Page:Encyclopædia Britannica, Ninth Edition, v. 9.djvu/358

 344 F L O IT R about a foot and a half in diameter. The lower is a little convex, to which the concavity of the upper must be fitted. In the middle of the upper stone is a round hole, and on one side is a long handle. The grinder sheds the corn gradually into the hole with one hand, and works the handle round with the other. The corn slides down the convexity of the lower stone, and by the motion of the upper is ground in its passage.&quot; The accompanying woodcut (fig. 4) illustrates the leading forms of these primi- FIG. 4. Querns. tive mills, a representing a pair of rubbing stones, b a pot quern, and c an ordinary quern with hole in the centre of the upper stone into which the grain was fed, another hole towards one side for receiving the handle, and in the lower stone a spout through which the ground meal was delivered. The nature of the water mills which were formerly common in Great Britain and Ireland, and which continued in use well into the present century, may be gathered from the following description of one visited by Sir Walter Scott during his voyage to the Shetland Islands, &c., in 1814 (Lockhart s Life). &quot; In our return, pass the upper end of the little lake of Cleik-him-in, which is divided by a rude causeway from another small loch, communicating with it, however, by a sluice, for the purpose of driving a mill. But such a mill ! The wheel is horizontal, with the cogs turned diagonally to the water ; the beam stands upright, and is inserted in a stone-quern of the old-fashioned con struction. This simple machine is inclosed in a hovel about the size of a pig-stye, and there is the mill ! There are about 500 such mills in Shetland, each incapable of grinding more than a sack at a time.&quot; The ordinary flour mill of the present day is a structure of comparatively few essential parts ; but in the arrange ment and mounting of thess the greatest amount of mechanical skill and experience has been exercised, and the accessories of the mill have been elaborated with much care, with the view of saving manual labour and perfecting the processes and results. Fully to appreciate the various processes of modern milling, it is necessary to bear in mind, not only that the wheat as delivered at the mill is dusty and mixed with sand and other refuse, but that it contains many light grains and seeds of foreign substances, which might be deleterious, and would certainly interfere with the appearance of the finished flour. Again the structure of the wheat grain itself must not be overlooked. A grain (caryopsis) of wheat is not a seed, but a fruit con sisting of a pericarp or outer envelope tightly adherent to its contained single seed. The envelope consists of several layers of ligneous tissue, within which are the embryo and a peculiar fermentive nitrogenous principle termed cerealin, and finally a central mass of thin cells filled with a white powdery substance largely composed of starch granules. The object of ordinary milling is to grind as perfectly as possible, without breaking the minute granules, the central substance of the grain, and to separate it from the embryo and outer husks, the former constituting the flour, and the latter the bran of the miller. Whole wheaten flour, on the other hand, consists of the entire grain ground up to a uniform mass. The machines and processes by which flour is prepared are very numerous, and are diverse in character; and it must further be said that, at the present moment, the whole industry is in a peculiarly unsettled and transition state. The system which has prevailed in the United Kingdom hitherto is what is known as ordinary or flat grinding with millstones ; but in the meantime a strong tendency is developing in favour of the use, either partially or entirely, of granulating or &quot; high milling,&quot; and of some of the various systems of roller grinding which have been introduced. In Hungary and Austria the system of high milling prevails, in which the action of the millstones con sists more in granulating than grinding ; and in connexion with that system of milling, the use of rollers is a prominent feature. To a limited extent also the principle of the disintegrator has been brought into operation, in which the grain is broken by the violent impact of studs or projections revolving in opposite directions with enormous velocity. Thus we have these various systems : (1) flat milling or grinding ; (2) high milling or granulation ; (3) roller mill ing or crushing; and (4) disentegrator milling or breaking. Flat or Ordinary Milling.- In the ordinary or flat mill stone milling of the United Kingdom there are three main points to consider (1) the cleaning and preparation of the wheat ; (2) the grinding ; and (3) the bolting or dressing of the ground products. The ordinary cleaning or screening apparatus through which the wheat, as received, passes, consists of a kind of cylindrical sieve of wire cloth, mounted in a sloping position, and having internal partitions so as to resemble an Archimedean screw. When the apparatus is set in motion, the grain, fed in at its upper end, tumbles from one division into another, thereby being freed from small refuse and sand, and as it issues at the lower extremity is subjected to a fan blast. For cleaning grain there are other kinds of apparatus, in which the prin ciple of aspiration, or drawing currents of air through the grain, is now extensively employed, the most frequently used being Child s aspirator. A further cleaning is sometimes given by Child s decorticator, an implement which can bo adjusted at will, for simply rubbing and scouring the grain, or for removing the thin bran and germ previous to tho operation of grinding. The &quot; Victor &quot; brush machine is a recently introduced and highly approved apparatus for polishing and finishing wheat, its peculiar feature being that the &quot; opposed brushes are constructed and worked in such a manner that they come in contact with every kernel of wheat in every conceivable position, and with as much force as the miller chooses to use thus polishing it on the ends better than any other machine can do, and this not only on one pair of brushes, but on several.&quot; The pre pared grain is next conveyed to the grinding apparatus, and here it may be said that, in moving the grain or flour horizontally, Archimedean screws working within an in closed casing are employed, while in lifting from one floor to another, small boxes mounted on an endless band worked over pulleys and similarly encased are used. The grinding machinery consists first of a bin containing the grain to be ground, from which it passes by a spout to the hopper, whence it is delivered by a feeding adjustment to tho stones. These constitute the distinctive feature of the entire mill, and upon their condition and delicate adjust ment the whole success of the milling operation turns. They consist of two flat cylindrical masses inclosed within a wooden or sheet metal case, the lower or &quot; bed-stone &quot; being permanently fixed, while the upper or &quot;runner&quot; is accurately pivoted and balanced over it. The average size of millstones is about 4 feet 2 inches in diameter by 12 inches in thickness ; and they are made of a hard but