This mill converts wheat into flour at the rate of about 500 sacks a day of 24 hours- a quantity nearly sufficient to supply bread for the entire population of a city like Edin burgh. [The above description applies to Messrs. Tod's mill as it stood in 1863. It was subsequently greatly extended; and, after being destroyed by fire in 1874, has been com pletely refitted.] The great government mill of St. Maur is the most remarkable mill in France.
There is a form of mill in use for some purposes wheiv the millstones are vertical, and called the edge-stone mill. It is sometimes, though rarely, used for grinding corn; but ,is much employed for cnishing oil-seeds and for grinding dye-stuffs, sugar, chemicals, and a multitude of other substances. The stones are generally of some hard rock, such as granite or sandstone, and from 5 to 7 feet in diameter. For such purposes as grinding clay or loam they are usually made of cast iron, and of a smaller size. The stones revolve in opposite directions, sometimes upon a fixed stone or metal bed, and at other times it is the bed-plate itself which revolves, and in so doing turns the edge stones which rest upon it.
Among the recent improvements in our flour-mills which have attracted considerable attention are: 1. The patent proCess of dressing the 'grinding surface of the milLstones by means of a peeuliar kind of diamond, which rapidly covers it with fine grooves. This is still, however, more largely, and perhaps more efficiently, done by the slower process with the rridging hammer; 2. The keeping down of the temperature of the millstones by means of a current of cold air; and 3. The introduction of Carr's patent disintegrater, which grinds wheat and other substances by means of two vertical iron disks about five feet in diameter, and a few inches apart, in each of which are several concentric rows of steel pegs, so arranged that those on the one disk overlap without touching those on the other. The disks are made to revolve rapidly in opposite directions, so as to grind the wheat by percussion.