“Now know ye that I, the said William Cookworthy, in pursuance of the said recited provisoe, do, by this my Deed in writing, declare and make known the nature of my said invention, and the quality of the materials, and manner in which the same is performed, which is as followeth (that is to say):-- “The materials of which the body of the said porcellain is composed are a stone and earth, or clay. The stone is known in the countys of Devon and Cornwall by the names of Moor-stone and Growan, which stones are generally composed of grains of stone or gravel of a white or whitish colour, with a mixture of talky shining particles. This gravel and these talky particles are cemented together by a petrified clay into very solid rocks, and immense quantities of them are found in both the above-mentioned countys. All these stones, exposed to a violent fire, melt without the addition of fluxes into a semi-transparent glass, differing in clearness and beauty according to the purity of the stone. The earth, or clay, for the most part lies in the valleys where the stone forms the hills. This earth is very frequently very white, tho’ sometimes of a yellowish or cream colour. It generally arises with a large mixture of talky micæ, or spangles, and a semi-transparent or whitish gravel. Some sorts have little of the micæ, or spangles, but the best clay for making porcellain always abounds in micæ, or spangles. The stone is prepared by levigation in a potter’s mill, in water in the usual manner, to a very fine powder. The clay is prepared by diluting it with water untill the mixture is rendered sufficiently thin for the gravell and micæ to subside; the white water containing the clay is then poured, or left to run off from the subsided micæ and gravell into proper vessells or reservoirs; and after it has settled a day or two, the clear water above it is to be then poured or drawn off, and the clay, or earth, reduced to a proper consistence by the common methods of exposing it to the sun and air, or laying it on chalk. This earth, or clay, gives the ware its whiteness and infusibility, as the stone doth its transparency and mellowness: they are therefore to be mix’d in different proportions, as the ware is intended to be more or less transparent; and the mixture is to be performed in the method used by potters, and well known (viz., by diluting the materials in water, passing the mixture through a fine sieve, and reducing it to a paste of a proper consistence for working in the way directed for the preparation of the clay). This paste is to be form’d into vessells, and these vessells, when biscuited, are to be dipp’d in the glaze, which is prepared of the levigated stone, with the addition of lime and fern-ashes, or an earth called magnesia alba, in such quantity as may make it properly fusible and transparent when it