Important as the bluing or coloring is, however, it is only one of the numerous operations or manipulations that take place in the beater.  Many of these, such as engine-sizing and body-coloring, require skill and constant watchfulness.  Here, too, if anywhere, adulteration takes place.  It is sometimes necessary to secure a fine-appearing paper at small cost, and it is profitable to add to its weight.  In such cases a process of “loading” takes place here, and clay or cheap, heavy fibers are added.  Clay is of value not only to increase the weight but also to render the paper more opaque, so as to prevent type or illustrations from showing through, while at the same time it makes possible a smoother surface by filling the pores in the paper.  But while it adds to the weight, clay must, of necessity, weaken the paper.  In engine-sizing, which is done in the beater, the size is thoroughly incorporated with the fibers as these revolve or flow around the engine.  This sizing renders the paper more nearly impervious to moisture.  The difference between a paper that is sized and that has a repellent surface which prevents the ink from settling into it when it is written upon, and an ordinary blotting-paper with its absorbent surface, is due entirely to the fact that the former is most carefully treated with sizing both in the beating engine and in the size tub or vat referred to later, whereas in the latter paper it is omitted.  If the paper is to be tinted or body-colored, colors made from aniline are generally used.  Only in the highest grade of writing-paper and in some few papers that demand colors fast to the light is any other order of coloring matter employed.  As may be easily imagined, considerable skill is required to secure exactly the desired tint, and to get the coloring matter so evenly mixed that each small fiber shall receive its proper tint, and thus to insure that the paper when finished shall be of uniform color and not present a mottled appearance.

When the operations of the beating engine have been completed, a most interesting process begins which marks a vast advance over the earlier method of forming the sheets of paper with mould and deckel, straining off the water, and shaking the frame with a quick motion to mat the fibers together.  The patient striving toward something better which has marked all the centuries since man first learned to carve his rude records, finds its consummation in the process of making paper in a continuous web.  This result is accomplished by a machine first invented by Louis Robert, a workman in a mill at Enonnes, France, who obtained a French patent, with a bounty of eight thousand francs for its development.  This he later sold to M. Didot, the proprietor of the mill, who crossed the Channel into England, where, with the aid of a skilled mechanic, the machine was in a measure perfected, and then sold to Henry and Sealy Fourdrinier.  They, with the further aid of Bryan Donkin, their employee and expert