  We report the results of a survey of OVI 1032 absorption along the lines of
sight to 25 white dwarfs in the local interstellar medium (LISM) obtained with
the Far Ultraviolet Spectroscopic Explorer (FUSE). We find that interstellar
OVI absorption along all sightlines is generally weak, and in a number of
cases, completely absent. No OVI absorption was detected with significance
greater than 2 sigma for 12 of the 25 stars, where the 1 sigma uncertainty is 4
mA, equivalent to an OVI column density of ~3 x 10^12 cm^-2. Of the remaining
stars, most have column densities N(OVI) < 10^13 cm^-2 and no column densities
exceed 1.7 x 10^13 cm^-2. For lines of sight to hot (T_eff > 40,000 K) white
dwarfs, there is some evidence that the OVI absorption may be at least
partially photospheric or circumstellar in origin. We interpret the "patchy"
distribution of OVI absorption in terms of a model where OVI is formed in
evaporative interfaces between cool clouds and the hot, diffuse gas in the
Local Bubble (LB). If the clouds contain tangled or tangential magnetic fields,
then thermal conduction will be quenched over most of the cloud surface, and
OVI will be formed only in local "patches" where conduction is allowed to
operate. We find an average OVI space density in the LISM of 2.4 x 10^-8 cm^-3,
which is similar to, or slightly larger than, the value in the Galactic disk
over kpc scales. This local density implies an average OVI column density of ~7
x 10^12 cm^-2 over a path length of 100 pc within the LB. The OVI data
presented here appears to be inconsistent with the model proposed by
Breitschwerdt & Schmutzler (1994), in which highly ionized gas at low kinetic
temperature (~50,000 K) permeates the LB. Our survey results are consistent
with the supernova-driven cavity picture of Cox & Smith (1974).
