The largest description of corn-mills in the present day are driven either by water, wind, or steam. Watermills were in use amongst the Romans, who established several of them in this island ; the mill-course of one of these was discovered some years back near Manchester. Windmills, we believe, .were likewise known to them ; but the application of steam to this purpose is of very recent date, the first steam-mills established in this or any other country being those erected by Bolton and Watt, neat Blackfriars' Bridge, and named the 411bion Mills. Whatever be the nature of the driving power, the grinding apparatus is nearly alike in all their mills ; and as both windmills and water mills are employed for various purposes besides that of grinding corn, we propose, under the head WATERMILL and WINDMILL, to notice the methods of applying the power derived from these sources, and shall, in this place, give a description of a mill of modern construction, as driven by steam : we should, however, observe, that under the bead BARKER'S MILL, the reader will find a water corn mill of a simple description.
We shall preface our description of the mill by a short account of the form and the manner of facing the millstones. In order to cut or grind the corn, both the upper and under millstones have channels or furrows cut in them, proceeding obliquely from the centre to the circumference, as shown in the figure on p. 155. The furrows are cut perpendicularly on one side, and ob liquely on the other, into the stone, which gives to each furrow an inclined plane, up which the corn is forced by the revolution of the upper stone, which crushes it and bruises it so as to make it grind easier when it falls upon the spaces between the furrows. • These are cut the same way in both stones, where they lie on their backs (as above represented), which makes them run crossways to each other, when the upper stone a is inverted, and its furrowed side applied to the furrowed side of b. When the furrows become blunt and shallow by wearing, the running-stone must be taken up, and both stones new dressed with a chisel ; and every time that the stone is taken up, a small portion of tallow should be applied to the bush of the spindle.
The grinding surface of the under millstone is a little convex from the edge to the centre, as exhibited in the annexed section at A, and that of the upper stone a little more con cave ; so that they are furthest from one another in the middle, and come gradually nearer towards the edges. By this means, the corn at its first entrance between the stones is only bruised ; but as it goes further on towards the circumference, or edge, it is cut smaller and smaller, but at last finely ground just before it comes out from between them.
But although, in the diagram above given, the concavity in the upper stone corresponds with that described by several authors, we believe that the upper stone is not usually cut away to a greater extent beyond the mill-eye than that shown in the figure in the margin p. 151, where the grain is shown entering the mill-eye, and passing through the apertures of the rind c, it enters the cavity underneath ; here it gradually gets broken, bruised or coarsely ground, and from thence the finest portion enters between the parallel surface of the mill stones, and by degrees passes from between them at their peripheries, being constantly urged outwards by the pressure of the grain in the middle, as well as by the centrifugal force. The rind c is an iron cross let into the upper
millstone, and is fixed to the spindle e ; and the cavity f is filled completely by a bush (generally of wood), in which the spindle revolves. The trundle g, (driven by a cog wheel, which is actuated by the first mover,) gives motion to the spindle and the upper stone. The surface of the upper stone is brought to a perfectly parallel position with respect to the other, by means of four equi distant regulating screws, acting upon a brass box A, in which the lower extremity of the spindle works; so that the slightest movement of the box, effected by the screws, makes a cor respondent alteration in the position of the upper stone, enabling it to be adjusted to the lower one with the nicest precision and the greatest facility. • We shall now proceed to describe the engraving on p. 166, which represents a very compact arrangement of a mill, having four pair of stones driven by a steam-engine. The stones are placed at equal distances from the centre of a square platform, resting upon cast-iron columns, and the driving is arranged beneath the platform, and supported by a framing of iron fixed to the columns. a is the horizontal shaft driven by the steam-engine, on which is fixed the bevil wheel b, working into another bevil-wheel c, of equal diameter, fixed upon the same vertical shaft which carries the large spur-wheel d ; this spur-wheel works into four pinions e e,• fixed upon the spindles f f of the upper millstones, only two of which can be seen; g g are indented pinions, for the purpose of agitating the sieveirplaced over the hoppers, for preventing stones and other extraneous sub stances entering the hopper; ii are the upper millstones; k k the lowermillstones; 11 the hoppers, from which the corn descends into a swinging kind of hopper, called the shoe, which is continually shaken by a short bar of iron screwed into the upper end of the spindle, and having four prongs, which, striking the shoe from side to side, distributes the corn equally over the eye of the mill stone.
The spindles of the mill-stone are supported on the iron levers se es, which can be raised or lowered to adjust the stones, by means of regulating screws at an; o o are screws to raise the pinions e e, and cast them out of Beer. The under, or bed stones, are partly sunk into circular holes in the platform, and firmly wedged therein, and a circular case incloses each pair of stones, leaving a space of about two inches all round them ; and the corn, reduced to the state of meal, is thrown, by the centrifugal force of the stones, out in all direc tions into the case, from whence it is conveyed to the bolting machine, which is driven by a band from the drum-wheel t. The bolting inachiqe is not shown, as the reader will find a description of an improved one under the word BovriNe