Search instead for "Giaconda". Yeats include some of the following in The Oxford Book of Modern Verse:

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La Gioconda is, in the truest sense, Leonardo's masterpiece, the revealing instance of his mode of thought and work. In suggestiveness, only the Melancholia of Duerer is comparable to it; and no crude symbolism disturbs the effect of its subdued and graceful mystery. We all know the face and hands of the figure, set in its marble chair, in that cirque of fantastic rocks, as in some faint light under sea. Perhaps of all ancient pictures time has chilled it least.* As often happens with works in which invention seems to reach its limits, there is an element in it given to, not invented by, the master. In that inestimable folio of drawings, once in the possession of Vasari, were certain designs by Verrocchio, faces of such impressive beauty that Leonardo in his boyhood copied them many times. It is hard not to connect with these designs of the elder, by-past master, as with its germinal principle, the unfathomable smile, always with a touch of something sinister in it, which plays over all Leonardo's work. Besides, the picture is a portrait. From childhood we see this image defining itself on the fabric of his dreams; and but for express historical testimony, we might fancy that this was but his ideal lady, embodied and beheld at last. What was the relationship of a living Florentine to this creature of his thought? By means of what strange affinities had the person and the dream grown up thus apart, and yet so closely together? Present from the first incorporeally in Leonardo's thought, dimly traced in the designs of Verrocchio, she is found present at last in Il Giocondo's house. That there is much of mere portraiture in the picture is attested by the legend that by artificial means, the presence of mimes and flute-players, that subtle expression was protracted on the face. Again, was it in four years and by renewed labour never really completed, or in four months and as by stroke of magic, that the image was projected?

*Yet for Vasari there was some further magic of crimson in the lips and cheeks, lost for us.

The presence that thus rose so strangely beside the waters, is expressive of what in the ways of a thousand years men had come to desire. Hers is the head upon which all "the ends of the world are come," and the eyelids are a little weary. It is a beauty wrought out from within upon the flesh, the deposit, little cell by cell, of strange thoughts and fantastic reveries and exquisite passions. Set it for a moment beside one of those white Greek goddesses or beautiful women of antiquity, and how would they be troubled by this beauty, into which the soul with all its maladies has passed! All the thoughts and experience of the world have etched and moulded there, in that which they have of power to refine and make expressive the outward form, the animalism of Greece, the lust of Rome, the reverie of the middle age with its spiritual ambition and imaginative loves, the return of the Pagan world, the sins of the Borgias. She is older than the rocks among which she sits; like the vampire, she has been dead many times, and learned the secrets of the grave; and has been a diver in deep seas, and keeps their fallen day about her; and trafficked for strange webs with Eastern merchants: and, as Leda, was the mother of Helen of Troy, and, as Saint Anne, the mother of Mary; and all this has been to her but as the sound of lyres and flutes, and lives only in the delicacy with which it has moulded the changing lineaments, and tinged the eyelids and the hands. The fancy of a perpetual life, sweeping together ten thousand experiences, is an old one; and modern thought has conceived the idea of humanity as wrought upon by, and summing up in itself, all modes of thought and life. Certainly Lady Lisa might stand as the embodiment of the old fancy, the symbol of the modern idea.
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