To-day a designer always seeks to make a machine self-acting, to limit the operator’s task to starting, directing, and stopping, all with the utmost facility and the least possible exertion. So far has success gone in this direction that a single tender in a cotton-mill may have charge of sixteen Northrop looms, and go to dinner leaving all at work. In case that a thread breaks in any of them, the loom will stop of itself and no harm will be done, the only loss consisting in the time during which the wheels and levers have lain idle. A stop-motion at its simplest is a fork through which the thread travels; as the thread moves forward, the fork is bent downward extending a light coiled spring; should the thread break, the spring instantly lifts the fork, which in rising stops the machine. Among the most noteworthy automatic machines are the presses which take a continuous roll of paper, print both sides, cut it into leaves, fold these, paste them at the back, and, if desired, sew them together and attach a cover. Such a press stands for the union of several operations once distinct; it argues great ingenuity, careful planning, with paper exactly adapted to the stresses it must encounter, while the ink is of a quick-drying variety. [Illustration: Dexter feeding mechanism. Dexter Folder Co., New York.] The Dexter Feeding Mechanism. Binding operations and a good deal of printing have to deal with separate sheets of paper or card. To feed these to presses, folders or binders was for many years a task for the hand. To-day the Dexter Folder Company, of New York, in a diversity of machines supersedes this toil by an ingenious imitation of manual movements. The uppermost sheet of paper in a pile is for a moment held down at A by a rubber finger, during that moment a small rubber roller B slightly buckles the sheet; at the same time an airblast lifts the sheet from its pile; that done, all in a twinkling, finger A rises and the sheet passes either into a press or a folding machine. So nicely limited is the pathway for the paper that no more than one sheet can pass at a time; if two or more sheets present themselves, the feeding mechanism stops, bringing the press or folder to a standstill. As each sheet passes from under the rubber fingers, the table bearing the pile of paper is lifted by just one thickness of paper. Self-Acting Appliances in Metallurgy.