among mechanics, a tool used in metal, &c., in order to smooth, polish, or cut.

This instrument is of iron, or forged steel, cut in little furrows, with chisels and a mallet, this and that way, and of this or that depth, according to the grain or touch required. After cutting the file, it must be tempered with a composition of chimney-pan, very hard and dry, diluted, and wrought up with urine, vinegar, and salt; the whole being reduced to the consistence of mustard. Tempering the files consists in rubbing them over with this composition, and covering them in loam; after which they are put in a charcoal fire, and taken out by that time they have acquired a cherry colour, which is known by a small rod of the same steel put in along with them. Being taken out of the fire, they are thrown into cold spring-water; and when cold, they are cleaned with charcoal and a rag; and being clean and dry, are kept from rust by laying them up in wheat bran. Iron files require more heating than steel ones. Files are of different forms, sizes, cuts, and degrees of fineness, according to the different uses and occasions for which they are made.

in the art of war, a row of soldiers, standing one behind another, which is the depth of the battalion. FIN

or squadron. The files of a battalion of foot are generally three deep; as are sometimes those of a squadron of horse. The files must be straight, and parallel one to another.