Chap. XIII.

MILLS.

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diameter, each performing 123 revolutions in a minute, and grinding five bushels of cornper hour, so that when the mill is in full work 120 bushels of corn are ground in that time,as well as dressed by eight machines.

Tlie fly-wheel that communicates the motion is on the left of the figure ; the main shafthas its bearings in plummer blocks bolted to cast-iron frames ; on it are two bevelledwheels 8 feet in diameter, which engage two others, 5 feet 4 inches in diameter, placed onthe main vertical shafts, which have their bearing at the lower end, on another cast-ironframe, and on brasses and other plummer blocks attached to the floor of the mill. Theshafts are all placed in a well or circular mass of bulwark, and the large cog-wheels aliove,] 0 feet in diameter, turn six toothed wheels set round their circumference, upon thespindles of which the upper millstone is fixed, and revolves very rapidly.

The corn is laid on the upper floor, and then by spouts conducted first to screening ma-chines or cylindrical sieves, arranged somewhat like an Archimedean screw; it is admittedat one end, and in its course passes over a larger surface of wire j when cleaned of the sandand dust, it falls into a hopp(^, from which it passes by spouts to the millstones.

On the second floor of the mill the dressing machine and bolting mills are arranged,which are put in motion by a bevelled wheel on an horizontal shaft, which can be put inor out of gear with the vertical shaft at pleasure. The machinery for raising the sacks issuspended on the beams of the roof; it consists of a barrel and a system of wheel-work putin motion by a bevelled wheel on the top of the vertical shaft.

The millstones are composed of a number of pieces attached together by a strongcement, and further secured by iron hoops passing round their circumference: on the

1 ig. 1610.

MILLSTONES.

upper and lower millstones are grooves or channels cut obliquely from the circumference,to within an inch and a half of the centres: eight long channels divide the stone into asmany portions, in each of which four others are usually cut; these furrows are sunk insuch a manner that one side is perpendicular, and the other oblique, and one being placedupon the other, the sharp edges meet, and effectually cut the com, which passes betweenthem. In bedding millstone, great care must be taken to have them perfectly level, andfirm on their bearing; they are sometimes supported by a timber frame, which is wedgedup from the floor, but more frequently an adjustment is effected with an iron frame andscrews.

The bed stone in the figure is fixed in an iron case, which can be raised or lowered byturning the iron screws beneath, and at the side are other screws which move the stonelaterally when required: when the iron cross or damsel above revolves, it strikes the shoeunder the hopper, and gives it a tremulous motion, which causes the wheat to pass downfrom it to the millstones, in proportion to the velocity of the motion. The upper mill-

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