Bottle glass is the cheapest kind, and made of ordinary materials; these are generally sand, with lime, and sometimes clay, and alkaline ashes of any kind. The green color is owing to impurities in the ashes, generally to oxyd of iron. This glass is hard, strong, and less subject to corrosion by acids than flint glass. For bottles containing the effervescing wines, great care is necessary in the making ; the materials must be thoroughly mixed, when the mass is in a state of fusion, and the thickness should be uniform throughout, in order to resist the pressure of the contained carbonic acid. The loss of bottles by bursting, in the champagne trade, is from twenty to thirty per cent ; a machine has been contrived to tost their strength, which ought to be equal to bear the pressure of from twenty-five to thirty-five atmospheres. In hcttles to contain acids, the alkali and the linta should be chemically united, to prevent action of the acid.