The various motives that have been specified—namely, interlaced-work, step-patterns, key-patterns, spirals, and zoömorphs—are not always found in combination, except in the MSS., sculptured stones, and metalwork of the best period. The step-patterns are, as a rule, only found in the early MSS. and on the enamelled settings of metalwork. Foliage is a distinctly non-Celtic element, and wherever it occurs it is a proof of Anglian influence from Northumbria. As the decadence of Celtic art set in the spirals disappeared first, and then the key-patterns, leaving only interlaced-work and zoömorphs, which survived even after the Norman conquest. Key-patterns survived in a debased form in the architectural details of the churches of the twelfth century in Ireland, but not in Scotland or Wales. By the geometrical perfection of the Celtic ornament is meant that there are hardly ever any mistakes in the setting-out and complete execution of the designs. Thus in the interlaced-work every cord laps under and over with unfailing regularity (never over two or under two), and all the cords are joined up so as not to leave any loose ends. All the details of the spiralwork are executed with the minutest care, and there is never a broken line or pseudo-spiral. In the zoömorphic designs the beasts are all provided with the proper number of limbs and are complete in every respect down to the smallest detail. The inferiority of the figure drawing in Christian Celtic art to the ornament will be dealt with subsequently in its proper place. We will now proceed to examine in detail the different motives made use of in the Celtic art of the Christian period in Great Britain. INTERLACED-WORK The interlaced ornament used in Celtic art may be divided into the following classes:— (1) Regular plaitwork, without any breaks. (2) Broken plaitwork, with breaks made in an irregular way. (3) Knotwork. (4) Circular knotwork. (5) Triangular knotwork. (6) Ringwork or chainwork. Interlaced-work is the predominant motive of the Celtic style of the Christian period. It lasted longer in time than any other motive, and its geographical distribution extends over a larger area. It is very seldom that one motive is used by itself for the decoration of a stone monument, metal object, or page of a MS.; but where this is the case the motive chosen is invariably interlaced-work, and not a key-pattern, spiral, or zoömorph. As instances of sculptured monuments decorated entirely with interlaced-work we have the cross at Neuadd Siarman, Brecknockshire, and the cross-shaft at St. Neot, Cornwall. The evolution of knotwork from plaitwork cannot better be studied anywhere than in the decoration of the Welsh crosses. Let us now endeavour to trace the various stages in the process by which the higher forms of Celtic interlaced-work were arrived at.