A characteristic of Roman jewels executed in Britain is their ornamentation with enamels. The metal employed is generally bronze, the surface of which is ornamented by the champlevé process; that is to say, it is incised or grooved out (though sometimes stamped or cast) in such a manner as to leave floral or geometrical patterns in relief, and into the sunk spaces thus formed are fused opaque enamels, principally red, yellow, green, blue, and white. This enamelling is generally found upon brooches both of the circular and of the bow-shaped type. The fronts of the circular brooches are flat, or raised like a shield into several compartments of different colours. The pin, which is hidden, moves freely on a pivot, and its point is held by a catch. The finest specimen, discovered in London, was formerly in the collection of Lord Hastings, from whom it was acquired by the British Museum. It is a circular flat plaque, the pattern on which consists of four quatrefoils with blue centres on a red ground, and four small circles of yellow enamel between them. In the centre is the revolving figure of a dolphin (Pl. XI, 7). Brooches enamelled in a somewhat similar manner have been found in France at Mont Beuvray, near Autun, and are preserved in the Musée des Antiquités Nationales at St. Germain.[8] [8] Bulliot (J. G.), _Fouilles de Mont Beuvray (ancienne Bibracte) de 1867 à 1895_. 1899. Quite different are certain ornaments set with slices cut from rods of millefiori glass, which were executed for the most part during the decline of the Roman power. One of the most elaborate is a brooch found at Pont-y-Saison, near Chepstow, Monmouthshire, in 1861, and preserved among other Romano-British antiquities in the British Museum. It has an elaborate pattern of chequered squares of red, white, and blue (Pl. XI, 6). Brooches of the Gallo-Roman and early Merovingian period appear to have been also decorated in this manner. Of bow-shaped brooches, or fibulæ, there exists a considerable number of varieties. Among these we may distinguish the #T#-shaped fibula with long cylindrical head, and a wide flat bow with sunk designs filled with enamel. In another variety the bow passes through a horizontal disc in its centre and assumes a form resembling a tassel. Another common variety is the crossbow form, either with a spiral or hinged head. In many Roman fibulæ the pin works on a hinge, but in the variety known as the harp-shaped, the sheath of the pin is filled in with a triangular plate, pierced or solid, and the head is slightly expanded to suit the coils of a spring.