英文科学读本 第五册·Lesson 56 The Cotton Manufacture

Lesson 56 The Cotton Manufacture

In our country cotton has flourished ever since the first years of settlement, but our exports of the fiber did not begin till 1770. In that year the first shipment of 20,000 lbs. was made. The great invention of the cotton gin by Eli Whitney in 1793, and the cheapening of the process of cultivation, as well as of cleansing, increased our exports to 17,789,803 lbs. in 1800, and to 3,450,000,000 lbs. in 1890.

When, nearly three hundred years ago, the cotton manufacture was first introduced into Europe, all the work was done by hand. It is now almost entirely accomplished by machinery and steam. Abundance of cheap coal is therefore an essential, and this is commonly supplied by the coal-fields in the neighborhood of the great centres of manufacture.

If we examine a piece of calico side by side with some raw cotton-wool, we shall see, from the nature of the fabric, that the whole work of manufacture resolves itself into two great processes. The short, matted fibers of the raw cotton must be formed into lengths of yarn or thread, and these threads must be woven into a web.

It would be impossible to attempt to convey a notion of the intricate machinery by which the various processes are carried out. We must be content with trying to grasp the broad principles on which they are worked.

The first step, then, towards making the tangled fibers of the raw cotton into yarn must be to draw them out and separate them. This is done in a machine called a willow, which is practically a large box in which rollers, fitted with iron spikes, are made to revolve rapidly. The raw cotton is put into the box, and the spikes, as they revolve, catch it up, tear and loosen the fibers, and shake it free from dust and dirt. From the willow the loosened fibers are passed on to the carding machine, which consists of a number of revolving brushes made of iron wire. Carding is only another word for combing or brushing. The work of the carding machine is to brush out, and lay straight and parallel, the cotton fibers, just as a girl brushes out her long hair. The carded cotton passes out from this machine like a thin, white film, and is called a sliver. The slivers are taken to another machine, in which they are gradually drawn out and slightly twisted again and again by a process called roving, till they are longer, stronger, and finer than they were. In this state they are ready to be spun into yarn. In the spinning-machine the rove (as the loose thread is called) is lengthened and strengthened, by being still further twisted, and it leaves the spinner as yarn, ready for the weaver's loom. The strong sewing-cotton, which is used for needlework, is made of several yarns twisted together.

Our lessons on flax and linen-making, in one of the earlier stages, made us familiar with the broad principles which underlie the process of weaving. You, no doubt, remember that in all woven fabrics the web consists of two sets of threads, arranged at right angles to each other, one called the warp, the other the weft or woof.

If we examine a large piece of calico as it comes from the draper, we shall see on either side a finished edge or border, which will not unravel. We call it the selvage. The material was woven in one long piece, probably hundreds of yards in length, but the width of the piece is the same throughout, and is marked by this selvage, or self-edge.

The threads of the warp are arranged by stretching a number of rests, or bobbins of yarn, side by side between two yarn-rollers, one in front, the other at the back of the loom. The warp, when finally arranged, tells the width of the intended fabric. The thread which is to form the woof is wound on a shuttle—a sort of reel pointed at each end.

The first thing, after seeing the warp arranged and the woof wound on the shuttle, is to strengthen the threads by giving them a dressing of that peculiar kind of size called starch gum, which we have spoken of many times as a preparation from baked starch.

This done, the weaver takes his place in front of one of the yarn-rollers, which is called the cloth-beam, and begins the work. We have omitted, however, to notice one point—an important one. Before the weaving begins, the warp is attached to a sort of movable frame, called a heddle, in such a way that the alternate threads can be raised or lowered at will. One set of the threads are raised while the alternate threads are lowered, and lowered while they are raised.

The weaver passes the shuttle, with its woof, from right to left between these two sets of threads—that is, over one set and under the others. Then the heddle is made to change the positions of these alternate threads, lowering one set and raising the others, after which the shuttle is returned between the two as before, and so the work goes on.

There is but one thread of the woof or weft, and it is carried from side to side by the shuttle. The fact of its passing each time between the alternate sets of warp threads forms the selvage at the sides of the cloth. It is important to remember that this is the mode of working the simple hand-loom. All our woven goods are now made in enormous, steam power-looms worked by machinery too intricate for us to consider here. But if we can follow the working of the hand-loom, we shall be able to understand the principle of even the ponderous machinery of our great cotton mills.