This consists of two or three iron or steel blades extending the full width of the machine and carried by specially constructed arms from a strong central shaft. The edges of these beater blades are made somewhat sharp, and they strike down the cotton from the feed roller at the rate of 2000 or more blows per minute. This of course carries the opening work of the cotton of the first beater to a still further degree, and as in this case the cotton is also struck down upon "beater bars" or cleaning bars, a further quantity of loosened impurities passes through the bars. As before, another powerful fan creates an air current by which the cotton is carried away from the beater and placed upon a pair of "Cages." From this point the cotton is conducted in the form of a sheet between four heavy calender or compression rollers, the rollers being superimposed over each other, and the cotton receiving three compressions in its passage. This makes a much more solid and tractable sheet of cotton, and it is now simply wound upon an iron roller in the form of a roll of cotton termed a "lap," being now ready for the subsequent process, as shown in the illustration (Fig. 14). Image: FIG. 14.--Scutching machine with "lap" at the back. =Scutching.=--This term obviously means beating, and the process itself is simply a repetition of the opening and cleaning properties of the opener, these objects being attained to a greater degree of perfection. For the best classes of cotton it is often deemed sufficient to pass it through the opener alone, and then to immediately transfer the lap to the process of carding. For some cottons it is the practice to pass the cotton through two scutchers in addition to the opener, while in other cases it is the practice to use one scutcher only in addition to the opener. In the scutcher it is the most common practice to take four laps from the opener and to place them in a specially constructed creel and resting on a travelling "lattice" or apron. By this they are slowly unwound and the four sheets are laid one upon another and passed in one combined sheet, through feed rollers, to a two or three bladed beater, exactly like the second one described when treating upon the double opener. Also, exactly in the same manner, a lap is formed ready for the immediately succeeding process of carding. In the scutcher the doubling of four laps together tends to produce a sheet of cotton more uniform in thickness and weight than that from the opener. This object of equality of lap is also invariably aided by what are termed Automatic Feed Regulators, which regulate the weight of cotton given to the beater to something like a continuous uniformity. The action is clearly seen in the illustration. =Carding.=--By many persons this is deemed to be the most important operation in cotton spinning. Its several duties may be stated as follows:--