Now, if we turn from these general considerations to examine the nature of the West of England ware, we find some difficulty in drawing a line between the early, partly experimental, porcelain made at Plymouth and the later, more successful, products of the Bristol kilns. Nor will the mark, the alchemist’s sign for Jupiter[251] (PL. E. 83), first used on the Plymouth porcelain, help us much, for the same mark was certainly used to some extent after Cookworthy’s migration to Bristol. To Plymouth we must attribute the plain white ware with a glaze of dull hue, disfigured by dark lines where the glaze lies thick in the interstices. Cookworthy, we know, attempted to make his glaze from the Cornish stone without the addition of any other substances.[252] In other cases he followed the recipe given by the Père D’Entrecolles, and gave greater fusibility to the growan-stone by adding a small quantity of a frit made from a mixture of lime and fern ashes. Cookworthy even ventured to follow the Chinese plan, and applied the glaze to the raw [Illustration: _PLATE XLVIII._ 1--PLYMOUTH, WHITE GLAZED WARE 2--BRISTOL, COLOURED ENAMELS] or very slightly baked paste. The blue and white made by him, if we may judge from the little mug in the British Museum, with the arms of Plymouth and the date, March 14, 1768, was of very poor quality. The Oriental designs on his enamelled porcelain seem to have come to him by way of Chantilly. More successful was the plain white ware modelled in relief, in a way that often calls to mind the early work of Bow. A good example is the ‘Tridacna’ salt-cellar in the former Jermyn Street collection.