1048

THEORY AND PRACTICE OF ENGINEERING.

Book 11.

stone is fixed upon tlie shaft by means of a cross with a segmental top, which is firmly at-tached to it, and the octangular axle passes through the iron box on which this upper stonehangs

, 1 ~ —

Fig. 1611.

In the Victualling Yard at Deptford, the millstones, which are not quite 4 feet indiameter, make 120 revolutions in a minute, and answer admirably well; though theygenerally vary from 4 feet 6 inches to 5 feet in diameter, and make from 80 to 100 revo-lutions in a minute.

The Dressing Machine is a hollow cylinder or frame, covered with wire cloth of differentdegrees of fineness, that is, with 64, 60, 38, and 16 meshes to the inch, that which hasthe smallest space being at the upper end: its axle is inclined to the same angle as thebolting mill. Within the cylinder, which is stationary, is a reel, to the rails of which areattached brushes, which, in their revolution, act against the interior wire surface of thecylinder; the meal is conducted within it by a spout or hopper, and is thus rubbed throughthe wire, the finest passing through the upper end, the second through the next division,

Fig. 1612.

Fig. 1613.

DRESSING MACHINES.

and the bran through the lower end : the cylinder being enclosed in a tight case, the flourcannot escape; there are usually four divisions within it, to collect the varieties of flour asthey are rubbed through : hence they are called, firsts seconds, thirds, and pollard Thepinion upon which the brushes move can be made to revolve either way, so that the motionof the machine can be reversed to suit the brushes, when they become bent in one position.

The Bolting Mill consists of a reel fitted to an axle which revolves with great rapidity,and is covered with a cloth called duck : in the box containing the reel are a number ofwooden bars called beaters, against which the cloth strikes with such violence that theflour is separated from the coarser parts or pollard.