GRINDSTONES, from the Latin Gyrandus, are circu lar stones, a few inches thick, which are mounted on a spindle, and turned with a common winch, for the purpose of grinding edge tools. When a great number of these stones are driven by machinery for the purpose of cutlery, they are called blade mills or grind mills. Grindstones are formed of a gritstone, in which the grains of silex are firmly cemented to each other by a siliceous or other hard cemenu the interstices not being filled up as in other kinds of sand stone. The following is a list of the grindstone quarries in England, with their degrees of fineness, drawn up, we believe, by Mr Farcy, for Dr Rees's Cyceofliedia: Ashover, N. W. (hill quart y) Derbyshire, middling.
Beely Moor, E. of the town. Derbyshire, coarse.
Belper, S. E (Hungcrhilc) Derbyshire, middling.
Biddulph-flall, N. \V. of Leek, Staffordshire, coarse.
Bilstone, S. E. of Wolverhampton, Staffordshire, mid dling.
Bolsover, N. W. (nunnery) Derbyshire, middling. Bredsal Moor, N. of Derby, middling.
Brinclif-edge, S. E. of Sheffield, Yorkshire, fine. Buxton, N. (COrbar) Derbyshire, fine.
Dailey Moor, E. of the town, Derbyshire, coarse. Gate-head fell, miles south from Chester Ward, Durham.
Glossop, Derbyshire, coarse.
Ilarthill, S. E. Yorkshire, fine.
llooton-Roberts, near Rotherham, York, middling. Horsley, N. of Derby, fine.
Lane-top, N. of Sheffield, Yorkshire, whitening. Little Eaton, N. of Derby,•coarse.
Milford, S. of Belper, Derbyshire, coarse. Molecopt-hill, S. of Congleton, Cheshire, coarse. Morley-moor, N. of Derby, fine.
Norton, W. (Hemp-yard lane) Derbyshire, fine. Overton (Gregory) in Ashover, Derbyshire, coarse. Pole SN% 011 11, S. E. of Tam worth, Warwick.
Purton, \V. of Wolverhampton, Staffordshire, fine. Ridgeway (Lum-delph) in Eckington, Derbyshire, fine. Stanley, N. E. of Derby, fine.
Stanton by Dale, E. of Derbyshire, fine.
Stanton Moor, N E. of \Vinster, Derbyshire, coarse. Therberg, near Rothe' ham, Yorkshire, fine.
Treton, ditto, ditto, fine.
Warton E. of Tantwolth, Warwickshire.
Wickersley, near Rothetham, Yorkshire, middling.• \Yokes, near Barnsley, Yorkshire.
Thu most extensive grindstone quarries are those near Gateshead. They are sent to all quartets of the globe, under the name of Newcastle grindstones, and constitute a great branch of the trade of Newcastle and Gateshead.
The explosion of grindstones when in motion is a phe nomenon which has frequently happened, and which has been atuibuted to the effect of the centrifugal force, and to the expansion of the wooden tt edges.. On the Sth June 1768, a very singular accident of this kind happened to a cutler at Ivry-sur Seine, near Paris, who was grinding kitchen utensils. The stone flew into the au. apparently on fire, and burst into innumerable fragments, with a dreadful noise. One of tho fragments, of about three pounds weight, flew over a building 40 feet high, and alighted 108 feet beyond it in the' garden, where it broke the branch of a lime tree. Another fragment, of nearly the same size, grazed the parasol of a young lady who was standing beside the cutler. A part of the stone was found upon the pavement reduced to powder. A similar accident happened to a cutler at Strasburg, who was kill ed by the explosion.
Our readers will find sonic curious facts relative to grindstones, and to their sudden explosions while they are at work, in the Encyclopedic Illethodique, art. Toon NEUR ; collection ilcademique, torn. xiii. p. 45 48, 413. and tom. xii p. 109 ; Mem. .dcad. Par. 1762. Hist. p. 37 ; and Id. 1768.