In plain weaving, as in fig. 1, of which linen or calico may be the examples, the yarn or threads simply cross each other, going alternately above and below. The thread which runs from end to end of the cloth is called the “warp,” and that from side to side the “weft” or “woof.” In nearly all wearing the weft is the same, but in “figured” or “twilled” fabrics the warp is so arranged that a pattern shall be formed, as is seen on towels, table-cloths, &c. In plain weaving, the threads are first wound off, of the required quantity and length, on a frame called a “warping frame;” they are then wound on a roller, side by side, and attached to the “loom,” or machine for weaving, through which they run, also side by side. Near the end they are attached to what are called heddles, which consist of threads stretched in an upright frame, having loops near their centres; a pair of these is used in plain weaving, one half of the warp threads being attached to the loops of one, and the rest to those of the other heddle, alternately, thus--first a thread through a loop of one heddle, then another through a loop of the other heddle, and so on. These heddles can be raised alternately by a pulley attached to treadles worked by the weaver’s feet, and it follows, that when one of the heddles is raised, every alternate thread of the warp is raised also, a space of a triangular form being left (fig. 2). Through this space the weaver throws the “shuttle” (fig. 3), which is a piece of wood pointed at each end, bearing a reel of “weft” in its centre, which weft-thread unwinds as it is thrown through. The other heddle is then raised, and the shuttle thrown back again, each time leaving a line of weft behind it. In this way the crossings of all plain fabrics are produced, a contrivance being used between each throw to press the weft close to the former one. If instead of one half of the warp-threads being up and the other half down at the time the shuttle is thrown, one only is raised at every fifth thread, the intervening four being down, and the one that is raised differing at each throw of the shuttle, a kind of structure is produced called “tweeled” or “twilled,” such as satin, bombazine, &c.; fig. 4 shows the appearance of the edge of such a structure. If the warp consists of alternate threads of different colors, white and blue for example, it is clear that either color will predominate where the warp thread of that particular color is most seen. In fig. 5, _a a a a_ represent white, and _b b b b_ blue threads, and this will show how the pattern on any structure, although the same on both sides, is blue on the one side where it is white on the other, as in damasks, or raised on one side where it is sunk on the other, as in dimity, or diaper. Illustration: FIG. 5. (‡ DUAL COLOR WEAVE.) BLEACHING. Illustration: BLEACHING WORKS.