exterior coating to become opaque, and peel off film by film, and layer by layer, in siliceous opalescent matter, sometimes in iridescent tints, until the whole mass had become reduced materially in weight; leaving part of the interior only, of a transparent substance, comparatively porous and weakened in structure by the loss of alkali.

Dr. Faraday, who kindly examined a piece of this fragment, proved that it softened by the blow-pipe, and took the impression of a file. He found no trace of lead, and but little lime; and the chief part of the alkali was considered potash. No doubt, therefore, exists of its being ancient Glass. The large quantity of alkali in comparison with the sand causes its peculiar lightness; its excess together with caloric has induced exudation, roughness of surface, and the dislocation of some of its particles; it having throughout small cracks, as if caused not by friction but by the loss of the cementing properties of its alkali.

Another fragment of Glass, considered equally ancient (by Mr. Roach Smith) as the former, is of a greenish tint; it has, no doubt, iron in its constituents; and, from its compound character, is as perfect as at the hour it was manufactured. Its specific gravity is 2600. It has small projecting solid lumps at regular distances from each other, intended for ornament.

A third fragment is of blown diamond pattern of heavy Glass: it has slight white coating or film, which yields to, and can be removed by, the nail; is otherwise perfectly colourless and transparent, and about the same specific gravity as modern Flint Glass—viz., 3144. It has a polished surface, and is in excellent preservation.

The two latter fragments being in so high a state of preservation would lead to the conclusion that their conservative