It was at this time, and chiefly under the influence of Brongniart,[196] that the palette of the enameller was enlarged by the introduction of so many new colours, the employment of which gives a new _cachet_ to the decoration of the nineteenth century. Perhaps the most important advance was in the employment of oxide of zinc in the flux, by means of which the colours of many metallic oxides are developed and sometimes altered. The green derived from chromium is essentially a nineteenth century colour, and as it resists the highest temperature this green can be used, like the cobalt blue, as an under-glaze colour. From the chromate of lead an orange-red is obtained--the _rouge cornalia_, a crude and dangerous colour, and one that does not withstand high temperatures. An orange-yellow from uranium, and a deep and uniform black from iridium, were also introduced at this time or not long afterwards. The ‘English pink,’ the lilac tint so extensively used in the transfer-printing of earthenware, was successfully imitated by adding a small quantity of oxide of chromium to a flux containing oxides of tin, lime, and alumina. The celadon green of Sèvres is derived, not from the protoxide of iron, but from the sesqui-oxide of chromium, with the addition of a minute quantity of copper. Brongniart’s great work, the _Traité des Arts Céramiques_, still remains our main authority on the technical and scientific side of the art of the potter, and it was he who, by establishing the museum and organising the laboratories at Sèvres, made that town a centre for all who are interested not only in the special branch of porcelain, but in the whole field of ceramic art. The position established by him has been well maintained by his successors, by Salvétat, by Ebelmen, by Deck, and at the present time by MM. Lauth and Vogt on the technical side--above all by Édouard Garnier, the present director of the Sèvres Museum.[197] These men have succeeded, in spite of much opposition, in again bringing the national manufactory of porcelain at least on to a level with the artistic movement of the day.