It is however undoubtedly on his jasper that his fame with succeeding generations has been based:—the white classical figures, designed by Flaxman or by Hackwood, embossed on a blue or black ground. The discovery of the jasper body, with its admixture of barium sulphate, gave him a perfectly white hard stoneware body, which would take a high fire, and become semi-vitrified without glazing. The body could be stained light or dark blue, pink, green or black, by the addition of suitable oxides, and then formed the ground of his jasper ware; while the white body, pressed into small plaster moulds, taken out and then “sprigged on,” formed the ornamental embossments. This jasper ware could be used, and is still found, as panels in Adam fireplaces, with Flaxman’s “Dancing Hours” or “Medusa Head” clean cut on the blue plaque; as cameo medallions, bearing the heads of personages of state, for show cabinets; or as vases under a glass case, such as the Portland Vase, completed in 1790. And it is this jasper ware that is called to mind when “Old Wedgwood” is spoken of by amateurs. A proper description is impossible here of these Jasper or Black Basalt vases, statues or plaques, in which he received the invaluable assistance of Flaxman as a modeller, and the advice of every gentleman of the period who prided himself upon his taste. Description of manufacture and details of patterns must alike be left to special monographs, such as that of Prof. Church. To complete a bald account of Wedgwood’s career as a potter we must add the following notes. Between the years 1759 and 1769 he perfected the cream colour, between 1766 and 1769 the black Etruscan ware was brought to its highest perfection; the jasper body and glaze was undergoing development from 1773 to 1777, and the jasper dip from 1780 to 1786. His mechanical bent showed itself in a persistent and successful effort to develop the turning lathe so as to give a ribbed surface to the ware. This he called “engine turning,” and it is a device which has been largely employed ever since on decorative pieces. In 1783 he invented a neat pyrometre for registering the heat of ovens, and was elected in consequence a Fellow of the Royal Society. His great partner Bentley died in 1780, and for a few years Wedgwood carried on his works alone; but in 1790 he took into partnership his three sons John, Josiah and Thomas, and his sister’s son Thomas Byerley. The style and title of the Firm which had been “Wedgwood and Bentley” from 1768-80, “Wedgwood” from 1780-90, now became for a short time “Wedgwood, Sons and Byerley.” In 1793 his sons John and Thomas, having no aptitude for the systematic work of a master-potter, and being rich enough to be idle, retired from the firm, and conveyed their shares to the younger Josiah. Till Thomas Byerley’s death in 1810, the firm was known as “Wedgwood, Son and Byerley.”[108]