Fairbairn's stones or the Fairbairn mill (pi. 4, fig. 15) are formed each of several blocks of French burr, a very hard, siliceous vet porous mineral. These blocks are fitted together, cemented with gypsum, and bound with iron bands. They are 4 feet iu diameter by about t foot thick. The working-face of the stones is dressed flat and is grooved, but the face of the upper stone is slightly concave for a small distance from the central aperture, to admit the grain between the stones, which are enclosed in a cylindrical case (C) supported by a bell-shaped cone (B) upon a strong oblong rectangular box (A) secured to a foundation by bolts. This box is provided with an adjustable bearing (G), for carrying the main driving-shaft which by means of the mortised bevel-gears (II, I) turns the upper stone. A pivot-bearing (k) of bronze, supporting the mill spindle (J) and permitting it to turn freely therein, is carried in a case (b) fitted to the upper shelf of the box. By means of a screw (A') outside the box, connected with a lever (AT) carrying a saddle (n) on its middle, the spindle is raised or lowered at pleasure for different finenesses of grinding. The upper end of the spindle turns freely in a tight central adjustable bush (L) fixed in the under stone.
The central eye of the upper stone is supplied with a rynd (Al into which the ends of the cross-pin (c) project. This almost universal method of connection of spindle with stone balances the stone freely upon the end of the spindle and permits an unconstrained action of the grinding sur faces upon the grain.
Combined with the rend, on its top, is a cup-like cavity with central cone, which, in connection with the telescope tube (0), surrounds the funnel up to the hopper (E), and is made adjustable, as to its vertical position, by the lever P. The chain and hand-wheel screw (q) enable the miller at any time to regulate the supply of grain to the mill from the hopper. This ingenious device permits an even and regulated flow of the grain over the entire lip of the cup when the mill is running, the cen trifugal force being the active agent in propelling the grain from the cen tre of the cup over its lip. The flour is taken from the annular space between the stones and case (C) by a spout into a conveyer, which con ducts it to another part of the mill-house, for separation and packing. Each mill is provided with a lifting apparatus, by which the upper stone may readily be removed and turned over for redressing, and as readily replaced.
The (fil. 4, figs. 5, 6) is designed for pulverizing grain or unfibrons materials without subjecting them to compression or friction. Sonic substances, such as superphosphate of lime, contain moisture, and these by crushing become pasty. It was found that when a lump of the material thrown into the air was struck a rapid blow with a stick it became completely shattered, bursting into minute fragments, as though under the action of sonic explosive force. This principle is applied in the disintegrator by causing pieces of the material to fly radially through it under centrifugal force generated by the rapid rotation of the machine. These flying pieces, being smartly struck by a succession of rotating beat ers, the blows being delivered with extreme rapidity in alternately opposite directions, are shattered to atoms by the repeated collisions against the beaters. As the particles struck can offer no resistance hut that which is due to their own inertia, without aid from any solid abutment to support them under impact, no compression or friction, as in grinding by stones, is employed, and the moving-power of the beaters is not neutralized and absorbed by any such unyielding abutment. The whole power ap plied to the machine is utilized in the effort to connninute the material, except that consumed by the resistance of the air and the slight friction of the accessible shaft-bearings. Foreign substances will pass harmlessly
through the machine; the beaters cannot become choked, nor can any parts get out of order, since they all revolve entirely clear of one another. When operating upon grain, the beaters run continuously through their interspaces, but not perceptibly near one another; therefore they do not require stoppage or expense for redressing, as do millstones. The beating force is doubled, because the heaters move in opposite directions, at, say, four hundred revolutions per minute. Each individual grain of wheat is only a fraction of a second in passing the beaters, and in being converted into flour is not heated above r ro° Fahr.
This disintegrating-machine is shown in side-elevation (fig. 6) and in vertical section CAL 4, fig. 5), exhibiting two circular discs (A, B), each secured on a separate shaft (D, E) in the same line, and these discs are driven in opposite directions by belts on either of the pulleys shown. The central solid disc on shaft D carries an extension-disc (A) studded with five concentric rows of pins or beaters, whose outer ends are secured in rings; intermediate and alternate to these are four similar TOWS of beaters, secured to the opposite disc B, which differs from the disc A in having a central opening for the admission of the material. The disc B is sustained and carried by the central solid hub (C), secured on the end of the shaft (E) by two concentric rows of bolts, which permit the passage of all the mate rial from the spout (G) radially to the action of the beaters. The heater pins are of -inch round steel pitched to about 2 inches. The grain is delivered through the central opening of the casing (B) into the innermost cage by a spout (G), which divides into two over the shaft (E); the grain is instantly projected through the machine in every direction, and is tho roughly beaten into flour before it escapes from the machine at its outer circumference. Being confined by the case (F), the flour falls to the bot tom, and is removed by the screw-conveyer (H).
Transportable is curious to trace the history of the means by which large armies have been supplied with food. In the early period of Roman history the only article of food issued to the soldiers was grain, which was ground by means of a hand-mill, and thiA mill was a part of each man's equipment. The modern systems of warfare and the advance in mechanical appliances have led to the construction of more efficient grinding-mills for army service. As an example may be mentioned the floating mills employed during the siege of Sebastopol (1854-55). Two vessels were each fitted up with four mills, which were driven by gears on the propeller-shafts of the vessels. Disconnecting devices were provided, so that the mills could be run while the vessels were at anchor or in berth or the stones thrown out of gear when the vessels were under headway. It is worthy of note that grinding was successfully performed, even in heavy swells while at sea, by the same power that propelled the vessels. These mills were built by Fairbairn.
Millstones driven by I (pl. 5) exhibits a com plete milling-plant, having in working position two run of burrs, which are connected with the usual elevating- and conveying-machines. The mill is driven by a turbine at the base of a timber flume. The shaft of the turbine-wheel, which is extended to the level of the millstones, carries two small pulleys having direct belt-connection with the pulleys on the mill spindles. A third pulley drives a vertical shaft, which transmits power to the elevators, conveyers, etc. As the individual parts and their combina tion are so clearly shown by the illustration, an extended description is unnecessary.