After settling for a time the clear juice is drawn off and the scum, mud and cloudy liquor left in the tank. As a vast amount of liquor must be handled every hour, it is not practicable to have tank capacity great enough to admit of the liquor standing a sufficient length of time for every particle of foreign matter to settle, so as an adjunct to the settling tank, filters are used. These are cylindrical iron tanks, packed tightly with ordinary wood fiber, known as excelsior. The juice is conducted to these filters, and as it percolates through the excelsior, practically all of the remaining foreign matter is caught and retained in the fiber. The clear juice is then run to the receiving tanks for the evaporators and the mud and scum that remain are drawn off into mud tanks, where more lime is added and the mass stirred up. Finally it is delivered to the filter presses, where the mud and other impurities are taken out and the clear liquor containing sugar is sent to the evaporators. Another method for cleaning, called “precipitation in motion,” is to carefully lime the juice and then heat it in closed vessels and under sufficient pressure to carry it through a pipe to large insulated settling tanks. These settling tanks, usually of sheet steel, are made in the form of truncated cones with conical bottoms, the small diameter of the tank being at the top. Suspended in the center is a vertical cylinder somewhat less in diameter than the upper part of the tank. This cylinder extends downward about eight feet to a point opposite the largest diameter, which makes the area between the circumference of the suspended cylinder and the tank at that point very much greater than the area of the cylinder itself. This difference in area is necessary to retard the flow of the juice and allow the sediment, mud and insoluble solids to be deposited at the bottom of the tank. The juice is delivered by a pipe into the top of the cylinder which projects a few inches above the edge of the surrounding settling tank. It passes slowly down the central passageway, turns at the bottom, where its speed is materially slackened, and goes out through a pipe line connected to the side of the tank just below the upper edge. There are several other methods in general use, but in all of them the principle of settling, upon which the separation or cleaning depends, is the difference in specific gravity between the juice and the dirt. A high and even temperature should be maintained by preventing radiation, as lowering the temperature would increase the specific gravity and viscosity of the juice without increasing that of the dirt in equal proportion. [Illustration: TWELVE-ROLLER MILL] [Illustration: MODERN CRUSHING PLANT—TWO FIFTEEN-ROLLER MILLS AND CRUSHERS. CAPACITY, ONE HUNDRED AND FIVE TONS PER HOUR]