The conditions of the process of beating carried out with a Hollander permit of considerable alteration, so that these changes in the fibre are not surprising when properly understood. In fact, it is now conceded that a close study of the theory and practice of beating is likely to bring about still more remarkable improvements in this important department of the paper-maker's work. The quality and character of the paper made may be varied with-- (1) The origin of the raw material, _e.g._, rags, esparto, or wood; (2) The condition of the material, _e.g._, old or new rags, green or mature esparto, mechanical or chemical wood pulp; (3) The time occupied in beating, _e.g._, four hours for an ordinary rag printing and twelve hours for a rag parchment; (4) The state of the beater knives, _e.g._, sharp tackle for blottings and dull tackle for cartridge papers; (5) The speed of the beater roll, also its weight; (6) The rate at which the beater roll is lowered on to the bedplate; (7) The temperature of the contents of the engine. _The Beater Roll._--If the beater roll is fitted with sharp knives, and this is put down close to the bedplate quickly, the fibres are cut up short, and they do not assimilate the water. If the roll is fitted with dull knives, or "tackle," as it is sometimes called, and it is lowered gradually, the fibres are drawn and bruised out without being greatly shortened. In this condition the stuff becomes very "wet," or "greasy," as it is termed. The cellulose enters into association with water when beaten for many hours, and the pulp in the beating engine changes into a curious greasy-like mass of a semi-transparent character. Rag pulp beaten for a long time produces a hard, translucent, dense sheet of paper. Flax thread beaten 48 to 60 hours is used in practice for the manufacture of gramophone horns and similar purposes. Soft porous papers like blottings, filtering papers, heavy chromos, litho papers, antiques, light printings, are made from pulps which are beaten quickly with the roll put down close to the bedplate soon after the stuff has been filled in. With strong, dense, hard papers, such as parchments, banks, greaseproofs and the like, the pulp is beaten slowly and the roll lowered gradually. The nature of the pulp and the time occupied in beating are also important factors in producing these different papers, three to four hours being ample for an ordinary wood pulp printing, whereas a wood pulp parchment requires seven to eight hours.