  We present excellent resolution and high sensitivity Very Large Array (VLA)
observations of the 21cm HI line emission from the face-on galaxy NGC 1058,
providing the first reliable study of the HI profile shapes throughout the
entire disk of an external galaxy. Our observations show an intriguing picture
of the interstellar medium; throughout this galaxy velocity-- dispersions range
between 4 to 15 km/sec but are not correlated with star formation, stars or the
gaseous spiral arms. The velocity dispersions decrease with radius, but this
global trend has a large scatter as there are several isolated, resolved
regions of high dispersion. The decline of star light with radius is much
steeper than that of the velocity dispersions or that of the energy in the gas
motions.
