I

Chap. XIII.

MILLS.

1049

[_ 1

Fig. 1614.

The reel has six bars fixed in an axle which works in a circle, and at the upper end is‘22^ inches in diameter, and diminishes gradually to 20£ inches at the lower or tail end :when at work it is turned with sufficient velocity to make the bolting cloth swell out to itsfullest extent, and occasion the beaters to force the flour through the meshes of the cloth ina constant stream.

Some bolting machines have a contrivance applied to them containing a spring, whichfacilitates the dressing of the flour : it consists of a cylindrical ring of iron, into which areriveted six elastic arms : at the end of each is a hook, to receive a loop attached to thetail leather of the bolting cloth, causing a more uniform action to be kept up.

The Mortar Mill is composed of a vertical shaft or spindle, to which the millstone is at-tached, revolving on a bed upon which the limestone or chalk to be pounded is thrown :curved pieces of iron, called rakes, are fixed to the shaft, and revolve round in a regularmanner to keep the iron bed free from any impediment to its regular motion : when thelime is properly ground, it is passed into another mill, where it is mixed with its pro-portion of sand, and triturated or compounded by the action of constantly revolving

II’j i

Fig. 1616.

MILL FOR MIXING MORTAR.

rakes, attached to the arms of a horizontal wheel that moves round in a circular bed.The pug mills are upon a similar construction, and have a post in the middle with along lever, to which the horse is applied The lime and sand thrown into the trough arethen mixed by the revolving rake fixed at the lower part of the upright shaft.

Mills for grinding Cement are formed like the corn mill, with the addition of two ironrollers, shown under the right hand hopper, which receive motion from a spur-wheelattached on the main shaft : by means of the rollers the cement stone is first broken downinto a powder or small fragments, after which it is hoisted to the top of the mill in sacks,and then put into the hopper, whence it passes off to the millstones; the lower one beingfixed, and the upper put in motion by the machinery.

The millstones are grooved or channelled obliquely, from the circumference, as in theflour mill, and make about 150 revolutions in a minute : when the cement is ground, itpasses out at the circumference of the stones into a spout, which conveys it to two sieves,separating the fine powder from the coarse : the sieves placed beneath the large horizontalwheel have a rapid reciprocating motion by a rod and crank attached to the smalt spur-wheel, which is turned by the larger wheel just mentioned.

To the right of the figure is a mortar mill, which works by means of the spur wheel,and into which the cement powder is put, when prepared for use. At Sheerness dock-yard a twelve horse-power steam engine was made use of to work a similar cementmill.