at either end.  Two gateways have been ascribed to Donatello, but there is nothing either in their architecture or the treatment of their heraldic decoration, which is distinctive of the sculptor.[82] There can be no doubt that Donatello was employed as architect by the Chapter of Sant’ Antonio at Padua,[83] and his love of buildings is constantly shown in the background of his reliefs.  But the strongest testimony to his architectural skill is derived from the fact that he was commissioned in 1416 to make a model for the then unfinished cupola of the Cathedral at Florence.  Brunellesco and Nanni di Banco also received similar orders.  Brunellesco alone understood the immense difficulty of the task, and in the next year he announced his return to Rome for further research.  In 1418 the sum of two hundred gold florins was offered for the best model, and in 1419 Ghiberti, Nanni di Banco, Donatello and Brunellesco all received payments for models.  Donatello’s was made of brick.  Ultimately the work was entrusted to Brunellesco, who overcame the ignorance and intrigues which he encountered from all sides, his two staunch friends being Donatello and Luca della Robbia.  As to the nature of Donatello’s models we know nothing; it is, however, clear that his opinion was at one time considered among the best available on a problem which required knowledge of engineering.  As a military engineer Donatello was a failure.  He was sent in 1429 with other artists to construct a huge dam outside the besieged town of Lucca, in order to flood or isolate the city.  The amateur and dilettante of the Renaissance found a rare opportunity in warfare; and this passion for war and its preparations occurs frequently among these early artists.  Leonardo designed scores of military engines.  Francesco di Giorgio has left a whole bookful of such sketches, in one of which he anticipates the torpedo-boat.[84] So, too, Michael Angelo took his share in erecting fortifications, though he did not fritter away so much time on experiments as some of his contemporaries.  Donatello and his colleagues did not even leave us plans to compensate for their ignominious failure.  One is struck by the confidence of these Renaissance people, not only in art but in every walk of life.  They were so sure of success, that failure came to be regarded as surprising, and very unprofessional.  Michael Angelo had no conception of possible failure.  He embarked upon the colossal statue of the Pope when quite inexperienced in casting; he was the first to taunt Leonardo on his failure to make the equestrian statue.  When somebody failed, the work was handed over to another man, who was expected to succeed.  Thus Ciuffagni had to abandon an unpromising statue, quod male et inepte ipsam laboravit,[85] and the David of Michael Angelo was made from a block of marble upon which Agostino di Duccio had already made fruitless attempts.

[Footnote 80:  The niche was completed about 1424-5.  There is a drawing of it in Vettorio Ghiberti’s Note-book, p. 70.  Landucci, in his “Diario Fiorentino,” says that Verrocchio’s group was placed in it on June 21, 1483.]