With all this of magnificent accomplishment in painting, which sets him on a pinnacle by himself in this great department of art, it might be thought that Leonardo's main claim to recognition was because of his painting. He himself, however, would have been the first to object to estimation of him on any such grounds. He probably scarcely considered himself to be a painter at all, or at least occupied himself with painting only in his leisure moments. He beat Michelangelo once in a competition in sculpture, but doubtless thought less of himself as a sculptor than as a painter. He made what his generation declared to be the greatest equestrian statue {21} ever modelled and his generation knew what they meant by that, for they had before them two such triumphs of equestrian statuary as Donatello's "Gatamelata" and Verrocchio's "Colleoni." Just as in painting, when he wanted to do sculpture he could do it with a supreme perfection that is unrivalled. Strange as it may seem, Leonardo thought of himself as an engineer. He actually took on himself the contract for extending the canal system around Milan and accomplished it so well that his work still remains in use. During the course of this he invented the wheelbarrow, the movable derrick, the self-dumping derrick, various modes of moving rock, locks for canals and a system for maintaining a navigable level of water in rivers which were usually nearly dry in the summer time. Leonardo had the thorough appreciation of himself that genius is so likely to have and that in smaller men seems conceit. He knew that there was practically nothing to which he cared to turn his hand in which he could not work out original ideas. He was only in his middle twenties when he wrote the letter to Ludovico Sforza in which he tells his future patron very calmly all the things he might be expected to do if the Duke should have need of them.