12. Nature has supplied us with a great variety of substances from which paper may be fabricated, as flax, hemp, cotton, straw, grass, and the bark of several kinds of trees; but the fibres of the three first productions, in the form of rags, are the most usual materials. Most of these are primarily purchased from the people at large, by retail booksellers, country merchants, and pedlers, who in turn dispose of them to persons called rag-merchants, or directly to the paper-makers. When the rags come from the original collectors, all kinds are mixed together; but they are assorted according to their color and the nature of their original fibre, either by the rag-merchants, or by the paper-makers themselves. 13. In our attempts to afford the reader an idea of this manufacture in general, letter-paper has been selected, as affording the best means of illustration; since for this kind of paper, the best stock is employed, and the greatest skill is exerted in every stage of the process. 14. The process of the manufacture is commenced by cutting the rags into small pieces, by the aid of a sharp instrument, commonly a piece of a scythe, which is placed in a position nearly perpendicular before the operator. In the reduction of very coarse rags, such as sail-cloth, a cutting machine is also employed. Then, with the view of sifting out the loose particles of dirt, the rags are deposited in a large octagonal sieve made of coarse wire, and placed in a close box in a horizontal position. The sieve is moved by machinery, like the bolt of a flour-mill. 15. The second stage of the process consists chiefly in the reduction of the rags to a _pulp_. This is effected by the action of a cutting machine, the essential parts of which are two sets of blunt knives, the one stationary, and the other revolving. The machine is placed in a large elliptical tub, in which the rags are also deposited, with a suitable quantity of water. The liquid and fibrous contents of the tub are kept moving in a circle by the action of the machine, through which it passes at one point of its revolution. 16. The maceration occupies from ten to twenty hours, according as the material is more or less rigid; and, during part of this time, water is permitted to run in at one side of the tub, and out at the other, to render the pulp perfectly clean. Towards the close of this process, the pulp, if necessary, is bleached by means of chloride of lime, and oil of vitriol. It is also sometimes colored by adding a quantity of dye-stuff. The bleaching and coloring are effected without interrupting the action of the machine. The rags having been thus reduced, the pulp, together with a suitable quantity of water, is let out into a reservoir, from which it is drawn off into a _vat_, as fast as it may be needed for the production of the paper.