  A time-of-flight spectrometer of neutrons in the energy range (0.05 --
2.5)$\mu$eV is described.
  This spectrometer has been tested my measuring the total and differential
neutron cross sections for a number of materials: Al, Cu, $^{6}$LiF, Si, Zr,
teflon, polyethylene and liquid fluoropolymers, that are essential for
experiments in the physics of ultracold neutrons.
