Fig. 1. An ancient Roman fragment of Glass of the smeltz character. It was exhumed in the city of London, near Moorfields, and is now possessed by Mr. Roach Smith: it is a melange of yellowish-white enamel, with a very dark iron red. Specific gravity, 2576.

Fig. 2. Has the projecting Roman pillars, as described in the manipulatory portion of this work, (see page 104;) and, like most of the Compound Glasses, has scarcely undergone any decomposition whatever. Specific gravity, 2483. Also Mr. R. Smith's.

Fig. 3. Is a very rare specimen from Mr. R. Smith's collection, and displays the great perfection of ancient Glass cutting. It formed part of an elegant drinking-cup. One peculiarity is, its lightness; it being but little more than twice its weight of water—viz., of a specific gravity 2049. It is quite colourless.

The ancients had their White Glasses both of simple and compound character; the latter were by far the most conservative. Specimens of the former, in the British Museum, and in private hands, are in a state of considerable decomposition. The heat of the burning lava which overwhelmed the devoted cities of Herculaneum and Pompeii, may have had great effect in destroying part of the alkaline properties, (much greater than the ordinary influence of the atmospheric air,) and thus causing, in the partial decomposition, the