The painters who worked in enamel occupy a section of miniature work apart, although in many instances the best known enamellers painted portraits also on ivory or on vellum, but they are especially known for their works in enamel. There is little need for us here to do more than define enamel work as a vitreous glaze attached by fusion to a metallic ground, but only those who have attempted to paint portraits in enamel can have any idea of the enormous difficulty of this method of portraiture when fine results are desired. Of all the men who were successful in this most complicated process, Jean Petitot stands out supreme, and his portraits, as a rule excessively minute in size, are distinguished by a delicacy of detail, marvellous in its microscopic exactitude. When it is remembered that the colours were painted on to the panel of gold in the form of a powder, only slightly mingled with a medium, that they did not represent by their tint the colour they were to present when fused, and that the slightest error in the fusing would ruin the plate and cause the colours to run into one another, the marvel is but enhanced when the exquisite works produced by this incomparable artist are examined. The specimen from Mr. Ward Usher's collection (Plate XXXV.), which is illustrated in colour, is a good example of Petitot's portrait of _Louis XIV._ He painted the face of "_Le Roi Soleil_" so often that he must have become familiar with every detail of it, and there is hardly any collection of his works which cannot boast of one of these wonderful little enamels. The story of the painter himself is of considerable interest, and the details of his religious difficulties and of his return to Geneva are well set forth in a book about him written by E. Stroehlin, and published in Geneva in 1905; while some further special information more recently discovered can be found in an article by the writer of this essay in the "Nineteenth Century" for January 1908. He left behind him a wonderful little pocket-book containing his own and his wife's portraits, and a narrative of part of his career, written by him in beautiful handwriting. His own portrait belongs to the Earl of Dartrey, and there are some wonderful examples of his work in the Louvre; but the best of his portraits are in England, and there is no collection to rival that of South Kensington in this respect. Perhaps his most extraordinary work is the box belonging to Mr. Alfred de Rothschild, which has fourteen portraits upon it; but his largest, with one exception, is that of _Mary, Duchess of Richmond and Lenox_, which we illustrate from Mr. Pierpont Morgan's collection (Plate XXXVI., No. 2). It is signed and dated 1643 and is 5-1/2 inches square, the only miniature exceeding it in size being that at Chatsworth, representing the Countess of Southampton, and dated 1642. The latter is, however, unfortunately damaged, whereas the one in Mr. Pierpont Morgan's collection is quite perfect.