A vessel filled with gas is divided into two equal parts `1` and `2` by a thin heat-insulating partition with two holes. One hole has a small diameter, and the other has a very large diameter (in comparsion with the mean free path of molecules). In part `2` the gas is kept at a temperature `eta` times higher than that of part `1` How will the concentration of molecules in part `2` change and how many times after the large hole is closed ?