It has often happened that stonecutters in the quarries of Florence, in the old Republican times, have become celebrated sculptors, like Mino da Fiesole, Desiderio da Settignano, and Cronaca. Canova and Vincenzo Vela were also quarrymen, and Hugh Miller, from working as a mason, became a highly-esteemed geologist. Andrea del Castagno, a shepherd of Mugello, one day, when overtaken by a storm, took refuge in an oratory, where a house-painter was daubing a picture of the Virgin. From thenceforth he felt an irresistible desire to imitate him, and practised drawing figures in charcoal whenever he could; so much so, that his fame soon spread among the peasants, and, afterwards, by the assistance of Bernadino de’ Medici, who enabled him to study, he became a celebrated painter. Vespasiano de’ Bisticci, a Florentine paper-maker, whose profession involved the handling of many books, and contact with a great number of literary and learned men, took to literature himself. More frequently, however, opportunity is only the last drop which makes the vessel run over. This is so true that the cases in which genius has manifested itself in spite of adverse circumstances and even violent opposition, are innumerable. It is sufficient to recall Boccaccio, Goldoni, Muratori, Leopardi, Ascoli, Cellini, Cavour, Petrarch, Metastasio, and, finally, Socrates, who was obliged to cut and carve stones. All our recent great musicians--Wagner, Rossini, Verdi--were misunderstood in their youth. Long ago, it was said, “He to whom Nature would not tell it, would not be told by a thousand Athens and a thousand Romes.”[280] Circumstances, then, and a certain degree of civilization gain acceptance and toleration for genius and its discoveries which, under other conditions, would have either passed unnoticed, or met with ridicule, and even persecution. History shows that great discoveries are rarely absolute novelties, and that they have long existed as toys or curiosities. “Steam,” says Fournier, “was a plaything for children in the time of Hero of Alexandria, and Anthemius of Tralles. The human mind and the needs of our race have to work by experience, a million times over, before deducing all the consequences of a fact.[281] In 1765, Spedding offered _portable gas_, prepared and ready for use, to the corporation of Whitehaven, and was refused. At a later date came Chaussier, Minkelers, Lebon, and Windsor, who had no other merit than that of appropriating his discovery. Coal had been known ever since the fifteenth century; in 1543 Blasco de Garay appears to have propelled a vessel by steam and paddles in the port of Barcelona; the screw-steamer was invented before 1790. When Papin experimented with steam navigation, he met with nothing but derision, and was treated as a charlatan. When the screw was at last applied, Sauvage, who had invented it, never saw it in action, except from the prison where he was confined for debt.