One may notice here one of Orcagna's limitations. "He was unable to draw the nude. On this inability followed a coldness to the value of flowing lines, and to the power of unity in composition; neither could he indicate motion or buoyancy in flying or floating figures" (_On the Old Road_, i. § 78). Compare especially the flying angels in the two little pictures 571 and 572, with such figures as those by Botticelli (1034), and it will be seen at once how inferior Orcagna's knowledge was. 573-5. THE NATIVITY, ADORATION, AND RESURRECTION. _Orcagna_ (part of the altar-piece, 569). These panels are very rude and "conventional": nothing can be more absurd, for instance, than the sleeping sheep and shepherds at the top of the Nativity; but they are interesting, if only by comparison with later pictures of the same subjects. Such a comparison shows how constant the traditional ways of representing these events were, and how individual choice was shown in beautifying the traditions. From this point of view the Nativity is specially interesting. "This beautiful little picture," says Mr. Hodgson, R.A., "is a good example of the simplest and most perfectly symbolical treatment of the subject. In design and composition the painter has thought only how to convey the story with the utmost clearness and simplicity. It is what it was intended to be, a Scripture story made visible to those who could not read. Naturalism, _i.e._ the actual representation of the aspect of nature, is not thought of, no more at least than was necessary to make the meaning of the painted symbol equivalent to that of the word: rock for rock, ox for ox, and ass for ass. The degree of naturalism aimed at in such scenes can be tested pretty accurately by the treatment of the nimbus. A flat circular expanse of gold inserted into a picture must necessarily be destructive of all illusion--it is treated as a symbol, a thing non-existent, but as a necessary traditional observance. When naturalism was aimed at, the nimbus was looked upon as an actual existing corona of golden light which the saint carried about with him, and it was drawn in perspective, according to the turn of his head" (_Magazine of Art_, 1890, p. 39). Turn next to the Nativity by Piero della Francesca (908)--a picture painted 100 years later. The symbolism is already mixed up with some conscious striving after objects beautiful in themselves. To a generation later still belongs Botticelli's "Nativity" (1034). It is full, as we shall see, of doctrinal symbolism, but it strikes the imagination also by the pomp and pageantry of the angelic host, and appeals to the senses by its flowing lines and gorgeous colourings. Yet in all these pictures of the Nativity there are certain fixed elements. One feature never absent is the introduction of the ox and the ass, suggested by a text from Habakkuk, iii. 4, "He shall lie down between the ox and the ass." A second point is that Joseph "sits apart, apparently weary or in