It was found in experiments on the adiabatic magnetic mirror machine `Ogryonok' that loss of fast ions to the mirros and walls of the chamber was mainly from the region of the magnetic channel. The reason for this loss is scattering of the ions by a local perturbation of the magnetic field created by the magnetic channel. Measurements were made of the extent of the perturbation and its character. It was found that replacing the magnetic channel by an electrostatic one led to a marked decrease in the stream of fast ions lost to the mirrors and walls, leaving no preferential region for the source of ion loss. By creating a controlled local perturbation of the dipole type we were able to measure some parameters of scattering of fast ions on perturbations of this type.