The most imaginative of inventors, Piero di Cosimo was as an observer a stupendous realist. Unlike most other Florentine painters of his period, he was essentially a painter, not a designer. He felt the tangible epidermis of things, rather than their abstract form, and based his art on colouristic 'valeurs,' rather than on linear patterns. One of Piero's earliest pictures, acquired in 1932 by the Wadsworth Athenaeum at Hartford, Connecticut, is generally supposed to represent the myth of Hylas and the nymphs. Boccaccio's 'Vitruvian' interpretation of Vulcan throws light on the iconography of a less known, picture by Piero di Cosimo which was formerly in the collection of Lord Lothian in Dalkeith and has been acquired by the National Gallery of Canada. The system on which Piero di Cosimo's evolutionistic compositions are based bears some resemblance to the theological division of human history into the era ante legem, the era sub lege, and the era sub gratia.