This material is only worked in the soft and plastic state. In pottery, it is attached to the potter's wheel or horizontal lathe, by its own adhesiveness alone, and is turned by the hands and blunt wooden tools; it is also pressed into moulds of metal and plaster of Paris, some of which are mounted on the lathe when the objects are smoothed within and moulded without. Lathes with vibrating mandrels, or possessing the movement of the roseengine, are likewise employed lor the production of some works in pottery and china. The artists who model in clay, use blunt instruments, mostly of wood, which arc rounded at the ends; and all artizans cut or divide this material with a stretched pack-thread, or a metal wire. The clay for superior pottery works and modelling, often called pipe-clay, is decomposed felspar, it is mostly obtained from Cornwall and Devon; and the importance of the Stourbridge, and some other refractory clays, in the construction of crucibles and fire-bricks for a variety of purposes in the arts, must not be overlooked. See Appendix, Note O, Page 957 Vol. II.

* Flint, when first raised, may be split with remarkable precision, with the imperfectly flat conchoidal fracture, as may be well observed in gun-flints, the perfection of the keen edges thus produced, exceeds that of any which may be obtained upon similar substances by art; when the water is completely dried out of the flint it breaks with the ordinary onchoidal fracture.