From the “sorting” and “shredding” room the rags are conveyed to the “cutter,” where they are cut and chopped by revolving knives, leaving them in small pieces and much freer from dust and grit.  Various ingenious devices are employed for removing metal and other hard and injurious matter, magnetic brushes serving this purpose in some mills.  When the “cutter” has finished its work, the still very dirty rags go for a further cleansing to the “devil,” or “whipper,” a hollow cone with spikes projecting within, against which work the spikes of a drum, dashing the rags about at great speed.  Human lives are often freed of their baser elements and restored to purity and beauty through the chastening influences of tribulation or adversity; in like manner the “whipper” carries the rags forward a step in the process of purification that is necessary before they can be brought to their highest usefulness.  But the cleansing process, which is only a preparation for what is to follow, does not end with the “whipper,” which has served merely to loosen, not to dislodge, a great deal of dust and dirt.  The final operation in the preliminary cleaning is performed by the “duster” proper, which is a conical revolving sieve.  As the mass of rags is tossed and shaken about, the loosened dust is carried away by the suction of the air, which draws the dust particles into tubes furnished with suction fans.  In most modern mills the rags are carried forward from the “duster” on an endless belt, and a careful watch is kept upon them as they emerge to detect the presence of unchopped pieces, buttons, or other foreign substances.  The journey of the rags over this endless belt or conveyor terminates in a receiving-room, in the floor of which there are several openings, and immediately below these the mouths of the “digesters,” which are in a room beneath.  The “digesters,” as they are suggestively and appropriately termed, are huge revolving boilers, usually upright, which often have as great a diameter as eight feet, with a height of twenty-two feet and a digestive capacity of upward of five tons of rags each.  The rags that are to be “cooked” are fed in to the “digesters” through the openings in the floor, and the great movable manhole plates are then put in place and closed, hermetically sealing the openings or mouths through which the boilers have been fed, these having first been charged with a mixed solution of lime and soda and with live hot steam in lieu of gastric juice as a digesting fluid and force.  In some mills the boilers are placed in a horizontal position, while in others they are in the form of a large ball or globe, in either case being operated in the manner described; those of upright form, however, are most commonly in use.  The rags are boiled under steam pressure of about forty pounds to the square inch, and the cooking is continued from twelve to fourteen hours.