It takes about seven or eight years to finish a mosaic copy of a painting of the ordinary historical size, two men being constantly employed. It generally costs from eight to ten thousand crowns, but the time and expense are of course regulated by the intricacy of the subject and quantity of work. Raphael's _Transfiguration_, cost about 12,000 crowns, and the labour of nine years, ten men constantly working at it. The late works, are, however, of very inferior execution. The slab upon which the mosaic is made, is generally of Travertine, (or Tiburtine) stones, connected together by iron cramps. Upon the surface of this a mastic or cementing paste, is gradually spread, as the progress of the work makes it wanted, which forms the adhesive ground, or bed, on which the mosaic is laid. This mastic is composed of fine lime from burnt marble, and finely powdered Travertine stone, mixed to the consistence of a paste, with strong linseed oil. Into this paste are stuck the _smalts_, of which the mosaic picture is formed. They are a mixed species of opaque vitrified glass, partaking of the mixed nature of stone and glass, and composed of a variety of minerals and materials, coloured for the most part, with different metallic oxydes. Of these no less than 1,700 different shades are in use; they are manufactured in Rome in the form of long, slender rods like wires, of different degrees of thickness, and are cut into pieces of the requisite sizes, from the smallest pin point to an inch. When the picture is completely finished, and the cement thoroughly dried, it is highly polished. Mosaic, though an ancient art, is not merely a revived, but an improved one; for the Romans only used coloured marbles, or natural stones in its composition, which admitted of comparatively little variety; but the invention of smalts has given it a far wider range, and made the imitation of painting far closer. The mosaic work at Florence is totally different to this, being merely inlaying in _pietre dure_, or natural precious stones, of every variety, which forms beautiful, and very costly imitations of shells, flowers, figures, &c. but bears no similitude to painting. Besides this government establishment at Rome, there are hundreds of artists, or artisans, who carry on the manufactory of mosaics on a small scale. Snuff-boxes, rings, necklaces, brooches, earrings, &c. are made in immense quantity; and since the English flocked in such numbers to Rome, all the streets leading to the Piazza di Spagna are lined with the shops of these _Musaicisti_, &c.