HISTORICAL DEVELOPMENT OF MILLING PROC ESSES. Long before the dawn of history cereals formed an important article of food for the human race, especially for that portion of it in haldting temperate climates. At first these grains were used in the wild state, without grind ing or cooking. But agriculture was one of the earliest arts of civilization to be developed, and the cereals the first of the agricultural products to receive cultivation. It must have been dis covered very early that both in ease of mastica tion and in flavor grain is much improved by grinding, so that the first milling processes came soon after the cultivation of the soil. At first a mere breaking up into coarse fragments by means of a mortar and pestle, or its substitute, was all that was attempted. This primitive form of milling, whose adoption constituted the first step in the art, still survives among certain peoples of rude civilization. The second step in the development of milling processes was taken when for the mortar and pestle were substituted two roughened grinding surfaces, placed close together, between which the grain was reduced to powder. This use of the upper and nether mill stone for grinding grain also dates back to pre historic t hues. An improvement over this simple device is the quern, or hand-mill, still used among semi-civilized peoples. In the quern the upper stone is pierced and turned on a pin on the nether stone: the upper stoop is grasped by a handle consisting of a stick thrust into its edge. The use of animal and then of water power to turn the millstones value much later. The first successful steam flou•-mill was erected in London in 1784. The use of millstones for grinding flour was universal until the close of the eighteenth century, and is still so common, especially in small 'customs' mills, that a brief deseriplion of this process of milling is given. The mill stones arc ma 1 of f o: .noir-s...one, a form of silica as hard as flint but not so brittle. They are usually from four to six feet. in diameter. and each consists of a number of pieces strongly' cemented and hound together with iron hoops.
The grinding surface of each stone is furrowed or grooved, one side of each groove being cut per pendicularly and the other side being inclined to the surface of the stone. The grooves on each stone are furrowed exactly alike: thus the sharp edges of the gnxives on t he one come against those on the other, and so cut the grain to pieces.
Fig. 1 shows a section of a llour-mill. The millstones are nt a, the lower of which is firmly fixed, and the upper is made to revolve, on a shaft which passes up through the lower one, is de:•ribed below. It is el:timed that in 18fI4 70 E. N. LaCroix, a Follett miller, iud pendently invented a system of roller milling similar to the flung:Irian system, and installed it in onc of the great Hour mills of tt intro duction marked an eimeli in the produelion of kineriean Hour. The essence of this new process at a speed of one hundred revolutions per minute, more or less. Motion is communicated by the spur-wheel b, which is driven by a water-wheel or other power. The grain, previously cleaned. is supplied to the millstones by means of the hop per, c, connected with which there is a valve, d, for regulating the supply. Passing through a hole in the centre of the upper millstone. it comes in between the two, where it is ground, and thrown out on all sides by means of the cen trifugal force. The millstones are, of course, in closed, and the flour passes down through the spout, e, to the worm at f. which carries it along to elevators. a. These raise it up to the floor, on which the dressing-machine, h, is placed. This is a cylinder, which was formerly made of wire cloth of various degrees of fineness, and conse quently separated the flour into different qual ities, but no part of it large enough in the open ings to let through the bran, which passed out at the end. Silk is now preferred to wire-cloth for dressing the flour. Hoppers, i, are placed below the dressing-machine. by means of which the flour and bran are filled into sacks; No. I being fine flour; No. 2. seconds: and No. 3, bran.