5th and 6th. Successive stages of expansion, by constant and rapid rotation.
7th. Final expansion into a flat circular sheet.
8th. The sheet of glass, held on a kind of fork, being placed into the annealing oven.
When cold, the sheets of glass are cut into two unequal pieces, one of which contains the knot, and are packed with straw in wooden crates, in which they are forwarded to the warehouses, and from thence to the glaziers.
As plate glass is sometimes used for windows, a slight notice of it seems to be necessary in this place, in order that the reader may have a clear idea of the difference between these two descriptions of window glass.
The manufacture of plate glass is confined to very few hands, and great reluctance is manifested by the proprietors to permit visitors to inspect their works. The late Mr. Parkes, however, was permitted to visit the works of the British Plate Glass Company, at Ravenhead, and has recorded his observations in one of his valuable chemical essays, from which the following details are taken.