Precisely when and where the invention was made and first used we have no means of knowing. We may dismiss the story of the glazier from whose coat a silver button dropped on to the glass he was putting into the kiln, partly because the artist of whom the story is told, one James of Ulm, who worked in Italy and was beatified after his death, was not born till more than a hundred years later. It appears in York Minster, used very sparingly and tentatively, soon after 1300. I am not sure that there are any examples in France that can be dated quite so early, but it was certainly used there by 1310. Its first use was limited to such matters as differentiating the hair, or gold crowns, of figures from their faces, but the nave windows of York Minster show a progressive increase in its use. Yellow pot-metal is there still used for the larger pieces of yellow in the canopy, but an examination of the details in Plates XVII., XVIII. will show that stain is used in places to gild the crockets of the white pinnacles, the beak and claws of the white eagle in the border of XVII.c, and the flowers in the lower part of the border in XVII.a. The pieces that are yellow all over may, I think, be assumed to be pot-metal. It is not, however, till one gets well on in the century, to 1330 or 1340, that one finds such a free use of the stain in the grisaille as that in the windows at St. Ouen at Rouen, of which the detail is given in Plates XXVI.-XXX. [Sidenote: Combination of figures and grisaille.]