We observed 14 nearly face-on disk galaxies with the Arecibo 305 m tel
escope and found the double-horned H I profiles to have high-velocity
wings in 10 of these galaxies. Such wings can be caused by high-veloci
ty clouds, similar to those observed in our own Galaxy. Disk galaxy mo
dels were constructed that include both high-velocity clouds (modeled
as a component of galactic gas with a velocity dispersion of either 30
or 50 km s-1) and warped H I disks. We find that the high-velocity wi
ngs can be reproduced by models with high-velocity clouds but not by m
odels with warps that are similar to those observed in other galaxies.
If these wings are due to high-velocity clouds, then the mass of neut
ral hydrogen in high-velocity clouds for the 10 galaxies ranges from 6
x 10(7) M. to 4 x 10(9) M., which corresponds to 4%-14% of the total
H I in these galaxies. The galaxies with no detected high-velocity win
gs are also those with the lowest far-infrared fluxes as measured by I
RAS, which is consistent with the galactic fountain model in which the
young stellar population (responsible for most of the far-infrared em
ission) produces supernovae which then provide the kinetic energy of t
he high-velocity clouds.