or compound Glass, manufactured at the Falcon Works, (of a beautiful topaz tint, coloured by uranium, which became richer in hue by diminishing the usual proportion of lead, and by increasing the alkali,) fractured three months after it was cut. Complaints from purchasers at home and abroad reached the Works, and the whole had to be replaced at the expense of the manufacturer.

Excess of alkali causes continual exudation; the cementing property escapes, entire fracture is the result, and no remedy can check the evil. A piece of ancient light blue Glass, since it came into the possession the British Museum, has spontaneously fractured, and some parts almost to pulverization; an effect caused by its excess of impurity of alkali.

Formerly, lears were heated by the waste caloric of the furnace; they were elevated about six feet or more from the floor of the Glass-house, to catch the flame and warmth from the top of the furnace flues. This contrivance saved the entire lear fuel; but from the inconvenience and breakage caused by the Glass being taken up steps, and the impossibility of regulating the heat and smoke, it has been long since dis-used in England. Modern lears are placed a few feet above the floors of the Glass-house, as already described: they not only anneal the Glass better, but the saving of breakage, in comparison with the old system, is found to be considerable, and wholly covers the expense of separate fuel. The amount of breakage in the lears varies considerably; the minimum average may be taken at 2 per cent. upon the manufacture; under unfortunate or bad