The half-stuff supplied to these forms of beater is generally disintegrated to a greater extent in the breaker than is the case with those of the ordinary construction, as it is necessary to make it flow easily through them, and this could not be done if the fibres were kept long. A single passage of the pulp through the beater is sufficient to beat it up ready for making into paper. The chief advantages claimed for them is that they are more economical, both of time and power; also that the pulp is more regularly beaten. Certain new forms of beaters have lately been introduced in this country, and are rapidly gaining in favour, chiefly on account of the saving of driving power, and the space occupied, compared with the amount of “stuff” they are capable of beating. Fig. 35 shows the construction of Forbes’ patent engine, as manufactured by Messrs. G. & W. Bertram, of Edinburgh. This beater is divided into three channels. The rolls, one of which is shown uncovered, are placed in the outer channels, while in the centre one the mixing and circulating wheel a is placed, the peculiar construction of which enables it to throw the pulp alternately into the two outer channels, from whence, after passing under the rolls again, it enters the central channel at the other end of the beater. {123} In Umpherston’s patent engine great economy of space is effected by causing the pulp to travel over and under the backfall (_a_, Fig. 36). Another advantage is that the stuff circulates freely with less water than in the ordinary forms, thus increasing its output. It is also claimed that the pulp is beaten with less power, and as it is less liable to lodge in corners it is more evenly beaten. [Illustration: FIG. 35.] The construction of the engine will be readily understood by reference to Fig. 36. The direction which the stuff takes is indicated by the arrows. Cooke and Hibbert’s beater, as manufactured by Messrs. Masson, Scott and Bertram, resembles, to a certain extent, Gould’s engine, previously described; it differs from it, however, in that the discs are placed vertically, instead of horizontally. Moreover, the general construction of the beater more nearly resembles those in ordinary use. Fig. 37, which shows it in plan and in section at the line D E, illustrates its construction. [Illustration: FIG. 36.] [Illustration: FIG. 37.]