The method of classification of English drinking-glasses takes into consideration the types of the feet, the types of the bowls, and the types of the stems. There is the plain-footed glass, the glass with the folded foot (so called because the outer circle of the foot is folded back beneath it to strengthen it), the domed foot (shaped as its name suggests), and the domed-and-folded foot glass (a combination of dome and fold). The folded foot is a type which indicates early origin, just as those glasses which have the foot broader than the bowl indicate their origin to have been prior to the first quarter of the nineteenth century. As to types of bowls, there are the drawn bowl (bowl and stem drawn from a single piece of glass, as in the glasses of the seventeenth century); the bell-shaped bowl, the waist-formed bell bowl, the waisted bowl, the ovoid bowl, the straight-sided bowl, the straight-sided rectangular bowl, the ogee bowl, the lipped ogee bowl and the double ogee form. The waist-formed bell-shaped (waisted-bell) bowl is rarely met with--the early eighteenth century marks its decline--and the waisted bowl is uncommon also. The bell-shaped bowls seem longest to have maintained favor. The Bristol Glass Works originated the ogee bowl shapes, which date from the middle of the eighteenth century. As to the types of stems, the earliest in design is the baluster stem, in use as early as 1680, and popular till 1730; the plain stem, most frequently met with in glasses from 1700 to 1750; the air-twist stem, in vogue from 1725 to 1775, and perhaps later; the opaque white twist stem, dating from 1745 till the end of the century; the air and opaque white twist stem, the color twist stem, and the cut stem, dating from about the middle of the eighteenth century. Air-bubbles imprisoned in the stems of glasses have given to this type of glass the name of “tear-glass.” Almost without exception the “tears” have their points downward, although glasses showing the reverse of this have in rare instances been met with. The air-twist stems are an evolution of the tears. The glass containing air-bubbles came to be heated and drawn out and ingeniously manipulated in such a way as to produce the effect of twisted filaments which formed such patterns within the glass as one now and then chances to find. Before manipulation the bubbles were produced artificially by pricking into the glass, softened by heat and covered over, in turn, with a film of molten glass. The opaque white twist stem, and also the color twist stem, were obtained after the Venetian fashion of making Millefiori glass, described in Chapter XXVII (page 221), as derived from the Roman glass of antiquity. Rare specimens of stems are found with delicate tints of blue and red among the filaments.