These are hollow cylinders of iron or zinc perforated with a very large number of small holes through which the air rushes, leaving the cotton, as it were, plastered on the outer surfaces of the cages.
It is usual to have a pair of these cages, working one over the other like the pair of rollers in a wringing machine.
The cotton now passes between two pairs of small guide rollers, and is fed by the second pair to a second beater, but of very different construction from the first one.
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]).
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.