Machine-made lace has been brought to an advanced state of perfection, and Nottingham in England, where the first machines were set up, is now the great centre of this industry. The machine on which lace is made is a development of the stocking-knitting machine, and lace nets were first made on these machines about 1770. Heathcote, of Nottingham, invented the bobbin net machine, and Leaver invented the lace machine which is still in use with various improvements and modifications. Almost any kind of lace can now be imitated by the machine, but it is easily distinguished from the hand-made varieties by the greater regularity of texture, the absence in the machine-made point lace of any imitation of the button-hole stitch and of the elaborate plaiting that is found in the pillow hand-made laces. CHAPTER VII. MOSAICS. The word mosaic is applied generally to a decorative work executed with small cubes or tesseræ made from various coloured marbles or enamels, cut into convenient sizes according to the requirements or scale of the design. These cubes of enamels or marbles are placed in a bed of cement which is first spread on the surface of the wall or panel. The composition of this cement has varied in the different periods and countries and according to the nature of the ground which receives it. The Italian method is to spread on the wall a thick coating of mastic cement composed of marble dust or powdered stone, lime, and linseed oil; when this cement is partly set a coating of fine plaster is laid on the top and brought up to the level of the intended surface of the mosaic; the design is traced on this surface, and the plaster is then cut away with a fine small chisel, little by little, just sufficient at a time to receive a small quantity of the tesseræ or cubes, which are first dipped in moist cement and inserted in their proper places, matching the colour copied from the cartoon. When the work is finished the surface is brought to a uniform level by a polishing process. Some of the earlier kinds of mosaic were composed of pieces of marble or other stones cut in geometric slabs or rectangular shapes; this kind was called by the Romans _lithostratum_, and was used chiefly in pavements; _opus sectile_ is a kind of pavement mosaic made of different colours, the marbles being cut into small regular portions; _opus tesselatum_ is a variety of the _opus sextile_, but has its component parts made of geometric forms in which straight and parallel lines predominate in the design; and _opus vermiculatum_ has its tesseræ composed of small cubes or bits of enamel (glass mosaic), terra-cotta, or marble, which are cut into all kinds of shapes, so as to form a more pliant or softer contour to the proposed design. This latter variety is used in picture mosaics and in the goldsmiths’ work and jewellery made at the present time in Rome and Venice.