MILLS.
Of the various mechanical processes by which the condition of natural products is changed, that of pulverizing is the simplest; and the earliest human contrivances were doubtless of the nature of mills for crushing and grinding fruits and seeds.
The term mil/ was originally restricted to denote the various forms of apparatus by which grain is ground into flour or meal, and the equivalent word in the Latin and its allied languages still retains this signification (Lat. mola ; It. mulino; Sp. molino; Fr. mou/in). In modern English usage, however, the term .is applied to nearly all machines and combina tions of machinery which consist chiefly of wheel-work and its co-ordi nate appliances, by which raw materials are changed into new forms and conditions; and the mill generally takes its name either from the principle of its action, as "rolling-mill," "saw-mill," or from the materials upon which it acts, as "cotton-mill," "corn-mill," and the like.
The present section will be chiefly devoted to the consideration of mills used for grinding grain. These will be considered under three divisions: (r) those comprising sncli mealing implements as are operated exclusively by hand: these have been employed from the earliest period of human history to the present time; (2) those in which one of a pair of stones is formed for continued rotary motion, and which may be driven by baud-, animal-, water-, or wind-power: such have also been employed during the greater part of historic time; and (3) those which combine in one system of connected machinery all the necessary contrivances for grinding, sep arating, cleaning, packing, and automatically moving the grain and meal from one part of the mill-house to another and to and from the several ma chines ; also for receiving the grain from transports and for delivering the packed flour to the same. These mills have been perfected almost entirely
within the present century. To these there is added a fourth division, which embraces mills constructed on principles similar to those employed 21 for grinding grain, and used not only for the reduction of substances to powder, but also for the crushing of olives, minerals, and ores, and for the comminuting and mixing of confections, drugs, chemicals, materials for paints, ceramics, etc. The mills of this class will be considered according to their mode of action—namely, (r) crushing and (2) grinding.