V. Often in association with this horrible design we find, in Greek works, one which is as beautiful as this is painful--that egg and dart moulding, whose perfection in its place and way, has never been surpassed. And why is this? Simply because the form of which it is chiefly composed is one not only familiar to us in the soft housing of the bird's nest, but happens to be that of nearly every pebble that rolls and murmurs under the surf of the sea, on all its endless shore. And with that a peculiar accuracy; for the mass which bears the light in this moulding is _not_ in good Greek work, as in the frieze of the Erechtheum, merely of the shape of an egg. It is _flattened_ on the upper surface, with a delicacy and keen sense of variety in the curve which it is impossible too highly to praise, attaining exactly that flattened, imperfect oval, which, in nine cases out of ten, will be the form of the pebble lifted at random from the rolled beach. Leave out this flatness, and the moulding is vulgar instantly. It is singular also that the insertion of this rounded form in the hollow recess has a _painted_ type in the plumage of the Argus pheasant, the eyes of whose feathers are so shaded as exactly to represent an oval form placed in a hollow. VI. It will evidently follow, upon our application of this test of natural resemblance, that we shall at once conclude that all perfectly beautiful forms must be composed of curves; since there is hardly any common natural form in which it is possible to discover a straight line. Nevertheless, Architecture, having necessarily to deal with straight lines essential to its purposes in many instances and to the expression of its power in others, must frequently be content with that measure of beauty which is consistent with such primal forms; and we may presume that utmost measure of beauty to have been attained when the arrangements of such lines are consistent with the most frequent natural groupings of them we can discover, although, to find right lines in nature at all, we may be compelled to do violence to her finished work, break through the sculptured and colored surfaces of her crags, and examine the processes of their crystallisation.