The present is scarcely a fitting occasion upon which to state in any detail the grounds upon which I have been led to this conclusion, but I have little doubt that any student will be struck by the identity of practice of Roman, Indian, and Moor, who will refer to the practical descriptions of the various modes of the formation of terraces given by Vitruvius, by Captain Phipps, in "The Barrackmaster's Assistant,"[41] and by John Windus, in his "Journey to Mequinez."[42] I have elsewhere noticed the command the descendants of the Moors seemed to retain over all operations of plaster and lime work throughout Spain, as evidenced by the beauty and elaboration of the Mudejar style in those materials, long after they ceased to be the dominant race in the localities in which they continued to practice their old technical arts. [Illustration: PLATE 71 GRANADA. THE ALHAMBRA. FROM THE HALL OF THE AMBASSADORS. BLACK ON WHITE. FULL SIZE GLASS INLAY. MDW 1869] PLATE LXXI. _GRANADA.--THE ALHAMBRA._ DETAIL OF GLASS INLAY FROM THE HALL OF THE AMBASSADORS. THIS little pattern which forms the centre, or eye--the point of departure in fact--of an elaborate geometrical mosaic has been most carefully traced and copied from the original, which yet remains in the centre of the dado on the side of the window on the right of the Sultan's throne in the Hall of the Ambassadors. It may thus be said to occupy an especial post of honour and so to challenge, as it were, curiosity and admiration. Both these a close inspection thoroughly justifies, since in all the history of the manufacture of vitrified substances I know nothing more curious and puzzling. The pattern is in bluish-black on a white ground; and both ground and inlay are made apparently in two separate pieces of glass, and in two only. The most minute inspection shows no joint whatever on the surface of either coloured material; at the same time it establishes the fact that the ground has been made with the whole pattern sunk "en creux," and that the inlay has been made in one piece--practically a specimen of glass lace--and fixed into the cavity of the ground with a very fine calcareous cement, made probably of lime and white of egg. To inlay glass in glass involves little difficulty, if ground and inlay are as it were fused together; but to produce a ground apparently in glass, and to inlay it with so fine a pattern, both "au froid," is a perfect marvel in vitreous manufacture.