_Dutch Process._--A layer of spent tan is placed on the floor of the stack (a chamber with walls of brick some 25 feet high, and a vertical opening from top to base through which the men enter), upon which are arranged earthenware pots partially filled with dilute acetic acid. Strips of lead are then placed on small square “cockney” pots, or more rarely in the form of folded grids, inside deep, long “castle” pots, and the whole covered with boards, resting on special “bearer pots” containing dilute acetic acid. Ten to fifteen of such layers (blue beds) one on the top of the other are built into the stacks to a height of some 20 feet. When completed, the stacks remain for 80 to 100 days before being emptied. During this period the temperature rises to 75° to 80° C., considerable evolution of carbonic acid gas takes place, and the lead is converted first into acetate and subsequently the white basic carbonate. The layers (white beds) are uncovered and the corroded strips (corrosions) collected by hand. They are placed in trays and carried to heavy steel rollers by means of which and subsequent raking in wash becks the carbonate is detached from the uncorroded central core of blue lead. In many factories corrosions are now conveyed from the stacks to the wash becks or rollers by travelling cranes. The recovered blue lead is removed in a wet state to be remelted and recast. The corrosions, after passing through the rollers and wash becks, are shovelled on to a picking-board and transferred gradually to the grindstones. From the stones the ground pulp passes to the settling becks through several gratings of fine copper mesh. In the form of pulp the material is ladled by hand into bowls for conveyance to the drying stoves. When dry, the contents of the bowl are emptied into barrels and headed, or into hoppers, from whence the material is conveyed to be packed either by hand or automatically by mechanical packers, or to be converted into paint.