  The flow velocity of solid 4He through a porous membrane frozen into a
crystal has been measured in the temperature interval 0.1 - 1.8 K. A flat
capacitor consisting of a metalized plastic porous membrane and a bulk
electrode is applied and the gap in the capacitor was filled with examined
helium. The flow of helium through the membrane pores is caused by a d.c.
voltage applied to the capacitor plates. Above T~1K the velocity of solid 4He
flow decreases with lowering temperature following the Arrhenius law with the
activation energy of the process closed to that of vacancies. At low
temperatures the velocity is practically independent of temperature, which
suggests a transition in 4He from the classical thermally activated
vacancy-related flow to the quantum plastic flow.
