The second of the two pieces is a cast iron bottom, K, which works on a hinge-joint, and which is perforated with a large number of holes for giving passage to the oil that has traversed the hair cloth cushion of which we shall speak further on. These holes must correspond accurately with the radial conduits presented by plate, E, and through which flows the oil to a circular channel running around this same piece. In order to exactly maintain such a relation between the holes and channels, the piece, E, is provided with a stirrup-iron, d, that passes around one of the columns, C, of the hydraulic press. The entire filter thus constructed is attached to one of the columns, C', of the hydraulic press in such a way that it can revolve around it. For this purpose, the column is surrounded by an iron sleeve, L, cast in two pieces, and which in its lower position rests on the shoulder, e, of the column. The filter is connected with the sleeve by means of screws, as shown in Fig. 6. We shall now describe the mechanism for loosening the band, I, and moving the bottom, K. The band, I (Figs. 5 to 9), is cleft at a point in its circumference corresponding to one of the joints of the shell, F, and carries at each side of the cleft a bearing in which turns freely a steel pin. One of these latter, i, is cylindrical, and the other, j, has eccentric extremities that are connected with the former by two small iron rods, k and l. The upper extremity of the pin, j, is provided with a bent lever-handle, M, and the lower one carries in its turn a small disk, m, the use of which will be explained further on. It results from such an arrangement that by acting on the lever, M, with the band, and by reason of the eccentricity of the pin, j, the two extremities of the band, I, may be made to approach or recede at the will of the operator. The position of nearest approximation is limited by the abutting of the hook at the end of the lever, M, against the side of the filter. This latter position corresponds to the moment of charging the apparatus (Fig. 6), while the contrary one indicates the moment that the oil cake falls (Fig. 4). Although the separation is but a few millimeters, it is sufficient for disengaging and allowing the cake to drop.