  We demonstrate that pulsar timing measurements may potentially be able to
detect the presence of dark matter substructure within our own galaxy. As dark
matter substructure transits near the line-of-sight between a pulsar and an
observer, the change in the gravitational field will result in a delay of the
light-travel-time of photons. We calculate the effect of this delay due to
transiting dark matter substructure and find that the effect on pulsar timing
ought to be observable over decadal timescales for a wide range of substructure
masses and density profiles. We find that transiting dark matter substructure
with masses above 0.01 solar masses ought to be detectable at present by these
means. With improved measurements, this method may be able to distinguish
between baryonic, thermal non-baryonic, and non-thermal non-baryonic types of
dark matter. Additionally, information about structure formation on small
scales and the density profiles of galactic dark matter substructure can be
extracted via this method.
