FLORENTINE MOSAIC AND ENAMELLED SLATE.

In this manufactory, maintained by the liberality of the successive Grand Dukes of Tuscany , agates andother hard stones are cut into shapes which, when set together, form a picture, on a flat surface, of shells,flowers, foliage, or other objects. The difference of these pictures from representations of the same subjectsin glass mosaic consists principally in the pieces having a large surface, and being cut into the form of theobject, the variety in the shade of the colour being the natural tint of the stone itself; it is, therefore, morelimited in its scope, inasmuch as glass mosaic, being composed of pieces of any size and of any colour, maybe made to represent the most finished pictures; whereas the inlaid agate-work, from the gradation of tints andcolours being entirely dependent on the natural tints of the stones, is only fit for simple designs composed ofoutlines and a few colours; though indeed it is wonderful to see how beautiful and varied are the works whichfrom time to time have emanated from the above-mentioned Fabrica Ducale. The materials employed are agates,chalcedony, jasper of various colours, lapis lazuli, and other stones suitable by their colours, hardness, and polish.Stones less hard than the above are also used, such as giallo antico, Oriental alabaster, &c., which are valuablefrom their beautiful colour and polish; other substances, not mineral, are likewise introduced—such as mother-of-pearl, and red coral. The ground is made from either rosso antico or more generally nero antico. Formerlythe subjects sought to be represented were such as the Pantheon, tomb of Cecilia Metella, &c.; the result was,however, not very satisfactory, thus furnishing one of the many examples of the impropriety of proceeding withan unpliant material beyond those conventional forms, which of themselves give evidence of the limit to whichthey should be employed. The more suitable subjects now represented are shells, corals, flowers, vases, andfoliage; these are made up on tables, paper-weights, brooches, vases, &c. In the Fabrica Ducale works of alarger description are manufactured, such as the beautiful altar-piece lately completed of pietra dura mosaic, forthe Medicean sepulchral chapel of St. Lorenzo. In the Galleria there is a beautiful pietra dura table. Alsoseveral in the Pitti Palace, some of which made the memorable journey to Paris , and appeared in the galleryof Apollo in the Louvre.

The cutting of the agates is effected by a bow strung with an iron wire, and emery, which produce thesame result as the thin iron wheel of our lapidaries. By these means the agates are cut into slices aboutthe eighth of an inch thick; they are then polished, and by the above bow and wire are cut into therequired forms. A slab of sandstone, about half an inch in thickness, supplies a temporary base, on whichthe various pieces forming the objects are put together and cemented. The material, whatever it may be,which is to form the ground colour, is then cut into slices of the same thickness, and adjusted so as to coverthe whole table-top. By means of the wire, pieces of the exact size of the objects are cut out of this ground,which is then cemented on to a base of sandstone of the same size, and the pieces being removed from thetemporary base, are also cemented into the vacuities cut in the ground, thus producing the representationintended. The cement used is a composition of wax, turpentine, and resin. The inlaying of marbles andagates has long been carried on at Matlock, in Derbyshire ; but no attempts had been made to proceed beyondthe most commonplace subjects, such as scrap-tables, &c., in which form or design seem to have been thelast things thought of, till about 1833 , when an imitation of Florentine work was tried in such subjects asbutterflies and birds. At a later period the work was advanced to the production of sprays of flowers.In 1840 Mr. Woodruff, the gentleman who has executed the beautiful tables now engraved, produceda table-top, in which were introduced groups of birds, flowers, and fruit, which was at the time considereda great step in advance, and was purchased by the late Duke of Cambridge. Mr. Woodruff subsequentlyreceived the patronage of the late Queen Dowager, her present Majesty, and many of the nobility; amongstwhom the Duke of Devonshire has shown the greatest interest in the manufacture, and much advanced it byallowing the free inspection of the beautiful specimens of Florentine work in his possession at Chatsworth.The specimens we give were made for H.R.H. Prince Albert , from the designs of Mr. Gruner, and were veryproperly the objects of a Prize medal for their excellent execution.

The subject occupying the centre of the present Plate is an imitation of Florentine mosaic, executed byMr. Magnus, in his interesting manufacture of enamelled slate. The extreme hardness of the artificialsurface of this material is truly remarkable. It is produced by applying to the finely-rubbed slate numerouscoats of japanning, the whole being constantly baked, at a very high temperature. The texture of marbleis given to it, by an ingenious application of the ordinary practice of book-marbling, modified with muchjudgment by Mr. Magnus; whose endeavours to combine economy of production with the greatest possibleamount of good taste, are highly to be commended.