The quality of the rags depends very much upon the state of civilization of the countries which produce them; the lower the degree of civilization, the more coarse and filthy are the rags. When the rags are received at the mill, they are sorted according to their respective qualities; for if rags of different qualities were ground at the same engine, the finest and best parts would be ground and carried off before the coarser were sufficiently reduced to make a pulp. In the sorting of rags intended for the manufacture of fine paper, hems and seams are kept apart, and coarse cloth separated from fine. Cloth made of tow should be separated from that made from linen, cloth of hemp from cloth of flax. Even the degree of wear should be attended to, for if rags comparatively new are mixed with those which are much worn, the one will be reduced to a good pulp, while the other is so completely ground up as to pass through the hair strainers; thus occasioning not only loss of material, but loss of beauty in the paper; for the smooth velvet softness of some papers may be produced by the finer particles thus carried off. The pulp produced from imperfectly sorted rags has a cloudy appearance, in consequence of some parts being less reduced than others, and the paper made from it is also cloudy or thicker in some parts than in others, as is evident on holding a sheet up before the light. When it is necessary to mix different qualities of rags together to produce different qualities of paper, the rags should be ground separately, and the various pulps mixed together afterwards. The rag-merchants sort rags into five qualities, known as Nos. 1, 2, 3, 4, and 5. No. 1, or _superfine_, consisting wholly of linen, is used for the finest writing-papers. No. 5 is canvas, and may, after bleaching, be used for inferior printing-papers. There is also _rag-bagging_, or the canvas sacks in which the rags are packed; also cotton colored rags of all colors, but the blue is usually sorted out for making blue paper. Common papers are made from rag-bagging and cotton rags. An operation sometimes required after unpacking the rags, is to put them into a _duster_, which is a cylinder four feet in diameter and five feet long, covered with a wire net and inclosed in a tight box to confine the dust. A quantity of rags being put into this cylinder, it is made to rotate rapidly on its axis, and thus a good deal of dust is shaken out, which might otherwise vitiate the air of the rag-cutting room. [Illustration: Fig. 2.--CUTTING RAGS.]