  There are a number of theoretical and observational hints that large numbers
of low-mass galaxies composed entirely of dark matter exist in the field. The
theoretical considerations follow from the prediction of cold dark matter
theory that there exist many low-mass galaxies for every massive one. The
observational considerations follow from the observed paucity of these low-mass
galaxies in the field but not in dense clusters of galaxies; this suggests that
the lack of small galaxies in the field is due to the inhibition of star
formation in the galaxies as opposed to the fact that their small dark matter
halos do not exist. In this work we outline the likely properties of low-mass
dark galaxies, and describe observational strategies for finding them, and
where in the sky to search. The results are presented as a function of the
global properties of dark matter, in particular the presence or absence of a
substantial baryonic dark matter component. If the dark matter is purely cold
and has a Navarro, Frenk and White density profile, directly detecting dark
galaxies will only be feasible with present technology if the galaxy has a
maximum velocity dispersion in excess of 70 km/s, in which case the dark
galaxies could strongly lens background objects. This is much higher than the
maximum velocity dispersions in most dwarf galaxies. If the dark matter in
galaxy halos has a baryonic component close to the cosmic ratio, the
possibility of directly detecting dark galaxies is much more realistic; the
optimal method of detection will depend on the nature of the dark matter. A
number of more indirect methods are also discussed.
