Abstract: A filter used for separating solids from liquids, the filter having a surface on which a filter cake is formed with the solids and being adapted to treat said cake. The filter utilizes a housing; a stirring apparatus disposed within the housing, said apparatus including stirring arms and a first motor for rotating the arms; and at least one second motor for raising and lower the apparatus. The second motor includes a hydraulic cylinder having a piston which is raised and lowered by hydraulic pressure. The piston is connected to the apparatus to raise and lower the apparatus in accordance with the movement of the piston. The cylinder has a first port above the piston and a second port below the piston. The piston is raised when the pressure applied at the second port is higher than that applied at the first port, and is lowered to lower the apparatus when the pressure applied at the first port is higher than that applied at the second port.