  We use the thermo-mechanical effect to create a chemical potential difference
between two liquid reservoirs connected to each other through Vycor rods in
series with solid hcp 4He to confirm that a DC flux of atoms takes place below
600 mK, but find that the flux falls abruptly in the vicinity of 80 mK. It is
impossible to add density to a solid freshly made at 60 mK and samples freshly
made at 60 mK do not allow mass flux, even when raised in temperature to 200
mK. Solids created above 300 mK and cooled to 60 mK accept added density and
demonstrate finite mass flux.
