  We consider scattering of elastic waves on parallel wedge dislocations in the
geometric theory of defects or, equivalently, scattering of point particles and
light rays on cosmic strings. Dislocations are described as torsion
singularities located on parallel lines, and trajectories of phonons are
assumed to be the corresponding extremals. Extremals are found for arbitrary
distribution of the dislocations in the monopole, dipole, and quadrupole
approximation and the scattering angle is obtained. Examples of continuous
distribution of wedge and edge dislocations are considered. We have found that
for deficit angles close to -2\pi a star located behind a cosmic string may
have any even number of images, 2,4,6,... The close relationship between
dislocations and conformal maps is elucidated in detail.
