‘On reaching the ground floor again, our now clean wheat is first passed through the “grading” or “sizing” reels, which separate it into two sizes, and then it enters the mill proper. It should be said here that the milling industry of the world has been revolutionised within the past few years by the substitution of steel rollers for the old millstones. The process of crushing or grinding, however, by steel rollers is accomplished in a very gradual manner, as will be explained: First come the “break rolls.” These are solid steel rollers set in pairs, with corrugated surfaces; this gives them a cutting action. Wheat is passed through five successive pairs of these rollers. The first are about 1/16th inch apart, and only break or bruise the grain slightly. Each successive pair is set closer, and carries the bruising a step further. But this is only half the business. After each set of rollers the grain goes through a “purifier,” which is either a sieve of some kind or an aspirator, or both together, and the object is always the same—namely, to separate the solid particles of the broken wheat from the lighter ones. The former are, or rather will eventually be, flour; the latter constitute “offal.” And the whole art of milling is merely an extension of this process; first reduction, then separation, repeated over and over again. As the grain passes through each successive set of rollers it is broken up finer and ever finer, and the separating action of the “purifier” accompanies it step by step. The solid particles grow smaller and smaller, the “offal” correspondingly finer and finer. This is the process in brief, but there are endless complications and refinements on the way. For instance, the solid particles are not only separated but are themselves divided into groups according to size. Then the offal often undergoes a further purifying process. Then the purifiers differ—some are complex, others simple; some of wire, others of silk; some revolve, others oscillate; some are “aspirated,” others not; and so forth. Meanwhile, at the end of the five rolls and five purifiers, which make up our breaking department, we have got three products: (_a_) semolina; (_b_) middlings; (_c_) offal. The first two are practically varieties of the same—_i.e._, both solid particles, which will afterwards be flour, but of different sizes. They are half way between grain and flour—hence the term “middlings.”