  We investigate two recent parameterizations of the galactic magnetic field
with respect to their impact on cosmic nuclei traversing the field. We present
a comprehensive study of the size of angular deflections, dispersion in the
arrival probability distributions, multiplicity in the images of arrival on
Earth, variance in field transparency, and influence of the turbulent field
components. To remain restricted to ballistic deflections, a cosmic nucleus
with energy E and charge Z should have a rigidity above E/Z=6 EV. In view of
the differences resulting from the two field parameterizations as a measure of
current knowledge in the galactic field, this rigidity threshold may have to be
increased. For a point source search with E/Z>60 EV, field uncertainties
increase the required signal events for discovery moderately for sources in the
northern and southern regions, but substantially for sources near the galactic
disk.
