FLINT. A mineral consisting of 98 silica, 0.50 lime, 0.25 alumina, 0.25 oxide of iron, I loss. The domestic use of this stone, for producing light by collision against steel, is well known. It is also much used in gun-locks for firing the powder. The manufacture of gun-flints employs numerous hands in this country ; as independently of the large quantity required for home use, consi derable shipments of them are made to various parts of the world, where the mineral is not supplied by nature. The manufacture of gun-flints was for a long time kept secret ; and we are indebted to M. Dolimien for the first pub lished account of the method practised in France, which he has given in the Memoire de l'Institate National de Sciences. The masses of flint which are best fitted for this purpose, are of a convex surface, approaching to lobular. The best flint nodules are generally from two to twenty pounds weight ; the colour should be uniform in the same nodule ; their transparency should be sufficient to admit letters to be distinguished through a piece of the stone of a quarter of a line thick, laid close upon the paper. Their fracture should be
perfectly smooth and equal throughout, and the fragments slightly colloidal. The last of these properties is the most essential, since on it depends the facility with which the nodule is divided into gun-flints. All flints that prove deficient in any one of the above characters, either naturally or by a long exposure to the air, are called intractible, and rejected by the workmen. There are several hammers and a chisel employed in the operation of fashioning the flints, by which means it is said that a clever workman is able to manufacture a thousand flints in the space of three days. Gun-flints are also manufactured at Purfleet in Kent, and in various other parts of England, in a very superior style.