What, however, can seem more simple than this discovery? It is even difficult to understand why it was not made before, when we remember not only that the printing of blocks engraved in relief had been practised since the beginning of the fifteenth century, but that the niellatori themselves were in the habit of taking, first in clay and then in sulphur, an impression and a counter-impression of their work before applying the enamel. What should seem more simple than to have taken a direct proof on a thin elastic body such as paper? But it is always easy to criticise after the event, and to point out the road of progress when the end has been attained. Who knows if to-day there is not lying at our very hand some discovery which yet we never think of grasping, and if our present blindness will not be the cause of similar wonder to our successors? At any rate, Finiguerra had found the solution of the problem by 1452. This was put beyond doubt on the day towards the close of the last century (1797), when Zani discovered, in the Print-Room of the Paris Library, a niello by Finiguerra printed on paper of indisputable date. [Illustration: FIG. 16.--FINIGUERRA. The "Pax" of the Baptistery of St. John at Florence.] This little print, or rather proof, taken before the plate was put in niello, of a "Pax"[17] engraved by the Florentine goldsmith for the Baptistery of St. John, represents the Coronation of the Virgin. It measures only 130 millimetres by 87. As regards its size, therefore, the "Coronation" is really only a vignette; but it is a vignette handled with such knowledge and style, and informed with so deep a feeling for beauty, that it would bear with perfect impunity the ordeal of being enlarged a hundred times and transferred to a canvas or a wall. Its claims as an archæological specimen, and the value that four centuries have added to this small piece of perishable paper, must assuredly neither be forgotten nor misunderstood by any one. Yet he would be ill-advised, on the other hand, who should regard this masterpiece of art as a mere historical curiosity. [Illustration: FIG. 17.--ITALIAN NIELLO. (Fifteenth Century.)] [Illustration: FIG. 18. ITALIAN NIELLO. (Fifteenth Century.)]