~Pulping.~--The idea of pulping is also due to Abel. By its means a very much more uniform material is obtained. The process is carried out in an apparatus known as a "Beater" or "Hollander" (Fig. 15, _a, b_). It consists of a kind of wooden tank some 2 or 3 feet deep of an oblong shape, in which a wheel carrying a series of knives is made to revolve, the floor of the tank being sloped up so as to almost touch the revolving wheels. This part of the floor, known as the "craw," is a solid piece of oak, and a box of knives is fixed into it, against which the knives in the revolving wheel are pressed. The beater is divided into two parts--the working side, in which the cotton is cut and torn between the knife edges in the revolving cylinder and those in the box; and the running side, into which the cotton passes after passing under the cylinder. The wheel is generally boxed in to prevent the cotton from being thrown out during its revolution. The cotton is thus in constant motion, continually travelling round, and passing between the knives in the revolving cylinder and those in the box fixed in the wooden block beneath it. The beater is kept full of water, and the cotton is gradually reduced to a condition of pulp. The wheel revolves at the rate of 100 to 150 times a minute. [Illustration: FIG. 16_a_.--POACHER FOR WASHING GUN-COTTON.] [Illustration: FIG. 16_b_.--PLAN OF THE POACHER.] [Illustration: FIG. 16_c_.--ANOTHER FORM OF POACHER.] When the gun-cotton is judged to be sufficiently fine, the contents of the beater are run into another very similar piece of machinery, known as the "poacher" (Fig. 16, _a, b, c_), in which the gun-cotton is continuously agitated together with a large quantity of water, which can be easily run off and replaced as often as required. When the material is first run into the poacher from the beater, the water with which it is then mixed is first run away and clean water added. The paddle wheel is then set in motion, and at intervals fresh water is added. There is a strainer at the bottom of the poacher which enables the water to be drawn off without disturbing the cotton pulp. After the gun-cotton has been in the poacher for some time, a sample should be taken by holding a rather large mesh sieve in the current for a minute or so. The pulp will thus partly pass through and partly be caught upon the sieve, and an average sample will be thus obtained. The sample is squeezed out by hand, bottled, and taken to the laboratory to be tested by the heat test for purity. It first, however, requires to be dried. This is best done by placing the sample between coarse filter paper, and then putting it under a hand-screw press, where it can be subjected to a tolerably severe pressure for about three minutes. It is then rubbed up very finely with the hands, and placed upon a paper tray, about 6 inches by 4-1/2 inches, which is then placed inside a water oven upon a shelf of coarse wire gauze, the temperature of the