Finally, about the beginning of the sixteenth century, enamel paints of other colours were employed, and painting _upon_ glass marks the last stage in the European technique of window glass. While the colours, unlike the opaque brown, were translucent, they lacked the brilliance and purity as well as the richness and depth of pot metal. But by this time, as in other kinds of decoration, the designers were absorbed with details. A favourite task enforced upon them was the insertion of heraldic insignia in the windows, and brushwork was the only method that could reproduce the complicated devices of “quartering” the coats of arms. Window decoration, in fact, had ceased to be an art of glass work and become confused with the art of painting. The end of glass decoration was completed when the window was filled with rectangular panes of white glass, on which the painter depicted figures of saints or symbolical nymphs, as Sir Joshua Reynolds, for example, did in the windows of the ante-chapel of =New College=, =Oxford=. This masterpiece of the trivial is popular, but represents a debased taste, founded upon a complete ignorance of the glass-technique, for Sir Joshua called in to his assistance a china painter! =Vaulting.=--The treatment of the roofing displays more variety in English Gothic than in French. Wooden ceilings, which we will return to presently, often replaced the vaulting and the latter also became distinguished by elements that were only sparingly, if at all, employed in France. The French, as we have noted, constructed the diagonal as well as the longitudinal and transverse ribs with pointed profiles, so that their vaults were domical. The English, on the contrary, frequently used the half-circle for the diagonal ribs. Thus the vaults have level tops or _ridges_, the latter being marked by ridge ribs. =Tiercerons.=--In England, during the thirteenth century, as in France, the plain four-part ribbed vault was used, as in the naves of =Salisbury= and =Gloucester=, and the aisles of =Peterborough=. Toward the end of the century, however, came in the use of subordinate ribs, called _tiercerons_. These were introduced between the transverse and diagonal ribs, as may be seen in the nave vaulting of =Westminster Abbey=. Their purpose was to decrease the pressure on the main ribs, and for their own further security a _ridge_ rib was employed for them to abut on at the top.