Flint, or Silts, L. a kind of opaque stone, which is, in general, of a roundish form, covered with a white crust, of a smooth-uniform texture, and .so hard, as to emit fire, when stricken against steel. It is chiefly used in the ma-nufacture of glass. - For this purpose the hardest flints are selected, such as will resist the file, and become white when calcined. They are first cleansed from the white crust adhering to them; then burnt in a strong fire, and thrown, white red-hot, into cold water. After cleaning them of the ashes, the flints are finely pulverized in an iron mortar, and passed through a sieve. Weak aqua-fortis is next poured on the powder, with a view to dissolve any particles of iron perhaps acquired from the mortar. This mixture is to be repeatedly stirred, and then left to-subside, after which the liquor is to be poured off, the powder washed several times with hot water, and, lastly, dried. In this state it is fit to be converted into glass.

In the year 1/42, an oil was prepared from f'ints by Messrs. Betton and Wellington, of Shrewsbury, for which they ob-tained a patent. It may be made of 4oz. of flints calcined, pulverized, and mixed with 12 oz. of salt of tartar. These ingredients are next to be melted together in a crucible over a strong fire, and rum into an open glass, which strongly attracts moisture from the air, and . is completely soluble in water, excepting a small portion of earthy matter. This glass is then to be pulverized, and set in a cellar where it will spontaneously liquefy into an oil;j which the patentees have affirmed to be efficacious in curing obstinate rheumatisms. - We doubt, however, the utility of this medicine, as there are other local remedies, more proper and efficacious in that painful complaint. - See Rheumatism.