§ XXVI. 4. Forms of Fire (Flames and Rays). If neither the sea nor the rock can be imagined, still less the devouring fire. It has been symbolised by radiation both in painting and sculpture, for the most part in the latter very unsuccessfully. It was suggested to me, not long ago,[66] that zigzag decorations of Norman architects were typical of light springing from the half-set orb of the sun; the resemblance to the ordinary sun type is indeed remarkable, but I believe accidental. I shall give you, in my large plates, two curious instances of radiation in brick ornament above arches, but I think these also without any very luminous intention. The imitations of fire in the torches of Cupids and genii, and burning in tops of urns, which attest and represent the mephitic inspirations of the seventeenth century in most London churches, and in monuments all over civilised Europe, together with the gilded rays of Romanist altars, may be left to such mercy as the reader is inclined to show them. § XXVII. 5. Forms of Air (Clouds). Hardly more manageable than flames, and of no ornamental use, their majesty being in scale and color, and inimitable in marble. They are lightly traced in much of the cinque cento sculpture; very boldly and grandly in the strange Last Judgment in the porch of St. Maclou at Rouen, described in the "Seven Lamps." But the most elaborate imitations are altogether of recent date, arranged in concretions like flattened sacks, forty or fifty feet above the altars of continental churches, mixed with the gilded truncheons intended for sunbeams above alluded to. § XXVIII. 6. Shells. I place these lowest in the scale (after inorganic forms) as being moulds or coats of organism; not themselves organic. The sense of this, and of their being mere emptiness and deserted houses, must always prevent them, however beautiful in their lines, from being largely used in ornamentation. It is better to take the line and leave the shell. One form, indeed, that of the cockle, has been in all ages used as the decoration of half domes, which were named conchas from their shell form: and I believe the wrinkled lip of the cockle, so used, to have been the origin, in some parts of Europe at least, of the exuberant foliation of the round arch. The scallop also is a pretty radiant form, and mingles well with other symbols when it is needed. The crab is always as delightful as a grotesque, for here we suppose the beast inside the shell; and he sustains his part in a lively manner among the other signs of the zodiac, with the scorpion; or scattered upon sculptured shores, as beside the Bronze Boar of Florence. We shall find him in a basket at Venice, at the base of one of the Piazzetta shafts.