drawn out, the bubble elongated into a tube, and when the stem was twisted, the tube acquired a spiral shape. Now as the tube was filled with air, which had a different refractive capacity to the glass which surrounded it, the effect of the light falling upon it was to produce a kind of silvery radiance like that of quicksilver. The phenomenon is familiar to anyone who has ever plunged a substance like wool, which contains air-bubbles entangled among its meshes, under water. The bubbles are transformed into drops like quicksilver. So with the tear and the tube drawn from it in the air-twisted stem. Naturally the decorative potentialities of this phenomenon were speedily recognised and utilised, and the air-twisted stems are among the most characteristic and the most beautiful features of all old English glasses. The bowls were usually of the same general shape as those with incised and ribbon-twisted stems. The earlier varieties are “waisted,” the later ones frequently assume the bell shape. They are often engraved, the early ones with the Tudor rose, with its five petals, while the later ones affect the Stuart variety with six petals. The earliest stems have necks and collars--there was considerable difficulty in joining the air-twisted stem on to the bowl without damaging the twist. Later varieties have necks only. The collars are sometimes knopped, _i.e._ have knobs attached, and the stems themselves are shouldered. I have dealt at some length with the air-twisted stems, since this is a characteristic English variety, and one to which the brilliant English flint glass was specially adapted. Consequently the type persisted for a considerable period. The later varieties, however, achieve some little distinction by the adoption of the bell-shaped bowl. _Drawn Stems._--I have already suggested that the fusion of the air-twisted stem, in order to join it to the bowl, not unfrequently resulted in damage to the twist. It was an obvious solution of the difficulty to draw the stem out from the surplus molten metal at the base of the bowl. If, previously, a series of air-bubbles was introduced into this mass, each in the process of drawing out became elongated into a tube, and we have the possibility, by planting “tears” in effective positions, and then [Illustration: FIG. 42. The figures given above illustrate certain of the characteristic features of Old English glasses. Thus Fig. 1 is an example of a double-knopped stem, each of the bulges being technically known as a “knop.” The foot is “domed.” No. 2 is an illustration of a shoulder and collar, the shoulder being the bulge near the top, and the collar the ring above it, which was originally devised to hide any clumsiness in joining the stem to the bowl. No. 3 is a “flanged” bowl, No. 4 a “waisted” bowl, and No. 5 shows an air-twisted stem. ]