The best of these do not essentially differ from each other, nor from the white leads of other manufactories. The latter variety, being prepared from flake white, is usually the greyer of the two. 7. PATTISON'S WHITE, OR OXYCHLORIDE OF LEAD Is a mixture of chloride and oxide of lead, formed by precipitating a solution of chloride of lead with soda, potash, lime, or baryta, in the caustic or hydrated state. It would appear that when the oxychloride is used as a paint, the oxide contained in it gives rise to an oleate of lead, and, in consequence of this saponaceous matter, is capable of spreading over an extended surface. The product has been described as possessing properties which are superior to those of white lead, inasmuch as it does not so readily blacken as the latter body. Dr. Ure, however, found that water removes the chloride of lead from the paint compounded of this article, and, consequently, that it is not so effectual as the carbonate. As an artist's pigment, a partially soluble compound of lead can decidedly not be eligible. 8. ROMAN WHITE Is of the purest white colour, and differs only from blanc d'argent in the warm flesh tint of the external surface of the large square masses in which it is commonly prepared. Besides the foregoing, there are other white leads, generally foreign, cheaper, and adulterated. Many of these are mixed with a small quantity of charcoal, indigo, or Prussian blue, so that the dead yellowish shade which they present may be enlivened to a brighter hue. Among them may be named-- 9. CERUSE. A French variety, not necessarily, but not unfrequently, mixed with different chalky earths in various proportions; and the following Belgian kinds: 10. DUTCH WHITE, Containing three fourths of sulphate of baryta. 11. HAMBURGH WHITE. A mixture of two parts of heavy spar and one of the plumbous compound. 12. KREMSER WHITE, Differing from the rest in being unadulterated. 13. VENETIAN WHITE Composed of heavy spar and the carbonate in equal proportions. ZINC WHITES. 14. CHINESE WHITE.