It is precisely because such phrases are not part of the current idiom that they give distinction to the style. This, however, he failed to see. It is a great matter to observe propriety in these several modes of expression, as also in compound words, strange (or rare) words, and so forth.
The quote: But the greatest thing by far is to have a command of metaphor. This alone cannot be imparted by another; it is the mark of genius, for to make good metaphors implies an eye for resemblances.
Of the various kinds of words, the compound are best adapted to Dithyrambs, rare words to heroic poetry, metaphors to iambic. In heroic poetry, indeed, all these varieties are serviceable. But in iambic verse, which reproduces, as far as may be, familiar speech, the most appropriate words are those which are found even in prose. These are,--the current or proper, the metaphorical, the ornamental. Concerning Tragedy and imitation by means of action this may suffice.