the receding side. We have also performed artificial observations
of galaxy models in an attempt to match the PV diagrams. The results of a
statistical analysis also favor a gradient of ~30 km/s/kpc. We compare these
results with an entirely ballistic model of disk-halo flow, and find a strong
dichotomy between the observed kinematics and those predicted by the model. The
disagreement is worse than we have found for other galaxies in previous
studies. The conclusions of this paper are compared to results from two other
galaxies, NGC 5775 and NGC 891. We find that the vertical gradient in rotation
speed, per unit EDIG scale height, for all three galaxies is consistent with a
constant magnitude (within the errors) of approximately 15-25 km/s/scaleheight,
independent of radius. This relationship is also true within the galaxy NGC
4302. We also discuss how the gradient depends on the distribution and
morphology of the EDIG and the star formation rates of the galaxies, and
consequences for the origin of the gas.
